Metal/ceramic bonding substrate and method for producing same
09713253 ยท 2017-07-18
Assignee
Inventors
- Hideyo Osanai (Nagano, JP)
- Takayuki Takahashi (Nagano, JP)
- Satoru Ideguchi (Nagano, JP)
- Hirotaka Kotani (Nagano, JP)
Cpc classification
Y10T428/2462
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H01L2924/0002
ELECTRICITY
H05K1/053
ELECTRICITY
H01L21/481
ELECTRICITY
B22D19/0081
PERFORMING OPERATIONS; TRANSPORTING
Y10T428/2457
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H05K2201/2009
ELECTRICITY
H05K2203/128
ELECTRICITY
H01L2924/00
ELECTRICITY
H01L2924/0002
ELECTRICITY
Y10T428/12618
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H01L2924/00
ELECTRICITY
H01L23/3735
ELECTRICITY
Y10T428/24942
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
B21D39/00
PERFORMING OPERATIONS; TRANSPORTING
H01L23/373
ELECTRICITY
H01L21/48
ELECTRICITY
B22D19/00
PERFORMING OPERATIONS; TRANSPORTING
H05K1/05
ELECTRICITY
H05K3/02
ELECTRICITY
Abstract
A metal/ceramic bonding substrate includes: a ceramic substrate; a metal plate bonded directly to one side of the ceramic substrate; a metal base plate bonded directly to the other side of the ceramic substrate; and a reinforcing member having a higher strength than that of the metal base plate, the reinforcing member being arranged so as to extend from one of both end faces of the metal base plate to the other end face thereof without interrupting that the metal base plate extends between a bonded surface of the metal base plate to the ceramic substrate and the opposite surface thereof.
Claims
1. A metal/ceramic bonding substrate comprising: a ceramic substrate; a metal plate bonded directly to one side of the ceramic substrate; a metal base plate bonded directly to the other side of the ceramic substrate; and a reinforcing plate member arranged so as to extend from one of both end faces in the directions of one of longitudinal and lateral directions of the metal base plate to the other end face thereof without interrupting that the metal base plate extends between a bonded surface of the metal base plate to the ceramic substrate and the opposite surface thereof, the reinforcing plate member extending in parallel to the bonded surface, both end faces in longitudinal directions of the reinforcing plate member being exposed to the outside, the whole surface of the reinforcing plate member except for the both end faces thereof being bonded directly to the metal base plate.
2. A metal/ceramic bonding substrate as set forth in claim 1, wherein said metal base plate has a portion extending in directions perpendicular to said bonded surface.
3. A metal/ceramic bonding substrate as set forth in claim 1, wherein said reinforcing plate member has a surface which extends in parallel to said bonded surface and which has a portion facing said ceramic substrate, the portion of the surface of said reinforcing plate member having a smaller area than that of said bonded surface.
4. A metal/ceramic bonding substrate as set forth in claim 1, wherein said reinforcing plate member comprises a plurality of plate or rod members which are arranged on a plane extending in parallel to said bonded surface and which are spaced from each other at predetermined intervals to extend in parallel to each other.
5. A metal/ceramic bonding substrate as set forth in claim 1, wherein said reinforcing plate member is a lattice-shaped plate member comprising a plurality of longitudinal plate portions, which are arranged on a plane extending in parallel to said bonded surface and which are spaced from each other at predetermined intervals to extend in longitudinal directions of said metal base plate, and a plurality of lateral plate portions which are spaced from each other at predetermined intervals to extend in lateral directions of said metal base plate to connect the longitudinal plate portions to each other.
6. A metal/ceramic bonding substrate as set forth in claim 1, wherein said reinforcing plate member is made of a steel or a metal which contains iron and at least one selected from the group consisting of nickel, cobalt, copper and manganese.
7. A metal/ceramic bonding substrate as set forth in claim 1, wherein said reinforcing plate member is made of at least one ceramic selected from the group consisting of alumina, aluminum nitride, silicon nitride and silicon carbide.
8. A metal/ceramic bonding substrate as set forth in claim 1, wherein said metal base plate is made of aluminum or an aluminum alloy.
9. A metal/ceramic bonding substrate as set forth in claim 1, wherein said metal plate is made of aluminum or an aluminum alloy.
10. A metal/ceramic bonding substrate as set forth in claim 1, wherein said ceramic substrate is made of at least one ceramic selected from the group consisting of alumina, aluminum nitride, silicon nitride and silicon carbide.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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BEST MODE FOR CARRYING OUT THE INVENTION
(46) Referring to the accompanying drawings, the preferred embodiments of a metal/ceramic bonding substrate according to the present invention, and a method for producing the same will be described below.
(47) [First Preferred Embodiment]
(48) As shown in
(49) As shown in
(50) The reinforcing members 16 are arranged on a plane (an imaginary plane) substantially parallel to the bonded surface of the metal base member 10 to the ceramic substrate 12, and are spaced from each other to extend in substantially parallel to each other (two of the reinforcing members 16 are arranged on both sides of a central one of the reinforcing members 16 in this preferred embodiment). If gaps are thus provided between the adjacent reinforcing members 16 to be arranged directly below electronic parts, such as power elements, which are mounted on the metal plate 14, when heat generated from the electronic parts, such as the power elements, conducts through the insulating ceramic substrate 12 and the metal base plate 10 downwards to be radiated, heat conduction to the bottom face of the metal base plate 10 (the opposite surface to the bonded surface of the metal base plate 10 to the ceramic substrate 12) is not inhibited, so that it is possible to provide a metal/ceramic bonding substrate having excellent radiating performance.
(51) The metal base plate 10 and the metal plate 14 are preferably made of aluminum or an aluminum alloy from the standpoints of electric conductivity, thermal conductivity and reliability of bonding to the ceramic substrate. The ceramic substrate 12 is preferably made of at least one of alumina, aluminum nitride, silicon nitride and silicon carbide. The reinforcing members 16 are preferably made of a metal which has a higher melting point and a higher strength than those of the metal base plate 10, and more preferably made of a steel or iron containing metal which is inexpensive and which has a high strength. The iron containing metal is preferably a metal which contains iron and at least one selected from the group consisting of nickel, cobalt, copper and manganese. In particular, the metal/ceramic bonding substrate is easy to greatly warp by thermal stress generated during bonding due to the difference in thermal expansion coefficient between the metal and the ceramic and/or by thermal stress generated during a heat treatment for mounting electronic parts, such as power elements, on the metal/ceramic bonding substrate and/or during the use of the metal/ceramic bonding substrate. In order to suppress such warpage, the reinforcing members 16 are preferably made of 42 Alloy (an alloy containing nickel mixed with iron), inver (an alloy of iron and nickel, nondeforming steel), kovar (an alloy containing nickel, cobalt and so forth mixed with iron), which have a low thermal expansion coefficient, SPPC (common steel) having a high strength, or the like. The thickness of each of the reinforcing members 16 is preferably in the range of from 0.5 mm to 2.0 mm. Each of the reinforcing members 16 is preferably coated with Ni plating or the like in order to suppress a reaction with the metal base plate 10.
(52) The metal/ceramic bonding substrate in the preferred embodiment shown in
(53) As shown in
(54) As shown in
(55) As shown in
(56) The upper mold member 24 has an inlet (not shown) for injecting a molten metal into the metal base plate forming portion 24a from an injecting nozzle (not shown). The lower mold member 22 has a molten metal passage (not shown) which extends between the metal base plate forming portion 22a and the metal plate forming portion 22c for establishing a communication between the metal base plate forming portion 22a and the metal plate forming portion 22c even if the ceramic substrate 12 is housed in the ceramic substrate housing portion 22b.
(57) In this preferred embodiment, the metal base plate forming portion 22a of the lower mold member 22 and the metal base plate forming portion 24a of the upper mold member 24 have the recessed portions 22d and the recessed portions 24d as the reinforcing member supporting portions, respectively. However, the metal base plate forming portion 22a of the lower mold member 22 or the metal base plate forming portion 24a of the upper mold member 24 may have recessed portions, each of which has the same shape and size as those of a corresponding one of both end portions of a corresponding one of the reinforcing members 16 in longitudinal directions.
(58) In order to use such a mold 20 for producing the preferred embodiment of a metal/ceramic bonding substrate shown in
(59) The molten metal is preferably injected into the mold 20 as follows. First, the mold 20 is moved into a furnace (not shown), and the interior of the furnace is caused to be in an atmosphere of nitrogen to decrease the oxygen concentration therein to 100 ppm or less, preferably 10 ppm or less. Then, the mold 20 is heated to a molten metal injecting temperature (e.g., 600 to 800 C. when a molten metal of aluminum is injected) by the temperature control of a heater. Thereafter, a molten metal, which is heated to the molten metal injecting temperature and which is previously measured, is pressurized at a predetermined pressure by nitrogen gas to be injected into the mold 20 from the inlet. If the molten metal is thus injected, it is possible to prevent large bonding defects from being produced between the metal and the ceramic. After the molten metal is injected into the mold 20, nitrogen gas is preferably blown into the inlet from a nozzle (not shown) to cool and solidify the molten metal in the mold 20 while pressurizing the molten metal at a predetermined pressure. The predetermined pressure applied by nitrogen gas during the injection and cooling of the molten metal is preferably in the range of from 1 kPa to 100 kPa, more preferably in the range of from 3 kPa to 80 kPa, and most preferably in the range of from 5 kPa to 15 kPa. If the pressure is too low, it is difficult to allow the molten metal to be injected into the mold 20. If the pressure is too high, there is the possibility that the positions of the reinforcing members 16 may be shifted and/or the mold 20 may be damaged. In particular, when a high pressure of not less than 1 MPa is applied if the mold 20 of carbon is used, there is the possibility that the mold 20 may be broken and/or the molten metal may leak from the mold 20 and/or the positions of the reinforcing members 16 and ceramic substrate 12 may be shifted.
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(62) Furthermore, when the metal base plate 10 has mounting holes for mounting a heat sink thereon by means of screws, if holes are formed in the reinforcing member so as to correspond to the mounting holes and if the mounting holes of the metal base plate 10 are arranged so as to be surrounded by the reinforcing member, it is possible to improve the strength of the screwed portions. Since the screwed portions hardly have an influence on heat radiation, the reinforcing member may be exposed to the outside from the metal base plate 10 in the screwed portions.
(63) Examples of the first preferred embodiment of a metal/ceramic bonding substrate and a method for producing the same according to the present invention will be described below in detail.
EXAMPLE 1
(64) First, there was prepared a mold of carbon having a similar shape to that of the mold 20 shown in
(65) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage of the metal base plate 10 in longitudinal directions (the distance in vertical directions between the tangential plane of the central portion of the metal base plate 10 and one of the end portions thereof when the bottom face of the metal base plate 10 was arranged on the horizontal plane) was measured by a laser displacement meter, assuming that the amount of warpage was positive (+) when the metal base plate 10 warps downwardly (concavely) and negative () when the metal base plate 10 warps upwardly (convexly). As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 12 was 10 m.
(66) With respect to the metal/ceramic bonding substrate heated on a hot plate to cause the surface temperature of the substrate to be 260 C., the amount of warpage in longitudinal directions of the ceramic substrate 12 was measured. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was +200 m.
(67) After heating, the ceramic substrate 12 has no deficiencies such as cracks, and the electrical performance such as insulating performance of the metal/ceramic bonding substrate was good. The bonding of the metal plate 14 to the ceramic substrate 12, the bonding of the metal base plate 10 to the substrate 12, and the bonding of the metal base plate 10 to the reinforcing members 16 were good without causing any deficiencies.
EXAMPLE 2
(68) There was produced a metal/ceramic bonding substrate by the same method as that in Example 1, except that there were used a single reinforcing member 16 having a size of 150 mm50 mm1.0 mm and a mold 20 corresponding thereto.
(69) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage of the metal base plate 10 was measured by the same method as that in Example 1. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was +10 m.
(70) With respect to the metal/ceramic bonding substrate heated on a hot plate to cause the surface temperature of the substrate to be 260 C., the amount of warpage in longitudinal directions of the ceramic substrate 12 was measured. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was +298 m.
EXAMPLE 3
(71) There was produced a metal/ceramic bonding substrate by the same method as that in Example 1, except that there were used a single reinforcing member 16 having a size of 150 mm50 mm0.6 mm and a mold 20 corresponding thereto.
(72) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage of the metal base plate 10 was measured by the same method as that in Example 1. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was 20 m.
(73) With respect to the metal/ceramic bonding substrate heated on a hot plate to cause the surface temperature of the substrate to be 260 C., the amount of warpage in longitudinal directions of the ceramic substrate 12 was measured. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was +500 m.
COMPARATIVE EXAMPLE 1
(74) There was produced a metal/ceramic bonding substrate by the same method as that in Example 1, except that there were used no reinforcing member and a mold 20 corresponding thereto.
(75) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage of the metal base plate 10 was measured by the same method as that in Example 1. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was 30 m.
(76) With respect to the metal/ceramic bonding substrate heated on a hot plate to cause the surface temperature of the substrate to be 260 C., the amount of warpage in longitudinal directions of the ceramic substrate 12 was measured. As a result, the amount of warpage in longitudinal directions of the ceramic substrate 12 was +900 m.
(77) [Second Preferred Embodiment]
(78) As shown in
(79) As shown in
(80) The reinforcing members 316 are arranged on a plane (an imaginary plane) substantially parallel to the bonded surface of the metal base member 310 to the ceramic substrate 312, and are spaced from each other to extend in substantially parallel to each other (three of the reinforcing members 316 are arranged on each of both sides of a central one of the reinforcing members 316 in this preferred embodiment). If gaps are thus provided between the adjacent reinforcing members 316 to be arranged directly below electronic parts, such as power elements, which are mounted on the metal plate 314, when heat generated from the electronic parts, such as the power elements, conducts through the insulating ceramic substrate 312 and the metal base plate 310 downwards to be radiated, heat conduction to the bottom face of the metal base plate 310 is not inhibited, so that it is possible to provide a metal/ceramic bonding substrate having excellent radiating performance.
(81) The metal base plate 310 and the metal plate 314 are preferably made of aluminum or an aluminum alloy from the standpoints of electric conductivity, thermal conductivity and reliability of bonding to the ceramic substrate. The ceramic substrate 312 and the reinforcing members 316 are preferably made of at least one of alumina, aluminum nitride, silicon nitride and silicon carbide.
(82) The metal/ceramic bonding substrate in the preferred embodiment shown in
(83) As shown in
(84) As shown in
(85) As shown in
(86) The upper mold member 324 has an inlet (not shown) for injecting a molten metal into the metal base plate forming portion 324a from an injecting nozzle (not shown). The lower mold member 322 has a molten metal passage (not shown) which extends between the metal base plate forming portion 322a and the metal plate forming portion 322c for establishing a communication between the metal base plate forming portion 322a and the metal plate forming portion 322c even if the ceramic substrate 312 is housed in the ceramic substrate housing portion 322b.
(87) In this preferred embodiment, the metal base plate forming portion 322d of the lower mold member 322 has recessed portions 322a as reinforcing member supporting portions. However, the metal base plate forming portion 324a of the upper mold member 324 may have recessed portions, each of which has the same shape and size as those of a corresponding one of both end portions in longitudinal directions of a corresponding one of the reinforcing members 316. Alternatively, both of the metal base plate forming portion 322a of the lower mold member 322 and the metal base plate forming portion 324a of the upper mold member 24 have recessed portions so that both end portions of each of the reinforcing members 316 have the same shape and size as those of a corresponding one of the spaces defined by the recessed portions.
(88) In order to use such a mold 320 for producing the preferred embodiment of a metal/ceramic bonding substrate shown in
(89) The molten metal is preferably injected into the mold 320 as follows. First, the mold 320 is moved into a furnace (not shown), and the interior of the furnace is caused to be in an atmosphere of nitrogen to decrease the oxygen concentration therein to 100 ppm or less, preferably 10 ppm or less. Then, the mold 320 is heated to a molten metal injecting temperature (e.g., 600 to 800 C. when a molten metal of aluminum is injected) by the temperature control of a heater. Thereafter, a molten metal, which is heated to the molten metal injecting temperature and which is previously measured, is pressurized at a predetermined pressure by nitrogen gas to be injected into the mold 320 from the inlet. If the molten metal is thus injected, it is possible to prevent large bonding defects from being produced between the metal and the ceramic. After the molten metal is injected into the mold 320, nitrogen gas is preferably blown into the inlet from a nozzle (not shown) to cool and solidify the molten metal in the mold 320 while pressurizing the molten metal at a predetermined pressure. The predetermined pressure applied by nitrogen gas during the injection and cooling of the molten metal is preferably in the range of from 1 kPa to 100 kPa, more preferably in the range of from 3 kPa to 80 kPa, and most preferably in the range of from 5 kPa to 15 kPa. If the pressure is too low, it is difficult to allow the molten metal to be injected into the mold 320. If the pressure is too high, there is the possibility that the positions of the reinforcing members 316 may be shifted and/or the mold 320 may be damaged. In particular, when a high pressure of not less than 1 MPa is applied if the mold 320 of carbon is used, there is the possibility that the mold 320 may be broken and/or the molten metal may leak from the mold 320 and/or the positions of the reinforcing members 316 and ceramic substrate 312 may be shifted.
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(91) In this modified example, three elongated reinforcing plate members 416 having rectangular planar and sectional shapes are arranged on a plane (an imaginary plane) substantially parallel to the bonded surface of a metal base member 410 to a ceramic substrate 412, and are spaced from each other to extend in substantially parallel to each other (three reinforcing members 416 are arranged at regular intervals so that one of the reinforcing members 416 is arranged on each of both sides of a central one of the reinforcing members 416 in this preferred embodiment). The thickness (in the thickness directions of the metal base plate 410) of each of the reinforcing members 416 is greater than the width (in directions along the bonded surface of the metal base plate 410 to the ceramic substrate 412) thereof. Since other constructions are same as those in the above-described second preferred embodiment, 100 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted.
(92) In this modified example, since the thickness (in the thickness directions of the metal base plate 410) of each of the reinforcing members 416 is greater than the width (in directions along the bonded surface of the metal base plate 410 to the ceramic substrate 412) thereof, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance in the thickness directions of the metal base plate 420 and which has a small amount of warpage and a small variation in warpage. That is, the area of each of the reinforcing members 416 for inhibiting heat radiation in the thickness directions of the metal base plate 420 is decreased by reducing the width (in directions along the bonded surface of the metal base plate 410 to the ceramic substrate 412) of a corresponding one of the reinforcing members 416. In addition, the reinforcing members 416 can be difficult to be bent with respect to the warpage of the metal base plate 410 by increasing the thickness (in the thickness directions of the metal base plate 410) of each of the reinforcing members 416. Moreover, it is possible to reduce costs by decreasing the used amount of the reinforcing members 416.
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(94) In this modified example, three elongated reinforcing plate members 516 having rectangular planar and sectional shapes are arranged on a plane (an imaginary plane) substantially parallel to the bonded surface of a metal base member 510 to a ceramic substrate 512, and are spaced from each other to extend in substantially parallel to each other (three reinforcing members 516 are arranged at regular intervals so that one of the reinforcing members 516 is arranged on each of both sides of a central one of the reinforcing members 516 in this preferred embodiment). In addition, similar three elongated reinforcing plate members 516 contact the bottom faces of the above-described three reinforcing members 516 and are spaced from each other to extend in directions substantially perpendicular to the above-described three reinforcing members 516 (three reinforcing members 516 are arranged at regular intervals so that one of the reinforcing members 516 is arranged on each of both sides of a central one of the reinforcing members 516 in this preferred embodiment). The thickness (in the thickness directions of the metal base plate 510) of each of the reinforcing members 516 is greater than the width (in directions along the bonded surface of the metal base plate 510 to the ceramic substrate 512) thereof. Since other constructions are same as those in the above-described second preferred embodiment, 200 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted.
(95) In this modified example, since the thickness (in the thickness directions of the metal base plate 510) of each of the reinforcing members 516 is greater than the width (in directions along the bonded surface of the metal base plate 510 to the ceramic substrate 512) thereof, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance in the thickness directions of the metal base plate 510 and which has a small amount of warpage in longitudinal and lateral directions and a small variation in warpage. That is, the area of each of the reinforcing members 516 for inhibiting heat radiation in the thickness directions of the metal base plate 510 is decreased by reducing the width (in directions along the bonded surface of the metal base plate 510 to the ceramic substrate 512) thereof. In addition, the reinforcing members 516 can be difficult to be bent with respect to the warpage of the metal base plate 510 in longitudinal and lateral directions by increasing the thickness (in the thickness directions of the metal base plate 510) of each of the reinforcing members 516. Moreover, it is possible to reduce costs by decreasing the used amount of the reinforcing members 516.
(96)
(97) In this modified example, a single reinforcing plate member 616, which is narrower than the width of the bottom face of a metal base plate 610 and which has the same length as that of the bottom face thereof, is arranged on the central portion of the bottom face of the metal base plate 610 in longitudinal directions so as to extend over the whole length of the bottom face thereof. Since other constructions are same as those in the above-described second preferred embodiment, 300 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted. In this modified example, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance and which has a small amount of warpage and a small variation in warpage.
(98)
(99) In this modified example, a single reinforcing plate member 718, which is shorter than the length of the bottom face of a metal base plate 710 and which has the same width as that of the bottom face thereof, is arranged in the metal base plate 710 so as to be spaced from reinforcing members 716 toward the bottom face of the metal base plate 710 in the thickness directions thereof while extending over the whole width of the metal base plate 710 in directions substantially perpendicular to the reinforcing members 716. Since other constructions are same as those in the above-described second preferred embodiment, 400 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted. In this modified example, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance and which has a small amount of warpage and a small variation in warpage.
(100)
(101) In this modified example, reinforcing plate members 816 are arranged so as to cover the side faces of a metal base plate 810. Since other constructions are same as those in the above-described second preferred embodiment, 500 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted. In this modified example, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance and which has a small amount of warpage and a small variation in warpage.
(102)
(103) In this modified example, a single reinforcing plate member 916, which has a substantially rectangular planar shape and which is smaller than the major face of a metal base plate 910, is arranged in the substantially central portion of the metal base plate 910 in thickness directions to extend in substantially parallel to the major face of the metal base plate 910. Since other constructions are same as those in the above-described second preferred embodiment, 600 is added to each of the reference numbers of corresponding portions in the second preferred embodiment to be shown in the figures, and the description thereof is omitted. In this modified example, it is possible to produce a metal/ceramic bonding substrate which has excellent radiating performance and which has a small amount of warpage and a small variation in warpage.
(104) Examples of the second preferred embodiment of a metal/ceramic bonding substrate and a method for producing the same according to the present invention will be described below in detail.
EXAMPLE 4
(105) First, there was prepared a mold of carbon having a similar shape to that of the mold 320 shown in
(106) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal plate 314 for a circuit pattern in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured at a span of 45 mm by a laser displacement meter, assuming that the amount of warpage was positive (+) when the surface of the metal plate 314 warps downwardly (concavely) and negative () when the surface of the metal plate 314 warps upwardly (convexly). While the ceramic substrate having a square planar shape has been used in Examples 5 through 17 and Comparative Examples 2 and 3 in addition to this example, it is assumed for convenience that the directions along one side of the square are longitudinal directions and that the directions perpendicular to the longitudinal directions are lateral directions. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 36 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 198 m.
(107) After a furnace passing treatment for holding the obtained metal/ceramic bonding substrate at 410 C. for 10 minutes in a furnace was carried out once, three times, five times and ten times, the amount of warpage of the metal/ceramic bonding substrate was measured. As a result, after the furnace passing treatment was carried out once, the amount of warpage in the longitudinal directions was 33 m, and the amount of warpage in the lateral directions was 264 m. After the furnace passing treatment was carried out three times, the amount of warpage in the longitudinal directions was 57 m, and the amount of warpage in the lateral directions was 309 m. After the furnace passing treatment was carried out five times, the amount of warpage in the longitudinal directions was 69 m, and the amount of warpage in the lateral directions was 342 m. After the furnace passing treatment was carried out ten times, the amount of warpage in the longitudinal directions was 90 m, and the amount of warpage in the lateral directions was 390 m.
(108) After the furnace passing treatment was carried out ten times, the ceramic substrate 312 has no deficiencies such as cracks, and the electrical performance such as insulating performance of the metal/ceramic bonding substrate was good. The bonding of the metal plate 314 to the ceramic substrate 312, the bonding of the metal base plate 310 to the substrate 312, and the bonding of the metal base plate 310 to the reinforcing members 316 were good without causing any deficiencies.
EXAMPLE 5
(109) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that there were used a single reinforcing member 316 having a size of 80 mm50 mm0.6 mm and a mold 320 corresponding thereto.
(110) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal plate 314 was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 36 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 45 m.
(111) After a furnace passing treatment for holding the obtained metal/ceramic bonding substrate at 410 C. for 10 minutes in a furnace was carried out once, three times, five times and ten times, the amount of warpage of the metal/ceramic bonding substrate was measured. As a result, after the furnace passing treatment was carried out once, the amount of warpage in the longitudinal directions was 42 m, and the amount of warpage in the lateral directions was 42 m. After the furnace passing treatment was carried out three times, the amount of warpage in the longitudinal directions was 18 m, and the amount of warpage in the lateral directions was 18 m. After the furnace passing treatment was carried out five times, the amount of warpage in the longitudinal directions was 30 m, and the amount of warpage in the lateral directions was 27 m. After the furnace passing treatment was carried out ten times, the amount of warpage in the longitudinal directions was 63 m, and the amount of warpage in the lateral directions was 63 m.
COMPARATIVE EXAMPLE 2
(112) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that no reinforcing member 316 was used as shown in
(113) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal plate 1014 was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 1012 was 231 m, and the amount of warpage in the lateral directions of the ceramic substrate 1012 was 201 m.
(114) After a furnace passing treatment for holding the obtained metal/ceramic bonding substrate at 410 C. for 10 minutes in a furnace was carried out once, three times, five times and ten times, the amount of warpage of the metal/ceramic bonding substrate was measured. As a result, after the furnace passing treatment was carried out once, the amount of warpage in the longitudinal directions was 273 m, and the amount of warpage in the lateral directions was 252 m. After the furnace passing treatment was carried out three times, the amount of warpage in the longitudinal directions was 321 m, and the amount of warpage in the lateral directions was 294 m. After the furnace passing treatment was carried out five times, the amount of warpage in the longitudinal directions was 351 m, and the amount of warpage in the lateral directions was 333 m. After the furnace passing treatment was carried out ten times, the amount of warpage in the longitudinal directions was 399 m, and the amount of warpage in the lateral directions was 393 m.
EXAMPLE 6
(115) With respect to another metal/ceramic bonding substrate produced by the same method as that in Example 4, the amount of warpage at the central portion on the surface of a metal plate 314 for a circuit pattern was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of a ceramic substrate 312 was 46 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 201 m.
(116) With respect to the obtained metal/ceramic bonding substrate, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured at a span of 60 mm by a laser displacement meter, assuming that the amount of warpage was positive (+) when the surface of the metal plate 314 warps downwardly (concavely) and negative () when the surface of the metal plate 314 warps upwardly (convexly). As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 84 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 336 m.
EXAMPLE 7
(117) With respect to another metal/ceramic bonding substrate produced by the same method as that in Example 6, the amount of warpage at the central portion on the surface of a metal plate 314 for a circuit pattern was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of a ceramic substrate 312 was 27 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 45 m.
(118) With respect to the obtained metal/ceramic bonding substrate, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 33 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 78 m.
EXAMPLE 8
(119) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that there were used a single reinforcing member 316 having a size of 80 mm60 mm0.6 mm and a mold 320 corresponding thereto.
(120) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal plate 314 for a circuit pattern was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 21 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 21 m.
(121) With respect to the obtained metal/ceramic bonding substrate, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 30 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 39 m.
EXAMPLE 9
(122) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(123) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal plate 614 for a circuit pattern was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 612 was 45 m, and the amount of warpage in the lateral directions of the ceramic substrate 612 was 15 m.
(124) With respect to the obtained metal/ceramic bonding substrate, the amount of warpage at the central portion on the surface of the metal base plate 610 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 612 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 612 was 72 m, and the amount of warpage in the lateral directions of the ceramic substrate 612 was 42 m.
COMPARATIVE EXAMPLE 3
(125) With respect to another metal/ceramic bonding substrate produced by the same method as that in Comparative Example 2, the amount of warpage at the central portion on the surface of a metal plate 1014 for a circuit pattern was measured by the same method as that in Example 4. As a result, the amount of warpage in the longitudinal directions of a ceramic substrate 1012 was 213 m, and the amount of warpage in the lateral directions of the ceramic substrate 1012 was 177 m.
(126) With respect to the obtained metal/ceramic bonding substrate, the amount of warpage at the central portion on the surface of the metal base plate 1010 for a circuit pattern in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 1012 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 1012 was 387 m, and the amount of warpage in the lateral directions of the ceramic substrate 1012 was 345 m.
EXAMPLE 10
(127) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that three reinforcing members 316 having a size of 80 mm10 mm0.6 mm were used for forming a metal plate 314 for a circuit pattern having a size of 48 mm48 mm0.4 mm and a metal base plate 310 having a size of 70 mm70 mm4 mm.
(128) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 30 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 30 m.
EXAMPLE 11
(129) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that three reinforcing members 316 having a size of 80 mm3 mm0.6 mm were used for forming a metal plate 314 for a circuit pattern having a size of 48 mm48 mm0.4 mm and a metal base plate 310 having a size of 70 mm70 mm4 mm.
(130) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 25 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 25 m.
EXAMPLE 12
(131) There was produced a metal/ceramic bonding substrate by the same method as that in Example 4, except that three reinforcing members 316 having a size of 80 mm10 mm0.6 mm were used for forming a metal plate 314 for a circuit pattern having a size of 48 mm48 mm0.4 mm and a metal base plate 310 having a size of 70 mm70 mm8 mm.
(132) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 310 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 312 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 312 was 35 m, and the amount of warpage in the lateral directions of the ceramic substrate 312 was 35 m.
EXAMPLE 13
(133) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(134) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 410 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 412 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 412 was 38 m, and the amount of warpage in the lateral directions of the ceramic substrate 412 was 38 m.
EXAMPLE 14
(135) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(136) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 510 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 512 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 512 was 36 m, and the amount of warpage in the lateral directions of the ceramic substrate 512 was 38 m.
EXAMPLE 15
(137) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(138) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 610 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 612 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 612 was 25 m, and the amount of warpage in the lateral directions of the ceramic substrate 612 was 35 m.
EXAMPLE 16
(139) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(140) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 710 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 712 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 712 was 32 m, and the amount of warpage in the lateral directions of the ceramic substrate 712 was 22 m.
EXAMPLE 17
(141) There was produced a metal/ceramic bonding substrate having a similar shape to that of the metal/ceramic bonding substrate shown in
(142) With respect to the metal/ceramic bonding substrate thus obtained, the amount of warpage at the central portion on the surface of the metal base plate 810 in longitudinal directions and lateral directions (perpendicular to the longitudinal directions) of the ceramic substrate 812 was measured by the same method as that in Example 6. As a result, the amount of warpage in the longitudinal directions of the ceramic substrate 812 was 43 m, and the amount of warpage in the lateral directions of the ceramic substrate 812 was 38 m.
(143) Furthermore, after the radiating performance in thickness directions of each of the metal/ceramic bonding substrates in Examples 4 and 14 was examined, the decreasing rate of heat discharge thereof was only 3% or less in comparison with that on the reverse face of the metal/ceramic bonding substrate in Comparative Example 2. Therefore, in these examples, it is possible to restrain the warpage of the metal/ceramic bonding substrate while the radiating performance thereof is hardly deteriorated.
(144) [Third Preferred Embodiment]
(145) It is considered that a base plate of aluminum or an aluminum alloy is formed so as to surround a metal plate of copper or the like, which has a higher thermal conductivity than that of aluminum and the aluminum alloy, when a metal/ceramic bonding substrate integrated with the base plate is produced by the molten metal bonding method.
(146) However, when a base plate of aluminum was formed so as to surround a copper plate by the molten metal bonding method, it was found that there is the possibility that a rigid and fragile intermetallic compound or solid solution of Al and Cu may be formed to deteriorate the reliability of the metal/ceramic bonding substrate, such as the thermal shock resistance of the metal/ceramic bonding substrate and the bonding strength of the base plate to the ceramic substrate, and the thermal conductivity thereof. It was also found that there is the possibility that the base plate may be removed from the boundary face thereof to the ceramic substrate. Moreover, it was found that it is not possible to restrain the amount of diffusion of Al and Cu.
(147) Therefore, the third preferred embodiment of a metal/ceramic bonding substrate according to the present invention is designed to prevent the formation of the intermetallic compound or solid solution of the metal and Al while preventing the diffusion of the metal and Al, even if a base plate of aluminum or an aluminum alloy is formed so as to surround a metal plate of a metal, which has a higher thermal conductivity than that of aluminum or the aluminum alloy, when a metal/ceramic bonding substrate integrated with the base plate is produced by the molten metal bonding method.
(148) As shown in
(149) The metal plate of the spray-coated member 2016 is preferably made of a metal which has a higher thermal conductivity than that of aluminum or the aluminum alloy, and more preferably made of copper or a copper alloy. The thickness of the metal plate is preferably in the range of from about 0.3 mm to about 5 mm, and more preferably in the range of from about 0.5 mm to about 3 mm. When the spray-coated member 2016, which is obtained by spray-coating the surface of the metal plate having the higher thermal conductivity than that of aluminum or the aluminum alloy, is thus arranged in the base plate 2010, it is possible to prevent the formation of the intermetallic compound or solid solution of the metal and Al, and it is possible to prevent the diffusion of the metal and Al, in addition to such effects that the metal plate of the metal having the higher thermal conductivity than that of the of aluminum or the aluminum alloy is arranged in the base plate to improve radiating performance, such as transient and saturated heat characteristics. Thus, it is possible to prevent the deterioration in reliability of the metal/ceramic bonding substrate, such as the deterioration of the thermal shock resistance of the metal/ceramic bonding substrate and the bonding strength of the base plate to the ceramic substrate, and it is possible to prevent the deterioration in thermal conductivity of the metal/ceramic bonding substrate.
(150) The metal/ceramic bonding substrate in the preferred embodiment shown in
(151) The spray coating is preferably the plasma spray coating. The plasma spray coating is a method comprising the steps of: generating a direct-current arc between a cathode and the inner surface of an anode nozzle; heating and expanding a working medium which is supplied from the back by the direct-current arc; allowing a severe ultra-high temperature jet (plasma jet) to jet from the nozzle; causing a powder of a spray-coating material, which is supplied into the plasma jet by the working medium, to be heated and accelerated by the plasma jet to collide with the surface of a substrate to form a coating (sprayed coating) thereon. As the working medium, argon gas or nitrogen gas may be used. Hydrogen gas may be added thereto. A mixed gas of argon and helium may be used. The spray-coating material may be a ceramic powder, and is preferably a ceramic powder which is at least one selected from the group consisting of aluminum oxide (Al.sub.2O.sub.3), aluminum nitride (AlN), silicon carbide (SiC) and silicon nitride (Si.sub.3N.sub.4). In order to prevent the diffusion of Al and a metal such as Cu by the sprayed coating, the thickness of the sprayed coating is preferably in the range of from about 0.01 mm to about 0.3 mm, and more preferably in the range of from about 0.02 mm to about 0.2 mm.
(152) As shown in
(153) In order to use such a mold 2020 for producing the preferred embodiment of a metal/ceramic bonding substrate shown in
(154)
(155)
(156) As this modified example, similar fins to the plurality of (plate-shaped) fins 2210a, which are formed on the bottom face of the base plate 2210 so as to be spaced from each other at regular intervals and which extend in substantially parallel to each other, (or pin-shaped fins arranged so as to be spaced from each other at regular intervals) may be formed on the bottom face of the metal base plate of any one of the metal/ceramic bonding substrates in the above-described first and second preferred embodiments and the modified examples thereof, and the shape of a metal base forming portion of a mold for forming the one of the metal/ceramic bonding substrates may be modified so as to correspond thereto.
(157) Examples of the preferred embodiment of a metal/ceramic bonding substrate and a method for producing the same according to the present invention will be described below in detail.
EXAMPLE 18
(158) A film of Al.sub.2O.sub.3 having a thickness of 0.1 mm was formed on a Cu plate having a thickness of 1 mm by the plasma spray coating to form a spray-coated member. After the spray-coated member and an AlN substrate were housed in a mold which is similar to the mold 2020 shown in
EXAMPLE 19
(159) A metal/ceramic bonding substrate integrated with a base plate was produced by the same method as that in Example 18, except that a Cu plate having a thickness of 3 mm was used. After a cross section obtained by cutting the metal/ceramic bonding substrate was observed, the diffusion of Cu and Al was not observed, and no intermetallic compound was observed. In addition, bonding deficiencies, such as voids, were not observed on the bonded boundary surface of the AlN substrate to the base plate and on the bonded boundary surface of the spray-coated member to the base plate, so that it was found that the bonding strength was sufficiently strong.
EXAMPLE 20
(160) A metal/ceramic bonding substrate integrated with a base plate was produced by the same method as that in Example 19, except that a film of Al.sub.2O.sub.3 having a thickness of 0.02 mm was formed by the plasma spray coating. After a cross section obtained by cutting the metal/ceramic bonding substrate was observed, the diffusion of Cu and Al was not observed, and no intermetallic compound was observed. In addition, bonding deficiencies, such as voids, were not observed on the bonded boundary surface of the AlN substrate to the base plate and on the bonded boundary surface of the spray-coated member to the base plate, so that it was found that the bonding strength was sufficiently strong.
EXAMPLE 21
(161) A metal/ceramic bonding substrate integrated with a base plate was produced by the same method as that in Example 19, except that a film of Al.sub.2O.sub.3 having a thickness of 0.05 mm was formed by the plasma spray coating. After a cross section obtained by cutting the metal/ceramic bonding substrate was observed, the diffusion of Cu and Al was not observed, and no intermetallic compound was observed. In addition, bonding deficiencies, such as voids, were not observed on the bonded boundary surface of the AlN substrate to the base plate and on the bonded boundary surface of the spray-coated member to the base plate, so that it was found that the bonding strength was sufficiently strong.
COMPARATIVE EXAMPLE 4
(162) A metal/ceramic bonding substrate integrated with a base plate was produced by the same method as that in Example 18, except that the Cu plate was not spray-coated by the plasma spray coating. After a cross section obtained by cutting the metal/ceramic bonding substrate was observed, the mutual diffusion of Cu and Al was observed, and intermetallic compounds were observed.