CA1207504A - Multi-gauge strip - Google Patents
Multi-gauge stripInfo
- Publication number
- CA1207504A CA1207504A CA000430242A CA430242A CA1207504A CA 1207504 A CA1207504 A CA 1207504A CA 000430242 A CA000430242 A CA 000430242A CA 430242 A CA430242 A CA 430242A CA 1207504 A CA1207504 A CA 1207504A
- Authority
- CA
- Canada
- Prior art keywords
- strip
- metal
- gauge
- thickness
- given length
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910052751 metal Inorganic materials 0.000 claims abstract description 84
- 239000002184 metal Substances 0.000 claims abstract description 84
- 238000000034 method Methods 0.000 claims abstract description 36
- 239000000463 material Substances 0.000 claims abstract description 34
- 238000005219 brazing Methods 0.000 claims abstract description 8
- 238000003466 welding Methods 0.000 claims abstract description 7
- 238000003754 machining Methods 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 4
- 229910000881 Cu alloy Inorganic materials 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 150000002739 metals Chemical class 0.000 description 7
- 239000002131 composite material Substances 0.000 description 5
- 238000005253 cladding Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910000521 B alloy Inorganic materials 0.000 description 1
- 241000905957 Channa melasoma Species 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 206010037660 Pyrexia Diseases 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 239000012459 cleaning agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 101150050071 proY gene Proteins 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Punching Or Piercing (AREA)
Abstract
ABSTRACT
An improved method and apparatus for the production of multi-gauge strip is disclosed wherein the multi-gauge strip 10 comprises a first strip of metal 12 having a first thickness 14 and extending longitudinally for a given length 16. A second strip of metal 18 has a second thickness 20, is narrower in width 22 than the first strip, and coextends longitudinally with the first strip of metal 12. The first and second strips of metal are intimately bonded in direct metal-to-metal contact without the use of a welding or brazing material. The multi-gauge strip has a first portion 24 extending the given length 16 with a third thickness 26 substantially equal to the sum of the first and second thicknesses 14 and 20 and a second portion 28 of substantially constant width 30 extending the given length 16 having a fourth thickness 32 substantially equal to the first thickness 14.
An improved method and apparatus for the production of multi-gauge strip is disclosed wherein the multi-gauge strip 10 comprises a first strip of metal 12 having a first thickness 14 and extending longitudinally for a given length 16. A second strip of metal 18 has a second thickness 20, is narrower in width 22 than the first strip, and coextends longitudinally with the first strip of metal 12. The first and second strips of metal are intimately bonded in direct metal-to-metal contact without the use of a welding or brazing material. The multi-gauge strip has a first portion 24 extending the given length 16 with a third thickness 26 substantially equal to the sum of the first and second thicknesses 14 and 20 and a second portion 28 of substantially constant width 30 extending the given length 16 having a fourth thickness 32 substantially equal to the first thickness 14.
Description
lZ075~4 A MULTI-GAUGE STRIP
Whlle the invention is su~ect to a wide range of applications, it is especially suited for use in the formation of multi-gauge strip suitable to produce articles- such as electrical l~adframes and will be particularly described in that connection.
A particular group of leadframes has the dual requirement of high strength and high thermal conduc-tivity~ Typically, the high thermal conductivity is required to dissipate hea~ ~rom an electronic device mounted or conn~cted to the leadframe. Failure to dissipate sufficient hezt may cause malfunction o~ the electronic devlce. In addition, high strength ls required so that the leadframe can be handled both manu~lly and automatically without distortion of the lead4rame.
In the past, different metals used t~ construct leadf~ames provided sufficient conductivity but compromlsed the deslred strength. In other cases, suf~icient strength was obtained, but the metal lacked the deslred conductivity. The problem is further complicated by the requirement that the leadframe3 have "thick and ~hin portions". A thick gauge provldes improved heat dissipation while a thin gauge, being more easlly'formed a~d soldered, provides connecting le~s. ~he present invention provides a multi-gauge strip which fulfills all the above-mentioned requirements by bonding two different strips of metal and machining them to different gauges.
, 30 A technique is known to pressure bond materials by - r~lling-them together in accordance with the principles set forth in U.S. Patent Nos. 3,381~364 and 3,397,045 both to Winter~ This technique intimately bonds at least two strips of metals together in metal-to-metal contact without the use of an intervening material such as a welding or brazing material.
.
Whlle the invention is su~ect to a wide range of applications, it is especially suited for use in the formation of multi-gauge strip suitable to produce articles- such as electrical l~adframes and will be particularly described in that connection.
A particular group of leadframes has the dual requirement of high strength and high thermal conduc-tivity~ Typically, the high thermal conductivity is required to dissipate hea~ ~rom an electronic device mounted or conn~cted to the leadframe. Failure to dissipate sufficient hezt may cause malfunction o~ the electronic devlce. In addition, high strength ls required so that the leadframe can be handled both manu~lly and automatically without distortion of the lead4rame.
In the past, different metals used t~ construct leadf~ames provided sufficient conductivity but compromlsed the deslred strength. In other cases, suf~icient strength was obtained, but the metal lacked the deslred conductivity. The problem is further complicated by the requirement that the leadframe3 have "thick and ~hin portions". A thick gauge provldes improved heat dissipation while a thin gauge, being more easlly'formed a~d soldered, provides connecting le~s. ~he present invention provides a multi-gauge strip which fulfills all the above-mentioned requirements by bonding two different strips of metal and machining them to different gauges.
, 30 A technique is known to pressure bond materials by - r~lling-them together in accordance with the principles set forth in U.S. Patent Nos. 3,381~364 and 3,397,045 both to Winter~ This technique intimately bonds at least two strips of metals together in metal-to-metal contact without the use of an intervening material such as a welding or brazing material.
.
-2- 11052-MB
Once the two sheets of metal have been ~oined together, it ~s necessary to continuously mill the resulting str~p to produce the desired variations in gauge. In IJ S. Patent No. 3,9~2,977 to Winter et al., - 5 a method o~ continuous sha~ing to produce a multiple gauge metal strlp is dlsclosed.
U.S. Patent No. 3,630,429 to Matsuda et al. di~-closes an apparatus to form composite metal wlre consi~ting o~ steel wi.re or the-llke cladded with a metal coverlng of aluminum or other metals. The apparatus-provides pressure bonding at a high temper-ature followed by shaving off any excess materlal created during the bonding process.
U.S~ Patent No. 3,465,419 to Keenan et ai di -closes, for example, a method o~ maklng decorativemetal stock wherein a plurality of metal layers are bonded together by known bonding techniques and recessing certain selective area portions of the laminated cladding by machinery~ drilling, or grinding.
This reference uses a bondlng technique di~feren~ from the prese~t invention an~ does-not provide ~or ~he longitudinal removal of metal from a strip as required by the present lnventlon.
- U.S. Patent No. 3,202,588 to Fromson discloses a method of making decoratlve metal sheet wherein two layers of material are metallur~ically bonded together, a protective coating applied to selected area3 of the exposed sur~ace o~ one of the layers and removal in the uncoated areas by grlnding, mllling, or etching. The present invention does not require a protecti~e coatlng because the shaving apparatus ls able to selectively remove the desired material.
U.S. Patent No. 3,826,627 to Pryor et al. discloses a decorative composite article wherein two materials may be bonded by ~y suitable technique such as pressure rolling as disclosed in U.S. Patent No. 3,3813364. Then, ~Z~7504
Once the two sheets of metal have been ~oined together, it ~s necessary to continuously mill the resulting str~p to produce the desired variations in gauge. In IJ S. Patent No. 3,9~2,977 to Winter et al., - 5 a method o~ continuous sha~ing to produce a multiple gauge metal strlp is dlsclosed.
U.S. Patent No. 3,630,429 to Matsuda et al. di~-closes an apparatus to form composite metal wlre consi~ting o~ steel wi.re or the-llke cladded with a metal coverlng of aluminum or other metals. The apparatus-provides pressure bonding at a high temper-ature followed by shaving off any excess materlal created during the bonding process.
U.S~ Patent No. 3,465,419 to Keenan et ai di -closes, for example, a method o~ maklng decorativemetal stock wherein a plurality of metal layers are bonded together by known bonding techniques and recessing certain selective area portions of the laminated cladding by machinery~ drilling, or grinding.
This reference uses a bondlng technique di~feren~ from the prese~t invention an~ does-not provide ~or ~he longitudinal removal of metal from a strip as required by the present lnventlon.
- U.S. Patent No. 3,202,588 to Fromson discloses a method of making decoratlve metal sheet wherein two layers of material are metallur~ically bonded together, a protective coating applied to selected area3 of the exposed sur~ace o~ one of the layers and removal in the uncoated areas by grlnding, mllling, or etching. The present invention does not require a protecti~e coatlng because the shaving apparatus ls able to selectively remove the desired material.
U.S. Patent No. 3,826,627 to Pryor et al. discloses a decorative composite article wherein two materials may be bonded by ~y suitable technique such as pressure rolling as disclosed in U.S. Patent No. 3,3813364. Then, ~Z~7504
-3- 11052-MB
- portions of one o~ the layers may be removed by a suitable method such as machining or chemical etching.
This reference does not disclose the concept of the present inventlon where the metal removal is accom-- 5 plished by a continuous shaving in the longitudinal direction of the-bonded strip material.
It i_ a problem under~ying the present invention to provlde an apparatus and method to form a multi-gauge strip useful ~or items having the requirements o~ high strength~ high thermal and electrical conductivity, and varlatlon in gauge.
It is an advantage of the present inventlon to provide an apparatus and method o~ forming multi-gauge ~trip which substantially obviates one or more of the limitations and disadvantages of the described prior arrangements.
It iQ a further advantage o~ the present invention to provide an apparatus and process for forming multl-gauge strip which can operate in a continuous manner.
It is a still further adva~tage of the present invention to provide an apparatus and process for forming multi-gauge strip which can be operated very qulckly, efficiently and, therefore, economically.
Accordingly, there has been provided zn improved method and apparatus for the production of multi-gauge strip wherein the multi-gauge strip comprises a first Qtrip o~ metal having a first thickness and extending longitudinally for a given length. The multi gauge strip also ha~ a second strip of metal having a seccnd thickne~s, being narrower ln width than the ~irst strip, and coextendlng longitudinally wlth the first strip of metal. The ~irst and second strips of metal are lntimately bonded in direct metal-to-metal contact without the use of a welding or brazing material. The multi~gauge strip has a first portion extending the given len~th with a third thickness substantially equal ~7S04
- portions of one o~ the layers may be removed by a suitable method such as machining or chemical etching.
This reference does not disclose the concept of the present inventlon where the metal removal is accom-- 5 plished by a continuous shaving in the longitudinal direction of the-bonded strip material.
It i_ a problem under~ying the present invention to provlde an apparatus and method to form a multi-gauge strip useful ~or items having the requirements o~ high strength~ high thermal and electrical conductivity, and varlatlon in gauge.
It is an advantage of the present inventlon to provide an apparatus and method o~ forming multi-gauge ~trip which substantially obviates one or more of the limitations and disadvantages of the described prior arrangements.
It iQ a further advantage o~ the present invention to provide an apparatus and process for forming multl-gauge strip which can operate in a continuous manner.
It is a still further adva~tage of the present invention to provide an apparatus and process for forming multi-gauge strip which can be operated very qulckly, efficiently and, therefore, economically.
Accordingly, there has been provided zn improved method and apparatus for the production of multi-gauge strip wherein the multi-gauge strip comprises a first Qtrip o~ metal having a first thickness and extending longitudinally for a given length. The multi gauge strip also ha~ a second strip of metal having a seccnd thickne~s, being narrower ln width than the ~irst strip, and coextendlng longitudinally wlth the first strip of metal. The ~irst and second strips of metal are lntimately bonded in direct metal-to-metal contact without the use of a welding or brazing material. The multi~gauge strip has a first portion extending the given len~th with a third thickness substantially equal ~7S04
-4- 11052-M~
to the sum of the first and 5econd thicknesses and a second portion of substantially constant width extending the given length having a fourth thickness substantially equal to the first thickness.
Also, the process of forming a multi-gauge strlp comprises the following steps: a first ~trip o~ metal extending longitudinally ~or a given length is provlded.
A second strlp of metal coextending longitudinally with the flrst strip i5 provided. The flrst and second strlps of metal are pressure bonded together in direct metal-to-metal contact without the use of a welding or brazing material. The resulting strip has a first layer ~ormed of the first strip o~ metal having a first thick-ness and a second layer formed of the second strip of mater~al having a second thickness. A longitudinal section of the second strip of metal is machined off of a given lengt~ to a depth so as to expos~ the first ~trip of' metal. A ftrst portlon of the multl-gauge strip, extending the given length~ has a third thickness substantially equal to the sum of the first and second thicknesses. A second portion of the multi-gauge strip, extending the given length, has a ~ourth thickness substantially equal to the ~irst thickness.
The invention and further developments of the - 25 invention are now elucidated by means of preferred embodiments shown in the drawings:
Figure 1 is a flow chart of the processes o~ the sub~ect in~ention;
F~gure ~ is a cross section o~ two bonded strips of material;
Figure 3 is a perspective view of a æhaved bonded strip before slitting;
Figure 4 is a perspective view of a multi-gauge strip;
Figure 5 is a top view o~ a stamped lead~rame; and Figure 6 is a view of a multl-gauge slrip having a slot in accordance with the present invention.
to the sum of the first and 5econd thicknesses and a second portion of substantially constant width extending the given length having a fourth thickness substantially equal to the first thickness.
Also, the process of forming a multi-gauge strlp comprises the following steps: a first ~trip o~ metal extending longitudinally ~or a given length is provlded.
A second strlp of metal coextending longitudinally with the flrst strip i5 provided. The flrst and second strlps of metal are pressure bonded together in direct metal-to-metal contact without the use of a welding or brazing material. The resulting strip has a first layer ~ormed of the first strip o~ metal having a first thick-ness and a second layer formed of the second strip of mater~al having a second thickness. A longitudinal section of the second strip of metal is machined off of a given lengt~ to a depth so as to expos~ the first ~trip of' metal. A ftrst portlon of the multl-gauge strip, extending the given length~ has a third thickness substantially equal to the sum of the first and second thicknesses. A second portion of the multi-gauge strip, extending the given length, has a ~ourth thickness substantially equal to the ~irst thickness.
The invention and further developments of the - 25 invention are now elucidated by means of preferred embodiments shown in the drawings:
Figure 1 is a flow chart of the processes o~ the sub~ect in~ention;
F~gure ~ is a cross section o~ two bonded strips of material;
Figure 3 is a perspective view of a æhaved bonded strip before slitting;
Figure 4 is a perspective view of a multi-gauge strip;
Figure 5 is a top view o~ a stamped lead~rame; and Figure 6 is a view of a multl-gauge slrip having a slot in accordance with the present invention.
-5- 11052-~B
In accordance with the present invention, a multi-gauge strip 10 is provided. The multi-gauge strip includes a first strlp of metal 12 having a first thickness 14 and extending longltudinally for a glven length 16. A se~ond strip of metal 18 having a second - thickness 209 iS narrower in width 22 than the sub-stantially constant width 23 of the first strip, and coextends longitudinally with the ~irst strlp o~ metal 12. The first and second strips of metals 12 and 18 are intimately bonded in direct metal-to-metal contact without the use of a welding-or brazing material whereby the multi-gauge strip 10 has a ~irst portion 24 extending the given length l6 havlng a third thlcXness 26 substantially equal to the sum of the first and second thicknesses 14 and 20, respectively. The multi-gauge strip also h s a second portion 28 of substantially constant wldth 30 extending the given length 16 and having a fourth thickness 32 substantially equal to the first thickness 14.
The present invention is concerned with producing a multi-gauge strip which is ideally suited to form a p~rticular family of lead~rames having the dual require-ment of high strength and high thermal conductivity.
Typically, when a given metal has su-~ficient conductivity, it la~ks the desired strength. Similarly, in a givPn metal having suf~lcient strength3 the metal lacks the desired conductivity. Further, the lead~rames have thick and thln gauges. The thick gauge is useful for con-ductlon, whlle the thin gauge, being ~ormable and solderable, is use~ul for comlecting legs. The present inverltion provides a proce~s and apparatus to quickly and efficiQntly form multi~gauge strip having both high conductivity and strength~
The ~irst strip 12 is formed of a material having high strength and sufficient thermal and electrical conductivity. This material is pre~erably a copper :~CD7504 - -6- 11052~B
alloy such as C510, C762, or C725. Since th~s material is used to form the connecting legs 34 of a leadframe requiring formability and solderability, the gauge is relativel~ thin. Due to the standards of the electronic industry, the legs usually have a thickness of either .015" or .018". Accordingl~, this is the pre~erred thickness of the material of the first strip 12. Of course, it is within the scope of the present in~ention to form the strip 12 of other alloys or metals and of other thicknesses.
The second strip 18 is formed of a high thermal and - electrical conductive material such as C1092, C1094, or CllO. Since the strip 18 is used as a heat sinkJ it is preferably thicker than the strip 12. Due to the standards of the industry with respect to the dimensions of leadframes, such as leadframe 36, the thickness 20 of the strip 18 is preferably .o50lt~ It is within the scope of the present invention to form the strip 18 of other materials such as metals or alloys which have the characteristic of high electrical and thermal conduc-tivit~.
In order to more fully understand the process by ~hich multi-gauge strip 10 is manufactured and formed into the leadfr~me 36 as shown in Figure 4, a detailed exempl~ry description follows. Referring to the flow diagram o~ Figure 1, block 40 represents a cleaning station w-here the metals ma~ be cleaned preparatory to joining. The cleaning process may be in accordance with that described in U.S. Patent No. 3,397,045 which includes a wet chemical cleaning treatment to degrease t~e metal surface. For example~ the metal may be immersed in a degreasing ~olvent such as trichlor-et~lene or ~n an inhib~ted solution o~ an alkaline cleaning agent such as a solution of tri~odium phosphate ~n ~ater at 160F. In addition, the surfaces to be joined may be mechanicall~ cleaned and roughened :1207504 -7~ 11052-MB
by mechanical wire brushing in accordance ~ith the lAtter reference if so desired. Although these processes may be desirable, the~ are not necessarily required and may be omitted if so desi~red.
The two strips of metal then mo~e to a bonding station represented by block 42. At this station, the strlps are intimately bonded in direct metal-to-metal contact without the use of a welding or brazing ~aterial. This bond~ng may be accomplished in 10 accordance with the posit bonding principles as set forth ln U.S. Patent No. 3~397,045-or 3,381,364. As described in those patents, the two strips of material are fed lnto a rolling mill at different speeds to form an-integrated composite strip of material where 15 the direct metal-to-metal contact is a substantially diffusionless interatomic bond. The integral composite sheet metal strip which is formed has good bond strength ~ith the core and cladding being b-onded L
together in di~rot metal-to-metal contact. The lnterface ~0 between the core and cladding is characterized b~ having greater contact area between the core and the cladding than between planar sheets and having a wave-like Interface with a plurality of peaks. The peaks are lrregular in distribution and have greater length than 25 height.
After the strip is bonded, the thickness 26 of the composite strip may be greater than desired. In this instance, the strip of material is preferably run through a rolling mill station represented by block 44 30 where it is reduced to the proper thicknes~ o~ approxi-matel~ .050". Of course, it may not be necessary to proY~de this station as the r~lling m~ll used for the bonding process ma~ ha~re already for~ed the strip to the desired th~ckness. ln either case, tne resulting 35 ~trip ~ill ha~e a ~irst la~er formed of the ~irst strip o~ metal and a second la~er formed o~ the second strip ~2~7504 -8- 11052-~B
of metal. The resulting strip will have a gl~en length 16, preferabl~ very long, and a general configuration as shown in Figure ?. Specifically, the first strip 12 will have a first thickness 14 which is preferably either .015" or .018" as described above. The second strip 18 will have a second thlckness 20 whlch is preferably .035". Also, the length of the bonded strip ~ill extend in a longitudinal direction indicatéd b~
arrow 45 for some given length 16. At th~s stage of the process, the strip may be approximatel~ 16~' wide.
The strip ma~ then be fed through a slitting station indicated b~ block 46 where the strip is slit into four longitudinal bonded strips having parallel outer edges. The slitting may be accomplished by any conventional device such as the slitters shown and described in U.S. Patent No. 3,706,246 to Keith.
Although this slitting operation is frequently required, it is within the scope of the present invention to forego this step in the event that the strip, which has been bonded and if necessary rerolled, is already the proper width.
The strip now enters a machining station indicated b~ block 48 where the machining is performed b~ draw sha~ing in accordance with the method and apparatus as taught in U.S. Patent No. 3,992,977. The method dlsclosed in that patent produces a multiple gauge metal strlp product of rectangular cross section possessing reg~ons of two or more Yarlable thicknesses proYiding a generally stepped surface configuration.
The maximl~m possible stock removal per pass in relation to the ~ield strength of the strip is determlned by ~easur~ng the amoun~ of the stoc~ remoYed up to the point where ~ielding of the strip occurs under tension.
The apparatus for shaving the strip is adjusted to re~o~e approximatel~ the maximum possible stock in a single shaYing pass ~ithout causing the metal strip to ~Z~7504 exceed its yield strength. The strip is dra~n under back tension through the apparatus and shaved to reduce by an amount confined to an area comprising from ~pproximately 5 to about 50% of the total surPace area.
The volume of the strip remoYed ranges from approxi-mately 10 to about 60~ as measured in relation to initial strip cross section area. The shavlng tool device described in the latter reference reduces the volume of the second strip 18 ln a ~anner as shown in the example of Figure 3. This sha~ing technlque has certain important ad~antages over conventional milling procedures in remov~ng ~aterial in a longitudin~l direction from the bonded strip. The adYantages ~nclude hIgher speeds of operation, easier scrap retr~e~al, and fewer passes in less time. The strip p~sses through the sha~ing apparatus one or more times as requlred until longitudinal sections of the second strip of metal 18 are removed for the given length 16 ~f the strip to a depth whereby the first strip of metal 12 is exposed. It is frequently necessary to run the strip through the shaving apparatus a number of times in order to remove the desired amount of material ~ithout exceeding the yield strength of the strip ~hereb~ it may rupture. This can be understood by referring to Figure 3 where two longitudinal sections ha~e been removed leaving three remaining longitudinal sections 50, 52 and 54 of the second strip of metal 18.
It is within the scope of the present invention to pro~lde any desired configuration of the strip, after it h~ left the machining or sha~lng station 48g as a matter of choice. For instance, there may be more or lese '~ =~
0~
.gr~oves cut 1n.tG the strlp at either less or greater thicknesses.
.The shaved strip may then be fed into a station 56 where it is slit in the manner described for ~tatIon 46.
In the example described herein, the strip as shown in -Figure 3 could be slit: into five ~epara~e strips of material; tw~ of these slits 57 and 58 would preferably be very close to the outer edges 59 and 60, respectively, of the strip in order to remove any excess material from the outer resulting multi-gauge strips. Two additional slits, at locations. designated as 62 and 64, would be centered between longitudinal sections 50, 52 and 54.
The final slit would be through the center o~ the -section 52 through the dotted line 66. The result of this slitting operation would be four, substantially identical, multl~auge strips with a configuration as shown in Figure 4. It should be noted, that although the slitting operation at station.56 may be independent from the shaving operation at station 48, the slitting apparatus may be incorporated directly into the line with the shaving apparatus whereby the strip is slit immediately after it has been s~aved down to the proper dimensions.
Finally, the strip may be coiled at station 68 into rolls~ of finished multi-gauge strip. Of course, it is not necessary that the strip be coiled~ but lt may be stored in any other desire.d manner.
Referring to Figure 4, there is illustrated a sectlon of the fini~hed multi-gauge strip in accordance with the example set ~orth.herein~ As mentioned herein above, the multi-gauge strip includes a first and second.portion 24 and 28, respectively.. The second portion 28 extends from khe ~irst portion to the longi-tudinal outer edge 72 of the first strip 12 of material.
~he longitudinal outer edge 74 of the first portion 24 formed by the second strip 18, is illustrated and ~07509~
~ 11052-MB
.
preferably extends at an approximate 90 angle to the top surface 76 of the first strip 12 in the second portion 28. However, it is within the scope of the invention to provide any preferred angle.
Once the multi-gauge strip is formed, it may be stamped out at a station 70 to form a leadframe uch as the type illustrated in-Figure 5. The stamping equip-ment may be of any conventional design. The leadframe is preferably used for mounting electrlc devices such as semi-conductors wherein the ~irst strip of metal 12 of the second portion 28 is formed into legs 34. These legs are ~oined to a dam bar 78 which is connected to the second portion 24 by a plurality of connectlon leads 8o. It can be appreciated that the second portion represented by 28 in Figure 4 includes the connecting legs 34, the dam bar 78, and the connection leads 80.
Accordingly, all of these have the same general thickness equal to the thickness 32 of the first strip 12. The second strip of metal 18 which partially forms the first portion 24 i~ adapted-to be a mountlng ~urface 82 for an - - electronic device (not shown). Since the second strip is an excellent conductor, it facilitates heat dissi-pation from the electronic device ~not shown). The leadframe- also includes cooling fins 84. The illu-strated leadframe is only exemplary and alternative configurations may be ~ust a~ easily produced.
Another embodiment of the present inventlon, as shown in Figure 6~ includes a longitudinal slot 90 in the first strip o~ metal 12 within the first portlon 24.
The number designations are the same as the ~irst embod~ment where the same element is represented. The longitudinal ~lot 90 extends the gi~en length 16 and has a minimum depth equal to the first thickness 32. The exposed inner surface of the second strip of material 18 has a length substantially equal to the slot 90 and is exposed through the slot. Of course, it is within the ~ZI)~504 -12- 11052-~B
scope o~ the present invent~on to select~ely remove metal at other propitious spots whereb~ electronic devices may be connected to both the surface 92 of the material 12 and to the second strip 18.
It is apparent that there has been proYided in accordance with this invention a multi-gauge strip and a method of producing the multi-gauge strip which fully satisfy the objects, means, and ad~antages set forth hereinbefore. While the invention has been described in combination with specific embodiments thereof, it is evident that man~ alternatiYes, modifications, and ~ariations will be apparent to those skilled in the art in light of the ~oregoing descrlption. Accordingl~, it is intended to embrace all such alternatives, modifi-cations, and variations as fall within the sp~rit andbroad scope of the appended claims.
In accordance with the present invention, a multi-gauge strip 10 is provided. The multi-gauge strip includes a first strlp of metal 12 having a first thickness 14 and extending longltudinally for a glven length 16. A se~ond strip of metal 18 having a second - thickness 209 iS narrower in width 22 than the sub-stantially constant width 23 of the first strip, and coextends longitudinally with the ~irst strlp o~ metal 12. The first and second strips of metals 12 and 18 are intimately bonded in direct metal-to-metal contact without the use of a welding-or brazing material whereby the multi-gauge strip 10 has a ~irst portion 24 extending the given length l6 havlng a third thlcXness 26 substantially equal to the sum of the first and second thicknesses 14 and 20, respectively. The multi-gauge strip also h s a second portion 28 of substantially constant wldth 30 extending the given length 16 and having a fourth thickness 32 substantially equal to the first thickness 14.
The present invention is concerned with producing a multi-gauge strip which is ideally suited to form a p~rticular family of lead~rames having the dual require-ment of high strength and high thermal conductivity.
Typically, when a given metal has su-~ficient conductivity, it la~ks the desired strength. Similarly, in a givPn metal having suf~lcient strength3 the metal lacks the desired conductivity. Further, the lead~rames have thick and thln gauges. The thick gauge is useful for con-ductlon, whlle the thin gauge, being ~ormable and solderable, is use~ul for comlecting legs. The present inverltion provides a proce~s and apparatus to quickly and efficiQntly form multi~gauge strip having both high conductivity and strength~
The ~irst strip 12 is formed of a material having high strength and sufficient thermal and electrical conductivity. This material is pre~erably a copper :~CD7504 - -6- 11052~B
alloy such as C510, C762, or C725. Since th~s material is used to form the connecting legs 34 of a leadframe requiring formability and solderability, the gauge is relativel~ thin. Due to the standards of the electronic industry, the legs usually have a thickness of either .015" or .018". Accordingl~, this is the pre~erred thickness of the material of the first strip 12. Of course, it is within the scope of the present in~ention to form the strip 12 of other alloys or metals and of other thicknesses.
The second strip 18 is formed of a high thermal and - electrical conductive material such as C1092, C1094, or CllO. Since the strip 18 is used as a heat sinkJ it is preferably thicker than the strip 12. Due to the standards of the industry with respect to the dimensions of leadframes, such as leadframe 36, the thickness 20 of the strip 18 is preferably .o50lt~ It is within the scope of the present invention to form the strip 18 of other materials such as metals or alloys which have the characteristic of high electrical and thermal conduc-tivit~.
In order to more fully understand the process by ~hich multi-gauge strip 10 is manufactured and formed into the leadfr~me 36 as shown in Figure 4, a detailed exempl~ry description follows. Referring to the flow diagram o~ Figure 1, block 40 represents a cleaning station w-here the metals ma~ be cleaned preparatory to joining. The cleaning process may be in accordance with that described in U.S. Patent No. 3,397,045 which includes a wet chemical cleaning treatment to degrease t~e metal surface. For example~ the metal may be immersed in a degreasing ~olvent such as trichlor-et~lene or ~n an inhib~ted solution o~ an alkaline cleaning agent such as a solution of tri~odium phosphate ~n ~ater at 160F. In addition, the surfaces to be joined may be mechanicall~ cleaned and roughened :1207504 -7~ 11052-MB
by mechanical wire brushing in accordance ~ith the lAtter reference if so desired. Although these processes may be desirable, the~ are not necessarily required and may be omitted if so desi~red.
The two strips of metal then mo~e to a bonding station represented by block 42. At this station, the strlps are intimately bonded in direct metal-to-metal contact without the use of a welding or brazing ~aterial. This bond~ng may be accomplished in 10 accordance with the posit bonding principles as set forth ln U.S. Patent No. 3~397,045-or 3,381,364. As described in those patents, the two strips of material are fed lnto a rolling mill at different speeds to form an-integrated composite strip of material where 15 the direct metal-to-metal contact is a substantially diffusionless interatomic bond. The integral composite sheet metal strip which is formed has good bond strength ~ith the core and cladding being b-onded L
together in di~rot metal-to-metal contact. The lnterface ~0 between the core and cladding is characterized b~ having greater contact area between the core and the cladding than between planar sheets and having a wave-like Interface with a plurality of peaks. The peaks are lrregular in distribution and have greater length than 25 height.
After the strip is bonded, the thickness 26 of the composite strip may be greater than desired. In this instance, the strip of material is preferably run through a rolling mill station represented by block 44 30 where it is reduced to the proper thicknes~ o~ approxi-matel~ .050". Of course, it may not be necessary to proY~de this station as the r~lling m~ll used for the bonding process ma~ ha~re already for~ed the strip to the desired th~ckness. ln either case, tne resulting 35 ~trip ~ill ha~e a ~irst la~er formed of the ~irst strip o~ metal and a second la~er formed o~ the second strip ~2~7504 -8- 11052-~B
of metal. The resulting strip will have a gl~en length 16, preferabl~ very long, and a general configuration as shown in Figure ?. Specifically, the first strip 12 will have a first thickness 14 which is preferably either .015" or .018" as described above. The second strip 18 will have a second thlckness 20 whlch is preferably .035". Also, the length of the bonded strip ~ill extend in a longitudinal direction indicatéd b~
arrow 45 for some given length 16. At th~s stage of the process, the strip may be approximatel~ 16~' wide.
The strip ma~ then be fed through a slitting station indicated b~ block 46 where the strip is slit into four longitudinal bonded strips having parallel outer edges. The slitting may be accomplished by any conventional device such as the slitters shown and described in U.S. Patent No. 3,706,246 to Keith.
Although this slitting operation is frequently required, it is within the scope of the present invention to forego this step in the event that the strip, which has been bonded and if necessary rerolled, is already the proper width.
The strip now enters a machining station indicated b~ block 48 where the machining is performed b~ draw sha~ing in accordance with the method and apparatus as taught in U.S. Patent No. 3,992,977. The method dlsclosed in that patent produces a multiple gauge metal strlp product of rectangular cross section possessing reg~ons of two or more Yarlable thicknesses proYiding a generally stepped surface configuration.
The maximl~m possible stock removal per pass in relation to the ~ield strength of the strip is determlned by ~easur~ng the amoun~ of the stoc~ remoYed up to the point where ~ielding of the strip occurs under tension.
The apparatus for shaving the strip is adjusted to re~o~e approximatel~ the maximum possible stock in a single shaYing pass ~ithout causing the metal strip to ~Z~7504 exceed its yield strength. The strip is dra~n under back tension through the apparatus and shaved to reduce by an amount confined to an area comprising from ~pproximately 5 to about 50% of the total surPace area.
The volume of the strip remoYed ranges from approxi-mately 10 to about 60~ as measured in relation to initial strip cross section area. The shavlng tool device described in the latter reference reduces the volume of the second strip 18 ln a ~anner as shown in the example of Figure 3. This sha~ing technlque has certain important ad~antages over conventional milling procedures in remov~ng ~aterial in a longitudin~l direction from the bonded strip. The adYantages ~nclude hIgher speeds of operation, easier scrap retr~e~al, and fewer passes in less time. The strip p~sses through the sha~ing apparatus one or more times as requlred until longitudinal sections of the second strip of metal 18 are removed for the given length 16 ~f the strip to a depth whereby the first strip of metal 12 is exposed. It is frequently necessary to run the strip through the shaving apparatus a number of times in order to remove the desired amount of material ~ithout exceeding the yield strength of the strip ~hereb~ it may rupture. This can be understood by referring to Figure 3 where two longitudinal sections ha~e been removed leaving three remaining longitudinal sections 50, 52 and 54 of the second strip of metal 18.
It is within the scope of the present invention to pro~lde any desired configuration of the strip, after it h~ left the machining or sha~lng station 48g as a matter of choice. For instance, there may be more or lese '~ =~
0~
.gr~oves cut 1n.tG the strlp at either less or greater thicknesses.
.The shaved strip may then be fed into a station 56 where it is slit in the manner described for ~tatIon 46.
In the example described herein, the strip as shown in -Figure 3 could be slit: into five ~epara~e strips of material; tw~ of these slits 57 and 58 would preferably be very close to the outer edges 59 and 60, respectively, of the strip in order to remove any excess material from the outer resulting multi-gauge strips. Two additional slits, at locations. designated as 62 and 64, would be centered between longitudinal sections 50, 52 and 54.
The final slit would be through the center o~ the -section 52 through the dotted line 66. The result of this slitting operation would be four, substantially identical, multl~auge strips with a configuration as shown in Figure 4. It should be noted, that although the slitting operation at station.56 may be independent from the shaving operation at station 48, the slitting apparatus may be incorporated directly into the line with the shaving apparatus whereby the strip is slit immediately after it has been s~aved down to the proper dimensions.
Finally, the strip may be coiled at station 68 into rolls~ of finished multi-gauge strip. Of course, it is not necessary that the strip be coiled~ but lt may be stored in any other desire.d manner.
Referring to Figure 4, there is illustrated a sectlon of the fini~hed multi-gauge strip in accordance with the example set ~orth.herein~ As mentioned herein above, the multi-gauge strip includes a first and second.portion 24 and 28, respectively.. The second portion 28 extends from khe ~irst portion to the longi-tudinal outer edge 72 of the first strip 12 of material.
~he longitudinal outer edge 74 of the first portion 24 formed by the second strip 18, is illustrated and ~07509~
~ 11052-MB
.
preferably extends at an approximate 90 angle to the top surface 76 of the first strip 12 in the second portion 28. However, it is within the scope of the invention to provide any preferred angle.
Once the multi-gauge strip is formed, it may be stamped out at a station 70 to form a leadframe uch as the type illustrated in-Figure 5. The stamping equip-ment may be of any conventional design. The leadframe is preferably used for mounting electrlc devices such as semi-conductors wherein the ~irst strip of metal 12 of the second portion 28 is formed into legs 34. These legs are ~oined to a dam bar 78 which is connected to the second portion 24 by a plurality of connectlon leads 8o. It can be appreciated that the second portion represented by 28 in Figure 4 includes the connecting legs 34, the dam bar 78, and the connection leads 80.
Accordingly, all of these have the same general thickness equal to the thickness 32 of the first strip 12. The second strip of metal 18 which partially forms the first portion 24 i~ adapted-to be a mountlng ~urface 82 for an - - electronic device (not shown). Since the second strip is an excellent conductor, it facilitates heat dissi-pation from the electronic device ~not shown). The leadframe- also includes cooling fins 84. The illu-strated leadframe is only exemplary and alternative configurations may be ~ust a~ easily produced.
Another embodiment of the present inventlon, as shown in Figure 6~ includes a longitudinal slot 90 in the first strip o~ metal 12 within the first portlon 24.
The number designations are the same as the ~irst embod~ment where the same element is represented. The longitudinal ~lot 90 extends the gi~en length 16 and has a minimum depth equal to the first thickness 32. The exposed inner surface of the second strip of material 18 has a length substantially equal to the slot 90 and is exposed through the slot. Of course, it is within the ~ZI)~504 -12- 11052-~B
scope o~ the present invent~on to select~ely remove metal at other propitious spots whereb~ electronic devices may be connected to both the surface 92 of the material 12 and to the second strip 18.
It is apparent that there has been proYided in accordance with this invention a multi-gauge strip and a method of producing the multi-gauge strip which fully satisfy the objects, means, and ad~antages set forth hereinbefore. While the invention has been described in combination with specific embodiments thereof, it is evident that man~ alternatiYes, modifications, and ~ariations will be apparent to those skilled in the art in light of the ~oregoing descrlption. Accordingl~, it is intended to embrace all such alternatives, modifi-cations, and variations as fall within the sp~rit andbroad scope of the appended claims.
Claims (14)
1. A multi-gauge strip useful in making leadframes for electronic devices, comprising:
a first strip of high strength metal suitable for forming electrical connectors having a first thick-ness and extending longitudinally for a given length;
a second strip of high condutivity metal, with a lower strength and higher conductivity than said first metal, having a second thickness greater than said first thickness, said second strip further being narrower in width than said first strip, and coextending longitudinally with said first strip of metal;
said first and second strips of metal being metallurgically bonded without the use of a welding or brazing material to form said multi-gauge strip;
the multi-gauge strip further having a first portion extending the given length, adapted to dissi-pate heat from an electronic device mounted thereto, said first portion formed from said first and second strips so as to have a third thickness substantially equal to the sum of the first and second thicknesses;
said multi-gauge strip also having a second portion adapted to form said electrical connectors, said second portion formed from said second strip so as to substantially extend the given length and have a fourth thickness substantially equal to the first thickness.
a first strip of high strength metal suitable for forming electrical connectors having a first thick-ness and extending longitudinally for a given length;
a second strip of high condutivity metal, with a lower strength and higher conductivity than said first metal, having a second thickness greater than said first thickness, said second strip further being narrower in width than said first strip, and coextending longitudinally with said first strip of metal;
said first and second strips of metal being metallurgically bonded without the use of a welding or brazing material to form said multi-gauge strip;
the multi-gauge strip further having a first portion extending the given length, adapted to dissi-pate heat from an electronic device mounted thereto, said first portion formed from said first and second strips so as to have a third thickness substantially equal to the sum of the first and second thicknesses;
said multi-gauge strip also having a second portion adapted to form said electrical connectors, said second portion formed from said second strip so as to substantially extend the given length and have a fourth thickness substantially equal to the first thickness.
2. A multi-gauge strip as in claim 1 wherein said first and second metal strips are selected from the group of copper alloys.
3. A multi-gauge strip as in claim 1 wherein the second portion extends from the first portion to a longitudinal outer edge of the first strip of material.
4. A multi-gauge strip as in claim 1 wherein a longitudinal slot is located in said first metal strip within the first portion, said longitudinal slot extends said given length and has a minimum depth equal to said first thickness, whereby the inner surface of said second strip of material having length equal to said slot is exposed through the slot.
5. A process of forming a multi-gauge strip comprising the steps of:
providing a first strip of metal extending longitudinally for a given length, providing a second strip of metal coextending longitudinally with said first strip, pressure bonding said first and second strips of metal together in direct metal-to-metal contact without the use of a welding or brazing material whereby the bonded strip has a first layer formed of said first strip of metal having a first thickness and a second layer formed of said second strip of metal having a second thickness, and machining off a longitudinal section of said second strip of metal for said given length to a depth to expose said first strip of metal of said given length prior to any other metal forming of said bonded strip, whereby a first portion of said multi-gauge strip, extending the given length, has a third thick-ness substantially equal to the first and second thicknesses and a second portion of said multi-gauge strip, extending the given length, has a fourth thick-ness substantially equal to the first thickness.
providing a first strip of metal extending longitudinally for a given length, providing a second strip of metal coextending longitudinally with said first strip, pressure bonding said first and second strips of metal together in direct metal-to-metal contact without the use of a welding or brazing material whereby the bonded strip has a first layer formed of said first strip of metal having a first thickness and a second layer formed of said second strip of metal having a second thickness, and machining off a longitudinal section of said second strip of metal for said given length to a depth to expose said first strip of metal of said given length prior to any other metal forming of said bonded strip, whereby a first portion of said multi-gauge strip, extending the given length, has a third thick-ness substantially equal to the first and second thicknesses and a second portion of said multi-gauge strip, extending the given length, has a fourth thick-ness substantially equal to the first thickness.
6. The process of claim 5 including the step of selecting said first strip of metal from a material of a higher strength than the second metal strip so that said multi-gauge strip is adaptable to function as electrical connectors.
7. The process of claim 6 including the step of selecting said second strip of metal from a material having a conductivity higher than the conductivity of said first strip of metal so that said multi-gauge strip is adaptable for dissipating heat from electrical devices adjoined to said multi-gauge strip.
8. The process of claim 5 wherein said step of machining off includes the step of draw shaving said bonded strip through a shaving apparatus to reduce the volume of said second strip.
9. The process of claim 8 wherein said step of pressure bonding includes the step of feeding the first and second strips of metal into a rolling mill at different speeds to form said bonded strip.
10. The process of claim 9 including the step of longitudinally slitting the bonded strip to form at least two strips with substantially parallel outer edges.
11. The process of claim 9 including the step of cleaning the surfaces of said first and second strips of metal, prior to bonding, to ensure good contact between the contacting surfaces of the strips of metal.
12. The process of claim 11 including the step of stamping out said multi-gauge strip to form a lead-frame adapted for mounting electronic devices.
13. The process of claim 5 including the step of machining a longitudinal slot in said first strip of metal within the first portion, extending said given length and having a minimum depth equal to said first thickness whereby the inner surface of said second strip of material, having a length substantially equal to the length of said slot, is exposed through the slot.
14. The process of claim 13 wherein said step of machining a longitudinal slot includes draw shaving said bonded strip through a shaving apparatus to reduce the volume of said first strip of material.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA000430242A CA1207504A (en) | 1983-06-13 | 1983-06-13 | Multi-gauge strip |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CA000430242A CA1207504A (en) | 1983-06-13 | 1983-06-13 | Multi-gauge strip |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1207504A true CA1207504A (en) | 1986-07-15 |
Family
ID=4125464
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000430242A Expired CA1207504A (en) | 1983-06-13 | 1983-06-13 | Multi-gauge strip |
Country Status (1)
Country | Link |
---|---|
CA (1) | CA1207504A (en) |
-
1983
- 1983-06-13 CA CA000430242A patent/CA1207504A/en not_active Expired
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