CA1153477A

CA1153477A - Die-stamped circuit board assembly having relief means and method of making

Info

Publication number: CA1153477A
Application number: CA000373080A
Authority: CA
Inventors: John W. Shaffer; Boyd G. Brower
Original assignee: GTE Products Corp
Current assignee: Osram Sylvania Inc
Priority date: 1980-03-19
Filing date: 1981-03-16
Publication date: 1983-09-06
Also published as: EP0036607B1; EP0036607A1; US4320572A; JPS56144423A; DE3164377D1

Abstract

D-22,510 TITLE: DIE-STAMPED CIRCUIT BOARD ASSEMBLY HAVING RELIEF MEANS AND
METHOD OF MAKING
ABSTRACT

A photoflash device circuit board assembly including a dielectric substrate and at least one switching element and conductor die-stamped therein. To assure that the delicate switch is not severed by the die's cutting edge during die-stamping, a relief means (e.g., slot) is provided within the substrate so that a segment of the switch can be aligned therewith. As an alternative, it is taught to provide stepped portions within the die's cutting edge to align with preselected portions of the switch and thus prevent total severance thereof.

Description

D-22,510 ~L~5;~77 t_ DESCRIPTION
TITLE: DIE-STAMPED CIRCUIT BOARD ASSEMBLY HAVING RELIEF MEANS AND
METHOD OF MAKING
TECHNICAL FIELD
The invention relates to electrically~activated, disposable photoflash devices and particularly to the circuit board assemblies utilized therein. The invention also relates to methods of making such assemblies.
BACKGROU~ID
Photoflash devices of the variety mentioned above typically include a circuit board having an insulative substrate with pre-established circuit patterns or "runs" thereon. Electrically connected at designated locations to this circuitry are a plurality (e.g., eight or ten) of high voltage flashlamps. The circuit board, with flash-lamps secured thereto, is located within a suitable, insulative housing having a light-transmitting cover (to permit the high intensity output from each flashlamp to passtherethrough) and at least one connector tab for attaching the device to a respective camera and electrically connecting the circuit board's circuitry to the power source (e.g., piezoelectic element) typically located therein.
Activation of the power source by the camera's user, such as by depressing the camera's shutter release button, results in a firing pulse being provided the circuitry and ignition of one of the device's flashlamps. One type of device containing a pair of opposing linear arrays of flashlamps and a singular, common connector tab is referred to in the art as a "flash bar", while another type, which is capable of being inverted and thus possessing two opposing connector tabs, is referred to as a "flip-flash". The "flip-flash" devices were designed primarily to substantially eliminate the photographic phenomenon known as "red-eye", which occurs when light is reflected by the retinae of subjects' eyes onto the photographic film to indicate the eyes' pupils as being red. These latter devices sub-stantially eliminate this possibility by spacing the illuminating flashlamp a specified distance from the camer's lens.

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One examp'le oF ~l~e ,lrnl^ulll(?lliio~ l "F'lasl~ " pllol:of'lash c!evice is describe~ in U.S. I~cl-t(?llt l~o. 3,~35-/,C,~,-I (J.J. Vetere et al). An example of an eiyl~ l'lash'lall)l) drray(!(i "F'lip l'l ash" is described in U.S. Patent No. ~,1'l3.~24 (D.E. /\rll1s~ron3 e~ a'l), while examples oF
ten lamp versions oF tl-lis produc~ ar~ describecl in U.S. Patent Nos. 4,152,751 (R.~. S-ind'lilltler e~ a'l) ancl ~,16~,007 (E.G. Audesse.
et al). All oF the above pa~ents are assiyned to the assignee of the instant invention.
As stated, the present inventi~n is concerned wi~h the manufacture of the circuit board assembly whicl1 eventually -Forms an inteyral part of the final photoflastl product. One example oF a known technique for mak;ng such componen~s (e.g., ~llose used in the aForedescribed "flash bar" device) has ~een to silk-sc.^een a silver conta~ning material over a ceramic-coa~ed s~e'l boarcl and thereaF~er oven-Pire the assembly to Fuse ~he silver parl:icles to a continuous conductor.
The steel board was ori~!irlally b'lallkecl From a strip of sa;d Inaterial?
sprayed or dipped ~i~h Ille cer;ll1lic, ar1d iired ~o procluce a hardened coating thereon. ~i'llc~screel1in~ ~n-l nven-Firin!J Followed. Another type of technique (e~t).S l~)r l:lluse culllponents usecl in many "f'lip-~0 -Flash" devices) a'lso invu'lved si'lle screenirlg ol` silver-con~aining material but insteacl on a styre~ne cupo'lymer, thertlloplast;c substrate (or board). The silver-c(lrntclinin~ Illal;eria'l, applied in paste Form, ~!as then subjectecl ~o eitlle1 a racli<ll:ion curing or tlOt a;r drying step. In both ol` ~he above exalilplc.~s~ l:lle cured si'lver-con~aining Inaterial served as the conduc(~ e circuit in the fin;shed device.
Yet another technique (as used in at least one embodin1ent of a "flip-flash" device) invulved approximate'ly the same procedures as used to manuFacture c;rcuil: I)oard asselllblies in such products as television sets. This pY~oce~is re~luired several steps, including photo-3~ resist coatin~ a cop~r-c'lacl sheet: of Iheno'l;c or other suitable base material and tller~aFter chelnica'lly removing (e.CJ., etching) khe un~esired copper. This com~oner1t was then tllorouyh'ly cleaned and coated with a`protective Fi'lm.
The aforementionecl ~echniques and resulting products contain several disadvantages. Silk-screeninl3, FUY~ example, requires utilization of pas~es which in turn are comprised of discrete silver !

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~53~7 . ~ .
particles loca~ed l:he;~ (l r~ ,n~ .y u l~ der. A1l:hou~h these pastes are even~lla'l'ly s~ i. Lu sollle rurl~l Or llecl~ ~rea~ en~ ~o hope-fully fuse said par~icles, 1:he rirli~lle~l ci rcu-itry unclerstandably is ; ¦
limited in its conductivi~y (ancl ~hlls possesses an inherent'ly higher resistance) in ccmparison I;o concluc~ors presell~ed in a solid sta~e.
Silk-screened circuitry is also susct-~ptible to containment oF dis-continuities as migll~ resul~ fronl tlUS~ or lint in~erference during the screening operation. l'he presence oF a screened silver layer also poses a problem when the chosen method For securing the device's flashlamps to the circuitry is solclering. Occasionally~ the silver layer has prevented proper wetl;in(l ~lur-ing this process. Still another inherent problem wi~h s;'llc-screening c~nductive circu;try ;s the i j ready opportunity for dinl~nsional impreciseness due to the horizontal flow (beneath the screen~ as ~he paste is Forced through the screen's pattern. In addi~ion, occasiolla'l smearing of the circuit run is practically unavoidab'le. 'rlle la-~er problems are particularly ~rouble-some to devices emp70yin~ hi~Jh vo`ll:acJe Flashlamps in that sparkoYer ~ I
can ~hen occur between ~he circui~'s e'lelllents, resulting in either , ¦
product -Failure or si~llultaneouc l'~s!)intJ oF two or more lamps. A
final disadvan~acJe ol` ~l~e alJuve prucesses is ~l~e rela~ive'ly high cost associated ~hercw-ith. r(~cl Ini~lu~ s u~i n(J pllol:o~re~sist coatin~, develop-ment, and subsequen~ cllemica'l relnoval are unders~andably costly in terms of both time ancl nlal;e~ria'l. Si'lk-scl^eenitlg is also understandably costly, particularly as a resu`lt oF usirlg tlle precious metal silver and ~he relative`ly ra~ ar ~F l:h(~ ~cr~n l~a~e~ria`ls typically used in this process.
The present invention overcomes the several, aForementioned disadvantages by emp'loyirl~ the techniqlle oF ~ie-stampin~ to thus accurately de~ine and position a conductive circuit on an insulative substrate without the need For photo-resists, chemical echtants, precious nletals, etc. In acldition to this, ancl oF equal or greater signi~icance, this techrriqlle as utilizecl in tlle presen-t invention defines a proceclure wherehy the clevice's circuit runs (or paths~
can be satis~actorily positioned ancl electrically connected to other elelnents which also constitute part oF the device's circu1try. One primary example of such an element as utilizecl in today's more recent D-22,510 ~ ~S 3 ~ 7 ~ ~

products is a radiation sensitive switch which is usually electrically connected in series with a respective flashlamp and adapted for receiving the radiant energy from the lamp upon ignition thereof. The switch will thus melt or shrink to define an open circuit almost instantaneously after Flashlamp ignition and thereby permit reliable flashing of the subsequent lamps in the device's array in rapid succession. An example of a radiation sensitive switch is described in U.S. patent No. 4,017,728 (E.G. Audesse et al), which is also assigned to the assignee of the presen-t invention. As described therein, these switches are each typica'lly comprised of a thin strip of polymeric material attached to the circuit board across a respective aperture provided thereinO A
typical ten-lamp array will include eight switches of this variety in view of the obvious understanding that the last fired lamp on each end of the array has no need for sucn an element. It is understood that the relatively delicate nature of such e'lements as radiation sensitive switches does not readily permit electrical connection thereto by a technique as relatively severe and demanding as die-stamping. Die-stamping has been utilized in the production of printed circuit components for use in products other than photoflash devices but only because such components (and therefore products) did not require such delicate elements as radiation sensitive switches therein. Typically, these products consisted of only a base or substrate, a solid metal conductor (e.g., copper foil), and a bonding adhesive. See, e.g., U.S. Patent Nos.
3,91i,716 (W. Weglin) and 3,990,142 (W. Weg'lin). The invention as will be described is thus deemed all the more unique and significant in that it not only assures positive electrical connection between the component's circuit runs and delicate switch elements but also provides for definition and securement of the circuit runs to the insulative substrate which forms an integral part of the final pro~ucts.

D-~2,510 ~ ~r~ 3 ~ 5-As will be understood From the followiny description, the present invention defines a circuit board assembly and method of making same wherein some deformation or severance to -the switch occurs but not to an extent that the operational capability thereof is adversely affected. By the term deformation is rneant -the occurrance of a substantial indentation to or compression of the original thickness of the switch. Illustrated examples are provided below. By the term severance is meant that the die-stamping procedure results in a cutting through of the total thickness of the switch by the die member. This may occur only at certain locations within the member or across the entire width thereof. Accordingly, it is possible using the teachings of the instant invention to manufacture a circuit board assembly using die-stamping but without the critical attention to parameter criteria deemed essential above.
It is believed therefore that a technique for manufacturing circuit board assemblies possessing the above capabilities and the products resulting therefrom will constitute significant avancements in the art.

DISCLOSURE OF THE INVENTION

It is, therefore, a primary object of the present invention to enhance the art of manufacturing circuit board assemblies for use in electrically activated photoflash products.

D-22 , 51 0 ~J
~534~7 - G --It is another ol~ e i~ ?lllif)`~ I:o ~r()\/i~le a circuit board assembly for use i n said pr~dllcts.
In accordance wi-l:i~ t~n-? ~ c~ ()t the inven~ion, there is provided a metho~i oF making a circuit board assembly comprisin9 -the steps of: (l) pOSitiOI1ill9 a dielectric substra~e on a base; (2) locating a-t least one switchirl~ elenlell~ on the substrate; (3) orien~ing a conductive st~ip over bo~h subs~rate and element~
engaging the strip wi~h a die melnL)er to press por~ions oF both the conductive strip and tlle sw1tchin~ element into -the substrate to effect electrical contact between the pressed strip and element with minor deFormation or sev~rance of the element; and (5) removing -the remaining, unpressed portions of ~:he strip From the substrate.
In accordance witll another aspeci of the invention there is provided a circuit board assembly which comprises a dielec~ric substrate, at leas~ one switch;rl~ elemetlt having a portion thereof pressed within the substr;.ll;e, a~! a con~uctive member also pressed within the substrate. ~t. leasl; part oF tlle conductive member is pos;tioned a~op the presse-l portiun o,' the switching element and in electrical contact therewi-th. A rel-,eF mealls is provided in the dielectric substrate to permit a seg:"ent of the switch;portion being pressed within ~he subs~ra~e to l~e posi-~ioned ~herein and/or aligned therewith such -that l:he se~mellt is no~ ~eFornlecl or severed during the pressing.
~RIEF DESCRIPTION Ol-: TIIE DRAIIII`I(JS
FIG. l is a partial ele~vatiorlal v-iew, in section, oF a photo-flash device incorporatin~ therein a circuit board assembly manufactured -in accordance with a preFerreci embodiment oF the invention;
FIGS. 2 and 3 are pa.tial elevational views, in section, of -the preliminary steps oF ~he l~etllod of the inv~ tion;
FIG. 4 is an enlarged, partial isometric view, partly in section, illustra-ting one oF the preFerred means oP die-stalnping a conductive member and par-t of a switching element within a dielectric substrate;
FIG. 5 is a partial elevat1OIlal view, in section, showing the die of FIG. 4 at its Full del)lh within the dielectric substrate of the invention;

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FIG. 6 repres~ncs i~n I?r;l~ln~!r-~ rlicll isol~letric view, partly in section, of the corl~uc~ive member an-I switcllirly e'lement as die-s~alllped in accor~anco wi~h ~iie lo.lcl~irl(~s 0l ~j1e IIILetjlOLI oF ~he inventioni FIG. 7 illustrates a ~ircuit board assembly wherein the assembly's dielectric subsi;ra~e~ c(~n~airls a pair oi~ space~ reliL?~Ineans ln accordance with a preferred emboclimell~ of ~he invention;
FIGS. 8 and 9 are par~ l e'levational views showing.-~he relative ;
positions of the dielectric substrate, switchiny element, and conductor member beFo~e and a-Fter l:he die-stampin~ of the element and conductor witilill the subs~ra-~e; an~ ;
FIG. 10 is a partia'l elevational ~/iew, itl seccion and as taken ~', along the line 10-10 in ~IG. 9, sho~irlg ~he ~;nal position of the pressed switch;ng elelnen~ ancl concIucGor withill ~he invention's ~5 dielectric subsirate.
BEST MODE FOR CARRYING our rll~ lNVilllION
For a better uncler~;tan(lirl.~l o~ t~le presell~ invention together with other and further ol-~iects, aclvalll:a~es ancl capabilities thereof, reference is made l:o ~ile lro'llowin~ clisclosure and appended claims in connection with thL~ above ~lescribe(i Irawings.
With particular relerellce l:o FIG. 1, ~here is illus~rated a partial elevationa'l ~Jie~I o~ an e'lectrically-ac~ivated photoflash device 20 i;lcorporatill~ a ~ircuil; boartl assembly 23 manuFactured in accordance with the ullique l~rinciples of ~he instant invention.
Device 20, like~Illally OF ~ilL? phO~:OIlaSll ClL~VjCeS described a~ove, includes a plastic housin~ witll rear and forward members 27 and 29, respectively. l'hese two members ma~Y be secured ~ogether, e.g., using cement, or it is a'lso possib'le to produce the en~ire housing ~rom a single member oP such nlaterial. Forward melllber 29 is light-transmitting to pernlit light emit~ecl From each oF the several flash-lamps 31 (only one shown) to pass l:heretllrough upon lamp ignition.
Ignition is achieved whell the de~/ice's end connector tab or tabs (not shown) are inser~e~ Wit)lill tlle socke~t of the canlera used there-with and the camera's shutter release bu~ton activated. A suitable firing pulse is produced ~y the camera's power source (e.g., piezoelectric elemet)t) ancl passe~l to ~he respecl:ive l!anlp 31 via the .

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connection providecl ai; the conr1ecl()r i;ab~ This plllse travels up through the device's circuil;ry 3~ which ~Orlll.S part oF assemb'ly 23. As shown in ~IG. '1, ~ e l;wo ~oncllictive 'leacl-in wires 35 (only one shown) of lanlp 31 are conl1ec~ecl ~o circu-i~ry 33, said means oF
connection accomp'lished by such Ille~llods as soldering or crilnping (e.g., using metal eyele-ts). Tlle leacl-in wii~es nlay also be Frictionally retained within slots or groove~s witl1ir1 the assembly's dielectric substra-te 36. PhotoF'Iasll devices oF this type also typically include a reflector 37 for prolnoting Forwarcl li~ht output. Reflector 37 is preferably oF almninllm-coated plas~ic and loca~ed immed;ately behind lamp 31. Device '10 Inay Fllrther include a sheet oF Flash-indica~ing material 3~ (e.n., biaxia'l'ly oriented polypropylene) which shrinks or melts whell sub;i?c~ed ~o heat ~rom lamp 31 through a pair oF aligned apertures witi1 1eF'Iector 37 and l:he substrate component 36 to thereby change the color viewahle throllgh the openings 4l (one shown) provi~:le~ l an in(lici.l sll~et ~13 (a'lso optional~. A user of the device is thus provi~led witll a reacly nleans oF ascerta;ning whether or not a particu'iar lamp or 9rolll) oF lanlps has been Plashed.
Understandably, rear 1nelllher ~:7 o1' I;he device's llousing is a'lso light-transmitting to permit viewing in tlle mallr1er dePined. Sheet 43 maybe oF paper or tilin cardt)uard.
As stated, photo~'lash clevices conl;airli~lg the above components (excluding of course a circuit board assembly procluced in accordance with the teachings o~ the inve1ltil)n) are known in tlle art with examples of such being described in de~ai'l, for examp'le, in the aforementioned patents. As also stated, i~ is ~urther known in the art to incorporate radiat;orl se11sitive switches as an importani element of such devices. r~eFe~rence is a~ain directed to assignee's patent 4,0l7,728. Thesc elemenl;s, rep~esented genera'lly as numeral 45 in FIG. 1, are also reFerre(l I:o in the art as radiant-energy-activated switches, quick-cliscor1necl: switches, etc., and typically comprise a length (strip) oF electrically conductiveg heat shrinlcable polymeric material attached tn the device's board member across a respective aperture 49 ~see be'low). 'I'he SWitCil being attached at its ends, the midportion tllereo~ is tllus spatia'l'ly suspended to avQid physical contact witll the heat-absonbill~ sur~aces oF the circuit board. This arrangement Inaximizes the speed with which shr~nking D-22,510 ~ ~ ~3~7 ~

and separation of the midportion occurs upon receipt of heat from adjacent lamp 31. As shown, lamp 31 and switch 45 are electrically connecked in series to assure proper connection between the afore-described power sour~e and remaining, unfired lamps which also form part of device 20. This mode of operation is fully described in the aforementioned patent 4,017,728 and further detail is not believed necessary.
Switch 45 comprises a thin strip of plastic preferably fabricated from a mono- or biaxially oriented polyethylene, polypropylene, polystyrene, polyester, or nylon. The polymeric material itself may be rendered conductive by additives such as carbons or it may be made surface conductive by deposition of a suitable conductive layer (e.g., aluminum) thereon. The performance of highly reflective materials, such as aluminized polypropylene, can be enhanced by applying a coating or spot (not shown) of dark, light-absorbing material (e.g.3 ink) on the surface of the switch which faces lamp 31.
As understood from the foregoing, it is essential that the opposing ends of switch 45 not only be properly secured to the board or substrate member 36 but also must be electrically connected to respective, designated portions of circuit 33. When using the aforementioned technique of silk-screening, this electrical connection was achieved by carrying the circuit pattern over the ends of the switch's strip. This procedure thus resulted in additional use of the expensive, silver-containing conductive material, yet another disadvantage added to the several cited above. In some prior devices, switch 45 was secured to board 36 using an adhesive tape with pressure thereafter applied to hopefully provide securement. This procedure alone did not prove altogether satisfactory, however, in that the strip was occasionally removed from the board during subsequent processes to which this product was subjected.
In accordance with the teachings of the present invention, switching element 45 and the conductive members 33 which form part of the overall circuitry for the finished circuit board assembly 23 are securedly positioned on the assembly's dielectric substrate 36 using a die-stamping process. As stated, this process permits deformation or severance of parts of the switch 45 D-22,510 10 but not to an extent that this component is rendered inoperative.
The unique result of this process is that the conductive members and switching element are positively secured within the substrate and also electrically connected. In addition, parame-ters such as material hardness and thickness do not require absolute compliance thereto.
With particular reference to FIGS. 2 and 3, there are shown the initial steps in manufacturing a circuit board assembly in accordance with the principles of the present invention. In FIG. 2, switching element 45, preferably comprised of the polyester Mylar (a trademark of the E.I. DuPont De Nemours and Company, Inc., of Wilmington, Delaware, U.S.A.) llaving a conductive (aluminum) layer thereon, is positioned above substrate 36 so as to align with a cylindrical-shaped aperture 49 with the substrate. The aluminum conductive layer (not shown) is understandably located on the upper surface of the Mylar. Aperture 49 in the finished product (device 20) permits radiant energy from flashlamp 31 to pass therethrough to the aforedescribed indicia sheet 43. Aperture 49 also serves to assure that a major portion of element 45 will not physically contact the upper surface of substrate 36. Such a surface, being heat~a~sorbing, could serve to reduce the operational effectiveness of element 45 during exposure thereof to the intense energy from flashlamp 31. Accordingly, element 45 is located on substrate 36 so as to bridge aperture 49 (See also FIGS. 4 and 7). Initial attachment of element 45 is achieved by providing a quantity of adhesive 51 at both ends of the striplike element. Adhesive 51, preferably of the pressure-sensitive variety, may be applied using any of the techniques well known in the art. The element 45 and adhesive are located on substrate 36 and a suitable pressure (sufficient to activate adhesive 51 and form a bond between the substrate and element at these locations) is applied downwardly on the element's upper surface. A roller or similar member can be used as the pressure applicator.
In FIG. 3, the combined substrate and element members are shown as being positioned on a base or platen 53 which forms part of the larger die-stamping machine. Base 53 preferably includes a recessed portion or cavity (not shown) therein to better retain substrate 36, with the substrate being positioned within said cavity. A thin strip of conductive material 55 is then oriented above the substrate 40 in the manner shown in FIG. 3, and is then lowered to substantially D-22,510 -1l-,r~3~7~7 cover both substrate and switching Plement. Material 55 is dead soft aluminum, having a thickness of about 0.002 inch. Once in position, the aluminum strip is engaged by two dies 57 and 57' which each are secured or form part of an upper platen 59 of the machine.
Platen 59 and dies 57 and 57' are preferably both comprised of steel (e.g., low carbon). The upper platen is lowered mechanically to effect said engagement with the positioned strip 55. Downward force is further applied by dies 57 and 57' until preselected portions 61 (FIGS. 5 and 6) of strip 55 and switching element 45 are pressed an established distance into the substrate (FIG. 5). A total force within the range of about 250 to 350 pounds per linear inch of cutting edge (of dies 57, 57') is applied using the materials and thicknesses described herein. The dielectric substrate, having a preferred thickness of about 0.043 inch, is embedded a depth of about 0.004 inch at its deepest location (immediately below the outer parallel cutting edges 63 of each die). Both end portions of the striplike switching element 45 are thus positively secured within substrate 36 on opposing sides of aperture 49. Element 45 possesses an original thickness of about 0.0005 inch to about 0.001 inch.
As stated, the selection of materials (having the proper ratios of thickness and hardness), die pressures, and die temperatures (if adhesives of the variety described herein are to be used) is not deemed too critical in the present invention because the invention permits partial deformation and/or severance to preestablished sections of the switch during the die-stamping procedure, but does not permit total severance thereof. Understandably, complete (or total) severance of the switch (across the entire width thereof) at the location of deepest die penetration could easily result in the switch being inoperative. The present invention thus permits use of substrate materials possessing a greater hardness (including at the initial stages of die-stamping) than switch 45. For example, it is possible, using the teachings herein, to utilize the thermosetting resin phenolic for substrate 36. In addition to the above significant advantages, it will be shown and described that the partial deformation of portions of switch 45 also serves to enhance switch securement to substrate 36 by permitting deep penetration within the substrate ~-2~,510 ~L~.3 ~ 12-by said deformed portions. This occurs~ of course, in situations where the substrate's material is tolerant of such penetration~ such as in the case where the polys-tyrenes are employed. Still further, the invention also provides for partial deformation of predetermined parts of the uncut sections of strip 55 to thus facilitate eventual removal of the unpresse~ portions of -the strip.
In F~GS. 4-6, there are illustrated the further steps of the method of the invention wher~in it is assured that complete severance of switch 45 at the location of die-stamping will not occur. More specifically, in FIG. 4 the parallel cutting edge 63 of die 57' is shown as including a pair of stepped (recessed) portions 65 therein which align with preselected areas "A" on the upper surface of the portion of switch 45 destined to be pressed within substrate 36. Accordingly, areas "A" will not be deformed or severed during pressing of switch 45 and the preselected portions 61 of aluminum strip 55 (shown in phantom in FIG. 4) within the substrate. Pressing is shown in FIG. 5 with the final con-Figuration for assembly 23 depicted in FIG. 6~ When a dinking depth of 0.004 inch is used and switch 45 has a thickness of about 0.001 inch, each step 65 has a depth ("D") of between 0.0005 inch and 0.0015 inch.
Additionally, each step preferably has a width ("W") of about 0.017 inch to about 0.020 inch when cutting a switch having an overall width (at the location of engagement by edge 63) of about 0.055 inch. Using two steps 65 thus assures that from about 0.034 inch to about 0.040 inch of the total width of switch 45 will remain nondeformed or nonsevered~ As will be shown below, the remaining parts of the switch (those below the areas immediately adjacent areas "A") will be either deFormed or completely severed. For purposes of clarity, these latter areas are referred to by the letter "B" in FIGS. 4 and 6. It is preferred that only one of the parallel cutting edges 63 of each die be provided with a pair of steps 65. Preferably a total of two steps per edge is employed but this number can vary, provided the above percentages of nondeformed areas remain approximately the same. In one embodiment of the invention, only a single step 65 was used per edge, said step having an overall width "W" of about 0.034 inch to about 0.640 inch and depth "D" of about 0.001 inch.

D-22,510 7~

The de-formal:io~l ol ~ as (~r ~ i;s) ~ l is l>ecter il'lus~rate~l in FIG. 6. I~ can be clean'ly ~ee~ erein tl~al: tl~e deeper penel;rating l~ortions ~P~ of ecl~e ~> (~1(,. ~) lllli(ll ,l'li(ln witil (lreas "B" serve ;
to deform the switch's upper surlC~ce a~ ~hese 'loca~ions and cause a permanent indentation therein. I~ is a'lso shown that these parts of switch ~5 more deeply pene~ra~e sul-strate 36 than the remainder of the switch, thus enhancing securemell~ oF ~he switch within the substrate. ' As stated, conduotive me~ er 6'1 is both positioned atop switch !
45 and also in electrical contact ~herewitll. Contact is Formed primarily at two loc~ions, the first bein~cJ at the extreme, substantially flattened or tapered edges71 of the conductive member defined by por~ion 61, and the second aloncJ the common arcuate surface (boundary) ,'3 between portion 61 and elemerl~ ~5. As shown, the conductive member is also oF su~si:antidlly arcuc~te cor-~iguration with ends 71 substantially tapered by tl~e clie stalllpill~ proce~llre. This final cnnfiguration is due to the (Jreater forces êxertecl a'long the outer, deeper penetra~ing paral'le'l ed~es 63 of ~he die in comparison to forces exerted at its more recessed ~ortions. It is shown ~hat only part of conductive member 61 lies atop and phys-ically encJages the embedded portion of switch ~5. l'his part is deemed of sufficient size~
however, to achieve the c~tact re~luired. The overlapping part also serves to assist in reterl~ n oF tlle embedded portion oF the switch.
The use oF parallel c~l~tin~'ed~es ~ understallclably pernlits some parts 25 oF strip 55 to remaill atta~lled to purtion(s) 61 aFter stamping, if ! ;
desired. These parts, e.~ 0 ln F~. 'I, are also die-stamped within substrate 47 by the apparatlls defilled herein and will constitute the remaining section of circuit 33. Parts 80 are not shown in the remaining FIGURES o~ the drawings ~or c'lariPication purposes. As to those sections oF s~rip 55 wi~icll are no~ die-s~anlped wi~hin substrate 36, however, removal is necessary. In the case oF the pressed conductive material constitutirlg melllber 6'1~ se~para~ion oF ~he non-pressed remainder (not shown) oF strip 55 understandably occurs along the edges 81 of those parts oF the conductor located immediately above non-deformed areas "A" o~ switch ~5. Removal was possible by manually lifting the non-pressecl alumirlum, causing it to tear along edges 81. This removal can be Faci'litated by adjusting the depth "D" of steps 65 such that those re~J-ions oF the aluminum inunediately D-22,510 ~ 77 -'14-above areas "A" are deformed or if desired, even comple-tely severed, thus eliminating the need for the aforemen-tioned tearing.
In FIGS. 7-10, there is shown an a'lternative method of making a circuit board assem~'ly wherein total severance of -the assembly's delicate switching element 45 is prevented. With particular reference to FIG. 7, relief means 85, each in the form of a slot 87, are provided within dielectric substrate 37 on opposite sides of aperture 49 and having access thereto. Each slot preferably extends through the entire thickness of substrate 36 to the bottom surface thereof. The Mylar switch 45 (shown in phantom in FIG. 7) is aligned over aperture 49 and slots 87 in the manner depicted in FIG.
7). Specifically, slots 87 are located under the end portions of the switch which are to be die-stamped within substrate 36 such that those segments (defined by dimension "S" in FIG. 8) of these end portions which are aligned with the respective slots cannot be severed by the cutting edge 63' of die 57" which effects the stamping. Edge 63', unlike edge 63 in the above embodiment, is planar and absent any steps or similar irregularities therein. The location of engagement with switch 45 by the parallel, planar cutting edges 63' are represented in FIG. 7 by the dashed lines 63'-63'. Clearly, these edges align with slots 87.
When emp'loying a switch 45 having an overall width of 0.055 inch, each slot 87 in turn possesses a width (dimension "SW") of only abut 0.015 inch. Therefore, the non-aligned parts of switch 45 (those outside dimension "S") are either deformed or severed by edge 63'. As shown in FIGS. 9 and 10, deformation occurs in t~ese locations and results in a reduction in thickness to switch 45 therein. The segment protected by slot 87 substantially retains its original thickness. As in the above, prior embodiment, those deformed portions of switch 45 become at least partially embedded within substrate 36 (see FIG. 9) to thus enhance switch attachment thereto in a manner simi'lar to that described above. It is also shown in FIG. 9 that at least a portion of the protected segment becomes positioned within slot 87 and remains so in the finished component.

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7~7 - Ir~
With particular re-Forerlc(-~ ~o l:l(;. '10, lt carl l~e seen that a part (9l) of strip 55 wllich is a'lso a'li~necl~/itl1 s'lot ~7 during the die-stampin~ procoss l~ c!vellte(.l F1()ll~l)oin(J cc~lnl)lete'ly severed by the die's cutting ecl~e. Sel)ara~ion of the non pressed aluminum strip ;s readily possible here also by simply teariny the strip along an edge oF this part I~ is also possible in this en~bodiment o-F the invention to Facili~a~e such removal by adjusting the depth of slot 87 such that this 1iart is deFormed by the die's cutting i edge It is fur-ther withir1 tlle scope oF ~he invention to sever ' part 9l and el;minate;the l,eed For tea1ing altogether, for example, by using a harder switch 1lla~erial ancl soFter substrate. With added regard to FIG. lO, the remain;ng, pressed port;on 61 oF the strip 55 assures the arcuate shape s;milar ~o that ;n FIG. 5. It is also fully understood ~hat in the enlbocliment of FIGS. 7-lO that each pressed end port;on oF switch 45 wi1'1 have a ooncluctive member 6l located thereon (as in FI~. 5) ar1cl in e'lectrica'l contac;t therewith. Thus, two opposed portions oF switch 45 are securecl within substrate 36 on opposite sides oF aperture ~9 to assure bridging thereoF. And 1 ¦
;n each instance a segment of eaci1 por~ion is protec~ed against severance by a relieP mea1ls 85 prov1~ecl wlthin the substrate.
Much of the adhesive (5'1) wllich was orig;nally appl;ed to the bottoms of the.ends oF switch 45 pressed within substrat~ 47 will be Forced out from under the switch durir1~ both oF the above operations, but some (nc;t shown) will rel1lairl to assist in retention. That adhesive 25 material which is Forcecl (or squee7ecl) out may se~tle within the ' recess 93 (FIG. 5) located un-ler tl1e non-covering portion oFInember 61.
Thus, switch 45 provi-les a re'liel l`~o~ ~his acihes'ive itl ~he nlanner illustrated in FIG. 5.
As also shown in FIG. 3, another adhesive 95 can be applied to the bottom of aluminunl strip 5~. 'rhe preFerreci adhesive is oF the hea~t sensitive var;ety (several oF which are well known in the art) and pre~erably possesses a quiclc reaction time. I~ can be applied directly to the bottonl oF strip 55 durincJ manuPacture thereoF or can be provided in separate, sheet for~ dhesiYe 95 has a thickness oF
about 0.0007 inch, ancl is act:ivated durinc~ the die-stamping process by heating each oF the top dies 57 anci 57'. PrePerrecl tenlperatures u~

~L53~77 Ir. -were within the range o~ a~ JI~ 32~ ~o ~100 ~1e~Jrces 1:arer1heit. The bottonl or ~axe me111b~r ~3 ne~(1 r~ a~e~1. ln ~11e s~ampintJ
operation~ the ad1~esivt~ n~inq ~ co11~n~on sl1r~'ace 73 wil'1 be ;
substantially sgueeze~1 ou~ in1O recess 93, thus further assur;ng the described positive contact alon~1 tllis surPace~. It was ~ound,however, that even iF ac1hesive was l;o re1nain a-t this location, adequate electrical contact was still attained Subsequent to both oP the aforedeFinecl stamping procedures, the upper platen 59 is withdrawn (e.g., ~o the original e'levation shown in FIG. 3) and the remaining, non-stan1ped part oF alu1ninun1 strip 55 removed.
Removal may be acconlplished by hancl, as clescribed, or a suitable stripping tool (e.g., ro'1ler) '' As an optional step, it may be desirable to engage prede-termined (e.g., the uppermost) portions o~ ~he defined, stamped conductive member 61 with a hea~ed die 97 (shown in phantom in FIG. l0) in the event that the heat sensi1;ive a-1hes-ive 1Ocated in~ ediately under these portions was not fu'1'1y exposed to ~he eleva~ed temperatures of dies 57 and 57'. I~ is unders~oo(1 that this is bu-t an optional ' ¦
step and may only be deslr~ or pnrl:ions oF the circuit board assembly's circuitry which will be sub~jectec1 to ~reat stress (e.g., insertion forces encol1ntercd d1lri1lt1 positioning of the finished devices 20 within the socket oP a respective camera). Die 77 would be heated to a temperature substantia'1ly the sanle For that of dies 57, 57', should this step be usecl.
Thus there has been shown anti described a new and unique circuit board assembly for use in a pho~oFlash device. In addition, there has been shown and described a new and unique method for making said assembly. It is understood -From the Foregoing description that the invention as described herein possesses all the signifîcant advantages cited above.
While there have been sho~rl and described what are at present considered the preferred embotJinler1ts of tbe invention, i~ will be obvlous to those skilled in t1le art that various changes and modiFi cations may be made therei1l withol1t departing froln the scope oF the inventlon as defined by the appended clai1ns.

Claims

- 17 - WHAT IS CLAIMED IS:

1. A method of making a circuit board assembly for use in a photoflash device wherein said assembly includes a dielectric sub-strate, at least one switching element, and at least, one electrical conductive member, said method comprising:
positioning said switching element at a predetermined location on a first surface of said substrate;
positioning said dielectric substrate on a base member;
orienting a thin strip of electrically conductive material over said dielectric substrate and said switching element;
engaging said thin strip of conductive material with a die member so as to press preselected portions of said conductive material and said switching element into said dielectric substrate sufficiently to secure said preselected portions of said conductive material and said element thereto and electrically connect said preselected portions of said conductive material and said element, said preselected portions of said conductive material pressed within said dielectric substrate defining said conductive member, said pressing of said preselected portions of said conductive material and said switching element deforming or severing at least one part of said switching element; and removing the non-pressed remainder of said electrically conductive material from said substrate material.

2. The method according to Claim 1 further including deforming or severing parts of said conductive material located relative to said deformed or severed part of said switching element during pressing of said conductive material within said substrate to facilitate said removal of said non-pressed conductive material.

3. The method according to Claim 1 further including providing at least one aperture within said dielectric substrate prior to positioning said switching element thereon and thereafter positioning said switching element on said substrate so as to substantially bridge said aperture.

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4. The method according to Claim 3 further including applying an adhesive to the portions of said switching element which contact said first surface of said dielectric substrate prior to said positioning of said element on said substrate.

5. The method according to Claim 4 wherein said positioning of said switching element having said adhesive thereon to said substrate is accomplished by the application of pressure to said switching element.

6. The method according to Claim 1 further including applying an adhesive to said preselected portions of said conductive material to be pressed into said substrate member prior to said engaging of said conductive material with said die member.

7. The method according to Claim 6 further including heating said die member to a predetermined temperature prior to said engaging of said strip of conductive material and thereafter effecting said engagement with said heated die member.

8. The method according to Claim 1 further including engaging a predetermined portion of said conductive member with a die member subsequent to said removal of said non-pressed remainder of said conductive material.

9. The method according to Claim 8 further including heating said die member which engages said predetermined portions of said conductive member to a preestablished temperature prior to said engaging and thereafter effecting said engagement of said conductive member with said heated die member.

10. A circuit board assembly for use within a photoflash device, said circuit board assembly comprising:
a dielectric substrate;
a switching element positioned on said dielectric substrate and having a portion thereof pressed within a surface of said dielectric substrate;
an electrically conductive member pressed within said dielectric substrate and having at least a part thereof located atop said pressed portion of said switching element and in electrical contact therewith; and D-22,510 relief means located within said dielectric substrate or forming a part thereof for permitting at least one segment of said portion of said switching element being pressed within said substrate to be positioned therein and/or aligned therewith during said pressing so as to prevent severing of said segment, at least one part of said pressed portion of said switching element located adjacent said segment being deformed or severed.

11. The circuit board assembly according to Claim 10 wherein said relief means comprises at least one slot located within said surface of said dielectric substrate, at least a portion of said segment being positioned within said slot.

12. The circuit board assembly according to Claim 11 wherein said slot extends through the thickness of said dielectric substrate.

13. The circuit board assembly according to Claim 11 wherein said dielectric substrate further includes at least one aperture therein, said switching element bridging said aperture, said slot located immediately adjacent said aperture and having access thereto.

14. The circuit board assembly according to Claim 13 wherein said switching element includes a second portion thereof pressed within said dielectric substrate on an opposing side of said aperture from the first portion, said assembly further including a second electrically conductive member pressed within said dielectric sub-strate and having at least a part thereof located atop and in electrical contact with said pressed second portion of said switching element.

15. The circuit board assembly according to Claim 14 including a second relief means located within said dielectric substrate on an opposing side of said aperture from the first relief means for per-mitting at least one segment of said second portion of said switching element to be positioned therein and/or aligned therewith during pressing of said second portion so as to prevent severing of said segment of said second portion, at least part of said pressed second portion of said switching element located adjacent said segment of said second portion being deformed or severed.

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16. The circuit board assembly according to Claim 15 wherein said second relief means comprises at least one slot, at least a portion of said segment of said second portion being positioned within said slot.

17. The circuit board assembly according to Claim 16 wherein said slot extends through the thickness of said dielectric substrate.

18. The circuit board assembly according to Claim 10 wherein the material of said dielectric substrate is selected from the group consisting of medium impact polystyrene, high impact polystyrene, and phenolic.

19. The circuit board assembly according to Claim 18 wherein the material of said switching element is selected from the group consisting of mono- or biaxially oriented polyethylene, polypropylene, polystyrene, polyester, or nylon.

20. The circuit board assembly according to Claim 19 wherein the material of said conductive member is dead soft aluminum.