WO2008154582A2

WO2008154582A2 - Semiconductor die coating and interconnection fixture and method

Info

Publication number: WO2008154582A2
Application number: PCT/US2008/066568
Authority: WO
Inventors: Scott Mcgrath; Terrence Caskey; Simon J.S. Mcelrea; Lawrence Douglas Andrews; Zongrong Liu
Original assignee: Vertical Circuits, Inc.
Priority date: 2007-06-11
Filing date: 2008-06-11
Publication date: 2008-12-18
Also published as: WO2008154582A3

Abstract

Fixtures for temporarily holding semiconductor die and for holding stacked die units, for application of a material such as electrical interconnection material to die edges, include a fixture frame, die or die stack supports, and a mask. Methods for applying material such as electrical interconnection material to die edges and to die stack units employ the fixtures using a mask lift-off step.

Description

SEMICONDUCTOR DIE COATING AND INTERCONNECTION FIXTURE AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Z. Liu et al. U. S Provisional Application No. 60/943,211 , filed June 11 , 2007, titled "Semiconductor die coating and interconnection fixture method".

[0002] This application is related to S. McGrath et al. International Application Docket No. VCIX 1027-3, titled "Coinstack method for optimized integrated circuit chip interconnection", which is being filed on the same date as this application, and which claims priority from S. McGrath et al. U.S. Provisional Application No. 60/943,252, filed June 11 , 2007, titled "Method for optimized integrated circuit chip interconnection". Each application referenced herein is hereby incorporated by reference.

BACKGROUND

[0003] This invention relates to applying a material in a selected pattern on edges of integrated circuit chips; and to electrical interconnection of integrated circuit chips and, particularly, to interconnection of assemblies including one or more integrated circuit chips. [0004] Applying a coating to semiconductor die edges and, particularly, interconnection of stacked die, presents a number of challenges.

SUMMARY

[0005] In general the invention features fixtures for temporarily holding semiconductor die, and for holding stacked die units, for application of a material to die edges, and methods employing the fixtures for application of material to die edges, and to stacks of die; in some general aspects the invention is particularly useful for electrical interconnection of die and particularly to stacked die units, and for electrically interconnecting stacks of die. [0006] In one general aspect the invention features a fixture including a framework configured and dimensioned to hold a number of die stack supports. The framework includes a pair of parallel members supported in the framework to provide a frame opening between the parallel members dimensioned to accommodate the length of the die stack supports. The die stack supports have first and second surfaces bounded by sides and ends. Stacked die units are mounted on the first surface of a die stack support such that die edges on which the material is to be deposited are situated toward a side of the support, and the support is loaded in the fixture. In some embodiments a mask is placed over a side of the loaded fixture such that openings in the mask expose the die edges on which the material is to be deposited. The material to be deposited can be applied in a pattern over the mask and the exposed die edges, and then the mask is removed, leaving the deposited material on the die edges. The die stack supports carrying the die stacks are then removed from the fixture, and the die stacks with deposited material are removed from the supports for further treatment. [0007] In some embodiments an electrically conductive material is deposited on the die edges, providing for electrical interconnection; accordingly in one aspect the invention features methods employing a fixture frame and mask for electrical interconnection of die or of stacks of die.

[0008] In some embodiments an adhesive or paste material is deposited on the die edges; the adhesive material may be a dielectric or an electrically conductive material. [0009] In some embodiments two or more materials, which may have different electrical properties for example, are deposited on the die edges, either using one mask or using two or more masks having the openings having the same or similar shape and dimensions, or using two or more masks having different openings.

[0010] The material may be deposited on the die edges by dispensing, for example through a hollow needle or jet or aperture; or by printing, for example by screen printing or by transfer printing; or by writing.

[0011] In some embodiments the die stack supports are disposable; in some embodiments the die stack supports can be repeatedly used. In some embodiments the mask is disposable; in other embodiments the mask can be repeatedly used. [0012] In some embodiments the framework is configured to ensure alignment of the supports; in some such embodiments the ends of the supports slide onto the parallel members in a tongue-and-groove configuration; in other such embodiments the parallel members are parallel rods and the ends of the supports are provided with holes configured so that the supports can slide onto the rods. [0013] Die stacks having any desired height (and any desired number of die) may be accommodated between the supports.

[0014] Optionally in some embodiments successive die stack supports are separated so that no contact of a support or a die mounted on a support contacts a die on another support. In some such embodiments the die stack supports are configured so that when they are loaded in the fixture sufficient separation is provided between the die stack supports to accommodate die stacks mounted on the supports. Or, spacers providing suitable spacing can be loaded in the fixture between supports.

[0015] In some embodiments a surface of each of the parallel members of the fixture frame is castellated (crenellated). The notches in the castellated surfaces of the parallel members are dimensioned to accommodate the thickness of the ends of the die stack supports, and the notches are spaced apart to accommodate, between the die stack supports, the thicknesses of die stacks mounted on the supports. [0016] In some embodiments the width of the die stack supports is about the same as a width of the die as measured perpendicularly to a die edge on which the material is to be deposited. In some embodiments the width of the die stack supports is less than a width of the die, yet sufficiently wide to provide adequate support for the die or die stack during processing. In some embodiments the width of the die stack supports is greater than a width of the die. In some embodiments (whatever may be the relative dimensions of the support and the die) the die are mounted on the support such that the die edge on which the material is to be deposited is about flush with, or stands proud of, the side of the die stack support. The length of the die stack support is sufficient in some embodiments to accommodate at least one die stack, in some embodiments two or more die stacks side-by-side. Adjacent die in each die stack may in some embodiments be affixed to one another by an adhesive. The die stacks may in some embodiments be removably affixed to the die stack support using an adhesive. [0017] The stacked die units according to the invention can be used for building computers, telecommunications equipment, and consumer and industrial electronics devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a diagrammatic sketch in elevational view showing a die stack interconnection fixture frame according to an embodiment of the invention. [0019] FIG. 2 is a diagrammatic sketch in elevational view showing die stacks mounted on a die stack support according to an embodiment of the invention, suitable for loading in a fixture frame according to an embodiment of the invention, such as is shown for example in FIG. 1. [0020] FIG. 3 is a diagrammatic sketch in elevational view showing die stack supports having die stacks mounted thereon, loaded in a frame according to an embodiment of the invention. [0021] FIG. 4 is a diagrammatic sketch in elevational view showing a mask applied onto a side of a loaded fixture according to an embodiment of the invention, such as is shown for example in FIG. 3.

[0022] FIG. 5 is a diagrammatic sketch in elevational view showing interconnect material deposited in a pattern over a masked and loaded fixture generally as in FIG. 4 according to an embodiment of the invention. [0023] FIG. 6 is a diagrammatic sketch in elevational view showing interconnected die stacks following removal of a mask from a loaded fixture generally as in FIG. 5 according to an embodiment of the invention.

[0024] FIG. 7 is a diagrammatic sketch in elevational view showing interconnected die stacks on a die stack support following removal from a fixture generally as in FIG. 6 according to an embodiment of the invention. [0025] FIG. 8 is a diagrammatic sketch in elevational view showing an interconnected two-die stack following separation from a support according to an embodiment of the invention. [0026] FIG. 9 is a diagrammatic sketch in elevational view illustrating second-level connection of an interconnected two-die stack to circuitry on a substrate, according to an embodiment of the invention.

[0027] FIG. 10 is a diagrammatic sketch in elevational view showing an interconnected two- die stack mounted on a substrate according to an embodiment of the invention.

[0028] FIG. 11 is a diagrammatic sketch in elevational view showing part of a die stack interconnection fixture frame according to another embodiment of the invention. [0029] FIG. 12 is a diagrammatic sketch in sectional view thru a die stack interconnection fixture frame according to an embodiment of the invention, as indicated at 12 - 12 in FIG. 11. [0030] FIG. 13 is a diagrammatic sketch in plan view, and FIG. 14 is a diagrammatic sketch in elevational view, showing die stacks mounted on a die stack support according to another embodiment of the invention, suitable for loading in a fixture frame according to an embodiment of the invention, such as is shown for example in FIG. 11. [0031] FIG. 15 is a diagrammatic sketch in elevational view, showing die stack supports having die stacks mounted thereon generally as in FIGs. 13, 14, loaded in a frame generally as in FIG. 11 according to an embodiment of the invention.

[0032] FIG. 16 is a diagrammatic sketch in elevational view showing a mask applied onto a side of a loaded fixture according to an embodiment of the invention, such as is shown for example in FIG. 15. DETAILED DESCRIPTION

[0033] The invention will now be described in further detail by reference to the drawings, which illustrate alternative embodiments of the invention. The drawings are diagrammatic, showing features of the invention and their relation to other features and structures, and are not made to scale. For improved clarity of presentation, in the FIGs. illustrating embodiments of the invention, elements corresponding to elements shown in other drawings are not all particularly renumbered, although they are all readily identifiable in all the FIGs. Also for clarity of presentation certain features are not shown in the FIGs., where not necessary for an understanding of the invention. [0034] The embodiments that are described herein are directed to deposition of an electrically conductive material for electrical interconnection of the die. Any of a variety of other materials may be deposited using various embodiments of the invention.

[0035] FIG. 1 shows an example of an embodiment of a die stack interconnection fixture frame. The frame 10 includes parallel members 12, 14, and brackets 11, 13. An inward-facing surface 16 of each parallel member is castellated; that is, the inward-facing surface 16 has spaced-apart slots 15. The slots are dimensioned to accept stack supports, shown for example generally at 20 in FIG. 2. Referring to FIG. 2, three die stacks 21 are removably mounted on a die mount surface of a die stack support 26, using an adhesive 27. In this example each die stack 21 is a two-die stack, having die 22, 24 affixed together using an adhesive 23. The slots 15 in the surfaces 16 of the frame members 12, 14 are sufficiently wide to accept the ends 25 of the support 26; that is, the width T1 of the slots is at least as great as thickness of the ends 25 of the support 26. The frame is dimensioned (e.g. by the length of the brackets) so that the distance across the frame accommodates the length of the die stack support; that is, the frame is dimensioned so that the distance L is great enough to accept the length of the support 26. In some embodiments the width T1 of the slots and the distance L between corresponding slots are great enough so that the loaded supports can be readily inserted; and in some embodiments the supports, the slots and the frame are configured so that once the loaded supports are inserted in the frame they are held in a desired orientation throughout subsequent processing.

[0036] The ends of the supports may have any of a variety of shapes, and the slots may be shaped to accommodate the ends of the supports accordingly. For example, one or both ends of the support may be chamfered, and the slot shaped so that the chamfer fits against a slanted part of the slot.

[0037] As shown in the Figures, the framework is illustrated as having four separate parts, namely the top and bottom brackets and the two parallel members. Alternatively, the framework may be provided as a unitary piece having top and bottom and side (slotted) portions. In such embodiments the frame is loaded by sliding the loaded supports each into the respective pair of opposing slots.

[0038] Or, for example, the framework may be provided in two pieces, one including the top and bottom bracket portions and one slotted side portion, and the other including the second slotted side member. In such embodiments the frame can be loaded by sliding the loaded supports, one end of each into a slot in the slotted side portion, and then aligning the slots of the second side member with the supports and sliding the second side member into place. A back plate may additionally be provided.

[0039] The supports can be temporarily secured in the frame by pins, or by resilient material associated with the slots, for example. Where the framework is provided as two pieces, as described above for example, the resilient material may be installed in the second side member. For example, a lengthwise groove may be provided in the inward-facing slotted surface of the second side member, and a length of resilient material (such as a strand of urethane) may be installed in the groove. When the second side member is slid into place, the resilient material in the groove presses against the ends of the supports to secure them. [0040] Or, for example, the framework may be provided as a single piece, having top and bottom bracket portions and first and second parallel slotted portions. The supports may be temporarily secured in the frame by pins, or by resilient material associated with the slots, for example. In some embodiments the second slotted portion is provided in the outer side with a lengthwise groove deep enough to reach the slots, and the supports are secured by a side bar having a tongue which fits into the groove. In some such embodiments a resilient material is provided in the groove, and the side bar is placed so that the tongue presses the resilient material against the ends of the supports to secure them.

[0041] Where the framework is provided as two pieces, as described above for example, the resilient material may be installed in the second side member. For example, a lengthwise groove may be provided in the inward-facing slotted surface of the second side member, and a length of resilient material (such as a strand of urethane) may be installed in the groove. When the second side member is slid into place, the resilient material in the groove presses against the ends of the supports to secure them.

[0042] In various embodiments, the die stacks may have any desired number of die. Stacks of 2ⁿ die (e.g., 2, as in these examples, or 4, 8, 16, 32, or 64 die) in a stacked die unit may be desirable for some uses, but one or three or any desired number of die may be interconnected in a stacked die unit according to various embodiments of the invention. Or, one or more die stacks may be carried on one (as shown in these examples) or both surfaces of a support. The separation between successive supports as mounted in the frame must be great enough to accommodate the desired die stack thicknesses and, accordingly, the interval T2 between adjacent slots 15 may be made greater or smaller as required for the particular die stacks to be treated in the fixture.

[0043] Alternatively, as may be appreciated, not all the slots need be occupied by supports. Accordingly, for processing thicker stacks (or stacks on both sides of the supports), where the interval between adjacent slots is insufficient to accommodate the thicker stacks or to accommodate stacks on both sides of successive supports as mounted, selected pairs of slots may be left unoccupied. Where every second pair of slots is left unoccupied, for example, the space between the surfaces of successive supports would be, for example, approximately equal to twice the interval T2 plus the slot width T1.

[0044] Also in various embodiments, one, or two or more die stacks (three in these examples) may be carried on a surface of the support. It may be desirable to provide supports of various lengths to accommodate more or fewer die stacks and, accordingly, to provide frames of various dimensions to accept the various supports.

[0045] Suitable materials for the parallel members include, for example, steel, aluminum alloy, polymers such as PEEK. Suitable materials for the brackets include, for example, steel, aluminum alloy. Suitable materials for the support include, for example, steel, aluminum alloy, ceramics such as steatite or alumina. Suitable adhesives for affixing die in the stacks include, for example, die attach adhesive paste or preform. Suitable adhesives for affixing die stacks to the support include, for example, a readily releasable adhesive such as, for example, a curable or partially curable adhesive that can be changed from an adhesive to nonadhesive by application of energy such as heat or radiation; or a time release adhesive. [0046] The use of an adhesive to secure the die or die stacks to the support is optional; in some configurations and orientations of the apparatus in use the die or die stacks may remain on the supports by their weight alone; or, a magnetic field may be applied to urge the die or die stacks against the support surface.

[0047] In some embodiments the die edges to be interconnected (presented toward the viewer in the FIGs.) are mounted on the support so that they are approximately flush with, or stand somewhat proud of, the side of the support. [0048] The supports carrying die stacks are loaded in the fixture. FIG. 3 shows supports carrying die stacks 20 generally as shown in FIG. 2 loaded in a fixture frame, generally as in FIG.1. The supports, and the die that are carried by them, are approximately aligned so that the die edges to be interconnected lie generally within a plane; it may be desirable in some embodiments for the surfaces of the fixture to be generally within the same plane as the die edges to be interconnected.

[0049] Then the loaded fixture is covered with a mask. FIG. 4 shows a mask 40 applied to the loaded fixture of FIG. 3. Openings, e.g., 42 in the mask 40 leave exposed the die edges of each stack, e.g., 22, 24, and the space between the die edges in each stack. It may be desirable to dimension the openings 42 such that a small space surrounding each die stack (or at least a small space next to each die edge) is additionally left exposed, as shown in these examples. In some embodiments the mask has the form of a film or sheet. Suitable materials for the mask include, for example, any of various plastics (organic polymers) such as polyester, or adhesive tapes; any of various metals such as steel, copper, aluminum; ceramics such as alumina; composite materials such as silica-alumina composites. The mask edges and openings can be formed by cutting or punching or etching, according to the workability of the mask material.

[0050] Then interconnect material (or other material) is deposited in a pattern over the mask and the die stack features that are exposed by the openings in the mask. FIG. 5 shows a masked loaded fixture as in FIG. 4, on which interconnect material has been dispensed in a serpentine path to form a connected series of parallel lines 52. The parallel lines cross the exposed die stack features, including the die 22, 24 and the space between the die in each stack. The lines additionally span a small space next to each die edge. [0051] The interconnect material may be a curable material and, depending upon the material and the technique, the interconnect material may be deposited in an uncured or partially cured state, and the material may be partially or additionally cured at an intermediate stage following dispense, and may be fully cured when dispense has been completed. Where the interconnect material is a curable material, it may be electrically conductive as deposited, or as partially or fully cured. Suitable electrically conductive polymers include polymers filled with conductive material in particle form such as, for example, metal-filled polymers, including, for example metal filled epoxy, metal filled thermosetting polymers, metal filled thermoplastic polymers, or an electrically conductive ink. A suitable interconnect material may be an electrically conductive polymer such as, for example, an epoxy containing a metal in a finely divided form, such as silver, gold, aluminum, copper or nickel; or carbon-filled epoxy. The conductive particles may range widely in size and shape; they may be for example nanoparticles or larger particles. In some embodiments the conductive material can be a partially-curable polymer; a partial cure may be performed at an earlier stage in the process, and a final cure or post-cure may be performed at a later stage to increase the robustness of the interconnection. In some embodiments the interconnect material provides a mechanical strength (for example, helping to hold the die together in the stack) as well as a reliable electrical interconnection. The interconnect material may be deposited by any of a variety of techniques. [0052] In some embodiments the interconnect material is deposited using an application tool such as, for example, a syringe or a nozzle. The material may be forced to exit the tool in a deposition direction generally toward the die edges to be interconnected, and the tool is moved over the mask and the die stacks in a work direction. The material may be extruded from the tool in a continuous flow, or, the material may exit the tool dropwise. In some embodiments the material exits the tool as a jet of droplets, and is deposited as dots which coalesce upon or following contact with a surface.

[0053] In some embodiments the interconnect material is deposited by stencil printing or screen printing, that is, by applying the material through a patterned stencil or screen. The stencil or screen may be employed in addition to the mask, as described above; or, in some such embodiments may constitute the mask, suitably configured to provide patterned openings.

[0054] After the interconnect material has been deposited over the mask and the mask openings, the mask is removed, lifting off the deposited material except at the openings, where the deposited material remains attached to the die stacks, as shown for example at 60 in FIG. 6. Where a curable or staged-curable interconnect material is used, the material may be cured or partially cured either prior to removal of the mask or at a later processing stage; it may for example be partially cured prior to removal of the mask and fully cured at a later processing stage, or it may be left uncured until some stage following removal of the mask. Then the supports, carrying the interconnected die stacks, are unloaded from the fixture frame. FIG. 7 shows a support 26, removed from the fixture frame, carrying three interconnected die stacks 60. Then the die stacks may be released from the support. A two- die stack is shown generally at 80 in FIG. 8. The die 82, 84 are affixed to one another by an adhesive 83. Die surfaces 81 , 85 constitute the surfaces of the die stack 80. The die 82, 84 are electrically interconnected by interconnect traces 88, which cross the die edges and span the space defined by the adhesive 83 between the die. Because the area exposed by the mask openings in this example included an area adjacent the die surfaces 81, 85, the interconnect traces 88 extend beyond the die stack surfaces as small nubs 87, 89. These nubs, at either surface of the die stack, can serve for second-level interconnection of the die stack to underlying circuitry such as conductive leads or pads 92 on a substrate 90, as shown in FIG. 9, to form a mounted stacked die assembly as shown in FIG. 10. The nubs are optional and may be omitted; accordingly, in various embodiments the nubs are present at one surface only of the die stack, or at both surfaces (as shown in the Figures), or are absent. [0055] In other embodiments the stacked die supports are not loaded separately in slots in the parallel members of the fixture frame. Instead, the stacked die supports are themselves stacked, one over another, and the parallel members of the frame serve to retain the stacked die supports in alignment for processing. FIGs. 11 and 12 show part of a fixture frame in an example of such an embodiment, and FIGs. 13 and 14 show a die stack support suitable for loading in such a fixture frame. The fixture frame includes parallel members 132, 134 and first bracket member 133 (and second bracket member 131 , see FIG. 15). Referring to FIGs. 13, 14, three die stacks 21 are removably mounted on a die mount surface of a die stack support 136 using an adhesive 27, generally as described with reference to FIG. 2. An inward- facing surface of each parallel member of the frame is provided with a lengthwise ridge 138, and end portions 137 of support 136 are each provided with a slot which is configured and dimensioned to accept the ridge 138 in a tongue-and groove manner. To load the stack- carrying supports 130 in the fixture frame, the slotted ends of a first support 130 are engaged with the ridges on the parallel members, and the support 130 is slid to the bracket 133. Additional supports 130 are successively slid onto the first one and then one onto another, to obtain the loaded frame shown for example in FIG. 15. Bracket 131 is positioned to cap the fixture frame assembly. In the example shown in these FIGs., the support members 136 are thicker at the ends so that successive support members do not rest upon the die stacks in a previously loaded support 130. Or, stated another way, a cavity is provided in the surface of the support members opposite the die stack mount surface, to accommodate the thickness of the die stacks in a previously loaded support 130.

[0056] In other embodiments the supports are planar on both surfaces, as shown for the supports 26 as shown in FIG. 2, and spacers are mounted in the fixture at the ends of the supports, to provide clearance to accommodate the die stacks. [0057] In still other embodiments successive supports may be permitted to rest upon the die stacks on previously loaded supports. [0058] After the fixture is loaded as shown in FIG. 15, the loaded fixture is covered with a mask. FIG. 16 shows a mask 160 applied to the loaded fixture of FIG. 15. Openings, e.g., 162, in the mask 160 leave exposed the parts of each stack on which the interconnect material is to be deposited, including at least the edges of the die, e.g., 22, 24, and the space between the die resulting from the thickness of the adhesive 23, in each stack. As described generally with reference to FIG. 4, it may be desirable to dimension the openings 162 such that a small space surrounding each die stack (or at least a small space next to each die edge) is additionally left exposed, as shown in these examples. [0059] Further treatment to completion of the die stacks can proceed generally as described with reference to FIGs. 5 through 8.

[0060] In the various embodiments of the invention as described above, individual die are stacked and treated. In other embodiments certain of the steps can be carried out at a wafer level, or by treatment of a block or row of die, rather than of single die. [0061] In the embodiments shown here for illustration, the interconnect material is deposited by moving the deposition tool in a series of antiparallel lines running generally perpendicular to the active sides of the die. In other embodiments (not shown in the FIGs.) this simple pattern may be varied and, in some embodiments the deposition tool may be moved in a zigzag or dogleg course over the stack face, to connect selected interconnect terminals. In some embodiments the deposition of material onto the stack face may be interrupted, particularly for example at the areas of separation of the respective stacked die units, so that it is not necessary to sever interconnect traces crossing the separation areas. Interruption of the deposition may be accomplished, for example, by a momentary stoppage of the flow of the material from the tool. Or, a mask may be placed over the separation areas prior to deposition and then stripped away following deposition, to remove the material from the masked areas in a lift-off process.

[0062] In some embodiments two or more deposition tools are employed at once to deposit interconnect material in the stack face. A row or an array of nozzles may be employed, for example, to deposit the interconnect material. [0063] In the examples shown, the mask covers the entire fixture frame opening and, in addition, margins of the mask cover an inner portion of the fixture frame elements. The mask need only cover areas of the loaded fixture onto which the interconnect material would otherwise undesirably be deposited. Accordingly, in other embodiments the mask covers at least the areas of the die stack supports that are located between the die stacks, and in some embodiments the mask covers most or all of the area of the sides of the die stack supports. [0064] Other embodiments are within the scope of the invention.

Claims

CLAIMS We claim:

1. A fixture for applying a patterned material to semiconductor die edges, comprising a framework configured and dimensioned to hold a number of die stack supports.

2. The fixture of claim 1 wherein the framework includes a pair of parallel members supported in the framework to provide a frame opening between the parallel members dimensioned to accommodate the length of the die stack supports.

3. The fixture of claim 1 , further comprising at least one said die stack support.

4. The fixture of claim 3 wherein each said die stack support includes first and second surfaces bounded by sides and ends.

5. A method for applying a patterned material to semiconductor die edges, comprising providing at least one die stack support, having first and second surfaces bounded by sides and ends, and a framework configured and dimensioned to hold at least one said die stack support; mounting at least one die stack onto at least one of the said first and second surfaces of the support, loading the support in the framework such that the die edges to which the material is to be applied face toward a side of the framework, and applying the material to the die edges.

6. The method of claim 5 wherein loading the support in the framework comprises aligning the support so that the die edges to which the material is to be applied lie generally in a plane.

7. The method of claim 6, further comprising, following loading the support in the framework and before applying the material to the die edges, placing a mask over the side of the loaded fixture such that openings in the mask expose the die edges.

8. The method of claim 7, further comprising, subsequent to applying the material to the die edges, removing the mask.

9. The method of claim 5, further comprising, subsequent to applying the material to the die edges, unloading the support form the framework.

10. The method of claim 9, further comprising, subsequent to unloading the support form the framework, unmounting the die stacks from the support.

11. The method of claim 5 wherein applying the material to the die edges comprises dispensing the material.

12. The method of claim 5 wherein applying the material to the die edges comprises applying an electrically conductive material.

13. The method of claim 5 wherein applying the material to the die edges comprises applying an electrically insulative material.

14. The method of claim 5 wherein applying the material to the die edges comprises applying at least two different materials, having different electrical properties.

15. The method of claim 12 wherein applying an electrically conductive material comprises applying an electrically conductive polymer.

16. The method of claim 5 wherein applying the material to the die edges comprises dispensing.

17. The method of claim 5 wherein applying the material to the die edges comprises printing.

18. The method of claim 5 wherein applying the material to the die edges comprises writing.

19. The fixture of claim 1 wherein the framework is configured to ensure alignment of the supports.

20. The fixture of claim 19 wherein the supports and the framework are configured so that the ends of the supports slide onto parallel members of the framework in a tongue-and-groove manner.

21. The fixture of claim 19 wherein the supports and the framework are configured so that the ends of the supports slide into slots in the parallel members of the framework.