JP2008172197A - Combined member of aluminum-ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To directly bond an aluminum member to a ceramic substrate without using any brazing filler metal so as to reduce the stress concentrated on the boundary surface by utilizing plastic deformation of the bonded metal, unlike a conventional manner in which radiating fins are directly bonded to a ceramic substrate by a brazing method to form a combined member of aluminum-ceramics and which is disadvantageous in that separation occurs at the boundary surface because of the difference in thermal expansion coefficient, resulting in weak bonding strength. <P>SOLUTION: In a combined member of aluminum-ceramics, a conductive member holding electronic components thereon is formed on one surface of a ceramic substrate, and a radiating fin assembly or a water-cooling jacket made of aluminum or an aluminum alloy is directly bonded to the other surface by a molten metal bonding method without using any intermediate material such as a brazing filler metal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aluminum-ceramic bonded body, and more particularly to an aluminum-ceramic bonded body having a heat dissipation function used for electronic parts. Furthermore, it is related with the electronic member for power modules.

  Conventionally, a circuit metal is bonded to one surface of a ceramic called a ceramic insulating substrate, a metal for heat dissipation is bonded to the other surface, and a semiconductor chip for current / voltage control is soldered on the circuit metal. It is known that a plurality of sheets, a metal base plate (heat sink) or a composite material are soldered and a heat radiation fin is attached to the back surface of the base plate via heat radiation grease.

  However, this structure has the following problems.

  (1) Since solder joining is frequently used, it is necessary to develop a new solder and a mounting method in order to eliminate lead.

  (2) A lot of solder joints are used, and there is a loss of heat conduction due to lead solder.

  (3) Since solder joining is frequently used, there is a problem of yield risk in manufacturing due to solder voids.

  (4) The thermal conductivity of the heat dissipating grease is extremely low.

  The above problems (1) to (3) can be solved by directly bonding the base integrated substrate, that is, the ceramic insulating substrate to the base plate. However, with regard to (4), the thermal conductivity of commercially available heat radiation grease is only a few W / m · K even if it is high. The resistance was large, and it was a bottleneck for improving performance.

Therefore, as shown in Patent Document 1, a prior art is known in which fins are directly attached to ceramics using a brazing method.
Japanese Patent Laid-Open No. 4-36352

  However, when aluminum fins with a large linear expansion coefficient and a large volume are directly attached to thin ceramics with a low linear expansion coefficient as in the above prior art, there is no problem at room temperature, but when the power module is actually operated Thus, when heating and cooling are repeated many times by switching, peeling occurs at the bonding interface between the ceramic and the aluminum or the ceramic is damaged due to the stress resulting from the difference between the linear expansion coefficients of the two.

  The present invention eliminates the above-mentioned drawbacks.

  The present invention is an aluminum-ceramic bonding body in which an electronic component mounting conductor is formed on one surface of a ceramic substrate, and a heat radiating fin made of aluminum or an aluminum alloy is directly bonded to the other surface. Direct bonding refers to a method of bonding a ceramic substrate and a metal without using an intermediate material such as a brazing material.

  The heat radiating fin has a shape larger than that of the ceramic substrate.

  In the aluminum-ceramic bonded body of the present invention, the electronic component mounting conductor is formed on one surface of the ceramic substrate, and the water cooling jacket made of aluminum or aluminum alloy is formed on the other surface by direct bonding. Features.

  The heat radiation fin or the water cooling jacket includes copper.

  The direct joining is a molten metal joining method.

  The main component of the ceramic substrate is one of alumina, aluminum nitride, and silicon nitride.

  The ceramic substrate includes a plurality of ceramic substrates.

  The present invention is characterized in that the above-mentioned aluminum-ceramic bonding body is used for an electronic component for a power module.

  As described above, in the present invention, the bonding force between the ceramic substrate and aluminum is stronger than the brazing method, and bonding defects are less likely to occur. In addition, in the brazing method, aluminum fins are once cast and processed from raw materials and bonded to ceramics via brazing material in a vacuum. It is possible to make a fin shape at the same time as joining ceramics and aluminum, which has great advantages in terms of heat dissipation, cost and production, and is suitable for mounting on high power electronic components such as power modules. There is a great advantage that an aluminum-ceramic bonded body having excellent properties can be easily obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared as the ceramic plate 1. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, it was further heated to 750 ° C., and aluminum oxide in a molten state having a purity of 4N was applied with a carbon cylinder to remove the oxide film and poured into the mold. In the mold, aluminum flows into one side (circuit side) of each ceramic so as to form a plate 2 having a thickness of 39 mm x 39 mm and 0.4 mm, and the other side (base side) 110 mm x Aluminum flows into a plate 3 having a thickness of 60 mm and a thickness of 5 mm. Further, the straight plate 4 having a height of 25 mm and a width of 5 mm is provided on the surface opposite to the surface in contact with the ceramic plate 1. It was shaped to flow so as to be formed at intervals of 5 mm parallel to the direction. The mold was cooled, the aluminum was solidified and bonded to the ceramic plate, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of the aluminum plate 2 having a thickness of 0.4 mm, and an etching process was performed with a ferric chloride solution to form a circuit pattern. Next, after removing the resist, 3 μm of electroless Ni-P plating was applied on the aluminum, and a base integrated substrate with fins in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 1 was obtained when the same material as in Example 1 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  The same effect as in Example 1 was obtained when the same material as in Example 1 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride.

  As the ceramic plate 1, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, it was further heated to 750 ° C., and the molten aluminum was removed by applying pressure with a carbon cylinder, and poured into the circuit side of the mold. In the mold, aluminum of 4N purity flows into one plate of 39mm x 39mm and 0.4mm thickness on one side of each ceramic, and 110mm x 60mm and 5mm in thickness with each ceramic connected to the other side. Aluminum with a purity of 99.7% (JIS No. 1070) flows into the plate 3, and this 5mm plate has a straight fin 4 with a height of 25mm and a width of 5mm on the surface opposite to the surface in contact with the ceramic. It was shaped to flow so as to be formed at intervals of 5 mm parallel to the direction. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of the aluminum plate 2 having a thickness of 0.4 mm, and an etching process was performed with a ferric chloride solution to form a circuit pattern. Next, after removing the resist, 3 μm of electroless Ni-P plating was applied on the aluminum, and a base integrated substrate with fins in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 4 was obtained when the same material as in Example 4 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  Using the same material as in Example 4 except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride, the same effect as in Example 4 was obtained.

  As the ceramic plate 1, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, the mixture was further heated to 750 ° C., and aluminum oxide in a molten state having a purity of 99.7% (JIS No. 1070) was applied with a carbon cylinder to remove the oxide film and poured into the mold. In the mold, aluminum flows into one side of each ceramic to form a plate of 39mm x 39mm and 0.4mm thickness, and the other side is a plate of 110mm x 60mm and thickness 5mm with each ceramic connected. In addition, aluminum flows into this 5 mm plate, and straight fins 4 having a height of 25 mm and a width of 5 mm are formed on the surface opposite to the surface in contact with the ceramic at intervals of 5 mm parallel to the longitudinal direction of the base. Shaped to flow into. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of the aluminum plate 2 having a thickness of 0.4 mm, and an etching process was performed with a ferric chloride solution to form a circuit pattern. Next, after removing the resist, 3 μm of electroless Ni-P plating was applied on the aluminum, and a base integrated substrate with fins in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 7 was obtained when the same material as in Example 7 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  Using the same material as in Example 7 except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride, the same effect as in Example 7 was obtained.

  As the ceramic plate 1, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, the mixture was further heated to 750 ° C., and a molten state of 99.5 wt% aluminum and 0.5 wt% copper was removed by applying pressure with a carbon cylinder and poured into the mold. The reason why copper is contained as the aluminum alloy is that the corrosion resistance of the fins is taken into consideration. In the mold, aluminum flows into one side of each ceramic to form a plate of 39mm x 39mm and 0.4mm thickness, and the other side is a plate of 110mm x 60mm and thickness 5mm with each ceramic connected. In addition, aluminum flows into this 5 mm plate, and straight fins 4 having a height of 25 mm and a width of 5 mm are formed on the surface opposite to the surface in contact with the ceramic at intervals of 5 mm parallel to the longitudinal direction of the base. Shaped to flow into. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of the aluminum plate 2 having a thickness of 0.4 mm, and an etching process was performed with a ferric chloride solution to form a circuit pattern. Next, after removing the resist, 3 μm of electroless Ni-P plating was applied on the aluminum, and a base integrated substrate with fins in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 10 was obtained when the same material as in Example 10 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  When the same material as in Example 10 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride, the same effect as in Example 10 was obtained.

  As shown in FIG. 2, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared as the ceramic plate 1. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, the mixture was further heated to 750 ° C., and a molten state of 99.5 wt% aluminum and 0.5 wt% copper was removed by applying pressure with a carbon cylinder and poured into the mold. The reason why the aluminum alloy contains copper is that corrosion resistance is taken into consideration. In the mold, aluminum flows into one side of each ceramic to form a plate of 39mm x 39mm and 0.4mm thickness, and the other side is a plate of 110mm x 60mm and thickness 50mm with each ceramic connected. Then, aluminum flowed in such a way that the meandering water channel 5 was formed in the 50 mm plate 3. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of the aluminum plate 2 having a thickness of 0.4 mm, and an etching process was performed with a ferric chloride solution to form a circuit pattern. Next, after removing the resist, 3 μm of electroless Ni—P plating was applied on the aluminum. The bottom surface of the plate 3 was closed with an aluminum plate 6 through a rubber seal 11, and a hole was made as an opening 8 for piping a rubber tube 7 in the position of the water channel 5 on the side surface of the plate 3. A groove was cut in the hole and a rubber tube 7 was attached via a joint to form a water cooling jacket integrated substrate in which the ceramic substrate was directly bonded to the two base plates. In this embodiment, the rubber seal 11 and the aluminum plate 3 are bonded with an adhesive to close the water channel 5, but may be screwed or spot welded.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 13 was obtained when the same material as in Example 13 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  The same effect as in Example 13 was obtained when the same material as in Example 13 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride.

  As shown in FIG. 3, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared as the ceramic plate 1. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, the mixture was further heated to 750 ° C., and a molten state of 99.5 wt% aluminum and 0.5 wt% copper was removed by applying pressure with a carbon cylinder and poured into the mold. In the mold, aluminum flows into one side of each ceramic to form a plate of 39mm x 39mm and 0.4mm thickness, and the other side is a plate of 110mm x 60mm and thickness 5mm with each ceramic connected. Furthermore, the aluminum flows into the plate so that the wall 9 with a width of 3 mm stands 30 mm vertically on the edge surface on the substrate contact side, and the height on the surface opposite to the surface in contact with the ceramic. The straight fins 4 having a width of 25 mm and a width of 5 mm were formed so as to flow in parallel with the longitudinal direction of the base at intervals of 5 mm. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of an aluminum plate having a thickness of 0.4 mm, and a circuit pattern was formed by etching with a ferric chloride solution. Next, after removing the resist, 3 μm of electroless Ni-P plating was applied on the aluminum, and a base-integrated substrate with fins with a ceramic substrate directly bonded to the base plate was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 16 was obtained when the same material as in Example 16 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  The same effect as in Example 16 was obtained when the same material as in Example 16 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride.

  As shown in FIG. 4, two alumina substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared as the ceramic plate 1. This was set in a carbon mold (not shown) at an interval of 10 mm and placed in a furnace. The inside of the furnace was set to an oxygen concentration of 100 ppm or less in a nitrogen atmosphere. In this state, the mixture was further heated to 750 ° C., and a molten state of 99.5 wt% aluminum and 0.5 wt% copper was removed by applying pressure with a carbon cylinder and poured into the mold. In the mold, aluminum flows into one side of each ceramic to form a plate of 39mm x 39mm and 0.4mm thickness, and the other side is a plate of 110mm x 60mm and thickness 5mm with each ceramic connected. Then, aluminum flowed in such a manner that the terminal block 10 having a size of 10 mm × 20 mm and a height of 3 mm was poured into the 5 mm plate 3 on two sides of the plate 2. The terminal block is bonded with 10 mm × 20 mm × 0.635 mm alumina, and 9 mm × 19 mm × 0.4 mm aluminum is bonded thereon. Further, an aluminum wire for connecting the chip and the terminal can be hit by ultrasonic bonding. The above-mentioned alumina is set in two molds in the same manner as the ceramic plate 1, but the height is different from the ceramic plate 1 by the height of the terminal block. Then, aluminum flows simultaneously with the plate 2 to form aluminum having the above thickness. In addition, the straight fins 4 having a height of 25 mm and a width of 5 mm were formed on the surface opposite to the surface in contact with the ceramic so as to flow in parallel with the longitudinal direction of the base at intervals of 5 mm. The mold was cooled, the aluminum was solidified and bonded to the ceramic, and then cooled to room temperature, and the bonded body was taken out from the mold. Thereafter, an etching resist having a predetermined shape was printed on the surface of an aluminum plate having a thickness of 0.4 mm, and a circuit pattern was formed by etching with a ferric chloride solution. Next, after removing the resist, 3 μm of electroless Ni—P plating was applied on the aluminum, and a base integrated substrate with finned terminal blocks in which two ceramic substrates were directly bonded to the base plate was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, the bonding interface between the ceramic and aluminum was examined again with an ultrasonic flaw detector, and no bonding defect was found. In addition, no crack was observed in ceramics.

  The same effect as in Example 19 was obtained when the same material as in Example 19 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  The same effect as in Example 19 was obtained when the same material as in Example 19 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride.

  (Comparative Example 1)

Aluminum metal plate with 99.7% purity (JIS1070), 110mm x 60mm, 30mm thickness is prepared, and straight fins with a height of 25mm and a width of 5mm are formed on one side at 5mm intervals parallel to the longitudinal direction by cutting with a milling machine Then, a base plate with fins was created. Two ceramic substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared. Next, two aluminum metal plates with a purity of 4N of 39 mm × 39 mm and 0.4 mm thickness and one base plate with fins were prepared. A brazing alloy foil having a composition of 95 wt% aluminum, 4 wt% copper, and 1 wt% magnesium and a thickness of 20 μm was produced. An aluminum metal plate having a thickness of 0.4 mm is laminated on one side of each ceramic plate, and an aluminum metal plate having a thickness of 5 mm is laminated on the other side via the 20 μm brazing alloy foil (the ceramics are placed on the aluminum metal plate having a thickness of 5 mm). In the form of 10mm spacing). While pressing this at 20 kgf / cm 2, the aluminum plate and the ceramic were joined at 630 ° C. in a vacuum of 10 ⁻⁴ Torr. After bonding, an etching resist having a predetermined shape was printed on the surface of an aluminum plate having a thickness of 0.4 mm and a circuit pattern was formed by etching with a ferric chloride solution. Next, after removing the resist, electroless Ni-P plating was applied to 3 μm on aluminum, and a base integrated substrate in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, when the interface between the ceramic and the aluminum was examined again with an ultrasonic flaw detector, peeling of about 10 mm from the edge of the substrate was observed at the interface between the ceramic and the aluminum metal plate with fins. No cracks were observed for ceramics.

  (Comparative Example 2)

  The same effect as in Comparative Example 1 was obtained when the same material as in Comparative Example 1 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  (Comparative Example 3)

  When the same material as in Comparative Example 1 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride, the same effect as in Comparative Example 1 was obtained.

  (Comparative Example 4)

Aluminum metal plate of purity 4N, 110mm × 60mm, thickness 30mm is prepared, and straight fins with a height of 25mm and a width of 5mm are formed on one side by a milling machine at intervals of 5mm parallel to the longitudinal direction, with fins A board was created. Two ceramic substrates having a thickness of 0.25 mm and a size of 40 mm × 40 mm were prepared. Next, two aluminum metal plates with a purity of 4N of 39 mm × 39 mm and 0.4 mm thickness and one base plate with fins were prepared. A brazing alloy foil having a composition of 95 wt% aluminum, 4 wt% copper, and 1 wt% magnesium and a thickness of 20 μm was produced. An aluminum metal plate having a thickness of 0.4 mm is laminated on one side of each ceramic plate, and an aluminum metal plate having a thickness of 5 mm is laminated on the other side via the 20 μm brazing alloy foil (the ceramics are placed on the aluminum metal plate having a thickness of 5 mm). In the form of 10mm spacing). While pressing this at 20 kgf / cm 2, the aluminum plate and the ceramic were joined at 630 ° C. in a vacuum of 10 ⁻⁴ Torr. After bonding, an etching resist having a predetermined shape was printed on the surface of an aluminum plate having a thickness of 0.4 mm and a circuit pattern was formed by etching with a ferric chloride solution. Next, after removing the resist, electroless Ni-P plating was applied to 3 μm on aluminum, and a base integrated substrate in which the ceramic substrate was directly bonded to the two base plates was obtained.

  Evaluation was performed as follows. First, when the bonded interface between the ceramic and the aluminum after plating (both aluminum circuit and ceramic, both aluminum base and ceramic) was examined with an ultrasonic flaw detector, no bonding defect was found. In addition, no crack was observed in ceramics. The sample was subjected to 3000 heat cycles of -40 ° C. for 30 minutes, 25 ° C. for 10 minutes, 125 ° C. for 30 minutes, and 25 ° C. for 10 minutes. Thereafter, when the interface between the ceramic and the aluminum was examined again with an ultrasonic flaw detector, peeling of about 10 mm from the edge of the substrate was observed at the interface between the ceramic and the aluminum metal plate with fins. No cracks were observed for ceramics.

  (Comparative Example 5)

  The same effect as in Comparative Example 4 was obtained when the same material as in Comparative Example 4 was used except that the thickness of the ceramic plate was 0.635 mm and the material was aluminum nitride.

  (Comparative Example 6)

  When the same material as in Comparative Example 4 was used except that the thickness of the ceramic plate was 0.32 mm and the material was silicon nitride, the same effect as in Comparative Example 4 was obtained.

  The above examples are shown in Table 1.

  Compared to soldering a ceramic circuit board on a metal base plate or a composite material as in the past, the present invention achieves environmentally friendly Pb-free because it does not use lead solder, and heat conduction by solder Loss, that is, heat dissipation is not deteriorated, and there is no risk of manufacturing yield due to solder voids in the assembly process. Also, the assembly process of soldering the metal base plate or the composite material can be eliminated. Furthermore, since no heat dissipating grease is used for close contact with the heat dissipating fins, deterioration of heat conduction can be prevented.

  As another prior art, a problem caused by solder can be avoided by joining a circuit forming aluminum plate and a heat radiation fin to a ceramic substrate such as aluminum nitride via an Al-based brazing material. However, when the power module is actually driven, or when the power module is used in a vehicle such as an automobile or a train, it is repeatedly heated and cooled due to switching and external environmental changes. In this case, the heating / cooling cycle, that is, the heat cycle is very severe, and peeling may occur at the bonding interface between the ceramic and the aluminum, or the ceramic may be damaged. The cause is known to be due to the thermal stress generated from the difference in thermal expansion coefficient of aluminum, which is a metal to be joined to ceramics, but the influence of the brazing material is also great. The brazing material is usually several to several hundreds of μm thick and seems to have less influence than the thickness of several mm to several tens of mm, like a heat radiating fin or heat radiating plate, but the brazing material layer is hard and brittle. 0.2 Since the heat stress generated due to the high proof stress is large, the brazing filler metal layer, which is the bonding interface, or the ceramic itself is destroyed.

  The present invention has realized that ceramics and aluminum are directly joined without using brazing material, and the stress concentrated on the joining interface is reduced by utilizing plastic deformation of the joining metal. As a result, heat cycle performance is dramatically higher than that using brazing filler metal, and room temperature → −40 ° C × 30 minutes → room temperature × 10 minutes → + 125 ° C × 30 minutes → room temperature × 10 minutes is one cycle. After 3000 cycles, there is no change in the bonding interface, that is, there is no destruction of the bonding interface or ceramics, and a highly reliable finned aluminum-ceramic bonding body that can be used for vehicles can be obtained. .

  Methods for directly bonding ceramics and aluminum include a molten metal bonding method, a direct bonding method in which an aluminum member is placed on a ceramic plate and heat bonded in an inert gas such as nitrogen, and an Al-Si eutectic bonding method. . In the molten metal joining method, a molten aluminum is poured into a mold having a ceramic substrate held at a predetermined position, and the molten metal is moved and solidified on the ceramic to be joined. This method is characterized in that it can easily cope with various fin shapes depending on the mold shape. Another method is characterized in that an aluminum member that has been processed into a predetermined fin shape by machining or casting in advance is bonded in nitrogen or in vacuum. The shape of the fin depends on the amount of heat generated by the elements mounted on the circuit board side, but usually it can be handled with a height of several centimeters, a width of several millimeters and a spacing of several millimeters as shown in FIG. Molds and machining can be done relatively easily.

  By making the shape larger than the ceramic substrate, it can be used as an adhesive part such as a plastic package in the power module manufacturing process using the part that protrudes from the ceramic, and it also has a structure in which compressive stress is applied to the fin side during cooling, It seems to contribute to heat cycle resistance. Further, it can be used as a reference surface for processing as a module assembly process, and is useful for assembly processes such as soldering, wire bonding, and packaging.

  In addition, since the heat radiating fin has a wall surrounding the ceramic substrate, it can be used as a container of an insulating gel instead of a plastic package in manufacturing a power module, and can be directly used as a component of the module.

  Since the heat dissipating fin has the terminal block, it is possible to eliminate the step of forming the metal / ceramic bonding substrate on the power module by soldering or bonding which has been conventionally performed. Moreover, corrosion resistance can be further improved by making the said radiation fin into aluminum containing copper.

  Furthermore, the structure of the present invention is an aluminum-ceramic bonding body in which an electronic component mounting conductor is formed on one surface of a ceramic substrate, and a water cooling jacket made of aluminum or an aluminum alloy is formed on the other surface by direct bonding. . By adopting the water cooling method, more stable cooling ability can be obtained, and the water cooling jacket is preferably an aluminum alloy containing copper from the viewpoint of corrosion resistance. As the direct bonding method, the molten metal bonding method is preferable because it can cope with various shapes and the bonding reliability is high.

  In addition, it is preferable to use aluminum nitride from the viewpoint of heat conduction, silicon nitride from the viewpoint of strength, and alumina from the viewpoint of cost, as the ceramic substrate, depending on the purpose. Is possible.

  As described above, by using the aluminum-ceramic bonding article of the present invention, it is possible to provide a power module that is excellent in heat dissipation and heat cycle resistance and that suppresses assembly cost.

It is a perspective view which shows the 1st Example of the aluminum ceramics joined body of this invention. It is a perspective view which shows the 2nd Example of the aluminum ceramics joined body of this invention. It is a perspective view which shows the 3rd Example of the aluminum-ceramics joined body of this invention. It is a perspective view which shows the 4th Example of the aluminum ceramics joined body of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ceramics board 2 Aluminum board 3 Board 4 Straight fin 5 Water channel 6 Aluminum board 7 Rubber tube 8 Opening 9 Wall 10 Terminal block

Claims (9)

  An aluminum / ceramic bonding article, wherein an electronic component mounting conductor is formed on one surface of a ceramic substrate, and a heat radiation fin made of aluminum or an aluminum alloy is formed on the other surface by direct bonding.   2. The aluminum / ceramic bonding article according to claim 1, wherein the radiating fin has a shape larger than that of the ceramic substrate.   3. The aluminum / ceramic bonding article according to claim 1, wherein the heat radiation fin contains copper.   An aluminum-ceramic bonding article, wherein an electronic component mounting conductor is formed on one surface of a ceramic substrate, and a water cooling jacket made of aluminum or an aluminum alloy is formed on the other surface by direct bonding.   5. The aluminum / ceramic bonding article according to claim 4, wherein the water cooling jacket contains copper.   6. The aluminum / ceramic bonding article according to claim 1, wherein the direct bonding is a molten metal bonding method.   7. The aluminum / ceramic bonding article according to claim 1, wherein the main component of the ceramic substrate is one of alumina, aluminum nitride, and silicon nitride.   8. The aluminum / ceramic bonding article according to claim 1, wherein a plurality of the ceramic substrates are provided.   A power module using the aluminum-ceramic bonded body according to any one of claims 1 to 8.

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