JP2019029510A - Aluminum-ceramic bonded substrate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make aluminum crystal grains finer while maintaining the conductivity and Vickers hardness of an aluminum plate bonded to a ceramic substrate when an aluminum-ceramic bonded substrate is manufactured using a mold. -Providing a ceramic bonded substrate and a method for manufacturing the same. SOLUTION: A coating material containing a crystal grain micronizing agent composed of at least one of aluminum boride and a titanium-aluminum-based metal compound is applied to the inner surface of an aluminum plate forming portion 12c of a mold 10, and a ceramic substrate 20 in the mold is applied. After pouring the molten aluminum into the mold so that it contacts one surface, the molten aluminum is cooled and solidified to form an aluminum circuit board 22 on one surface of the ceramic substrate and directly join it. Manufactures aluminum-ceramics bonded substrates. [Selection diagram] Fig. 1

Description

  The present invention relates to an aluminum-ceramic bonding substrate and a method for manufacturing the same, and in particular, aluminum in which an aluminum plate is bonded to a ceramic substrate by pouring molten aluminum into a mold in which the ceramic substrate is placed and then cooling to solidify the molten metal. The present invention relates to a ceramic bonded substrate and a manufacturing method thereof.

  In conventional power modules used to control large currents in electric vehicles, trains, machine tools, etc., a metal-ceramic insulating substrate is soldered to one side of a metal plate or composite material called a base plate. The semiconductor chip is fixed on the metal-ceramic insulating substrate by soldering. Further, a metal radiating fin or a cooling jacket is attached to the other surface (back surface) of the base plate through heat conductive grease by screwing or the like.

  Since the base plate and the semiconductor chip are soldered to the metal-ceramic insulating substrate by heating, the base plate is likely to warp due to the difference in thermal expansion coefficient between the joining members during soldering. Also, the heat generated from the semiconductor chip is released to the air and cooling water by the heat radiation fins and the cooling jacket through the metal-ceramic insulating substrate, the solder, and the base plate, so that the base plate warps during soldering. , The clearance when radiating fins and cooling jackets are attached to the base plate is increased, and the heat dissipation is extremely reduced. Furthermore, since the thermal conductivity of the solder itself is low, a higher heat dissipation is required for a power module through which a large current flows.

  In order to solve these problems, a metal-ceramic circuit board has been proposed in which a base plate made of aluminum or an aluminum alloy is directly bonded to a ceramic substrate without soldering between the base plate and the metal-ceramic insulating substrate. (For example, refer to Patent Document 1). In addition, as a mold for manufacturing such a metal-ceramic bonding substrate, a ceramic member is arranged inside, a molten metal is poured into the inside and brought into contact with both surfaces of the ceramic member, and then cooled and solidified. Thus, in the mold for joining the metal members to both surfaces of the ceramic member, when the ceramic member is arranged at a predetermined position in the mold, a space for forming the metal member is formed above and below the ceramic member. In addition, a mold has been proposed in which a molten metal flow path for communicating the upper and lower spaces of the ceramic member is formed, and a pouring port for pouring the molten metal is formed in the upper space of the ceramic member (for example, , See Patent Document 2).

  Aluminum ceramics in which an aluminum plate is bonded to a ceramic substrate by placing the ceramic substrate in such a mold, pouring molten aluminum into the mold, bringing it into contact with the surface of the ceramic substrate, and then cooling and solidifying. When manufacturing a bonded substrate, a mold release agent (carbon powder, silicon nitride powder, boron nitride powder, etc.) is applied in advance to the inner surface of the mold in order to prevent aluminum from being bonded (or adhered) to the mold. Yes.

  When a heat cycle is applied to such an aluminum-ceramic bonding substrate, thermal stress is generated due to the difference in thermal expansion between the ceramic and aluminum of the aluminum-ceramic bonding substrate, but aluminum is a soft metal. For this reason, the aluminum plate joined to the ceramic substrate is plastically deformed to relieve the stress. The strain at this time gathers at the aluminum crystal grain boundaries that are easily deformed, and a level difference occurs at the aluminum crystal grain boundaries. This step is dispersed and reduced when the crystal grain size of aluminum is small. However, when the crystal grain size is large, the crystal grain boundary is short, resulting in a large step.

  In addition, when an aluminum-ceramic bonding substrate is manufactured using a mold, the crystal grain size of aluminum bonded to the ceramic substrate becomes large, and a large step is generated at the crystal grain boundary of aluminum. When a thin semiconductor chip is mounted, stress is concentrated on the semiconductor chip due to the heat cycle during the mounting, and cracks are likely to occur.

  In order to solve such a problem, a method of refining crystal grains using a molten aluminum alloy such as an aluminum-silicon-boron alloy is known (see, for example, Patent Document 3).

JP 2002-76551 A (paragraph number 0015) Japanese Patent Laying-Open No. 2005-74434 (paragraph number 0008) JP 2008-253996 (paragraph number 0021)

  However, if a crystal grain is refined using a molten aluminum alloy such as an aluminum-silicon-boron alloy, the electrical conductivity of the aluminum plate bonded to the ceramic substrate is lowered and the electrical characteristics are deteriorated. There is a risk that the Vickers hardness will increase and the mechanical properties will deteriorate.

  Therefore, in view of such conventional problems, the present invention maintains the electrical conductivity and Vickers hardness of an aluminum plate bonded to a ceramic substrate when a mold is used to manufacture an aluminum-ceramic bonded substrate. An object of the present invention is to provide an aluminum-ceramic bonding substrate and a method for producing the same, which can make aluminum crystal grains fine.

  As a result of diligent research to solve the above problems, the present inventors have found that an aluminum plate forming portion that is a space for forming an aluminum plate, and a ceramic substrate on one surface of the aluminum plate formed in the aluminum plate forming portion. A mold in which a ceramic substrate housing portion, which is a space for housing a ceramic substrate so as to be in contact with each other, is prepared, and aluminum boride and a titanium-aluminum metal compound are formed on the inner surface of the aluminum plate forming portion of the mold. After applying a coating material containing at least one crystal grain refining agent, placing a ceramic substrate in the mold, pouring molten aluminum into the mold so as to be in contact with one surface of the ceramic substrate, aluminum By cooling and solidifying the molten metal, an aluminum plate is placed on one side of the ceramic substrate. If brought into formed directly bonded, it found that the crystal grains of the aluminum can be miniaturized while maintaining the electrical conductivity and Vickers hardness of the aluminum plate bonded to the ceramic substrate, thereby completing the present invention.

  That is, in the method for manufacturing an aluminum / ceramic bonding substrate according to the present invention, the ceramic substrate comes into contact with an aluminum plate forming portion which is a space for forming an aluminum plate and one surface of the aluminum plate formed in the aluminum plate forming portion. In this way, a mold having a ceramic substrate housing portion that is a space for housing a ceramic substrate is prepared, and at least one of aluminum boride and a titanium-aluminum metal compound is formed on the inner surface of the aluminum plate forming portion of the mold. Apply a coating material containing the crystal grain refining agent, place a ceramic substrate in this mold, pour molten aluminum into the mold so that it contacts one side of this ceramic substrate, and then cool the molten aluminum And solidify on one side of the ceramic substrate And characterized in that directly bonded to form aluminum plate.

In this method for producing an aluminum / ceramic bonding substrate, the aluminum boride is preferably at least one of aluminum diboride and aluminum dodecaboride, and the titanium-aluminum metal compound is preferably TiAl _3. . The content of the crystal grain refining agent in the coating material is preferably 0.1 to 15% by mass. The coating material may contain a release agent. In this case, the release agent preferably contains boron nitride, and the content of the release agent in the coating material is preferably 20% by mass or less. The coating material preferably contains a solvent, and the coating material is preferably applied by spray coating. Also, an aluminum base plate forming portion, which is a space for forming the aluminum base plate, is formed inside the mold, and when the molten aluminum is poured into the mold and brought into contact with one surface of the ceramic substrate, the other side of the ceramic substrate is formed. When an aluminum plate is formed on one surface of the ceramic substrate and directly bonded to the other surface of the ceramic substrate, an aluminum base plate may be formed on the other surface of the ceramic substrate and directly bonded.

  The aluminum-ceramic bonding substrate according to the present invention is a cross-section obtained by cutting an aluminum-ceramic bonding substrate in which the aluminum plate is directly bonded to one surface of the ceramic substrate and the aluminum base plate is directly bonded to the other surface in the thickness direction. In the invention, the number of aluminum crystal grains in a region of 10 mm × 0.4 mm of each cross section of the aluminum plate and the aluminum base plate is 10 or more and 8 or less, respectively.

  In this aluminum-ceramic bonding substrate, the aluminum plate preferably has a Vickers hardness Hv of 23 or less, and the aluminum plate preferably has a conductivity of 60% IACS or more.

  According to the present invention, when an aluminum-ceramic bonding substrate is manufactured using a mold, the aluminum crystal grains can be refined while maintaining the electrical conductivity and Vickers hardness of the aluminum plate bonded to the ceramic substrate. An aluminum-ceramic bonding substrate and a method for manufacturing the same can be provided.

It is sectional drawing of the casting_mold | template used in embodiment of the manufacturing method of the aluminum ceramics bonded substrate by this invention. FIG. 2 is a plan view of an aluminum-ceramic bonding substrate manufactured using the mold shown in FIG. 1. It is the IIB-IIB sectional view taken on the line of FIG. 2A. 4 is an optical micrograph of a cross section of the aluminum-ceramic bonding substrate obtained in Example 3. FIG.

  In the embodiment of the method for manufacturing an aluminum / ceramic bonding substrate according to the present invention, an aluminum plate forming portion which is a space for forming an aluminum plate and a ceramic substrate on one surface of the aluminum plate formed in the aluminum plate forming portion. A mold in which a ceramic substrate housing portion, which is a space for housing a ceramic substrate so as to contact, is prepared, and at least aluminum boride and a titanium-aluminum metal compound are formed on the inner surface of the aluminum plate forming portion of the mold. A coating material containing a crystal grain refining agent composed of one side is applied, a ceramic substrate is placed in the mold, and a molten aluminum (preferably pure Al (preferably Al. 99.000) is placed in contact with one surface of the ceramic substrate. 9 mass% or more or 99.99 mass% or more) molten aluminum) By solidifying the molten aluminum by cooling after pouring into the mold, thereby directly bonded to form an aluminum plate on one surface of the ceramic substrate. By this method, an aluminum-ceramic bonding substrate in which an aluminum plate having a small aluminum crystal grain size is bonded to a ceramic substrate can be manufactured. In particular, since a coating material containing a crystal grain refining agent is applied to the inner surface of the aluminum plate forming portion of the mold, the aluminum crystal grains near the surface of the aluminum plate joined to one surface of the ceramic substrate are refined. be able to.

In this method for producing an aluminum / ceramic bonding substrate, aluminum boride or a titanium-aluminum metal compound capable of refining crystal grains is used as a crystal grain refining agent as a solidification nucleus component of aluminum. When titanium diboride (TiB ₂ ) is used as the crystal grain refining agent, TiB ₂ has a low crystal grain refining ability and a large amount of TiB ₂ needs to be used, and it is uniformly applied to the inner surface of the mold. Therefore, at least one of aluminum boride and a titanium-aluminum metal compound is used. The aluminum boride is preferably at least one of aluminum diboride (AlB ₂ ) and aluminum dodecaboride (AlB ₁₂ ), and the titanium-aluminum-based metal compound is titanium trialuminide (TiAl ₃ ). Is preferred. In addition, it is preferable that content of the crystal grain refining agent in a coating material is 0.1-15 mass%.

The coating material may contain a release agent. This mold release agent can contain powders such as carbon (C), silicon nitride (Si ₃ N ₄ ), boron nitride (BN), etc. as a mold release component, but contains boron nitride (powder). preferable. The content of the release agent in the coating material is preferably 20% by mass or less, and more preferably 15% by mass or less. Moreover, it is preferable that content of the mold release component in a coating material is 5 mass% or less.

  The coating material preferably contains a solvent, and the coating material is preferably applied by spray coating. As this solvent, methyl isobutyl ketone (MIBK), dimethyl ether (DME), methyl ethyl ketone (MEK), and the like can be used, but methyl ethyl ketone (MEK) is preferably used.

  Also, an aluminum base plate forming portion, which is a space for forming the aluminum base plate, is formed inside the mold, and when the molten aluminum is poured into the mold and brought into contact with one surface of the ceramic substrate, the other side of the ceramic substrate is formed. When an aluminum plate is formed on one surface of the ceramic substrate and directly bonded to the other surface of the ceramic substrate, an aluminum base plate may be formed on the other surface of the ceramic substrate and directly bonded. The aluminum base plate may be an aluminum base plate in which a large number of pins and fins are integrally formed on a surface (back surface) opposite to the ceramic substrate. Further, a reinforcing material made of a ceramic substrate or the like may be disposed inside the aluminum base plate.

  The temperature of the molten aluminum poured into the mold is preferably 5 to 200 ° C., more preferably 20 to 200 ° C. higher than the melting point of aluminum (660 ° C.). In addition, the cooling rate when the molten aluminum is cooled and solidified (by cooling the mold) suppresses thermal shock to the ceramic substrate, prevents cracking of the ceramic substrate, and makes it difficult to increase the crystal grain size. A cooling rate in the range of, for example, 10 ° C./min to 100 ° C./min is preferred, and a cooling rate in the range of 20 ° C./min to 50 ° C./min is more preferred. The mold is preferably cooled by bringing the cooling plate into contact with the mold (the surface opposite to the pouring port) to cool the mold and solidify the molten aluminum. In this mold cooling, nitrogen gas is blown into the pouring port and the molten aluminum in the mold is cooled while being pressurized, and solidification starts from the molten aluminum in the mold facing the mold surface that the cooling plate contacts. It is preferable that the molten aluminum is sequentially solidified toward the molten aluminum on the pouring port side, and the molten aluminum on the pouring port side is solidified last.

  The ceramic substrate may be an oxide ceramic substrate such as alumina, or a non-oxide ceramic substrate such as aluminum nitride or silicon nitride. Further, as the mold, it is preferable to use a carbon mold that does not easily react with the molten aluminum as compared with the metal mold. In particular, when the molten metal is pressurized, gas remains between the mold and the molten metal. A porous carbon mold so that the remaining gas is allowed to pass through the mold and prevents the molten metal from passing through the mold so that the molten metal can easily reach the end of the mold. Is preferably used.

  According to the embodiment of the method for manufacturing an aluminum / ceramic bonding substrate described above, the number of aluminum crystal grains in a 50 mm × 50 mm region of the surface of the aluminum plate bonded to one surface of the ceramic substrate is 40 or more (preferably 70 or more, more preferably 100 or more, and most preferably 200 or more) (aluminum crystallites of an aluminum plate are refined) can be produced.

  In the embodiment of the method for manufacturing an aluminum-ceramic bonding substrate described above, an aluminum base plate forming portion, which is a space for forming an aluminum base plate, is formed inside the mold, and molten aluminum is poured into the mold. When making contact with one surface of the ceramic substrate, contact with the other surface of the ceramic substrate, and when forming an aluminum plate on one surface of the ceramic substrate and directly bonding it, an aluminum base is formed on the other surface of the ceramic substrate. When the plate is formed and directly bonded, the aluminum plate has a Vickers hardness Hv of 23 or less (preferably 22 or less, more preferably 21 or less) and a conductivity of 60% IACS or more (preferably 61% IACS or more). And more preferably 62% IACS or higher) Thus, in the cross section obtained by cutting the aluminum / ceramic bonding substrate in the thickness direction, the cross section of the aluminum plate (in the direction parallel to the main surface (plate surface) of the aluminum plate) 10 mm × (the side opposite to the ceramic substrate of the aluminum plate) There are 10 or more (preferably 12 or more) aluminum crystal grains in a 0.4 mm region (in the direction perpendicular to the plate surface), and in a 10 mm × 0.4 mm region of the cross section of the aluminum base plate. Bonded to one surface of an aluminum-ceramic bonding substrate (ie, the aluminum crystal particles of the aluminum base plate are not miniaturized) having 8 or less (preferably 6 or less) aluminum crystal grains Aluminum-ceramic having different number of aluminum crystal grains and different number of aluminum crystal grains bonded to the other surface It is possible to manufacture a bonding substrate.

  FIG. 1 schematically shows a mold used in an embodiment of a method for producing an aluminum / ceramic bonding substrate according to the present invention. As shown in FIG. 1, a mold 10 used in the method of manufacturing an aluminum / ceramic bonding substrate according to the present embodiment has a lower mold member 12 having a substantially rectangular planar shape, and a lid for the lower mold member 12. The upper mold member 14 has a substantially rectangular planar shape. On the upper surface of the lower mold member 12, a recess (aluminum base plate forming portion for forming the aluminum base plate) 12a having substantially the same shape and size as the aluminum base plate is formed. On the bottom surface of the aluminum base plate forming portion 12a, one or a plurality of recesses (one shown in FIG. 1) having substantially the same shape and size as the ceramic substrate (a ceramic substrate housing portion for housing the ceramic substrate). ) 12b is formed. On the bottom surface of each ceramic substrate housing portion 12b, one or a plurality of recesses (one is shown in FIG. 1) having substantially the same shape and size as the aluminum circuit board (aluminum for forming the aluminum circuit board). Circuit board forming portion) 12c is formed. On the bottom surface of the upper mold member 14 (the surface facing the lower mold member 12), a pouring port 14a for pouring molten metal into the mold 10 from a pouring nozzle (not shown) is formed. The lower mold member 12 is formed with a molten metal passage (not shown) extending between the aluminum base plate forming portion 12a and the aluminum circuit plate forming portion 12c, and the ceramic substrate is accommodated in the ceramic substrate accommodating portion 12b. In this case, the aluminum base plate forming portion 12a and the aluminum circuit plate forming portion 12c communicate with each other. Further, the pouring nozzle (not shown) has a narrow flow path communicating with an external melt supply section (not shown), and the aluminum melt supplied from the melt supply section is oxidized with aluminum through the narrow flow path. While removing the film, the molten metal can be poured into the mold 10 from the pouring port 14a.

  Next, a method for manufacturing an aluminum / ceramic bonding substrate using the mold 10 will be described. First, a coating material containing the above-mentioned crystal grain refining agent is applied to the inner surface of the aluminum circuit board forming portion 12c of the lower mold member 12 of the mold 10, and the ceramic substrate housing portion 12b of the lower mold member 12 of the mold 10 is applied. After the ceramic substrate is placed inside, the lower mold member 12 is covered with the upper mold member 14, and the aluminum base plate forming portion 12a of the mold 10 is poured and filled with molten aluminum (not shown). The molten metal is filled up to the aluminum circuit board forming portion 12c through the flow path, and then cooled to solidify the molten metal. Thus, as shown in FIG. 3, an aluminum-ceramic bonding in which one surface of the ceramic substrate 20 is directly bonded to the aluminum circuit board 22 and the aluminum base plate 24 is directly bonded to the other surface of the ceramic substrate 20. A substrate can be manufactured.

  A circuit pattern forming resist having a circuit pattern shape is printed on the aluminum circuit board 22 of the aluminum-ceramic bonding substrate thus manufactured, and unnecessary portions of the aluminum circuit board 22 are removed by etching, and then the circuit pattern forming resist is removed. The circuit pattern may be formed by peeling. Further, a portion such as a semiconductor chip on the aluminum circuit board 22 that needs to be soldered may be plated by Ni plating or the like.

As described above, when a coating material containing a crystal grain refining agent is applied to the inner surface of the aluminum circuit board forming portion 12c of the lower mold member 12 of the mold 10, generation of solidification nuclei of aluminum in the aluminum circuit board forming portion 12c is generated. As the number increases, the aluminum crystal grains of the aluminum circuit board 22 formed in the aluminum circuit board forming portion 12c are refined. On the other hand, instead of applying a coating material containing a crystal grain refining agent, instead of using a molten aluminum, a molten aluminum alloy containing an additive such as B or Ti is used. Starting from the particles (particles of crystal grain refining agents such as AlB ₂ and TiAl ₃ ), the number of aluminum alloy solidification nuclei increased during solidification of the molten metal, and the crystal grains of the aluminum alloy of the circuit board and the base board increased. It is refined as a whole. In addition, when an aluminum alloy melt containing an additive is used instead of an aluminum melt, due to changes in the composition of the melt (such as defects in the corners of circuit boards and base boards, shrinkage nests and voids, intergranular cracks, etc.) Structural defects may occur, and yield may be reduced.

  Hereinafter, examples of the aluminum-ceramic bonding substrate and the method for manufacturing the same according to the present invention will be described in detail.

[Example 1]
1% by mass of AlB ₂ (average particle diameter D ₅₀ = 6.6 μm) and 12.4% by mass of a release agent (LBN FK-26 manufactured by Showa Denko KK (20% by mass of BN (average particle diameter D ₅₀ = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent))) and 86.6 wt% methyl ethyl ketone coating material (of BN in the coating material) The content is 2.48% by mass) by a ball mill, and this coating material is substantially uniform (coating amount is substantially 0) on the entire inner surface of the metal circuit board forming portion of the mold similar to the mold 10 shown in FIG. (4 mg / cm ² ).

  Next, after a ceramic substrate made of aluminum nitride having a size of 70 mm × 70 mm × 0.6 mm is accommodated in the mold, the mold is placed in a furnace, the inside of the furnace is heated to 725 ° C., and the pressure is 11 kPa. An aluminum melt having a purity of 99.9% by mass (3N) (at a temperature of 725 ° C.) was poured into the mold.

  Thereafter, the cooling plate was brought into contact with the mold (the surface opposite to the pouring port) to cool the mold and solidify the molten aluminum. In this mold cooling, nitrogen gas is blown into the pouring port, and the molten aluminum in the mold is pressurized while being cooled at an average cooling rate of 50 ° C./min, and the mold facing the mold surface with which the cooling plate contacts. Solidification was started from the molten aluminum in the inner part, and the solidification was sequentially performed toward the molten aluminum on the pouring port side so that the molten aluminum on the pouring port side solidified last.

  In this way, the 65 mm × 65 mm × 0.6 mm aluminum plate (aluminum circuit board) is in direct contact with and joined to one surface of the ceramic substrate (the surface on the aluminum circuit board forming portion side) and the other surface (aluminum). An aluminum plate (aluminum base plate) of 80 mm × 100 mm × 1.5 mm is directly contacted and joined to the surface on the base plate forming part side, and this joined body is taken out from the mold, and FIG. 2A and FIG. An aluminum-ceramic bonding substrate as shown in 2B was obtained.

  After polishing the surface of the aluminum circuit board of the aluminum-ceramic bonding substrate thus obtained and performing an etching treatment with a ferric chloride solution, aluminum in a 50 mm × 50 mm region on the surface of the aluminum circuit board was obtained. When the number of crystal grains was counted visually, the number of crystal grains was 82. Further, the obtained aluminum-ceramic bonding substrate was put into a liquid phase thermal shock test apparatus, and after holding a thermal cycle of holding at −40 ° C. for 4 minutes and then holding at 125 ° C. for 4 minutes 1000 times, a laser displacement meter ( When the level difference of the crystal grain boundary on the surface of the aluminum circuit was measured by a high-precision shape measurement system K2-310 manufactured by Kozu Seiki Co., Ltd., the maximum value of the level difference was 121 μm.

[Example 2]
3% by mass of AlB ₂ (average particle diameter D ₅₀ = 6.6 μm) and 12.1% by mass of a release agent (LBN FK-26 manufactured by Showa Denko KK (20% by mass of BN (average particle diameter D ₅₀ = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent)) and 84.9 wt% methyl ethyl ketone (coating material of BN in the coating material) An aluminum-ceramic bonding substrate was prepared in the same manner as in Example 1 except that the content was 2.42% by mass), and the number of aluminum crystal grains on the surface of the aluminum circuit board and after the thermal cycle The maximum value of the step of the crystal grain boundary was obtained. As a result, the number of aluminum crystal grains was 115, and the maximum value of the crystal grain boundary step was 140 μm.

[Example 3]
4% by mass of AlB ₂ (average particle size D ₅₀ = 6.6 μm) and 12.0% by mass of release agent (LBN FK-26 (20% by mass of BN (average particle size D ₅₀ manufactured by Showa Denko KK)) = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent)) and 84.0 wt% methyl ethyl ketone (BN of coating material) The aluminum-ceramic bonding substrate was prepared by the same method as in Example 1 except that the content was 2.40% by mass), and the number of aluminum crystal grains on the surface of the aluminum circuit board and after the thermal cycle The maximum value of the step of the crystal grain boundary was obtained. As a result, the number of aluminum crystal grains was 92, and the maximum value of the step of the crystal grain boundary was 131 μm. The electrical conductivity of the aluminum circuit board was measured at 480 kHz using an eddy current conductivity meter (Sigma Test 2.069 manufactured by Nihon Felster Co., Ltd.) and found to be 63.3% IACS. Furthermore, the Vickers hardness Hv of the surface of the aluminum circuit board was measured by applying a test load of 1 kgf for 5 seconds with a micro Vickers hardness meter (HM-210 manufactured by Mitutoyo Corporation) and found to be 20.2.

  The obtained aluminum-ceramic bonding substrate was cut in the thickness direction, its cross section was polished, and after etching with a ferric chloride solution, aluminum crystal grains in the cross section were observed. As shown in FIG. 3, the crystal grains were refined in the aluminum circuit board 22 bonded to one surface of the ceramic substrate 20, but the crystal grains were coarse in the aluminum base plate 24 bonded to the other surface. In addition, 10 mm × (in a direction parallel to the main surface (plate surface) of the aluminum plate) of each cross section of the aluminum circuit plate 22 and the aluminum base plate 24 (perpendicular to the plate surface from the surface opposite to the ceramic substrate of the aluminum plate). When the number of aluminum crystal grains in a 0.4 mm region (in any direction) (at least part of the aluminum crystal grains present in the region) was visually counted from a 100 × optical micrograph, The number was 16 and the number of aluminum base plate 24 was 5.

[Example 4]
5% by mass of AlB ₂ (average particle diameter D ₅₀ = 6.6 μm) and 11.9% by mass of a release agent (LBN FK-26 manufactured by Showa Denko KK (20% by mass of BN (average particle diameter D ₅₀ = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent)) and 83.1 wt% methyl ethyl ketone coating material (of BN in the coating material) An aluminum-ceramic bonding substrate was prepared in the same manner as in Example 1 except that the content was 2.38% by mass), and the number of aluminum crystal grains on the surface of the aluminum circuit board and after the thermal cycle The maximum value of the step of the crystal grain boundary was obtained. As a result, the number of aluminum crystal grains was 112, and the maximum value of the step of the crystal grain boundary was 122 μm.

[Example 5]
10% by mass of AlB ₂ (average particle diameter D ₅₀ = 6.6 μm) and 11.3% by mass of a release agent (LBN FK-26 manufactured by Showa Denko KK (20% by mass of BN (average particle diameter D ₅₀ = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent))) and 78.8 wt% methyl ethyl ketone coating material (of BN in the coating material) An aluminum-ceramic bonding substrate was prepared in the same manner as in Example 1 except that the content was 2.26% by mass), and the number of aluminum crystal grains on the surface of the aluminum circuit board was determined. As a result, the number of aluminum crystal grains was 316.

[Example 6]
1% by mass of TiAl ₃ (average particle size D ₅₀ = 24 μm) and 12.4% by mass of a release agent (LBN FK-26 manufactured by Showa Denko KK (20% by mass of BN (average particle size D ₅₀ = 0) .23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent)) and 86.6 wt% methyl ethyl ketone (BN content in the coating material) Is 2.48 mass%), and an aluminum-ceramic bonding substrate is prepared by the same method as in Example 1, and the number of aluminum crystal grains on the surface of the aluminum circuit board and the crystal after the cooling and heating cycle. The maximum value of the grain boundary step was determined. As a result, the number of aluminum crystal grains was 375, and the maximum value of the step of the crystal grain boundary was 113 μm. Further, when the electrical conductivity of the aluminum circuit board and the surface Vickers hardness Hv were measured by the same method as in Example 3, the electrical conductivity was 62.1% IACS and the Vickers hardness Hv was 19.6. It was. Further, when the number of aluminum crystal grains in the 10 mm × 0.4 mm region of each cross section of the aluminum circuit board and the aluminum base board was visually counted by the same method as in Example 3, the aluminum circuit board had 16 The number was 5 for the aluminum base plate.

[Comparative Example 1]
Release agent of 12.5% by mass (LBN FK-26 manufactured by Showa Denko KK (release agent comprising 20% by mass of BN, 6.5% by mass of organic binder, and 73.5% by mass of solvent) ) And 87.5% by mass of methyl ethyl ketone (except that the content of BN in the coating material is 2.50% by mass). The number of aluminum crystal grains on the surface of the aluminum circuit board and the maximum value of the step of the crystal grain boundary after the cooling and heating cycle were obtained. As a result, the number of aluminum crystal grains was 21, and the maximum value of the step of the crystal grain boundary was 179 μm. Further, when the electrical conductivity of the aluminum circuit board and the surface Vickers hardness Hv were measured by the same method as in Example 3, the electrical conductivity was 62.1% IACS and the Vickers hardness Hv was 20.3. It was. Further, when the number of aluminum crystal grains in the 10 mm × 0.4 mm region of each cross section of the aluminum circuit board and the aluminum base plate was visually counted by the same method as in Example 3, it was 6 for the aluminum circuit board. The number was 4 for the aluminum base plate.

[Comparative Example 2]
1% by weight of TiB ₂ (average particle diameter D ₅₀ = 2.9 μm) and 12.4% by weight of release agent (LBN FK-26 (20% by weight of BN (average particle diameter D ₅₀ ) manufactured by Showa Denko KK) = 0.23 μm), 6.5 wt% organic binder and 73.5 wt% solvent release agent))) and 86.6 wt% methyl ethyl ketone coating material (of BN in the coating material) An aluminum-ceramic bonding substrate was produced by the same method as in Example 1 except that the content was 2.48% by mass), and the number of aluminum crystal grains on the surface of the aluminum circuit board was determined. There were 37.

[Comparative Example 3]
An aluminum alloy melt containing 0.4 mass% Si, 0.04 mass% B, and 0.01 mass% Fe with the balance being Al instead of the 99.9 mass% (3N) molten aluminum An aluminum-ceramic bonding substrate was produced by the same method as in Comparative Example 1 except that the number of aluminum crystal grains on the surface of the aluminum circuit board was determined. Further, when the electrical conductivity of the aluminum circuit board and the surface Vickers hardness Hv were measured by the same method as in Example 3, the electrical conductivity was 59.4% IACS and the Vickers hardness Hv was 25.2. It was. Further, when the number of aluminum crystal grains in the 10 mm × 0.4 mm region of each cross section of the aluminum circuit board and the aluminum base board was visually counted by the same method as in Example 3, the aluminum circuit board had 31 The number was 22 for the aluminum base plate.

[Comparative Example 4]
Instead of 99.9% by mass (3N) molten aluminum, 0.20 to 0.6% by mass of Si, 0.35% by mass or less of Fe, 0.10% by mass or less of Cu and 0.10% by mass % Mn, 0.45 to 0.9 mass% Mg, 0.10 mass% or less Cr, 0.10 mass% or less Zn, 0.10 mass% and other elements 0.15 mass% In addition, an aluminum-ceramic bonding substrate was prepared by the same method as in Comparative Example 1 except that a molten aluminum alloy (a molten JIS A6063 alloy) made of Al was used, and aluminum crystals on the surface of the aluminum circuit board were produced. When the number of grains was determined, it was 2212. Further, when the electrical conductivity of the aluminum circuit board and the surface Vickers hardness Hv were measured by the same method as in Example 3, the electrical conductivity was 50.4% IACS and the Vickers hardness Hv was 43.8. It was. Further, when the number of aluminum crystal grains in the 10 mm × 0.4 mm region of each cross section of the aluminum circuit board and the aluminum base plate was visually counted by the same method as in Example 3, it was 32 for the aluminum circuit board. The number was 33 for the aluminum base plate.

  The results of these examples and comparative examples are shown in Tables 1 and 2.

DESCRIPTION OF SYMBOLS 10 Mold 12 Lower mold member 12a Aluminum base board formation part 12b Ceramic substrate accommodating part 12c Aluminum circuit board formation part 14 Upper mold member 14a Pouring port 20 Ceramic board 22 Aluminum circuit board 24 Aluminum base board

Claims (13)

An aluminum plate forming portion that is a space for forming an aluminum plate, and a ceramic substrate housing portion that is a space for housing the ceramic substrate so that the ceramic substrate comes into contact with one surface of the aluminum plate formed in the aluminum plate forming portion. Is prepared, and a coating material containing a crystal grain refining agent composed of at least one of aluminum boride and a titanium-aluminum metal compound is applied to the inner surface of the aluminum plate forming portion of the mold. A ceramic substrate is placed in the mold, and after pouring the molten aluminum into the mold so as to be in contact with one surface of the ceramic substrate, the molten aluminum is cooled and solidified, whereby aluminum is applied to one surface of the ceramic substrate. Aluminium, characterized by forming a plate and bonding directly Manufacturing method of La mix bonded substrate. The method for producing an aluminum / ceramic bonding substrate according to claim 1, wherein the aluminum boride is at least one of aluminum diboride and aluminum dodecaboride. The titanium - and wherein the aluminum-based metal compound is TiAl _3, aluminum according to claim 1 - method of manufacturing a ceramic bonding substrate. The method for producing an aluminum-ceramic bonding substrate according to any one of claims 1 to 3, wherein the content of the crystal grain refining agent in the coating material is 0.1 to 15% by mass. The method for producing an aluminum / ceramic bonding substrate according to claim 1, wherein the coating material contains a release agent. 6. The method for producing an aluminum / ceramic bonding substrate according to claim 5, wherein the release agent contains boron nitride. 7. The method for producing an aluminum / ceramic bonding substrate according to claim 5, wherein the content of the release agent in the coating material is 20% by mass or less. The method for producing an aluminum / ceramic bonding substrate according to claim 1, wherein the coating material contains a solvent. The method for producing an aluminum-ceramic bonding substrate according to any one of claims 1 to 8, wherein the coating material is applied by spray coating. An aluminum base plate forming portion, which is a space for forming an aluminum base plate, is formed inside the mold, and when the molten aluminum is poured into the mold and brought into contact with one surface of the ceramic substrate, the ceramics An aluminum base plate is formed on the other surface of the ceramic substrate and directly bonded when the aluminum plate is formed on one surface of the ceramic substrate and directly bonded to the other surface of the ceramic substrate. A method for producing an aluminum-ceramic bonding substrate according to any one of claims 1 to 9. Each of the aluminum plate and the aluminum base plate is cut in the thickness direction of the aluminum-ceramic bonding substrate in which the aluminum plate is directly bonded to one surface of the ceramic substrate and the aluminum base plate is directly bonded to the other surface. An aluminum-ceramic bonding substrate, wherein the number of aluminum crystal grains in a region of 10 mm × 0.4 mm is 10 or more and 8 or less, respectively. The aluminum-ceramic bonding substrate according to claim 11, wherein the aluminum plate has a Vickers hardness Hv of 23 or less. The aluminum-ceramic bonding substrate according to claim 11 or 12, wherein the conductivity of the aluminum plate is 60% IACS or more.

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