CA1139013A - Structured copper strain buffer - Google Patents
Structured copper strain bufferInfo
- Publication number
- CA1139013A CA1139013A CA000321821A CA321821A CA1139013A CA 1139013 A CA1139013 A CA 1139013A CA 000321821 A CA000321821 A CA 000321821A CA 321821 A CA321821 A CA 321821A CA 1139013 A CA1139013 A CA 1139013A
- Authority
- CA
- Canada
- Prior art keywords
- copper
- strands
- strain buffer
- bundle
- metal foil
- 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
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/01—Chemical elements
- H01L2924/01029—Copper [Cu]
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- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A structured copper strain buffer, which is thermally and electrically conductive is provided for use with semiconductor electronic devices. A thermo-compression diffusion bond is used to attach a metallic foil two a structured copper disk to form the strain buffer. The individual strands of copper within the strain buffer are capable of independent movement.
The structured copper strain buffer provides a means of attachment to a semiconductor device without causing a stress to be generated at the attached surface of the device as the device expands and contacts with temperature changes.
A structured copper strain buffer, which is thermally and electrically conductive is provided for use with semiconductor electronic devices. A thermo-compression diffusion bond is used to attach a metallic foil two a structured copper disk to form the strain buffer. The individual strands of copper within the strain buffer are capable of independent movement.
The structured copper strain buffer provides a means of attachment to a semiconductor device without causing a stress to be generated at the attached surface of the device as the device expands and contacts with temperature changes.
Description
STRIJCTURED COPPER STRAIN BUFFER
.
Back~round of the _ vention This invention relates ~o strain buffers, and more particularly to structured copper s~rain buffers for achieving electrical and thermal co~nectivn to a semiconductor device wi~hou~ generating astress at the place of connection to ~he device.
Structured copper,as employed herein, is comprised of a bundle of straight filamentary s~rands of copper parallel to each other and closely packed together. The strands are of approximately equal length and generally form disks rangîng from .l cm. to 1 cm. in thickness.
Structured copper disks are by nature very fragile The s~rands tend to separate and cause the disk to all apart. Thus, a retaining ring around the structured copper is used to temporarily hold it together while it is being handled. In the prior art, structured copper was comprised of copper cable segments in order to increase its structural integrity. The strands of such struc~ured copper disks had less tendency to separate and all apart because they were twisted together; however, the disks had the corresponding disadvantage that the individual strands of copper were not free to move independently. Thus, the stress relieving capabilities of such s~ructured copper were Limited.
In the prior art, the ends of the strands of st~uctured copper disks were soldered together on one or both sides o the disk to increase its structural integrity Howeve~, s~ch layer of solder de~rades the thermal conduction proper~es o ~he structured copper. The stress relievin~ prope~ties Or ~he struc~ured copper disk are also impaired if solder flows into any of th~ spaces between the closely pack~d s trands o f copper .
The presen~ invention concerns a struc~ured copper s~rain buffer which exhibits structural integrity while still maintaining ~ubstantial stress relieving capability and high thermal conductivity. It should be apparent to those skilled in the art ~ha~ im2roved electronic performa~ce is to be gained from a semiconductor device attached to such structured copper strain buffer by virtue of the increased heat removal capacity and surface stress relief provided by the strain buffer.
It is an object of this invention to provide a structured copper strain buffer employi~g straight strands of copper and exhibiting substantial structural integrity~
It is ano~her object of this inven~ion to provide a structured copp~r strain buffer with substantial stress relieving capability and high thermal conductivity.
These and other objects of the invention will becorne apparent to those skilled in the ark upon consideration of the following description of the invention.
Brief Summary of the Invention The present invention is directed to increasing th~
struc~ural integrity of structured copper strain buffers, that ~5 is, decreasin~ the susceptibility of the individual strands of structured copper to become separated and fall apart. In accordance with the invention, a metallic foil is attached to one side of a piece of structured copper by means of a thermo-comp~ession diffusion bond between .he two mater al~.
A method and apparatus for forming such thermo-compression - ~D-10746 t3~
dif~usion bond are fully described and claimed in United States patent 4,252,263 issued February 24, 1981 -to Houston et al and assigned to the present assignee.
~riefly, in accordance with one preferred embodiment o~ the invention, a strain buffer comprises a metallic foil of gold or copper abuttingly joined to one side of a bundle of straight copper strands. The metallic foil and the bundle of copper strands are joined by a thermo-compression diffusion bond. The individual strands of structured copper in this structure are free to move, that is, free to expand and to contract with changes in temperature. The disclosed strain buffer has a substantial amount of structural integrity, so that it will not fall apart upon being subjected to normal handling.
In another embodiment of the invention, a strain buffer comprises a separate metallic foil abu-ttingly joined to each side of a structured copper disk.
When attached to the surface oE a semiconductor device, the disclosed structured copper strain buffer provides a good electrical and thermal connection to the device without causing a stress to be created at the attached surface of the device as it expands and contracts with temperature. The strain buffer has excellent thermal conduction properties such that it effic-iently draws heat away from the attached semiconductor device.
Description of the Drawings Figure 1 is a side view of one embodiment of a ` structured copper strain buffer constructed in accordance with the present invention.
Figure 2 is a side view of a structured copper disk ~ - 3 -~ 3~ ~ 3 RD-10746 encircled by a retaining ring.
Figure 3 is a top view ~f the structured copper disk o~ Figure 2.
Figure 4 is a side view of a thermo-compression diffusion bondi~g press which may be employed in fabricating the strain buffer of the present invention.
Figure 5 i~ a side view of a s~ructured copper disk with retaining ring, and metal foil attached to one side of the disk.
Figure 6 is a side view of a structured copper disk with retaining ring, and separate metallic foils attached ~o each side of the disk.
Figure 7 is a side view of another embodiment of the structured copper strain buffer of the invention, wherein a separate metallic foil is attached to each side thereof.
Figure 8 is a side view of the structuret copper strain buffer of Figure l attached to a semiconductor device.
Description of the Preferred Embodiment Figure 1 illustrates one embodiment of the structured copper strain buffer of the invention, wherein strain buffer 10 is comprised of a metallic foil 12 abuttingly joined to a structured copper disk 14. Copper, gold and o~her metals of appropriate characteristics may be used for metallic foil 12. Structured copper disk 14 is comprised of a bundle of straight filamentary strands of copper of approximately equal length. The strands of copper are closely packed together. Typically, the strands of copp~r are each 10 mils in diameter, although somewhat smaller or larger diameters are usable, Generally, best results are achieved when an aspeet ratio (length to di.ameter of the ~ RD-10746 copper strands) of 10 to 1 i5 used. Structured copper disks having a thickness ranging from .1 cm. to 1 cm. are typically used for disk 14 although disks of greater or smaller thickness may be used. Best strain relieving results are achieved when the copper strands are used with their natural oxide coating thereon. If cleaned strands of copper are used to form strain buffer 10, the strands tend to stick together and limit the buffer's stress relieving capability.
Thus, the strands should be coated with a non-sticking substance such as copper oxide.
A structured copper disk, being formed of independent, freely moving strands of copper is at that time, an inherently a fragile object. ~hus, as shown in Figure 2, structured copper disk 16 is provided with a retaining ring 18 to hold the strands of copper together during handling and processing. Figure 3 is a top view of structured copper disk 16 surrounded by retaining ring 18.
Referring again to structured copper strain buf~er 10 of Figure 1, metallic foil 12 and structured copper disk 14 are abuttingly joined together by thermo-compression diffusion bonding. Such bonding is readily performed in the diffusion bonding press described in the aforementioned United States patent 4,252,263. A diffusion bonding press 20 of this type is illustrated in Figure 4. Upper metallic plate 22 2S is oriented parallel to lower metallic plate 24 with a space therebetween. Metallic pressing block 26 is positioned at the center of the side of upper plate 22 facing lower plate 24. Metallic bolts 28 and 30 pass through respective holes in upper plate 22 and lower plate 24 and are threaded into lower plate 24 to connect the ~wo plates together as illustrated in Figure 4.
.
~ 3 ~ RD-10~46 Metallic bolts 28 and 30 are comprised of a s~eel other than stainless steel, while upper pla~:e 22, lower plate 24 and metallic pressin~ block 26 are comprised of stainless steel. To achieve the thermovco~pression diffusion bond between ~tructured copper disk 14 and metallic foil 12 to form strain buffer 10, it is necessary to position metallic foil 12 parallel ~o, and in con~act with, structured copper disk 16 as shown in Figure 5. This foil-disk assembly lg is ~hen placed between metallic pressing block ~6 and lower plate 24 of press 20 as shown in Figure 4. A conventional press is used ~o squeeze upper plate 22 and lower plate 24 together and while such pressure is applied ~o these plates, bolts 28 and 30 are tightened.
The thermo-com~ression diffusion bond between structured copper disk 16 and metal foil 12 is actually formed when press 20 containing foil-disk asse~bly 19 is placed in an inert atmosphere and heated to approximately 350C for approximately 15 minutes to 5 hours. When press 20 is so heated, upper plate 22, lower plate 24 and me~allic pressing block 26 expand to a greater total extent than do metallic bolts 28 and 30. Thus, a force is exerted between pressing block 26 and lower plate 24 resulting in the squeezing of structured copper disk 16 and metallic foil 12 togethe~ and the bonding of each to the other. Foil-disk assembly 19 is then removed from diffusion bonding press 20. Retaining ring 18 and any loose strands of structured copper outside the area of the diffusion bond are also removed from foil-disk assembly 19. The remaining structure thus formed constitutes structured copper strain buffer 10.
A strain buffer o additional structural integr~y ~3~ RD-10746 may be formed bY thermo-comDression diffusion bondin~ a metallic foil to both sides of a structured co~Per disk. Such a foil-disk assembly 32 is ormed ~y positioning metallic oils 12 and 34 on the opposite sides of structured copper disk 16 as shown in Figure 6. Foil-disk assembly 32 is then placed in di~fusion bonding press 20 and processed as described abo~e.
A structured copper strain buffer 36 with metallic foil on each side thereof, as show~l in Figure 7, is thus produced.
Figure 8 illustrates struc~ured copper strain bu~fer 10 attachea to a ~emiconductor device 40, For convenience, semiconductor device 40 is represented as a diode having a first electrode region 42 and a second electrode region 44, with electrode region 44 at~ached to buffer 10. However, other semiconductor devices such ~s transistors and thyristors may also be attached to structured copper strain buffers.
A tungsten bak-up plate 50 is alloyed to ti.e. at~ached to) the surface of first electrode region 42 as shown in Figure 8. Semiconductor device 40 comprised of silicon, for example, is a fragile structure. T~ngsten back-up plate 50 provides semiconductor device 40 with structural strength. The thermal coefficient of expansion of tungsten is approxima~ely the same as that of silicon such that the alloy formed a~ the interface of plate 50 and device 40 does not crack as device 40 expands and contracts with changes in tPmperature.
To attach a semiconductor device 40 to structured copper strain buffer 10~ the surface of electrode region 44 is first coated with a metallization comprised of a first metallic layer 46 and a second metallic layer 4~. First me~allic layer 46 may be comprised of titanium and is deposited directly on the surface of electrode region 44.
Second metallic l~yer 4~ may be comprised o coppe~ or gold.
~ RD-1074~
Strain buffer 10 is then brought into abutting contact with the metallized surface o electrode 44 to form device-buffer -assembly 38. A thermo-compression diffusion bond is formed .- between the metallized surface of electrode h4 and strain buffer.10 by positioning the device-buffer assem~ly 38 between plate 24 and pressing block 26 of diffusion bonding press 20 shown in Figure 5 ~nd performing the previously described procedure for forming a diffu~ion bond. In one embodiment of the invention, a metallization with a first metallic layer 46 with a thickness of a~out 200 A of titanium and a second metallic layer 48 with a thickness of about 10,000 R
of gold is applied on the surface of electrode region 44 to which strain buffer lO is bonded. The bond is made at a temperature of approximately 325C. in a nitrogen atmosphere.
Another embodiment of the invention is achieved when the metallization is comprised of a first layer 46 of titanium, a second layer 48 of silver and a third layer o~ gold.
Alternatively, strain buffer 10 need not be diffusion bonded to semiconductor device 40. The strain buffer lO is placed in abutment with electrode 44 of semiconductor device 40 such that strain buffer lO and device 40 bear against each other and form another embodiment of the invention.
As the operating temperature of semiconductor device 40 increases, the individual strands of structured .copper strain buffer lO are free to move in the plane of the structured copper disk as the device expands. Thus, the buffer provides a means of attachment to an electrode region which does not eause a thermally-induced stress to be present at the place of attachment. Strain buffer lO provides a good electrical connection to electrode re~ion 44 ~7hile '.~ 390~ 7~6 also providing a good thermal path away fro~ the device for heat generated at electrode region 44.
The fc>regoing describes a structured copper strain buffer employirlg straight strands of copper arranged in ~he form of a disk and attached to a metallic foil by thermo-compression diffusion bonding. l'he buffer exhibîts substantial structural integrity while still allowing individual movement o~ the separate strands of ~tructured copper within the plane of the disk ~uch that the buffer provides substantial stress relieving capability together with high thermal conductivity.
While only certain preferred features o~ the .invention have been shown by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to co~er all such modifications and changes as fall within the true spirit of the invention.
.
Back~round of the _ vention This invention relates ~o strain buffers, and more particularly to structured copper s~rain buffers for achieving electrical and thermal co~nectivn to a semiconductor device wi~hou~ generating astress at the place of connection to ~he device.
Structured copper,as employed herein, is comprised of a bundle of straight filamentary s~rands of copper parallel to each other and closely packed together. The strands are of approximately equal length and generally form disks rangîng from .l cm. to 1 cm. in thickness.
Structured copper disks are by nature very fragile The s~rands tend to separate and cause the disk to all apart. Thus, a retaining ring around the structured copper is used to temporarily hold it together while it is being handled. In the prior art, structured copper was comprised of copper cable segments in order to increase its structural integrity. The strands of such struc~ured copper disks had less tendency to separate and all apart because they were twisted together; however, the disks had the corresponding disadvantage that the individual strands of copper were not free to move independently. Thus, the stress relieving capabilities of such s~ructured copper were Limited.
In the prior art, the ends of the strands of st~uctured copper disks were soldered together on one or both sides o the disk to increase its structural integrity Howeve~, s~ch layer of solder de~rades the thermal conduction proper~es o ~he structured copper. The stress relievin~ prope~ties Or ~he struc~ured copper disk are also impaired if solder flows into any of th~ spaces between the closely pack~d s trands o f copper .
The presen~ invention concerns a struc~ured copper s~rain buffer which exhibits structural integrity while still maintaining ~ubstantial stress relieving capability and high thermal conductivity. It should be apparent to those skilled in the art ~ha~ im2roved electronic performa~ce is to be gained from a semiconductor device attached to such structured copper strain buffer by virtue of the increased heat removal capacity and surface stress relief provided by the strain buffer.
It is an object of this invention to provide a structured copper strain buffer employi~g straight strands of copper and exhibiting substantial structural integrity~
It is ano~her object of this inven~ion to provide a structured copp~r strain buffer with substantial stress relieving capability and high thermal conductivity.
These and other objects of the invention will becorne apparent to those skilled in the ark upon consideration of the following description of the invention.
Brief Summary of the Invention The present invention is directed to increasing th~
struc~ural integrity of structured copper strain buffers, that ~5 is, decreasin~ the susceptibility of the individual strands of structured copper to become separated and fall apart. In accordance with the invention, a metallic foil is attached to one side of a piece of structured copper by means of a thermo-comp~ession diffusion bond between .he two mater al~.
A method and apparatus for forming such thermo-compression - ~D-10746 t3~
dif~usion bond are fully described and claimed in United States patent 4,252,263 issued February 24, 1981 -to Houston et al and assigned to the present assignee.
~riefly, in accordance with one preferred embodiment o~ the invention, a strain buffer comprises a metallic foil of gold or copper abuttingly joined to one side of a bundle of straight copper strands. The metallic foil and the bundle of copper strands are joined by a thermo-compression diffusion bond. The individual strands of structured copper in this structure are free to move, that is, free to expand and to contract with changes in temperature. The disclosed strain buffer has a substantial amount of structural integrity, so that it will not fall apart upon being subjected to normal handling.
In another embodiment of the invention, a strain buffer comprises a separate metallic foil abu-ttingly joined to each side of a structured copper disk.
When attached to the surface oE a semiconductor device, the disclosed structured copper strain buffer provides a good electrical and thermal connection to the device without causing a stress to be created at the attached surface of the device as it expands and contracts with temperature. The strain buffer has excellent thermal conduction properties such that it effic-iently draws heat away from the attached semiconductor device.
Description of the Drawings Figure 1 is a side view of one embodiment of a ` structured copper strain buffer constructed in accordance with the present invention.
Figure 2 is a side view of a structured copper disk ~ - 3 -~ 3~ ~ 3 RD-10746 encircled by a retaining ring.
Figure 3 is a top view ~f the structured copper disk o~ Figure 2.
Figure 4 is a side view of a thermo-compression diffusion bondi~g press which may be employed in fabricating the strain buffer of the present invention.
Figure 5 i~ a side view of a s~ructured copper disk with retaining ring, and metal foil attached to one side of the disk.
Figure 6 is a side view of a structured copper disk with retaining ring, and separate metallic foils attached ~o each side of the disk.
Figure 7 is a side view of another embodiment of the structured copper strain buffer of the invention, wherein a separate metallic foil is attached to each side thereof.
Figure 8 is a side view of the structuret copper strain buffer of Figure l attached to a semiconductor device.
Description of the Preferred Embodiment Figure 1 illustrates one embodiment of the structured copper strain buffer of the invention, wherein strain buffer 10 is comprised of a metallic foil 12 abuttingly joined to a structured copper disk 14. Copper, gold and o~her metals of appropriate characteristics may be used for metallic foil 12. Structured copper disk 14 is comprised of a bundle of straight filamentary strands of copper of approximately equal length. The strands of copper are closely packed together. Typically, the strands of copp~r are each 10 mils in diameter, although somewhat smaller or larger diameters are usable, Generally, best results are achieved when an aspeet ratio (length to di.ameter of the ~ RD-10746 copper strands) of 10 to 1 i5 used. Structured copper disks having a thickness ranging from .1 cm. to 1 cm. are typically used for disk 14 although disks of greater or smaller thickness may be used. Best strain relieving results are achieved when the copper strands are used with their natural oxide coating thereon. If cleaned strands of copper are used to form strain buffer 10, the strands tend to stick together and limit the buffer's stress relieving capability.
Thus, the strands should be coated with a non-sticking substance such as copper oxide.
A structured copper disk, being formed of independent, freely moving strands of copper is at that time, an inherently a fragile object. ~hus, as shown in Figure 2, structured copper disk 16 is provided with a retaining ring 18 to hold the strands of copper together during handling and processing. Figure 3 is a top view of structured copper disk 16 surrounded by retaining ring 18.
Referring again to structured copper strain buf~er 10 of Figure 1, metallic foil 12 and structured copper disk 14 are abuttingly joined together by thermo-compression diffusion bonding. Such bonding is readily performed in the diffusion bonding press described in the aforementioned United States patent 4,252,263. A diffusion bonding press 20 of this type is illustrated in Figure 4. Upper metallic plate 22 2S is oriented parallel to lower metallic plate 24 with a space therebetween. Metallic pressing block 26 is positioned at the center of the side of upper plate 22 facing lower plate 24. Metallic bolts 28 and 30 pass through respective holes in upper plate 22 and lower plate 24 and are threaded into lower plate 24 to connect the ~wo plates together as illustrated in Figure 4.
.
~ 3 ~ RD-10~46 Metallic bolts 28 and 30 are comprised of a s~eel other than stainless steel, while upper pla~:e 22, lower plate 24 and metallic pressin~ block 26 are comprised of stainless steel. To achieve the thermovco~pression diffusion bond between ~tructured copper disk 14 and metallic foil 12 to form strain buffer 10, it is necessary to position metallic foil 12 parallel ~o, and in con~act with, structured copper disk 16 as shown in Figure 5. This foil-disk assembly lg is ~hen placed between metallic pressing block ~6 and lower plate 24 of press 20 as shown in Figure 4. A conventional press is used ~o squeeze upper plate 22 and lower plate 24 together and while such pressure is applied ~o these plates, bolts 28 and 30 are tightened.
The thermo-com~ression diffusion bond between structured copper disk 16 and metal foil 12 is actually formed when press 20 containing foil-disk asse~bly 19 is placed in an inert atmosphere and heated to approximately 350C for approximately 15 minutes to 5 hours. When press 20 is so heated, upper plate 22, lower plate 24 and me~allic pressing block 26 expand to a greater total extent than do metallic bolts 28 and 30. Thus, a force is exerted between pressing block 26 and lower plate 24 resulting in the squeezing of structured copper disk 16 and metallic foil 12 togethe~ and the bonding of each to the other. Foil-disk assembly 19 is then removed from diffusion bonding press 20. Retaining ring 18 and any loose strands of structured copper outside the area of the diffusion bond are also removed from foil-disk assembly 19. The remaining structure thus formed constitutes structured copper strain buffer 10.
A strain buffer o additional structural integr~y ~3~ RD-10746 may be formed bY thermo-comDression diffusion bondin~ a metallic foil to both sides of a structured co~Per disk. Such a foil-disk assembly 32 is ormed ~y positioning metallic oils 12 and 34 on the opposite sides of structured copper disk 16 as shown in Figure 6. Foil-disk assembly 32 is then placed in di~fusion bonding press 20 and processed as described abo~e.
A structured copper strain buffer 36 with metallic foil on each side thereof, as show~l in Figure 7, is thus produced.
Figure 8 illustrates struc~ured copper strain bu~fer 10 attachea to a ~emiconductor device 40, For convenience, semiconductor device 40 is represented as a diode having a first electrode region 42 and a second electrode region 44, with electrode region 44 at~ached to buffer 10. However, other semiconductor devices such ~s transistors and thyristors may also be attached to structured copper strain buffers.
A tungsten bak-up plate 50 is alloyed to ti.e. at~ached to) the surface of first electrode region 42 as shown in Figure 8. Semiconductor device 40 comprised of silicon, for example, is a fragile structure. T~ngsten back-up plate 50 provides semiconductor device 40 with structural strength. The thermal coefficient of expansion of tungsten is approxima~ely the same as that of silicon such that the alloy formed a~ the interface of plate 50 and device 40 does not crack as device 40 expands and contracts with changes in tPmperature.
To attach a semiconductor device 40 to structured copper strain buffer 10~ the surface of electrode region 44 is first coated with a metallization comprised of a first metallic layer 46 and a second metallic layer 4~. First me~allic layer 46 may be comprised of titanium and is deposited directly on the surface of electrode region 44.
Second metallic l~yer 4~ may be comprised o coppe~ or gold.
~ RD-1074~
Strain buffer 10 is then brought into abutting contact with the metallized surface o electrode 44 to form device-buffer -assembly 38. A thermo-compression diffusion bond is formed .- between the metallized surface of electrode h4 and strain buffer.10 by positioning the device-buffer assem~ly 38 between plate 24 and pressing block 26 of diffusion bonding press 20 shown in Figure 5 ~nd performing the previously described procedure for forming a diffu~ion bond. In one embodiment of the invention, a metallization with a first metallic layer 46 with a thickness of a~out 200 A of titanium and a second metallic layer 48 with a thickness of about 10,000 R
of gold is applied on the surface of electrode region 44 to which strain buffer lO is bonded. The bond is made at a temperature of approximately 325C. in a nitrogen atmosphere.
Another embodiment of the invention is achieved when the metallization is comprised of a first layer 46 of titanium, a second layer 48 of silver and a third layer o~ gold.
Alternatively, strain buffer 10 need not be diffusion bonded to semiconductor device 40. The strain buffer lO is placed in abutment with electrode 44 of semiconductor device 40 such that strain buffer lO and device 40 bear against each other and form another embodiment of the invention.
As the operating temperature of semiconductor device 40 increases, the individual strands of structured .copper strain buffer lO are free to move in the plane of the structured copper disk as the device expands. Thus, the buffer provides a means of attachment to an electrode region which does not eause a thermally-induced stress to be present at the place of attachment. Strain buffer lO provides a good electrical connection to electrode re~ion 44 ~7hile '.~ 390~ 7~6 also providing a good thermal path away fro~ the device for heat generated at electrode region 44.
The fc>regoing describes a structured copper strain buffer employirlg straight strands of copper arranged in ~he form of a disk and attached to a metallic foil by thermo-compression diffusion bonding. l'he buffer exhibîts substantial structural integrity while still allowing individual movement o~ the separate strands of ~tructured copper within the plane of the disk ~uch that the buffer provides substantial stress relieving capability together with high thermal conductivity.
While only certain preferred features o~ the .invention have been shown by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to co~er all such modifications and changes as fall within the true spirit of the invention.
Claims (14)
1. A thermally and electrically conductive strain buffer for semiconductor devices comprising:
a bundle of straight strands of copper, each of said strands being of substantially equal length and having an insulating coating thereon except at the ends of said strands, said strands being arranged substantially parallel with each other; and a continuous metal foil abuttingly joined to, and diffused into, a common end of said bundle of copper strands, said metal foil being adapted to be bonded to a semiconductor device so that said buffer can conduct heat efficiently away from said device with-out causing thermally-induced strain at the interface of said foil with said device.
a bundle of straight strands of copper, each of said strands being of substantially equal length and having an insulating coating thereon except at the ends of said strands, said strands being arranged substantially parallel with each other; and a continuous metal foil abuttingly joined to, and diffused into, a common end of said bundle of copper strands, said metal foil being adapted to be bonded to a semiconductor device so that said buffer can conduct heat efficiently away from said device with-out causing thermally-induced strain at the interface of said foil with said device.
2. The strain buffer of claim 1 wherein said metal foil is comprised of copper.
3. The strain buffer of claim 1 wherein said metal foil is comprised of gold.
4. The strain buffer of claim 1 wherein the length of said strands of copper is within the range of approximately .1 to 1 cm.
5. The strain buffer of claim 2 wherein the length of said strands of copper is within the range of approximately .1 to 1 cm.
6. The strain buffer of claim 3 wherein the length of said strands of copper is within the range of approximately .1 to 1 cm.
7. The strain buffer of claim 1, wherein a second continuous metal foil is abuttingly joined to, and diffused into, the end of said bundle of copper strands opposite said common end.
8. An electronic device having a thermally and electrically conductive connection thereto, comprising:
a bundle of straight strands of copper, each of said strands being of substantially equal length and having a non-sticking coating thereon except at the ends of said strands, said strands being arranged parallel with each other;
a continuous metal foil abuttingly joined to and diffused into a common end of said bundle of copper strands; and a semiconductor device having a first electrode region in contact with the end of said bundle of copper strands, opposite said common end, such that electric current is efficiently provided to said electrode region while heat is efficiently conducted away from said electrode region without causing thermally-induced strain at said electrode region.
a bundle of straight strands of copper, each of said strands being of substantially equal length and having a non-sticking coating thereon except at the ends of said strands, said strands being arranged parallel with each other;
a continuous metal foil abuttingly joined to and diffused into a common end of said bundle of copper strands; and a semiconductor device having a first electrode region in contact with the end of said bundle of copper strands, opposite said common end, such that electric current is efficiently provided to said electrode region while heat is efficiently conducted away from said electrode region without causing thermally-induced strain at said electrode region.
9. The electronic device of claim 8 wherein said semiconductor device uncludes a second electrode region.
10. The electronic device of claim 9 including a tungsten plate positioned in abutment with said second electrode region.
11. The electronic device of claim 8 wherein said first electrode region is bonded to the end at said bundle of copper strands opposite said common end.
12. The electronic device of claim 8 wherein the surface of said electrode is coated with a metallization comprised of one of the group consisting of titanium-gold, titanium-silver-gold, or titanium-copper.
13. The electronic device of claim 8 wherein
13. The electronic device of claim 8 wherein
Claim 13 continued:
a second continuous metal foil is abuttingly joined to, and diffused into, the end of said bundle of copper strands opposite said common end.
a second continuous metal foil is abuttingly joined to, and diffused into, the end of said bundle of copper strands opposite said common end.
14. The electronic device of claim 12 wherein a second continuous metal foil is abut-tingly joined to, and diffused into, the end of said bundle of copper strands opposite said common end.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US88910078A | 1978-03-22 | 1978-03-22 | |
| US889,100 | 1978-03-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139013A true CA1139013A (en) | 1983-01-04 |
Family
ID=25394504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000321821A Expired CA1139013A (en) | 1978-03-22 | 1979-02-16 | Structured copper strain buffer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1139013A (en) |
-
1979
- 1979-02-16 CA CA000321821A patent/CA1139013A/en not_active Expired
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