DE102007037165A1 - Wire installing method for smart card, involves providing connection of thin conducting wire and substrate surface, and fixing up wire for hardening connecting material by utilizing electrostatic pressing force on substrate - Google Patents

Abstract

The method involves providing connection of a thin conducting wire (1) and a substrate surface (4) by utilizing surface energy of a connecting material melted by a heat supply, where the connecting material coats the wire and the substrate surface. The wire is fixed up for hardening the connecting material by utilizing electrostatic pressing force on a substrate, where the connecting material is hot-melt glue. Electrostatic pressing force is produced when the conducting wire and electrodes (29, 51) are arranged under the substrate. An independent claim is also included for a device for installing a thin wire on a surface of a substrate.

Description

The This invention relates to methods and apparatus for machine, computer-controlled laying of thin wire on the surface of a substrate. Mainly it is about metallic wire, but also to wire made of non-metallic materials such as polymers, Glass or ceramics. For metallic wires is the scope of application is almost invisible to the eye electrical connection of microelectronic components and manufacture planar coils, for non-metallic mounting micro-mechanical and micro-optical components.

The production of electronic circuit boards by laying discrete wires on an insulating substrate had become known in the early years of printed circuit board technology by such keywords as "multiwire" technology or "wirewritten printed circuit board". The patents DE 23 26 861 . DE 32 47 344 . DE 26 10 283 . US 3,674,602 . US 4,648,180 and US 4,864,723 In general, they describe wire-laying devices with a laying head, which is guided over the substrate and thereby deposits a conductor wire on the substrate surface.

Meanwhile, printed circuit boards with directly laid wires are almost completely displaced by sheets with etched tracks. For special applications, however, it may still be advantageous to lay metal wire directly on an insulating substrate. This is how the patent describes US 7,000,314 round wires instead of etched tracks to improve the packing density and high frequency performance of a printed circuit board. The patent DE 196 18 917 states that the direct laying of wires is in some cases more advantageous than the production of conductor tracks by etching from a large-area deposited metal layer. Given a given circuit, this argument is generally more pronounced the larger the area of the substrate is, because the material and workload in the case of planar (deposition and etching) technology increase proportionally to the substrate surface, but only proportionally to the wire length in the laying technique. Of particular interest is the direct laying of insulated wire, such as in the form of inexpensive copper wire, because it can be easily realized by simply overlapping the wires insulating intersections. In contrast, when crossing bare wires, an insulating foil must be interposed as in EP 1 004 226 , and in etched circuits, a short circuit of the lines can be avoided only by consuming evasion into the third dimension. Widely used wire laying technology today for the production of so-called "antenna coils" for RFID transponders, such as in DE 44 10 732 executed. Finally, the in DE 102 47 553 For example, "Optical Display" disclosed the fact that, viewed perpendicularly to the substrate, a round conductor wire appears narrower than a typical etched conductor of the same cross-section. When the wire is laid on a glass substrate, this results in a higher optical transparency with respect to the etched conductor track when looking through the substrate wafer. If the wire diameter is chosen to be sufficiently small, for example below 25 μm, such connecting wires are virtually invisible to the unaided eye.

According to this prior art, the wire to be laid is unwound from a supply reel and guided in the laying head via a deflection channel or a deflection roller in the immediate vicinity of the substrate surface, that it is almost parallel to the same. It is then pressed by a pinch roller or other tool against the substrate surface and fixed thereon, as in the patent US 4,918,260 explicitly described. In this joining method, thermoplastic adhesives are preferably used, in particular hotmelt adhesives, which have first been applied as a coating to the wire or to the substrate surface. When laying this adhesive is brought by heating to melting and deliquescence and connects both joining partners as closely as possible. After cooling of the adhesive, the laid wire then permanently adheres to the substrate surface. Closely related joining methods by means of which a wire can be laid on a substrate surface are soldering and thermo-compression. They, too, exploit the surface tension of a molten bonding material to create a tight bond between the wire and the substrate surface. As is known, molten metal is used in printed circuit board technology where the connection must be electrically conductive, for example at the contact surfaces of electronic components ('bonding pads'). In this case, the joining methods soldering and thermocompression differ in the latter one of the materials to be joined itself becomes molten, while in the former the solder is additionally introduced as a lower-melting compound material.

A fundamental difficulty with all of these laying methods is the necessity for the wire to be pressed tightly onto the substrate surface for attachment. Only when it touches the surface directly - ie with a certain positive pressure force - will the heat dissipating bonding material simultaneously wet the wire and the substrate surface. Only then, it will spread through surface tension and capillary force and penetrate into the joint, as it is for a good Haf tion of the wire is necessary. Remains after melting even a small, finite distance between the wire and the substrate surface or the applied adhesive layers, so this flow process and the bonding does not take place.

There the wire to be laid is never perfectly straight and the substrate surface never perfectly flat, the pressure force must be sufficiently large, bend the wire so that it is everywhere the surface contour snugly. To the mentioned crossover isolated To consider wires, the "surface contour" here also include transverse wires, which already in an earlier step on the substrate surface were moved. Beyond them is the wire currently being laid pressed against the substrate. The pressing with a certain minimum force is thus successful Installation essential.

Pressing is one of the most critical process steps when installed by machine. Due to the mechanical contact, the pressure tool can deform the cross section of a thin wire. It can damage the surface or insulation of the wire and cause short circuits. As a result of the mechanical contact there is also a permanent risk that the pressure tool may be contaminated by abrasion of insulation material or adhesive and continuously cleaned, as in US 4,864,723 described in more detail. All these difficulties can be summarized by the term "handling the wire". They become larger, the thinner the wire to be laid. With wire diameters below 0.1 mm, they are usually so serious that the known methods of wire laying fail.

To solve these problems suggests US 6,400,882 a laying method in which the pressing force is generated quasi contactless. For this purpose, the bending stiffness of the wire is utilized. The wire, coming from a narrow, heated deflection tube, is pressed obliquely against the substrate surface at a shallow angle and adheres there. A special pressure tool is not required. However, this method solves the problems mentioned only partially, because indirectly affects the deflection tube as a pressure tool and is subject to the same abrasion and contamination problems. On the other hand, this method works only with thicker wires with sufficient bending stiffness, and thirdly, the pressing force exists only locally, immediately at the point of contact of the wire on the substrate. This situation may work with thick wire, but with thin wire pressure and heat transfer are not sufficient for a good bond.

This should after the following presentation of the heating problems be even better understood.

One Another problem occurs when laying thin wire The prior art in cases where a warming to melt an adhesive is required. If the heating occurs through Touching the wire with a hot pressure tool, there is a tendency for the wire not only to be on the substrate surface, but also sticks to the tool. When retracting the tool he can tear off from the substrate again. Will instead Contactless by heat radiation or blowing heated with hot air, so there is a risk uneven Warming. In the places where the wire is the substrate surface touched, so has good thermal contact will become Heat wire and surface together and glue together. In places with poor thermal contact, the wire becomes however, heat faster and higher than the substrate surface, resulting in overheating and decomposition of the adhesive and inadequate Bonding can result.

After all there is a risk of breakage if the substrate is brittle and only tolerates low thermal stresses. This problem exists especially when laying thin wire (diameter smaller than 50 μm) on glass substrates and heating by means of Radiation. Like a simple thermodynamic estimation shows, then it is not sufficient, only the wire on the Bonding desired temperature in the range of about 100-300 ° C to heat. If the substrate surface remains cold, then it cools the wire at the moment of contact due to its heat capacity very quickly, and the necessary for gluing flow the adhesive is omitted. For wires in the specified diameter range the temperature compensation takes place within less Microseconds during the flow associated with Mass transport process at least one order of magnitude is slower. For a successful wire laying is it is therefore essential to the substrate surface to heat under the wire to be laid. The one on it Overlying wire then has practically the same temperature with good contact as they are, and that is necessary for a good adhesion of the wire Flow can take place.

The Heating of the substrate surface generated in the substrate however, mechanical stresses are all the greater are, the higher the temperature and the larger the heated surface area are. To the danger mechanical failure due to these voltages to keep low is therefore desirable, the heated area so small as possible and yet, if only short time to reach the necessary temperature for gluing.

The invention thus has the task The reason for this is to generate the pressing force of the wire necessary for laying thin wire on a substrate against the substrate surface without contact along a certain section of the wire in the event that, during the pressing, in the pressed-on wire section, the substrate surface is at the flow temperature of the adhesive to heat up.

According to the invention This object is achieved in that the pressure force generated electrostatically becomes.

Of the substantial advantage of the laying method according to the invention compared to the prior art is that it is contactless, works without pressure tool, so that the wire and if necessary his insulation remains intact. There is no risk of contamination a pressure tool. Another advantage is that the electrostatic Pressure force on the entire support section of the wire acts. As a result, he nestles, as described, automatically to existing bumps and contours of the substrate surface in a way that is difficult with mechanical pressure tools is reachable. This nestling takes place already at room temperature and - as a result of melting at decreasing distance - only right at the higher melting temperature. The one on the wire Hot melt adhesive can therefore after melting quickly wet the substrate surface, leaving a secure connection results. Finally, it is generally advantageous that the electrostatic pressure works the better the thinner and more flexible is the wire to be laid. With it added the inventive method just in the field smallest wire diameter the known methods, here their have the greatest difficulties.

The inventive method and apparatus for Implementation of the same are exemplary in the drawings illustrated. Show it

1 a preferred device for laying a metal wire on an insulating substrate. The wire emerges from a pipe opening 24 out. The equilibrium between the electrostatic attraction and the laying tension sets a shallow angle 23 between wire and substrate surface.

2 (a) the cross section of an adhesive coated metal wire,

2 B) the cross section of a lacquer-insulated and coated with adhesive metal wire, and

2 (c) the cross section of a bare wire, each loosely spaced on the substrate, before bonding.

3 the cross sections 2 after melting and flowing the bonding material. The latter is in (a) and (b) the adhesive applied to the wire, in (c) the substrate material itself. The surface of the molten compound material has each taken the form of a minimal surface, the surface tension closely connects the wire and the substrate.

4 the crossing of two insulated metal wires in cross-section, after the flow of the adhesive. The last laid wire 11 clings to the first laid wire due to the electrostatic attraction 1 to the substrate surface.

5 a device for laying the wire similar to the device in 1 but with a pulley 36 instead of the pipe opening 24 ,

6 schematically the course of the electric field lines between the wire to be laid 1 and the electrode 29 under the substrate plate according to 1 or 5 ,

7 schematically the course of the electric field lines between the wire to be laid 1 and two electrodes 37 . 38 on the substrate surface next to the wire.

8th an alternative electrode arrangement for generating the electrostatic pressure force. Here is the wire 1 not connected; This device also works for non-metallic wires.

9 a device for contacting a component with the free end of a metal wire which is depressed by electrostatic attraction on the solder coated Kon contact surface, while a permanent connection is produced by laser soldering;

10 (a) bis (f) are sectional views of wire and electrode assemblies for generating electronic fields that press a wire to be laid on a substrate against the surface of the substrate;

11 (a) a schematically simplified shielding device for protecting a device (chip module or strap) against electric fields, in a 10 (a) to 10 (f) corresponding representation; and

11 (b) one of the shielding according to 11 (a) functionally analogous device with an auxiliary electrode to form a Faraday cage.

The most important elements for carrying out the process according to the invention are in 1 illustrated in the case that a hot-melt coated metallic wire to be laid on an insulating substrate plate. In the laying head 20 occurs the wire 1 from a pipe opening 24 and becomes electrostatic on the surface 4 pulled down the substrate plate. For this purpose, the wire and an electrode disposed under the substrate plate 29 to the poles 18 . 19 an electrical voltage source 32 connected. In 1 is the connection of the pole 19 the voltage source only to the edge of the laying head 20 drawn, but it is assumed here and in the following, that a continuing electrical connection to the wire 1 exists inside the head.

For laying the laying head 20 as a whole relative to the substrate surface in the direction 28 emotional. The wire is spooling 1 from the supply reel 26 from. He first runs through a braking device 27 , which provides for a predetermined tensile force F _{Z of} the wire, and further through the deflection tube 25 , Its opening 24 is located just above the substrate surface. In the with 35 designated section, the wire is stretched due to the tensile force F _Z and runs practically straight. It reaches the substrate surface at the point 8th at a shallow angle γ. The latter is in 1 with the reference number 23 Mistake. The point of contact 8th and the laying angle γ automatically adjust so that the component F _Z sin γ of the tensile force acting upwards perpendicular to the surface is always in equilibrium with the electrostatic force density which presses the wire onto the substrate. Typical values of the laying angle are γ = 1 ° ... 5 °. In the section 34 beyond the surface touch point 8th , the wire is then again practically straight. Due to the electrostatic pressure force, it lies closely on the substrate surface. Between the two rectilinear sections 33 and 35 there is a short transitional section 34 in which the wire is elastically curved.

In the edition section 33 the bonding of the wire to the substrate surface is effected by heating the latter, preferably only in a narrowly localized region. This is in 1 an example of a flame 30 hinted that from a burner tube 31 exits and is directed to the substrate surface. Because of the mentioned thermal stresses in the substrate, it is advantageous to measure the widths B _X (measured in the laying direction) and B _Y (perpendicular to the plane of the 1 measured) of the flame as small as possible to choose. A lower limit consists of the requirement that the flame must supply so much heating power that the heated area reaches the necessary temperature for melting and flowing of the adhesive.

Details of this bonding are in the 2 and 3 shown. A laid without pressure force wire 1 would be loose on the substrate. As a result of internal mechanical stresses, it would generally be curved, and there would be a certain irregularly wide fugue 9 between the wire and the surface. this shows 2 , With the pressure force, however, by the mutual electrostatic attraction of wire and electrode 29 The wire gets to the surface 4 pulled down, and the joint width 9 disappears. Now, when heated, the hot melt melts in cases (a) and (b) 3 , in (c) the surface 4 of the substrate, and after flow of the molten compound material results in 3 shown situation. Here's the hot glue 3 , first as a thin layer on the wire 1 or on its isolation 2 was applied, the substrate surface 4 wetted and redistributed due to its surface tension. He is in the fugue 9 invaded and fills them in the manner of fillets 5 out. In case (c), first the electrostatic force pulls the wire into the melting surface, and after wetting the surface tension then continues to act in the same way. Again, two flutes are formed 6 out.

Corresponding but more complex wetting and flow processes occur when two insulated wires cross over, as in FIG 4 sketched in cross-section. wire 1 with the insulation layer 2 was first laid and on the substrate surface 4 bonded. Over him then was the wire 11 with insulation layer 12 guided. It clings to it according to its flexural rigidity and electrostatic force 1 . 2 . 4 given contour. When heated, the hot melt also flows into the concavo-convex areas 7 ,

Further details and alternative embodiments of the method as well as typical parameters of the devices used can be found in the following more detailed description of said process steps, the terms characterizing the method, and the 5 to 9 ,

It is further simplified assuming that a round metal wire, which is thinly coated with hot melt adhesive, so called a "baked enamel", on an insulating substrate plate, such as glass, to be laid. More general embodiments of the method according to the invention and devices with other materials and other joining methods will be described below. The most important terms are these:
The wire is generally circular in cross-section. However, the electrostatic hold-down invention also works with other cross-sectional shapes, especially in rectangular Cross-section.

The mentioned advantages of the method according to the invention come particularly well if the wire diameter, respectively its thickness measured perpendicular to the surface, below of 50 microns, because then the bending stiffness of the wire is low. To a lesser extent, the benefits exist but also above this limit.

The laying tension F _Z must be selected to match the wire diameter used. A good clue to F _Z is the "winding pull" known from coil winding technology. It lies for wire diameter of 10 ... 100 microns in the range of 1 ... 100 cN and corresponds to a relative elongation of the wire of about 10 ^-3 . The laying tension F _Z is determined by the in 1 shown braking device 27 generated. Simple braking devices operate by friction by pulling the wire between preloaded brake shoes. This is for the device 27 indicated. However, there is a risk of abrasion and contamination. To avoid these problems, as well as higher demands on the adjustability and constancy of F _Z , the wire can be known to be guided over a roller, which is braked by a so-called "torque motor".

The laying speed. Since the relatively heavy substrates of interest here are typically horizontal, the relative movement necessary for laying takes place 28 expedient in such a way that the substrate is fixed and the lighter laying head is moved in a horizontal plane over it. The laying speed v _o should be at least 0.1 m / s for a cost-efficient mechanical laying of wires, better is 1 m / s and above.

Wire deflection. For laying the wire must be deflected from the initially approximately perpendicular feed direction in a nearly horizontal direction. In order for this deflection to result in as little internal tension in the wire as possible, either a gently bent deflection tube is used 25 use, as in 1 , or a pulley 36 according to 5 ,

The electrostatic pressure F _E on the wire section 33 acts is a consequence of the electrical voltage U between the wire 1 and the electrode 29 under the substrate. 6 shows in cross section how the electric field is distributed. In the area of the fugue 9 , between wire 1 and substrate 4 , the field strength is the largest. This results in one on the wire 1 downward force F _E (z). Here z means the distance of the wire from the surface, ie the width of the joint 9 , The maximum force is when the wire is resting (z = 0). As the joint z increases, it becomes smaller and disappears rapidly as z becomes larger than the wire diameter. It is proportional to the length L _{33 of} the wire section 33 , Therefore, it is useful to characterize them by a length-related force density, f _E (z) = F _E (z) / L ₃₃ , with the dimension [N / m].

The absolute magnitude of this force density f _E (z) depends in a complicated manner on the diameter and the coating of the wire, on the thickness of the substrate plate and its dielectric constant, and on the applied voltage. For simplification, however, for glass substrates of 4 mm thickness and insulated wires of average diameter at the minimum distance for rough calculations f _E (z = 0) ≈ 0.05 U ² [N / m] are used, where U is the rms value of the applied voltage in [kV] is. At a voltage of U = 2 kV, the maximum contact force density is therefore of the order of magnitude f _E ≈ 0.2 [N / m].

The laying angle 23 , which is due to the mentioned balance of forces, follows from a simple energy estimation, γ ≈ (2F E0 / F Z ) 1.2

Here, F _E0 = ∫f _E (z) dz means the length-related potential energy of the force density f _E (z), where the integration of z = 0 is to be performed up to a very large distance at which f _E (z) vanishes. This F _E0 has the dimension [N] of a force. For a wire of typical diameter 20 μm, its size is F _E0 ≈ 2U ² 10 ^-6 [N]. With U = 2 kV and a laying force of F _Z = 10 ^-2 N, the laying angle is set to γ ≈ 2.3 °.

The elastically curved wire section 34 is determined in its length L _K by the elastic bending stiffness S of the wire and the tensile force F _Z. As an approximation, L _K = (S / F _Z ) ^1/2 . For copper wires this length is in the order of magnitude L _K ≈ 0.1 ... 10 mm, if the wire diameter varies in the range 10 ... 100 μm.

The electrical voltage decisively determines the size the electrostatic pressure force. Because the force is square with the voltage increases, it is beneficial for the implementation of the invention Procedure to select the voltage as high as possible. A technical upper limit is due to the onset of corona discharge given sharp corners and edges, as well as by the electrical breakdown strength the substrate plate to be wired. In a practically executed Device for wire laying on a 4 mm thick glass pane was a voltage of U = 2 kV fully sufficient for laying 20 μm wire.

A well-known problem electrostatic Holds down is that accumulate at the dielectric interfaces electrical charges. They counteract the applied voltage in any case, thus weakening the electrostatic force. However, they can be largely avoided by quickly reversing the polarity of the applied voltage before even larger charges are built up. As a result, the charges are reduced and then new, with opposite signs, built. In order to dismantle it must then be reversed again, etc. Since the pressure force of U ² depends, it does not change at the polarity reversals. These polarity switches are used in 5 shown switches 57 , Equivalent to a DC voltage source 32 with such a periodic polarity switching 57 is the use of an alternating voltage source with symmetrical rectangular time course.

The electrodes for generating the electrostatic pressure force in the devices of 1 and 5 are the wire to be laid 1 and the counter electrode 29 , The latter may preferably be in the form of a thin metal foil or a conductive coated glass plate placed under the substrate. This particularly simple arrangement is also the cheapest. Given the stress U and moderate substrate thicknesses, it provides the greatest force.

Alternatively, instead of a counter electrode 29 two electrodes 37 . 38 be provided, which is at a small distance symmetrical to both sides of the wire to be laid 1 rest on the substrate surface, cf. 7 , They are going to the pole together 18 connected to the voltage source, at which in the previous examples, the electrode 29 was. Again, in the electric field that forms, the field strength in the region of the joint 9 maximum. For the wire 1 in turn results in a downward force, so a pressure to the surface 4 , This arrangement is advantageous for large substrate thicknesses.

Another alternative electrode arrangement for generating the electrostatic pressure force shows 8th , Here are a number of pairs of electrodes 56a . 56b used. It is advantageous to use a larger number of these electrode pairs. They are arranged in strips or as a checkerboard pattern under the substrate directly in the area where the wire to be laid is to be pressed. All pairs are electrically connected in parallel. One electrode of each pair is connected to the pole 18 connected to the voltage source, the other to the pole 19 , The switch 57 again allows to switch this assignment. The wire 1 is not connected to the voltage source here. Therefore, this electrode assembly is also suitable for laying single short pieces of wire, as well as for non-metallic "wires", commonly referred to as "fibers".

Advantageous Finally, there are similar arrangements of these Kind with electrode triples instead of pairs under the substrate. These triples are symmetrical and are phase shifted by 120 ° Sine AC voltages fed, so results in the spatial Medium over several electrode triples a particularly uniform pressure force.

In In all these cases, the electrodes, optionally including the wire to be laid over suitable electrical connections to the voltage source used be connected. In the case of a DC voltage source means This is because the connections are always electrically conductive have to. When using an AC source is Also suitable is a capacitive coupling of the electrodes.

The Safety of the operating personnel and the electronic to be wired Components deserve special attention in terms of high voltage, the to generate the pressure force is necessary. Practical experience with other electrostatic depressions show that too at voltages of 5 kV and more the personal protection simply by it can be ensured that the voltage source with a sufficiently high internal resistance is provided. He limits the possible fault current, for example to values <20 mA, so that even with accidental contact no danger to life the staff exists.

More difficult is the protection of sensitive electronic components against overvoltages that are galvanic or capacitive from the voltage source 32 can be overcoupled. In this regard, it is advantageous to the wire to be laid 1 basically to maintain earth potential, leaving only the counter electrode 29 at high voltage potential.

The substrate material was assumed to be "insulating" in the previously described embodiments. Decisive for such an evaluation of the electrical conductivity are not absolute values but the requirements of the electrostatic hold down and the laying process. Will the electrical resistance between wire 1 and counter electrode 29 denoted by R and the capacitance with C, the electrostatic attraction is only effective for a period of the order of τ = RC after switching on a DC voltage. Thereafter, the attraction decays quickly because, as mentioned, accumulate at interfaces electrical charges. Can the laying process, including the hardening of the glue, not be done in a time short of the one mentioned? Time constant τ is, so the already mentioned, fast repeated switching of the polarity must be applied. In this case, the frequency f _{U of} the switching must be so high that τf _U >> 1 applies.

For example, during wire laying on an insulating glass pane of 1 m ² size, the electrical resistance should be R = 1000 MΩ and the capacitance C = 1 nF. Then τ = 1 s, and the switching frequency should be significantly greater than 1 Hz.

Significantly higher frequencies are required when the substrate has some electrical conductivity. One example is wire laying on paper, for example for producing planar antenna coils for RFID transponders. With R = 1 MΩ and C = 100 pF, τ = 10 ^-4 s, and the switching frequency should be significantly greater than 10 kHz.

Next these referred to as "insulating" substrates such as Glass, ceramics, polymers, Teslin and synthetic materials, paper, wood, Leather u. a. are also electrically conductive materials as substrates, which are available as an endless roll or as a sheet, for wire laying suitable according to the method of the invention, so metals and coated with a conductive metal layer Insulators. On electrically conductive substrates can be in particular Lay insulated metal wires in the described manner. The wire and the substrate must be connected to the voltage source be connected so that the attraction between them comes. When the insulating layer is thin, such as in copper enameled wire, so it is already a small electrical Sufficient voltage, about 100 V. The inventive Laying method with electrodes under the substrate, in which the Wire is not connected, but only works with insulating Substrates, not with electrically conductive.

When melting bonding material is generally suitable for any material which becomes liquid when heated and in this state Wets and substrate surface wetted and by surface tension connects so that they remain permanently connected after cooling. The most important example are hot-melt adhesives, often also called "hot-melt adhesives" designated. On the one hand, they exist as multiply remeltable "Thermoplastics" and, on the other hand, as thermally reactive and then non-remeltable "thermosets". The melting Connecting material can also be a solder, so generally one Metal alloy whose melting point is below the melting point of wire and substrate lies. The joining process is then a soldering process, and an example of a solder for copper wire is tin solder. Finally comes as a melting compound material too the material of the substrate surface or the wire itself question. The joining process is then called thermocompression. The usually used pressure with a hot Tool can, according to the invention, at very thin Wires by the electrostatic pressure force and local Heating of the substrate surface added or completely replaced. In connection with thermocompression according to the prior art, the inventive Special process for insulated wires in the Way suitable that the wire to be connected first by means of the electrostatic pressure force immovable is fixed on the substrate, and then in conventional By means of a hot tool by pressure permanently is connected.

When using hot glue or solder as a connecting material, it is advantageous, this first as a thin layer 2 on the wire to be laid 1 to apply, as in 2 (a, b) indicated. When melting, it then fills the joints in a hollow-chinked manner 5 of the 3 , Alternatively, the bonding material may be used as a layer on the substrate surface. Even then, flutes form during melting, similar to the joints 6 of the 3 (c) ,

With Hot glue coated wire is more commercial than so-called "Backing wire" for producing self-supporting coils available. Differentiate the available types of hot melt adhesives in their softening temperatures, for example polyvinyl butyral (110 ° C), phenoxy resin (140 ° C), or modified aliphatic Polyamide (180 ° C).

• (a) kontinuierlich fortschreitendes Verlegen, wie es in den Drahtverlegemaschinen nach dem Stand der Technik ausgeführt wird. Dabei wird der Draht entlang einer vorher festgelegten und im Steuerrechner gespeicherten Verlegebahn abgespult und unmittelbar danach durch Erwär mung des Klebers mit dem Substrat permanent verbunden. Für diesen Prozess sind die in 1, 5, und 8 skizzierten Verlegeköpfe bestimmt.
• (b) Zweischritt-Verfahren, bei dem in einem ersten Schritt der Draht insgesamt ausgelegt und dabei während der Auslegezeit durch die elektrostatische Anziehung auf der Substratoberfläche niedergehalten wird. Die Erwärmung, die zur Verklebung führt, erfolgt erst danach im zweiten Schritt, sei es durch lokale Erwärmung der Substratoberfläche entlang der Verlegebahn oder durch Erwärmung der gesamten Substratoberfläche. Zwischen diesen beiden Fällen liegen weitere Möglichkeiten, den Verlegeprozess zu führen, indem der Draht abschnittsweise ausgelegt und dann der jeweilige Abschnitt erwärmt und verklebt wird, ehe der nächste Abschnitt begonnen wird. Auch kann es vorteilhaft sein, den Draht nur am Anfang und/oder Ende eines jeden Abschnitts zu verkleben, so dass er dazwischen geradlinig verläuft, mit dem gegebenen Verlegezug F_Z gespannt. Nach welcher dieser Möglichkeiten der Verlegeprozess im konkreten Fall tatsächlich geführt wird, kann von anderen Überlegungen abhängig gemacht werden, insbesondere von der verwendeten Wärmequelle und von der benötigten Verlegegeschwindigkeit.
• (c) Das erfindungsgemäße Verlegeverfahren kann schließlich auch in der Weise modifiziert werden, dass die Erwärmung der Substratoberfläche zuerst erfolgt und der Draht danach rasch, ehe die Oberfläche wieder abgekühlt ist, auf die Oberfläche aufgelegt und elektrostatisch angedrückt wird.

The laying process can be divided into the two steps of wire laying and wire bonding. According to the invention, the electrostatic attraction must already act during the first step at each point of the laying track and remain until the end of the second step. There are several alternatives for the temporal structure of these steps

• (a) Continuously progressing laying, as carried out in the wire laying machines of the prior art. In this case, the wire is unwound along a previously defined and stored in the control computer laying track and immediately afterwards by Erwär tion of the adhesive to the substrate permanently connected. For this process, the in 1 . 5 , and 8th sketched laying heads determined.
• (b) Two-step process in which, in a first step, the wire is laid out in its entirety while being held down on the substrate surface by the electrostatic attraction during the lay-out time. The heating, which leads to bonding, takes place only in the second step, be it by local heating of the substrate surface along the laying track or by heating the entire substrate surface. Between these two cases, there are further possibilities to carry out the laying process by laying the wire in sections and then heating and gluing the respective section before the next section is started. Also, it may be advantageous to glue the wire only at the beginning and / or end of each section, so that it runs straight between them, stretched with the given laying train F _Z. According to which of these possibilities the laying process is actually carried out in the specific case, it can be made dependent on other considerations, in particular on the heat source used and on the laying speed required.
• (c) Finally, the laying method according to the invention can also be modified in such a way that the heating of the substrate surface takes place first and the wire is then quickly placed on the surface and electrostatically pressed before the surface has cooled down again.

The Heating the substrate surface by machine Wire laying can be done by means of a flame or a hot air blower be made, the heat transfer through Convection takes place. Alternatively, the heater is the substrate surface possible by means of radiation, the radiation power absorbed in the substrate. For hot melt adhesives is the required Surface temperature about 100-300 ° C, with soldering and thermocompression it can be considerably higher lie, up to 1000 ° C. In any case, it is advantageous to control or regulate the supplied heat output that the maximum, permissible for the joining process Surface temperature is not exceeded. In particular, the heater should be turned off when the laying head stationary.

The Dynamics of the heating process is of interest for an optimal design of the heater. For continuous machine Laying with immediately following heating and bonding is it's beneficial to keep the heater as small as possible, sharply localized area of the substrate surface restrict. This reduces the mentioned mechanical Stresses in the substrate and the necessary heating power.

In the same sense, it is advantageous to limit the heating to a flat as possible area on the substrate surface. In radiant heating, this means that the wavelength of the heating radiation is to be selected so that it is as strong as possible, absorbed directly on the substrate surface. The necessary absorption coefficient of the substrate material follows from a consideration of the heat propagation in the substrate. If the extension of the heating device in the laying direction is designated by B _X , then the heating time of a surface point t _H = B _X / v _o . During this time, the heat penetrates from the surface a certain distance B _Z = 2gt _H ^1/2 into the interior of the substrate, where g indicates the thermal conductivity of the substrate. In comparison to this distance, the penetration depth of the radiation should be small, ie the absorption coefficient should be α> 1 / B _Z. For example, at a laying speed of v _o = 1 m / s and a Heizflecklänge of B _X = 1 mm, the heating time t _H = 1 millisecond. During this time, the heat penetrates into glass (g ≈ 0.001 m / s ^1/2 ) to a depth B _Z ≈ 50 μm. In order to almost completely absorb incident laser radiation over this distance, the substrate material must have an absorption coefficient α ≥ 10 ³ cm ^-1 at the laser wavelength. In this sense, the CO and CO ₂ lasers are particularly well suited for heating glass substrates.

A more detailed analysis of this heating dynamics also shows that the required heating power is scaled by v _o ^1/2 B _X ^1/2 B _Y and is about 10 W in the case described above.

An alternative form of fixing a wire according to the invention is in 9 outlined. Here carries a circuit board 41 an electronic component 42 with metallic contact surfaces 44 . 45 , The free end 48 of the wire 1 should by soldering mechanically and electrically with the contact surface 44 which takes over the role of the substrate here. For this, the laying head 20 at initially switched off voltage source 32 so controlled that the wire end 48 just above the contact surface 44 is positioned. The remaining distance 46 between wire and contact surface may be in the range of 0.03-0.3 mm, depending on the precision of the control. To fix the wire for soldering on the contact surface, the voltage source becomes 32 switched on. One of her poles is over the laying head with the wire 1 connected. Her other pole is with the second contact surface 45 connected to the component, or with a metallic surface of the board 41 or with an electrode 29 under the board. Due to the electrostatic attraction then the wire end 48 elastically bent downwards. It is approaching the contact surface 44 , which increases the attraction even more. At a sufficient level of the applied voltage U, it jumps against the contact surface and remains fixed there. The soldering is done by heating by means of a laser beam 50 that of a look 70 is focused on the contact surface. The melting compound used in this example is a solder layer, which is applied in a known manner as "tinning" on the contact surface and / or on the wire.

The amount of tension required for fixation depends on the flexural rigidity and the length of the free wire end as well as on the size the contact surface. Experience has shown that with a 20 μm copper wire with 10 mm free end, a voltage of 200 V is sufficient.

When the wire to be fixed is insulated, such as enameled copper wire, the insulating layer forms a natural stop, which is the minimum of the distance 46 certainly. A problem can be suspected here in case the wire is bare. In the state of fixation he short-circuits the voltage source, so that the low-holding force disappears. This problem, however, is a theoretical one. Practice shows that a bare wire is very well held down, as it is necessary for the solder joint. It bounces off the contact surface during impact, releasing the short circuit, but is immediately tightened again, etc. On average, it stays very close to the surface and also touches it, as is necessary for the solder to flow and moisten ,

• – zur Bewegung des Kopfes parallel zur Substratoberfläche, entlang vorgegebener, im Steuerungsrechner gespeicherter Bahnen, welche die zu verbindenden Kontaktpunkte sowie mögliche Klebepunkte enthalten,
• – zur Verbindung des Drahtes (zum 'bonden') an Bauelement- Kontaktflächen, die gewöhnlich Anfangs- und Endkontakte jeder zu verlegenden Verbindungsleitung darstellen,
• – zum Abschneiden des Drahtes nach Herstellung des Endkontaktes einer Leitung,
• – zum Vorschub des Drahtes, speziell nach dem Abschneiden, um ein kurzes Stück neuen Drahtes für den Anfangskontakt der nächsten zu verlegenden Leitung aus dem Verlegekopf unter die Kontaktiervorrichtung zu befördern, wie in 9 illustriert,
• – zur Abisolierung der Drahtenden, falls erforderlich,
• – zum Festhalten des Drahtes mittels einer Zange oder Klammer ('clamp'), wenn er in Form eines die elektrischen Kontaktstellen zugentlastenden Bogens ('loop') verlegt werden soll,
• – und möglicherweise die in 1 angedeutete Spule 26 mit einem größeren, für viele Arbeitsgänge ausreichenden Vorrat des Drahtes 1. Dies bietet sich gerade bei der Verlegung sehr dünner Drähte an, deren Masse gering ist und die bei externer Zuführung besonders reißgefährdet wären.

The laying head must, in addition to the said devices for braking and deflection of the wire contain a number of other devices that are familiar to the expert, and therefore need not be described in detail here. They include devices

• For movement of the head parallel to the substrate surface, along predetermined paths stored in the control computer, which contain the contact points to be connected as well as possible adhesive dots,
• For connecting the wire (for 'bonding') to device pads, which are usually start and end contacts of each interconnect to be laid,
• For cutting the wire after production of the end contact of a line,
• To feed the wire, especially after cutting, to convey a short piece of new wire for the initial contact of the next line to be laid from the laying head under the contacting device, as in 9 illustrated,
• - for stripping the wire ends, if necessary,
• - To hold the wire by means of a pair of pliers or clamp ('clamp'), if it is to be laid in the form of a strain relieving the electrical contact points ('loop'),
• - and possibly the in 1 indicated coil 26 with a larger supply of wire sufficient for many operations 1 , This is especially useful when laying very thin wires whose mass is low and which would be particularly susceptible to rupture with external supply.

The Laying rail, along which the wire is laid, is general curved. This requires the wire to be stuck throughout becomes. Alternatively, the web may be in the form of a polygon, where the wire is straight in sections and only at the corners must be glued to the substrate. This can be the advantage of a offer higher installation speed.

The laying tracks are determined from the circuit and the arrangement of the components of a program ('router') and stored in the control computer of the laying head. The latter must then be controlled during installation so that the point of contact 8th the laying track follows and at the same time the tensioned wire section 35 always tangential to the desired path.

Further Applications and alternative embodiments of the invention Processes can provide advantages in mounting micro-mechanical and micro-optical components as a substitute for the so-called "PSA". The latter are often used to a mounting surface or board a small component first temporarily to fix, the final later is attached. Is used in such assembly instead of pressure sensitive hot glue used with electrostatic pressure, so there is the advantageous Possibility to multiply the component when cold to move and adjust before it heats and sticks becomes. As explained, this fixation is on the substrate surface equally for naked as for isolated Metal wires possible, but also for non-metallic "Wires", such as textile fibers, polymer fibers and glass fibers, in particular also optical fibers. It must, as with the examples and drawings, the electrode assembly in concrete Case will be chosen according to which combination of conductivities (metallic or insulating) the wire to be laid and the substrate material represent.

The Purpose of the extent explained Wire laying methods for wire laying become crucial determined by the size of the achievable electrostatic Attraction that holds down the wire on the substrate. It can be achieved by increasing the applied voltage increase until an electrical breakdown occurs. On the one hand, the substrate is critical, on the other hand the medium surrounding the wire. The former limits the usable voltage at very thin substrate thickness, at about 0.1 mm and below. At this substrate thickness, the breakdown voltage is in the range from 1-10 kV, depending on the substrate material.

For thicker substrates, the usable voltage is limited by the dielectric strength of the medium surrounding the wire. If the voltage in air is increased so far that the electric field strength at the wire surface exceeds a value of approx. 3-10 kV / mm, a thin, tubular coro forms around the wire na discharge out. It takes the overshooting part of the voltage increase and thus limits the achievable force.

An extension of this limit is possible by modifying the medium surrounding the wire. An easy way is to make the wire laying in a vacuum. Then the problem of corona discharge is completely eliminated. Alternatively, the wiring can be done in a room filled with a gas of high dielectric strength and high pressure. This increases the voltage at which corona discharge starts. It is known from high-voltage technology that carbon dioxide CO ₂ and nitrogen N ₂ added with sulfur hexafluoride SF _{6 are} particularly suitable gases for this purpose. Both have a higher dielectric strength than air, and in both the dielectric strength increases monotonically with pressure. With them, the usable voltage can be increased by a factor of about 10-30 compared to atmospheric air, if a gas pressure up to 10 bar is used. Since the electrostatic force increases with the square of the voltage, the usable force can be increased in this way by a factor of about 100-1000. As a further alternative, an insulating liquid can be selected as the surrounding medium. The insulating oils used in high voltage engineering with dielectric strengths of 20 kV / mm and more allow similar voltage increases to air as the mentioned insulating gases under pressure.

As previously explained, it is for the machine Wire laying with practically interesting laying speeds advantageous, only a small, sharply localized area of Heat substrate surface with a laser beam. requirement this is due to a sufficiently strong absorption of the laser radiation through the substrate material. Since its absorption coefficient α (λ) generally depends on the used laser wavelength λ, arises for a given substrate material the problem, a suitable wavelength and a laser with sufficient to find high performance. This is not possible in every case or economically.

on the other hand it is possible in a simple way, the absorption capacity of the substrate, so that the radiation of a given laser is sufficiently strongly absorbed. This implies a coloring of the substrate, either in whole or only superficially on the wire-facing side, or a coating of this substrate side with a highly absorbent Material. The term coloration is generalized here understand, because the dye only needs at the laser wavelength used absorb. Be playing at all other wavelengths Absorbency does not matter. If the laser wavelength used lies beyond the visible in the ultraviolet or infrared, such as for example with typical diode lasers (λ = 808 nm) or the YAG laser (λ = 1064 nm), so so can Dyes are used in the visible spectral range only a practically negligible absorption so that the dye additive perceived by the eye Color of the substrate material not changed.

This method of superficial absorption enhancement is known in the art of so-called radiation-blasting of polymers and suitable dyes are commercially available. From the German patent applications DE 44 15 802 A1 and DE 102 52 007 A1 For example, suitable absorption-enhancing, tin dioxide-coated pigments having very low perceptible color effect are known for use in thermoplastics. The patent US 7,201,963 deals with absorption enhancing coatings of thermoplastics and the selection of suitable dyes.

If it is not important to avoid coloring, a blackening of the substrate material, for example by adding carbon black, is the simplest possibility of increasing the absorption. For example, a 0.1% soot admixture reduces the penetration of laser radiation to 0.1 mm. [see. Dirk Hänsch, "The Optical Properties of Polymers and their Significance for Transmittance Welding with Diode Lasers", Shaker Verlag 2001 . ISBN 3826590538 ]. This comes close to the required absorption coefficient α = 10 ³ cm ^-1 .

For local heating of the substrate to the melting temperature of the connecting material and the known from microwave ovens high frequency heating is suitable. It can be used for wire laying on non-metallic substrate materials that have a certain, not too low high-frequency absorption, such as polymers containing oxygen-containing molecular groups. For this, close over or beside the wire at the position of the heat source 30 an electrode is arranged, to which a high-frequency high voltage, for example 2.4 GHz, is applied. The electric field of this voltage penetrates the substrate material and heats it up. The heated substrate volume is the smaller, the closer the electrode to the substrate surface 4 located.

In the case of the method of wire laying described so far, essentially (apart from the variant according to FIG 8th ) a single extended counter electrode 29 used under the substrate. As a result, the electrostatic attraction f _E acting on the wire from this electrode is everywhere perpendicular to Surface of the substrate directed. This is in 10a illustrated. Will the counter electrode 29 However, limited in their lateral extent and arranged one or more times laterally to the wire as in the 10 (b) and 10 (c) represented by the arrow 55 represented attraction a lateral component, which can be advantageously used in the wire laying for the lateral control of the installation path, in particular for laying along curved laying paths.

This possibility of generating lateral forces by structuring the counterelectrode will be described with reference to the US Pat 10 (a) to 10 (f) drawn coordinate system explained in more detail. Here, a wire laying device is shown in cross-section, at one point in the area 35 where the wire is 1 the substrate surface 4 just not touched. In all in the 10 (a) to 10 (e) shown cases is the wire to be laid 1 to the pole 19 the voltage source 32 connected, and it is initially assumed that the extension of the electrodes in the X direction, perpendicular to the plane of the drawing, is substantially greater than the substrate thickness measured in the Z direction.

The 10 (b) shows the situation over the edge of the counter electrode 29 , which is shifted in relation to the wire in the positive Y-direction a piece. Gravity 55 from the wire to the counter electrode 29 directed, receives by this shift a positive Y component and therefore acts not only down, but also laterally. According to 10 (c) is also an auxiliary electrode 51 provided, the edge of which is slightly offset from the wire in the negative Y direction. She is with the same pole 19 the voltage source connected like the wire. At this edge of the auxiliary electrode 51 accumulates therefore the same charge as on the wire and thus acts repellent on the wire. The from the counter electrode 29 and the auxiliary electrode 51 forces exerted on the wire result in a total force 55 in positive Y direction. When interchanging the connections of the electrodes 29 and 51 , By means of a switch you get a total force in the negative Y direction. With these electrodes, the wire can therefore be deflected to one side or the other and so the installation path can be influenced. Incidentally, the latter depends on the size and direction of the laying tensile force F _{Z used} and on the bending stiffness of the wire.

Particularly advantageous for the wire laying along a fixed path is the arrangement according to 10 (d) with a single narrow, strip-shaped counter electrode 52 that follows the laying path. At any rate, it has an attractive effect on the wire 1 and allows its installation. The power 55 is simply directed downwards when the wire is just above the center of the counter electrode 52 located. However, the wire position deviates in positive or negative Y-direction from this central position, z. B. because the wire is bent or because the laying path is curved in the XY plane, so occurs a lateral force component that seeks to pull the wire in the middle layer. It causes (within certain limits) that the wire in its laying by the counter electrode 52 given path follows. The mentioned Y-force component, which always returns to the central position, can be increased by having the counterelectrode on both sides 52 strip-shaped auxiliary electrodes 51 respectively. 53 be placed on the potential of the wire 1 lie. Each of them then creates a repulsive Y-force component if the wire 1 As you approach it, it causes better centering of the wire over the counter electrode 52 , A comparable centering effect can according to 10 (e) be achieved by two auxiliary electrodes 54 and 56 on the substrate surface 4 be arranged on both sides of the installation path. They are with the same pole 19 the voltage source 32 connected like the wire 1 , Therefore, there is no attraction between them and the wire, but a weak repulsion force dependent on the distance and the environment. The counter electrode 29 has in this embodiment the continuous shape as in 10 (a) , For reasons of symmetry, that of the auxiliary electrodes 54 and 56 force exerted on the wire no Y component when the wire is centered over the gap between 54 and 56 located. In this case, only a downward total force, the counter electrode 29 is directed. Dodges the wire 1 However, laterally from the central position and approaching one of the auxiliary electrodes, so this exerts a repulsive, each returning to the center position of force.

According to this principle, the combination of attractive and repulsive force components also works according to the wire routing 10 (f) , Here is the wire 1 laid on the substrate in the form of a flat coil with several turns. In this case, there is typically the requirement that the individual turns of the coil form fit, as close to each other as possible to lay, as in accordance 10 (f) the wires shown in cross section 58 ver, and the wire 1 should be moved immediately afterwards as the next turn. This is achieved by the fact that the edge of the counter electrode 29 is positioned below the last threaded turns, for example by means of a designated displacement device. The attractive force 55 between this edge and the wire 1 then according to 10 (b) a positive Y-force component, the new turn laterally against the already laid turns 58 suppressed. Since the latter each sections of the wire 1 they all have the same electrical potential as the wire 1 , In 10 (f) is this by the dashed lines 59 indicated. Therefore, these turns work 58 weakly repulsive on the wire 1 similar to the auxiliary electrode 56 according to 10 (e) and can hinder its positive installation. This problem is solved in that a strip-shaped auxiliary electrode 54 is placed on the substrate surface, on the coil turns 58 opposite side of the wire 1 , This auxiliary electrode 54 will with the wire 1 electrically connected and therefore also acts repulsive on the wire. It thus compensates for the repulsive effect of the turns 58 and it allows the total force 55 towards the edge of the counter electrode 52 acts and actually leads to the positive installation.

The different electrical connections of the electrodes in the 10 (a) to 10 (f) with the poles 18 and 19 The voltage source allow a rough control of the direction of force. For a person skilled in the art, it will be obvious that in each case a fine control of the direction and magnitude of the force is also possible by applying individual electrodes to partial voltages of the voltage source 32 be connected. Furthermore, the person skilled in the art, on the basis of the cited illustrations, immediately recognizes that a finer structuring of the counterelectrode 29 and the auxiliary electrode 54 along the X and Y directions even more comprehensive design options for influencing the force 55 offers. By division of the counter electrode 29 In a 2-dimensional arrangement of many small sub-electrodes and applying appropriate partial voltages can be very general, even time-variable potential and force distributions f (X, Y, t) as a function of the place (X, Y) and the time (t) on the substrate surface 4 produce. When laying the wire follows the distribution, as far as its flexural rigidity and the direction and size of the laying tension F _Z allow. The wire adapts to the course of the electrically generated potential mountains, analogous to a watercourse that follows the path in a given topography, which results in a minimization of the potential energy.

When using an extended counterelectrode under the substrate, a uniformly high electric field strength prevails almost everywhere on the substrate surface, the direction of the field being perpendicular to the surface. Only in the immediate vicinity of the wire is the field distorted, like the 6 is removable. If direct electrical wiring is used to connect electronic components located on the substrate, they would be exposed to the described field between the wire and the counter electrode. For very sensitive components, this can be problematic, especially since the field generated for the development of force is an alternating electric field. Depending on the size, orientation and conductivity of a component, the influence voltages that occur in it can reach values that are associated with the risk of breakdown or even destruction of the component.

This danger can be avoided by shielding the component against the electric field during the laying of the wire. This is possible in a known manner by enclosing the component in a Faraday cage. This is a well-conductive shielding 61 suitable size over the vulnerable component 60 slipped and electrically with the counter electrode 29 connected. Together with the counter electrode 29 makes the hood 61 then a Faraday cage, but at the edge through a shallow gap 63 is interrupted. By choosing a sufficient width of this edge, the residual field strength, which still acts through the edge into the interior of the cage, can be kept small ( 11 (a) ).

According to the embodiment 11 (b) There is a similar Faraday cage in the hood 61 and the auxiliary electrode 61 / u is formed, which is arranged at the bottom of the substrate and to the potential of the wire 1 connected.

Instead of an application of heat-bonding, soldering or welding processes are for mechanical wire laying by means of electrostatic hold down other, low-heat joining methods suitable, which is based on using one already at ambient temperature more or less liquid or pasty adhesive based. In such methods, the adhesive is first to at least one of the joining partners, d. H. on the wire or on the substrate, or applied to both. In the subsequent wire laying process it is then important that the wire with a suitable pressure force is pressed against the surface of the substrate. Without such holddown would be due to generally existing curvatures of the wire and / or substrate surface of the contact of the Joining partner given only pointwise. Only with positive, Line contact allows the adhesive to flow and both Moisten joining partner together, so the cohesive Establish connection. The size of the pressure force determines the accuracy of the positive locking and, together with the Viscosity of the adhesive, the achievable adhesion of the adhesive Wire.

Thin adhesive flows quickly and is therefore able to fill in small gaps in the form-fitting, as they remain at moderately high pressure. However, low-viscosity adhesive offers only low adhesion. Sufficient adhesion is achieved only by a subsequent increase in viscosity, ie by curing the adhesive. It is used in hot-melt adhesives, soldering and welding processes Cooling causes, with low-heat adhesives by chemical reaction, triggered by the action of energy-rich radiation or chemical substances. Examples of such low viscosity adhesives with radiation curing are the light or UV curing acrylate adhesives widely used in printed circuit board manufacture; an example of chemical curing the moisture-responsive cyanoacrylate adhesives.

at high-viscosity adhesives curing can be omitted if sufficiently high pressure force is used. Because these adhesives hardly flow, is a closer fit, so one higher pressure force necessary than with low-viscosity adhesives. As an example like those of adhesive tapes and adhesive labels Her known high viscosity pressure sensitive adhesive serve.

When wire laying with low-heat adhesives, the necessary form-fitting holddown is achieved by pressing the wire with punches or similar tools to the substrate according to the prior art. In the description DE 10 2005 002 370 A1 the wire writing technique is only generally required a material connection, as an example it is stated that the wire is lowered onto the substrate and adhered by means of UV-curing adhesive dots. In the patent US 4,850,807 describes the use of a microencapsulated adhesive, which is released under sufficient pressure and causes the bonding. Again, of course, a pressure tool is necessary. There are the aforementioned dangers of wire deformation and damage, tool contamination and sticking of the wire to the punch instead of the substrate.

It follows as an extension of the task, also for the wire laying with liquid or pasty Adhesive the necessary pressure force of the wire to the substrate surface Non-contact along a certain section of the wire to generate and optionally for a physical or to maintain chemical curing for a while, which, according to the idea of the invention, by electrostatic Generation of the pressure force happens.

It is expedient in any case a pretreatment of the substrate in the sense of putting in a adhesion-friendly, the wetting promoting, reliably reproducible state, eg. As by wiping, brushing, washing, cleaning, gassing, spraying, irradiation, ionization, and the like, since here for the wire laying on an industrial scale, a high reliability of the installation process is essential. The laying must be independent from the weather (humidity, temperature) and the adhesion of the laid wire must not depend on any pretreatment of the substrate material (storage, packaging, contact, etc.), which may alter the adhesion properties of the surface. For example, a superficial etching with an (O ₂ + CF ₄ ) plasma, described in US 5,283,119 , a suitable method to ensure good adhesion to polymeric plastics regardless of the previous history.

In summary it can be stated that the described method is particularly is advantageously used in the laying and / or bonding thinnest, almost invisible metal wires on large transparent substrates. It allows a simple, safe handling the wires when laying and provides their secure fixation until the end of the fixation process. It is currently completing in the field of smallest wire diameter the conventional wire laying method, who have their biggest difficulties here. The inventive method is particularly suitable also for the production of transponders for use in Security documents such as passports or smart cards or the like.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 2326861 [0002]
• - DE 3247344 [0002]
• - DE 2610283 [0002]
• - US 3674602 [0002]
• US 4648180 [0002]
• - US 4864723 [0002, 0007]
• US 7000314 [0003]
• - DE 19618917 [0003]
• - EP 1004226 [0003]
• - DE 4410732 [0003]
• - DE 10247553 [0003]
• - US 4918260 [0004]
• US 6400882 [0008]
• - DE 4415802 A1 [0080]
• - DE 10252007 A1 [0080]
• US 7201963 [0080]
• - DE 102005002370 A1 [0095]
• US 4850807 [0095]
• - US 5283119 [0097]

Cited non-patent literature

• - Dirk Hänsch, "The Optical Properties of Polymers and Their Significance for Transmittance Welding with Diode Lasers ", Shaker Verlag 2001 [0081]
• - ISBN 3826590538 [0081]

Claims (38)

Method for laying thin wire ( 1 ) on the surface ( 4 ) of a substrate by means of a computer-controlled laying head ( 20 ) which is movable relative to the substrate and which unwinds the wire close to the surface and nearly parallel to the same with a defined tensile force, the connection of wire and surface being effected by means of the surface tension of a heat-fusion bonding material comprising 1 ) and substrate surface ( 4 ), characterized in that the wire ( 1 ) is fixed to the curing of the bonding material by means of electrostatic pressure force on the substrate. Joining method according to claim 1, characterized in that that the melting compound material is a hot glue is, or a solder or the substrate material itself, or the wire material itself is the melting compound material. Joining method according to claim 1 or 2, characterized in that - the wire ( 1 ) is electrically conductive, and - that the substrate is electrically insulating, and - that the electrostatic pressure force is generated by the conductive wire ( 1 ) and an electrode disposed under the substrate ( 29 ; 29 . 51 ) to the poles ( 18 . 19 ) of an electrical voltage source ( 32 ), or - by the conductive wire ( 1 ) to one pole ( 19 ) of an electrical voltage source ( 32 ) and two symmetrically next to the wire ( 1 ) arranged electrodes ( 37 . 38 ) together at the other pole ( 18 ). Joining method according to claim 1 or 2, wherein the wire is electrically conductive, characterized in that - the substrate has an electrically conductive surface layer, and - that the electrostatic pressure force is generated by the conductive wire ( 1 ) to one pole of the voltage source ( 32 ) and the conductive surface layer to the other pole ( 18 ). Joining method according to one of the claims 1 to 4, characterized in that the electrostatic pressure force only switched on when the wire over the intended Joint has been positioned. Joining method according to one of the claims 1 to 5, characterized in that the pressing force of the voltage a DC voltage source or the voltage of an AC voltage source is caused. Joining method according to claim 1 or 2, characterized in that - the substrate is electrically insulating, and - that the electrostatic pressure force of at least one pair of electrodes ( 56a . 56b ), which are arranged side by side at the laying point below the substrate and against the poles ( 18 . 19 ) are connected to the voltage source ( 8th ), or at least one triple of electrodes ( 51 . 52 . 53 ), which are arranged side by side at the laying point below the substrate and fed by an AC voltage source with three equal, sinusoidal, and 120 ° phase-shifted output voltages ( 10a ). Joining method according to one of the preceding Claims, characterized in that the internal resistance the voltage source is selected so high that their short-circuit current is less than 30 mA. Joining method according to one of the preceding Claims, characterized in that when attached Tension the substrate surface in an area where the Wire rests, at least heated to the melting temperature of the bonding material becomes. Joining method according to claim 9, characterized characterized in that the heating of the substrate surface done by a hot air blower, or by Heat radiation coming from the substrate in a near-surface Area is absorbed, or by laser radiation coming from the substrate is absorbed in a near-surface area. Device for laying thin wire on the surface of a substrate by means of a computer-controlled laying head ( 20 ), which is movable relative to the substrate and the wire ( 1 ) unwinding close to the surface and nearly parallel to the same with a defined tensile force, the bonding of wire and surface being effected by the surface tension of a heat-fusion bonding material which wets wire and substrate surface, characterized by at least one electrical voltage source ( 32 ) and at least one connected thereto and arranged in the vicinity of the wire electrode, by means of which the wire ( 1 ) can be fixed on the substrate until the bonding material has cured by electrostatic pressure. Wire laying apparatus according to claim 11, characterized in that the melting compound material is a hot melt adhesive ( 17 . 21 ) or a solder, or the substrate material itself, or that the wire material itself is the fusible bonding material. Wire laying device according to claim 11 or 12, characterized in that - the wire ( 1 ) is electrically conductive, the substrate is electrically insulating, and - that the electrode ( 29 ) placed under the substrate, and wire ( 1 ) and electrode ( 29 ) to the two poles ( 18 . 19 ) of the voltage source are connected, or - that two electrodes ( 54 . 56 ) symmetrically next to the wire on the substrate surface ( 4 ), and - the wire is connected to one pole of the voltage source and the two electrodes are connected in common to the other pole, or - the substrate has an electrically conductive surface layer, and - the wire is connected to one pole of the voltage source is and the conductive surface layer on the other. Wire laying device according to claim 11 or 12, characterized in that the voltage source ( 32 ) is a DC voltage source or an AC voltage source, and that at least two electrodes ( 29 . 51 . 52 . 53 . 54 . 56 ) are provided, which are arranged at the laying under or on the substrate so that their edges substantially parallel to the wire ( 1 ) and the electrodes to the poles ( 18 . 19 ) of the voltage source ( 32 ) are connected. Wire laying device according to one of the claims 11 to 14, characterized in that the short-circuit current of Voltage source is less than 30 mA. Wire laying device according to one of the claims 11 to 15, characterized by a heating device, which at applied voltage the substrate surface in an area where the wire rests, at least up to the melting temperature of the connecting material heated. Wire laying apparatus according to claim 16, characterized through a hot air blower that covers the substrate surface heated, or by a heat radiation source, their radiation in a near-surface region of the substrate surface is absorbed and thereby heats the substrate surface, or by a laser radiation source whose radiation in a near-surface area of the substrate surface is absorbed, thereby heating the substrate surface. Joining method according to a of the preceding claims, wherein the heating of the substrate by absorption of radiant energy in a surface area or a surface of the substrate near the surface, characterized in that during the application of the pre-fixing of the electric field used by the wire, that of the wire the substrate pressing force causes the dielectric strength The Electrode Substrate Wire Range generates increasing vacuum becomes. Joining method according to a of claims 1 to 17, characterized in that the Working area in which the fixation of the wire takes place on the substrate, during the period of time in which the wire is attached to the substrate pressing, electrostatic force is exerted, a the dielectric strength of the electrode / substrate / wire range increasing medium - gas or liquid - used becomes. Joining method according to claim 19, characterized in that the medium used to increase the dielectric strength is a gas, e.g. B. N ₂ or SF ₆ or a mixture of the two gases, which is held under an elevated pressure in a range up to 10 bar, z. B. a pressure between 5 and 10 bar, or a liquid which has a suitably high dielectric strength. Joining method according to a of the preceding claims, wherein the heating the fixing material takes place by absorption of laser radiation, which is used as a heating energy source, characterized that to increase the absorption of the laser radiation the Substrate material at least in a wire adjacent to the surface close range either by additives or a coating Dyes or pigments are added at the laser wavelength have a high absorption. Joining method according to a of claims 1 to 20, characterized in that the Heating the substrate surface by generating a high frequency field he follows. Joining method according to one of the preceding claims, characterized in that control electrodes ( 29 ; 29 . 51 ; 51 . 52 . 53 ) are provided, by means of which electric field components can be generated under the action of a lateral force on the wire ( 1 ) is achievable ( 10 (b) ). Joining method according to claim 23, characterized in that at least two electrodes ( 29 . 51 ) provided with partial voltages of the voltage source ( 32 ) can be acted upon. Joining method according to Claim 23 or Claim 24, characterized in that actuatable electrodes are used on both sides of the substrate with partial voltages of the voltage source become ( 10 (e) . 10 (f) ). Joining method according to one of claims 23 to 25, characterized in that at least one of the electrodes provided for generating transverse field components ( 29 ) is displaceable, preferably in a plane parallel to the laying plane of the wire ( 1 ) level. Joining method according to one of the preceding claims, characterized in that for the protection of an electronic component ( 60 ), with which the wire ( 1 ) must be electrically connectable, at least one electrically conductive shielding hood ( 61 ) is arranged on the side facing away from the substrate of the component and electrically arranged with a on the opposite side of the component of the substrate counter electrode ( 29 ; 61 / u ) connected is ( 11 (a) . 11 (b) ). Joining method according to claim 27, characterized in that the shielding electrodes ( 61 . 61 / u ) of the component to be protected ( 60 ) completely mask this. Joining method according to claim 1, wherein the fixing the wire is made on the substrate by means that are cohesive Communicate the wire with the substrate, marked by using a fluid at the laying temperature or pasty adhesive, due to its adhesion after temporarily electrostatic generated tightening force permanently holds the laid wire. Joining method according to claim 29, wherein the pressure-sensitive adhesive continuously or continuously during installation distributed detention sites locally on the substrate surface is applied. Joining method according to claim 29 or claim 30, characterized in that the pressure-sensitive adhesive during the laying process in the form of a thin layer in each case in that area ( 35 ) is applied, which immediately precedes the contact area, in which the wire already adheres to the substrate in contact with the adhesive. Joining method according to claim 29, characterized in that that the adhesive layer of adhesive even before laying the wire large area on the substrate surface is applied. Joining method according to claim 29, characterized in that that the adhesive adhere continuously during installation, in sections or continuously on the wire surface is applied. Joining method according to claim 29, characterized by using a reaction adhesive which is liquid or pasty at the laying temperature and which is curable by irradiation of high-energy radiation and which is hardened by irradiation in that area ( 33 ), where the wire rests positively on the substrate surface due to the electrostatic attraction. Joining method according to claim 34, characterized through the use of an adhesive that is protected by high-energy electromagnetic Radiation is curable, with the high-energy radiation electromagnetic radiation - UV, visible light or infrared radiation - is, which leads to the curing of the adhesive, or by an ionizing radiation curing the adhesive is triggerable. Joining method according to Claim 29, characterized by the use of a reaction adhesive which is liquid or pasty at the laying temperature and which is curable by chemical action, which takes place in such a manner that the adhesive is in the region ( 33 ) within which the wire rests positively on the substrate surface due to the electrostatic attraction force. Joining method according to claim 36, characterized in that that the chemical action to cure the pressure-sensitive adhesive by supplying a gaseous or liquid Hardener component takes place. Chip card for RFID applications, with at least a transponder comprising a wire-shaped antenna, characterized by their preparation using the procedures according to one of the preceding claims.