JP4864593B2 - Method for producing aluminum-silicon carbide composite - Google Patents

Description

The present invention relates to an aluminum-silicon carbide composite suitable as a base plate for a power module and a heat dissipation component using the same.

Today, as the integration and size of semiconductor elements increase, the amount of generated heat continues to increase, and the issue is how to efficiently dissipate heat. And, for example, a copper or aluminum metal circuit is formed on the surface of a ceramic substrate such as an aluminum nitride substrate or a silicon nitride substrate, and a metal heat sink made of copper or aluminum is formed on the back surface. The circuit board thus formed is used as a power module circuit board.

A typical heat dissipation structure of a conventional circuit board is formed by soldering a base plate via a metal plate, for example, a copper plate, on the back surface (heat dissipation surface) of the circuit board, and copper is generally used as a material for the base plate. It was the target. However, in this structure, when a thermal load is applied to the semiconductor device, a crack caused by a difference in thermal expansion coefficient between the base plate and the circuit board occurs in the solder layer, resulting in insufficient heat dissipation and the semiconductor element. There was a problem of malfunctioning or damaging.

Therefore, an aluminum alloy-silicon carbide composite has been proposed as a base plate having a thermal expansion coefficient close to that of a circuit board (Patent Document 1).
Japanese National Publication No. Hei 3-509860.

The base plate is often used by being joined to a heat radiating fin, and the shape and warpage of the joined portion are also important characteristics. For example, when joining the base plate to the heat radiating fins, generally, heat radiating grease with high thermal conductivity is applied, and screws are fixed to the heat radiating fins or the heat radiating unit using the holes provided on the peripheral edge of the base plate. If there are a lot of minute irregularities on the plate, a gap will be created between the base plate and the heat radiating fins, and even if high heat conductive heat dissipation grease is applied, the heat transfer will be significantly reduced, resulting in a ceramic circuit board, There existed a subject that the heat dissipation of the whole module comprised with a base board, a radiation fin, etc. will fall remarkably.

Therefore, in order to prevent a gap as much as possible between the base plate and the heat radiating fin, a base plate with a convex warp is used in advance. This warpage is usually obtained by applying pressure to the base plate under heating using a jig having a predetermined shape (Patent Document 2). However, the warpage obtained by this method has a problem that the amount of warpage varies and the shape is not constant, so that the quality is not stable. In addition, there is a problem in that a large gap is generated between the heat dissipating fins due to variations in the warp shape and surface irregularities.
Japanese Patent No. 3792180

A method of warping the surface of the base plate by machining has also been proposed, but the aluminum-silicon carbide composite is very hard and requires a lot of grinding using a tool such as diamond. There was a problem that the cost would be high.

Therefore, in order to solve the above problems, a flat silicon carbide porous body is impregnated with a metal containing aluminum as a main component, and an aluminum alloy layer made of a metal containing aluminum as a main component is provided on both main surfaces. A method of machining an aluminum alloy layer is proposed (Patent Document 3).
Japanese Patent No. 3732193

  However, the base plate manufactured using the above method has a thick surface aluminum alloy layer after machining, and as a result, the coefficient of thermal expansion of the base plate itself increases, and the ceramic circuit board is assembled during power module assembly. When the soldering is performed, a dent may occur on the heat dissipation surface of the ceramic circuit board.

  Furthermore, in the above method, there is a problem that advanced processing techniques are required to uniformly control the thickness of the aluminum alloy layers on both main surfaces and not to expose the aluminum-silicon carbide composite. there were.

The present invention has been made in view of the above situation, and an object thereof is to provide an aluminum-silicon carbide composite suitable as a base plate for a power module.

  As a result of diligent investigations to achieve the above object, the present inventor has obtained aluminum-silicon carbide obtained by impregnating a flat silicon carbide based porous material with a metal containing aluminum as a main component (hereinafter referred to as an aluminum alloy). In the porous composite, an aluminum alloy layer made of an aluminum alloy was formed on both main surfaces, the thickness of the aluminum alloy layer was controlled, and further, warp was applied in advance using the creep deformation of the aluminum-silicon carbide composite. Thereafter, the main surface subjected to warpage in the concave mold direction is subjected to surface grinding to expose the aluminum-silicon carbide composite, and further heat-treated at a temperature higher than the warpage treatment, whereby the aluminum-silicon carbide composite The present invention was completed by obtaining the knowledge that a convex warp having almost no depression can be formed on the exposed surface.

That is, the present invention provides an aluminum alloy layer in which a flat silicon carbide based porous material is impregnated with an aluminum alloy and has an aluminum alloy layer made of a metal mainly composed of aluminum having an average thickness of 10 to 150 μm on both main surfaces. A silicon carbide composite,
(1) Applying a predetermined amount of warp by creep deformation by applying heat at a temperature of 400 to 500 ° C. for 30 seconds or more while applying stress.
(2) The surface that has been warped in the concave direction is subjected to surface grinding to expose the aluminum-silicon carbide composite,
(3) By performing heat treatment at a temperature of 500 to 560 ° C. for 1 minute or longer, the creep deformation at the time of warping is removed,
It is a method for producing an aluminum-silicon carbide composite, wherein a convex warp is formed on a surface where the aluminum-silicon carbide composite is exposed.

In addition, the present invention is a method for producing an aluminum-silicon carbide based composite, wherein the aluminum-silicon carbide based composite is manufactured by a high-pressure forging method.

Furthermore, the present invention is characterized in that the amount of warpage of the surface from which the aluminum-silicon carbide composite is exposed is 20 to 200 μm per 10 cm in length, and the indentation depth in the surface is 50 μm or less. This is an aluminum-silicon carbide composite obtained by the above production method.

In addition, the present invention is an aluminum-silicon carbide composite having a thermal conductivity of 180 W / mK or more and a thermal expansion coefficient at a temperature of 150 ° C. of 9 × 10 ⁻⁶ / K or less. The aluminum-silicon carbide composite is a heat dissipating component formed by applying a Ni plating treatment to form a plating film having a thickness of 1 to 20 μm and bonding a ceramic substrate for mounting a semiconductor.

  The aluminum-silicon carbide composite of the present invention has characteristics of low thermal expansion and high thermal conductivity. By disposing a thin and uniform aluminum alloy layer on one main surface to be soldered to a ceramic circuit board of a flat aluminum-silicon carbide composite, by providing plating properties and grinding the heat radiation surface The flatness can be remarkably improved, and the heat dissipation after soldering with the ceramic circuit board is better than the conventional warping method. It is suitable as a plate.

  There are roughly two types of metal-ceramic composite production methods: impregnation and powder metallurgy. Among them, the powder metallurgy method has not been obtained in terms of characteristics such as thermal conductivity, and what is actually commercialized is the impregnation method. There are various methods of impregnation, and there are a method of performing under normal pressure and a method of performing under high pressure (high pressure forging method). High pressure forging methods include a molten metal forging method and a die casting method.

  A method suitable for the present invention is a high-pressure forging method in which impregnation is performed under high pressure, and either a molten metal forging method or a die casting method can be used, but a molten metal forging method is more preferable. The high-pressure forging method is a method in which a ceramic porous body (hereinafter referred to as a preform) is loaded in a high-pressure vessel, and a molten aluminum alloy is impregnated at a high temperature and high pressure to obtain a composite.

Hereinafter, the example of a manufacturing method by the molten metal forging method is demonstrated about this invention.
A silicon carbide powder as a raw material (a binder such as silica is added as necessary) is molded and fired to prepare a preform. The obtained preform may be subjected to surface processing as necessary in order to ensure a predetermined flatness. Although the method of laminating the preform to form one block is not particularly limited, for example, the following method may be mentioned. A method in which the preform is sandwiched and laminated with a release plate coated with a release agent to form one block, arranged on both surfaces of the preform so that fibers mainly composed of alumina or silica are in direct contact with each other, A method of forming a block by sandwiching it with a release plate, and further using a mold that forms a space of a desired shape combined from a plurality of members and one or more holes that connect the space and the outside. In this method, the preform is placed in a space in the mold and sandwiched between release plates coated with a release agent to form a single block.

Next, after preheating the block at about 500 to 750 ° C., one or more blocks are placed in a high-pressure vessel, and molten aluminum alloy is supplied as quickly as possible to prevent the temperature of the block from decreasing to 30 MPa or more. The aluminum-silicon carbide composite in which the aluminum alloy layers are provided on both main surfaces is obtained by pressurizing at a pressure of 1 to impregnate the aluminum alloy in the gaps of the preform. The impregnated product is annealed for the purpose of removing distortion during impregnation.

  The aluminum alloy in the aluminum-silicon carbide based composite of the present invention preferably has a melting point as low as possible in order to sufficiently penetrate into the voids of the preform when impregnated. Examples of such an aluminum alloy include an aluminum alloy containing 5 to 25% by mass of silicon. Further, it is preferable to contain magnesium because the bond between the silicon carbide particles and the metal portion becomes stronger. The metal components other than aluminum, silicon, and magnesium in the aluminum alloy are not particularly limited as long as the characteristics do not change extremely. For example, copper or the like may be contained.

  In the present invention, in order to form a uniform aluminum alloy layer having a predetermined thickness on the preform surface, the molded or fired product is surface-treated so that the in-plane thickness variation is 100 μm or less, preferably 30 μm or less. It is preferable. If the thickness variation in the surface of the preform exceeds 100 μm, the variation in the thickness of the surface aluminum alloy layer of the obtained aluminum-silicon carbide composite is undesirably large.

The preform is sandwiched and laminated between release plates coated with a release agent, or a molded body containing 5 to 40% by mass of fibers mainly composed of alumina or silica is sandwiched between release plates. It is preferable to laminate. By preliminarily arranging the formed body, there is an advantage that an aluminum alloy layer having a predetermined thickness can be formed and the thickness of the surface aluminum alloy layer can be controlled. When the fiber content of alumina or silica as a main component in the molded body is less than 5% by mass, it is difficult to control the thickness of the aluminum alloy layers on both main surfaces after impregnation. On the other hand, if the fiber content exceeds 40% by mass, the preform may be broken by the pressure during impregnation.

The annealing treatment for the purpose of removing the strain when the preform is impregnated with the aluminum alloy is preferably performed at a temperature of 500 ° C. to 560 ° C. for 1 minute or longer. When the annealing temperature is less than 500 ° C., the distortion inside the aluminum-silicon carbide composite is not sufficiently released, and the amount of warpage in the subsequent warp forming step may vary. On the other hand, when the annealing temperature exceeds 560 ° C., the aluminum alloy used in the impregnation may melt. When the annealing time is less than 1 minute, the strain inside the aluminum-silicon carbide composite is not sufficiently released even when the annealing temperature is 500 ° C. to 560 ° C., and the amount of warping in the subsequent warp forming step is small. May vary.

There is no restriction | limiting in particular regarding the manufacturing method of the porous silicon carbide molded object (henceforth a SiC preform) which concerns on this invention, It can manufacture by a well-known method. For example, it can be obtained by adding silica, alumina, or the like as a binder to silicon carbide powder, mixing, molding, and firing at 800 ° C. or higher. There is no restriction | limiting in particular also about a shaping | molding method, Press molding, extrusion molding, cast molding etc. can be used, and the shape-retaining binder can be used together as needed.

  Particularly important properties of the aluminum-silicon carbide composite are thermal conductivity and coefficient of thermal expansion. A higher silicon carbide (hereinafter referred to as SiC) content in the aluminum-silicon carbide composite is preferable because it has a higher thermal conductivity and a smaller thermal expansion coefficient, but is too high. The impregnation operation of the aluminum alloy is not easy. Practically, it is preferable to contain 40% by mass or more of coarse SiC particles of 40 μm or more, and the relative density of the SiC preform is in the range of 55 to 75%. Further, if the strength of the SiC preform is 3 MPa or more in bending strength, it is preferable that there is no fear of cracking during handling or impregnation.

  About raw material SiC powder for obtaining a SiC preform, it is preferred to adjust a particle size. This is because only the coarse powder has poor strength, and only the fine powder cannot provide a high thermal conductivity for the resulting composite. According to the inventor's study, for example, a mixed powder obtained by mixing 40 to 80% by mass of silicon carbide coarse powder having a particle diameter of 40 μm or more and 60 to 20% by mass of silicon carbide fine powder having a particle diameter of 15 μm or less. It is mentioned as preferable.

  The SiC preform is obtained by degreasing and firing a molded body of silicon carbide powder. When silica sol is used as a binder, if the firing temperature is 800 ° C. or higher, a preform having a bending strength of 3 MPa or more can be obtained regardless of the atmosphere during firing. In an oxidizing atmosphere, firing at a temperature exceeding 1100 ° C. may promote the oxidation of silicon carbide, which may decrease the thermal conductivity of the aluminum-silicon carbide composite. Therefore, it is desirable to bake at a temperature of 800 to 1100 ° C. in an oxidizing atmosphere. The firing time is appropriately determined in accordance with conditions such as the size of the SiC preform, the amount charged into the firing furnace, and the firing atmosphere.

  When the SiC preform according to the present invention adds a predetermined shape at the time of molding, the SiC preform is dried one by one, or by overlapping and drying using a spacer such as carbon between the SiC preforms. Warpage shape change can be prevented. Moreover, regarding the firing, it is possible to prevent the shape change accompanying the change of the internal structure by performing the same treatment as that at the time of drying.

  The shape of the SiC preform is preferably a flat plate having a rectangular shape (FIG. 1) or a shape (FIGS. 2 and 3) in which a portion surrounding a hole in the outer peripheral portion is added to the rectangle. In order to use the aluminum-silicon carbide based composite of the present invention as a power module base plate or the like after composite formation, it is necessary to form attachment holes and the like in the outer peripheral shape and the outer peripheral portion. In this case, the aluminum-silicon carbide based composite is very hard and requires a lot of grinding using a tool such as diamond, so that there is a problem that the cost increases. Therefore, it is preferable that the machined part is previously made of an aluminum alloy or a complex of easy workability made of ceramic fibers, ceramic particles and an aluminum alloy so that it can be easily machined.

Next, an example of a method for processing the obtained aluminum-silicon carbide composite will be described. The aluminum-silicon carbide based composite of the present invention can be easily machined using an apparatus such as an NC lathe or a machining center at the outer periphery and the hole. Moreover, there is no restriction | limiting in particular about the processing method of an outer peripheral part and a hole part, An aluminum-silicon carbide composite is used for an outer peripheral part or an outer peripheral part and a hole part using a water jet processing machine, an electric discharge machine, etc. It can also be processed so that is exposed. Furthermore, after producing an aluminum-silicon carbide composite using a SiC preform having a larger area than the obtained base plate shape, the outer peripheral portion, the hole, and the like of the base plate can be formed by the processing method. In the present invention, the thickness of the aluminum alloy layer provided on the surface of the aluminum-silicon carbide composite is controlled by adjusting the surface accuracy of the SiC preform and compositing using a unique lamination method.

The average thickness of the aluminum alloy layer provided on the surface of the aluminum-silicon carbide composite is 10 to 150 μm, preferably 30 to 100 μm. The thickness of the aluminum alloy layer can be adjusted to a predetermined thickness by grinding the surface of the composite. The aluminum alloy layer is necessary for ensuring plating adhesion when performing the plating treatment. If the average thickness is less than 10 μm, the aluminum-silicon carbide composite is partially exposed at the time of subsequent surface treatment such as pretreatment for plating, plating is not deposited on the portion, or plating adhesion is reduced. Problems may occur. On the other hand, since the aluminum-silicon carbide composite of the present invention has a structure in which one main surface exposes the aluminum-silicon carbide composite, the thickness of the aluminum alloy layer is the difference in thickness between the front and back aluminum alloy layers. It becomes. For this reason, if the average thickness exceeds 150 μm, the amount of warpage generated due to the difference in thermal expansion between the aluminum alloy layer and the aluminum-silicon carbide composite at the time of final annealing in the subsequent warp formation process becomes too large. When used as a base plate for a module, there may be a problem that the amount of warpage changes during a heating cycle.

In the present invention, warpage is formed in the flat aluminum-silicon carbide composite by the following method shown in FIG.
(1) Applying a predetermined amount of warp by creep deformation by applying heat at a temperature of 400 to 500 ° C. for 30 seconds or more while applying stress.
(2) The surface that has been warped in the concave direction is subjected to surface grinding to expose the aluminum-silicon carbide composite,
(3) By performing heat treatment at a temperature of 500 to 560 ° C. for 1 minute or longer, creep deformation at the time of warping is removed, and a convex warp is formed on the surface where the aluminum-silicon carbide composite is exposed.

First, the shape-processed aluminum-silicon carbide composite is subjected to heat treatment at a temperature of 400 to 500 ° C. for 30 seconds or more while applying stress to form a warp in the direction opposite to the desired direction on the heat dissipation surface side. By doing so, the aluminum-silicon carbide composite is subjected to creep deformation to impart warpage. When the treatment temperature is less than 400 ° C., sufficient creep deformation does not occur and the amount of warping is insufficient. Moreover, even if the processing temperature is 400 to 500 ° C., if the processing time is less than 30 seconds, similarly, sufficient creep deformation does not occur and the amount of warping is insufficient. On the other hand, regarding the upper limit of the processing temperature, since the creep deformation due to the warping step is removed in the annealing process of (3), the upper limit of the processing temperature is 500 ° C. It is. Further, the aluminum-silicon carbide composite after the warping treatment may be annealed at a temperature of 300 ° C. to 400 ° C. as necessary to remove the residual stress generated during the warping.

Next, the main surface of the warped surface of the composite that has been warped in the concave direction on the heat dissipation surface side is subjected to surface grinding so that the aluminum-silicon carbide composite is exposed. By grinding the heat radiating surface, the heat radiating surface of the composite can be made a flat surface without unevenness. The surface processing of the composite is not particularly limited, and for example, surface grinding can be performed with a surface grinding machine, a belt grinding machine or the like, and the heat radiation surface can be made flat without unevenness at low cost.

The aluminum-silicon carbide composite having the heat-dissipating surface subjected to surface grinding is annealed at a temperature of 500 ° C. to 560 ° C. for 1 minute or longer to provide a convex warp on the surface where the aluminum-silicon carbide composite is exposed. Form. The aluminum-silicon carbide composite of the present invention has an aluminum alloy layer on one main surface, and is generated due to a difference in thermal expansion between the aluminum alloy layer and the aluminum-silicon carbide composite by performing the annealing treatment. Warpage (warpage amount (1)) and the total warpage (warpage amount (2)) generated by removing the warpage formed by creep deformation of the aluminum-silicon carbide composite by the warping ( Warpage amount (1) + warpage amount (2)) occurs. If the annealing temperature is less than 500 ° C., the warp applied in the warping step may not be sufficiently removed, and the warp may change in a subsequent heat treatment step such as soldering. On the other hand, when the annealing temperature exceeds 560 ° C., the aluminum alloy used for impregnation may melt. Further, if the annealing time is less than 1 minute, even if the annealing temperature is 500 ° C. to 560 ° C., the warp applied in the warping process is not sufficiently removed, and warping occurs in the subsequent heat treatment process such as soldering. It may change. The warp forming method of the present invention is very excellent in warping stability when used as a base plate for a power module because the residual stress of the aluminum-silicon carbide composite is sufficiently removed by the annealing treatment. Further, in the warp forming method of the present invention, after the heat-radiating surface is grounded at one end, the residual stress is removed by annealing to form a warp. Therefore, the warp shape is a warp shape close to an ideal spherical shape. It becomes.

  When the aluminum-silicon carbide composite of the present invention is used as a base plate for a power module, depending on characteristics such as the coefficient of thermal expansion of each member used, the warp on the heat radiating surface side of the base plate is concave. In this case, in the warping step of (1), warping is performed in the direction in which the amount of warpage on the heat dissipating surface side increases, and after the heat dissipating surface is similarly surface ground, an annealing treatment is performed. By doing so, the heat radiating surface can also form a concave warped shape.

The amount of warpage after annealing of the exposed ground surface of the aluminum-silicon carbide composite is preferably 20 to 200 μm per 10 cm in length. When used as a base plate for power modules, if the ground surface that becomes the heat radiating surface warps into a concave shape, a gap is formed between the base plate and the heat radiating fins in the subsequent module assembly process. Even if it is applied, the heat transfer performance is remarkably lowered, and as a result, the heat release performance of the module composed of the ceramic circuit board, the base plate, the heat radiating fins and the like may be significantly lowered. On the other hand, if the amount of warpage exceeds 200 μm, cracks may occur in the base plate or the ceramic circuit board at the time of screwing at the time of joining to the radiating fin.

  In the present invention, the heat-radiating surface of the aluminum-silicon carbide composite can be formed into a shape with a few depressions and a recess depth of 50 μm or less by surface grinding. About the hollow depth of a thermal radiation surface, Preferably it is 30 micrometers or less. If the depth of the heat sink surface exceeds 50 μm, when used as a power module base plate, a gap will be created between the base plate and the heat dissipation fins in the subsequent module mounting process, even if high heat conductive heat dissipation grease is applied. However, the heat transfer performance may be significantly reduced, and as a result, the heat release performance of a module composed of a ceramic circuit board, a base plate, a heat radiation fin, or the like may be significantly reduced.

The power module base plate of the present invention is excellent in shape stability when a heat cycle test (which is held at a temperature of 350 ° C. for 10 minutes and then naturally cooled at room temperature), which is a measure of the reliability of the power module, is performed. For example, the amount of warpage change after 10 heat cycle tests under the above conditions is 30 μm or less per 10 cm length. If the amount of change in warpage exceeds 30 μm per 10 cm, when used as a base plate for a power module, a gap is generated between the heat dissipation fins during the heating cycle during use, and even if high heat conductive heat dissipation grease is applied. However, heat transferability may be significantly reduced.

  The aluminum-silicon carbide composite according to the present invention has good heat dissipation characteristics and stress relaxation properties, and is suitable, for example, as a base plate interposed between a ceramic circuit board and heat dissipation components such as heat dissipation fins. .

  When the aluminum-silicon carbide composite according to the present invention is used as a power module base plate, it is generally used by being joined to a ceramic circuit board by soldering. For this reason, it is necessary to apply Ni plating to the surface of the base plate. The plating method is not particularly limited, and any of electroless plating and electroplating may be used. The thickness of the Ni plating is preferably 1 to 20 μm. If the plating thickness is less than 1 μm, plating pinholes are partially generated, solder voids (voids) are generated during soldering, and the heat dissipation characteristics from the circuit board may be deteriorated. On the other hand, when the thickness of the Ni plating exceeds 20 μm, plating peeling may occur due to a difference in thermal expansion between the Ni plating film and the surface aluminum alloy. The purity of the Ni plating film is not particularly limited as long as it does not hinder the solder wettability, and even if it contains phosphorus, boron, or the like, there is no problem.

The aluminum-silicon carbide composite of the present invention preferably has a thermal conductivity of 180 W / mK or more and a thermal expansion coefficient of 150 ° C. or less of 9 × 10 ⁻⁶ / K. In addition to the above-mentioned effects, since it has a high thermal conductivity and a low expansion coefficient equivalent to that of a semiconductor component or a ceramic circuit board, a heat dissipating component using this, and a power module using it, have excellent heat dissipating characteristics, Further, it is difficult to be deformed even when subjected to a temperature change, and as a result, there is a feature that high reliability can be obtained.

Example 1
100 g of silicon carbide powder A (manufactured by Taiyo Random Company: NG-150, average particle size: 100 μm), 100 g of silicon carbide powder B (manufactured by Taiyo Random Company: NG-220, average particle size: 60 μm), silicon carbide powder C 100 g (Yakushima Electric Works: GC-1000F, average particle size: 10 μm) and 30 g of silica sol (Nissan Chemical: Snowtex) were weighed and mixed for 30 minutes with a stirring mixer, and then 190 mm × 140 mm × 5 It was press-molded at a pressure of 10 MPa into a flat plate having a size of 5 mm.

  The obtained molded body was dried at a temperature of 120 ° C. for 2 hours and then fired in the air at a temperature of 950 ° C. for 2 hours to obtain a SiC preform having a relative density of 65%. The obtained SiC preform was subjected to surface processing to a thickness of 5.8 mm using a diamond grindstone with a surface grinder, and then the outer peripheral portion was processed into the shape of FIG. . As a result of measuring the three-point bending strength of the obtained SiC preform, it was 5 MPa. Table 1 shows the thickness measurement results of the processed SiC preform. In addition, the thickness measurement point measured the center part which divided the preform into 9 parts.

The obtained SiC preform was sandwiched between 210 mm x 160 mm x 0.8 mm stainless steel plates coated with carbon on both sides, laminated 30 sheets, then placed 6 mm thick iron plates on both sides, and M10 bolts Six blocks were connected and tightened with a torque wrench so that the tightening torque in the surface direction was 3 Nm, thereby forming one block. Next, the integrated block was preheated to 600 ° C. in an electric furnace, and then placed in a preheated press mold having an inner diameter of 400 mmφ, and aluminum containing 12% by mass of silicon and 0.8% by mass of magnesium. The molten alloy was poured and pressurized at 100 MPa for 20 minutes to impregnate the silicon carbide based porous material with the aluminum alloy. After cooling to room temperature, cut along the shape of the release plate with a wet band saw, peel off the sandwiched stainless steel plate, and then anneal at 530 ° C for 3 hours to remove strain during impregnation An aluminum-silicon carbide composite was obtained.

The obtained aluminum-silicon carbide composite was formed with 8 mm diameter through-holes at 8 edges and 4 φ 4-4 mm countersinks at the edges, and the outer aluminum layer was processed with an NC lathe, The shape was 187 mm × 137 mm × 5.8 mm. Next, in order to give a warp to the aluminum-silicon carbide composite, an uneven mold provided with a spherical surface made of carbon and having a curvature radius of 15000 mm was prepared. This concavo-convex mold was mounted on a hot press and heated to bring the mold surface temperature to 470 ° C. The composite was placed between the concave and convex molds and pressed at 40 KPa. At this time, a thermocouple was brought into contact with the side surface of the composite to measure temperature. After maintaining the temperature of the composite at 450 ° C. for 3 minutes, the pressure was released, and the composite was naturally cooled to 50 ° C. Next, in order to remove the strain, annealing was performed for 1 hour at a temperature of 350 ° C. in an electric furnace. As a result of measuring the amount of warpage per 10 cm in length using the contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D-22), the resulting composite was added with a warp amount of 90 μm per 10 cm in length. It was.

The obtained aluminum-silicon carbide composite was ground by 0.8 mm using a diamond grindstone with a surface grinder on the surface warped in the concave direction to obtain a shape of 187 × 137 × 5 mm. did. Next, the obtained processed body was annealed in an electric furnace at a temperature of 530 ° C. for 1 hour in order to remove distortion during processing. Next, after blasting with alumina abrasive grains under the conditions of a pressure of 0.4 MPa and a conveyance speed of 1.0 m / min, electroless Ni—P and Ni—B plating were performed. A plating layer having a thickness of 8 μm (Ni—P: 6 μm + Ni—B: 2 μm) was formed on the composite surface.

From the obtained aluminum-silicon carbide composite, cut along the diagonal line of each sample by machining, and measure the thickness of the aluminum layer of one main surface exposed by cutting at 20 points equally spaced diagonally, The average thickness was calculated. Also, a thermal expansion coefficient measurement specimen (diameter 3 mm, length 10 mm) and a thermal conductivity measurement specimen (diameter 11 mm, thickness 3 mm) were prepared by grinding. Using each test piece, a thermal expansion coefficient of 25 to 250 ° C. was measured with a thermal dilatometer (Seiko Denshi Kogyo Co., Ltd .; TMA300), and a thermal conductivity at 25 ° C. was measured with a laser flash method (manufactured by Rigaku Corporation; LF / TCM-8510B). As for the warp shape, a contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D-22) was used, and the amount of warp and the depth of the depression per 10 cm length were measured. The obtained results are shown in Table 2. Moreover, the curvature shape measurement result of Example 1 by a contour shape measuring machine is shown in FIG.

  Using the plated product of Example 1, the plated product was placed on a hot plate heated to a temperature of 350 ° C. After the temperature reached 350 ° C., the product was held for 10 minutes, and then subjected to a heat cycle test that naturally cooled to room temperature. 10 times. The change in warpage per 10 cm length after the heat cycle test of Example 1 was 17 μm.

(Examples 2-7, Comparative Example 1)
The aluminum-silicon carbide composite of Example 1 was drilled with 7 mm diameter through-holes at 8 edges and 4 φ10-4 mm countersink holes, and the outer aluminum layer was processed with an NC lathe. Table 3 shows the results of measuring the amount of warpage per 10 cm in length using a contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D-22) after forming a shape of 187 mm × 137 mm × 5.8 mm. . Next, a concavo-convex mold made of carbon provided with a spherical surface having a radius of curvature shown in Table 3 was prepared. The composite was placed between the concave and convex molds and pressed at 40 KPa. At this time, a thermocouple was brought into contact with the side surface of the composite to measure temperature. After maintaining the temperature of the composite at 450 ° C. for 3 minutes, the pressure was released, and the composite was naturally cooled to 50 ° C. Next, in order to remove the strain, annealing was performed for 1 hour at a temperature of 350 ° C. in an electric furnace. Comparative Example 1 did not warp. The obtained composite was measured for the amount of warpage per 10 cm in length using a contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D-22). The results are shown in Table 3.

The obtained aluminum-silicon carbide composite was ground by 0.8 mm using a diamond grindstone with a surface grinder on the surface warped in the concave direction to obtain a shape of 187 × 137 × 5 mm. did. Next, the obtained processed body was annealed in an electric furnace at a temperature of 530 ° C. for 1 hour to remove distortion during processing, and then subjected to a contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D- 22) was used, and the amount of warpage per 10 cm length was measured. The results are shown in Table 3. Further, for Examples 2 to 7 and Comparative Example 1, the relationship between the warpage amount and the warpage amount after the final annealing treatment is shown in FIG.

(Example 8)
200 g of silicon carbide powder A (manufactured by Taiheiyo Random: NG-150, average particle size: 100 μm), 100 g of silicon carbide powder C (manufactured by Yakushima Electric: GC-1000F, average particle size: 10 μm), and silica sol (Nissan Chemical Co., Ltd.) (Product: Snowtex) A SiC preform having a relative density of 66% was obtained in the same manner as in Example 1 except that 30 g was used as a raw material. The obtained SiC preform was subjected to surface processing to a thickness of 5.8 mm using a diamond grindstone with a surface grinder, and then the outer peripheral portion was processed to 190 mm × 140 mm with a machining center.

Part of the obtained SiC preform was placed with 5% alumina fiber (made by Tanaka Paper Industries, purity 97%) of 190mm x 140mm x 0.4mm, and sandwiched between both sides with a stainless steel plate coated with carbon. After the lamination, 6 mm thick iron plates were arranged on both sides, connected with six M10 bolts, and tightened with a torque wrench so that the tightening torque in the surface direction was 3 Nm to form one block. The obtained laminate produced an aluminum-silicon carbide composite in the same manner as in Example 1. The obtained composite was processed with 8 mm diameter through-holes at 8 edges and 4 φ4-4 countersink holes at the periphery, and the outer periphery was 187 × 137 mm (corner area) with a water jet processing machine. Was processed to R7 mm).

Next, in order to give a warp to the aluminum-silicon carbide composite, an uneven mold provided with a spherical surface made of carbon and having a curvature radius of 12000 mm was prepared. This concavo-convex mold was mounted on a hot press and heated to bring the mold surface temperature to 470 ° C. The composite was placed between the concave and convex molds and pressed at 40 KPa. At this time, a thermocouple was brought into contact with the side surface of the composite to measure temperature. After maintaining the temperature of the composite at 450 ° C. for 3 minutes, the pressure was released, and the composite was naturally cooled to 50 ° C. Next, in order to remove the strain, annealing was performed for 1 hour at a temperature of 350 ° C. in an electric furnace. The obtained composite was measured for the amount of warpage per 10 cm length using a contour shape measuring machine (manufactured by Tokyo Seimitsu Co., Ltd .; contour record 1600D-22). As a result, a warp amount of 120 μm per 10 cm length was added. It was.

The obtained aluminum-silicon carbide composite was ground by 0.8 mm using a diamond grindstone with a surface grinder on the surface warped in the concave direction to obtain a shape of 187 × 137 × 5 mm. did. Next, the obtained processed body was annealed in an electric furnace at a temperature of 530 ° C. for 1 hour in order to remove distortion during processing. Next, after blasting with alumina abrasive grains under the conditions of a pressure of 0.4 MPa and a conveyance speed of 1.0 m / min, electroless Ni—P and Ni—B plating were performed. A plating layer having a thickness of 8 μm (Ni—P: 6 μm + Ni—B: 2 μm) was formed on the composite surface. The obtained composite was evaluated in the same manner as in Example 1. Table 4 shows the obtained results.

Example 9
An aluminum-silicon carbide based composite was produced in the same manner as in Example 1 except that the preform shape of Example 8 was changed to 180 × 110 × 5.8 mm (see FIG. 1), warped, and machined. The plating process was performed. The obtained composite was evaluated in the same manner as in Example 1, and the results are shown in Table 5.

Explanatory drawing which shows one Embodiment of the aluminum-silicon carbide composite for base plates used by this invention Explanatory drawing which shows one Embodiment of the aluminum-silicon carbide composite for base plates used by this invention Explanatory drawing which shows one Embodiment of the aluminum-silicon carbide composite for base plates used by this invention Warpage formation flow diagram of the present invention Warpage shape measurement result by contour shape measuring machine of Example 1 Relationship between warpage amount of Examples 2 to 7 and Comparative Example 1 and warpage amount after final annealing treatment

Explanation of symbols

a) Aluminum-silicon carbide composite b) Aluminum alloy c) φ7 mm through hole
d) Surface aluminum alloy layer e) Aluminum-silicon carbide composite f) φ10-4 mm countersink g) Aluminum-silicon carbide composite h) M4 mm tap screw

Claims (2)

Aluminum-carbonized with a flat silicon carbide porous body impregnated with a metal mainly composed of aluminum and having an aluminum alloy layer composed of a metal composed mainly of aluminum having an average thickness of 10 to 150 μm on both principal surfaces. A silicon composite,
(1) Applying a predetermined amount of warp by creep deformation by applying heat at a temperature of 400 to 500 ° C. for 30 seconds or more while applying stress.
(2) The surface that has been warped in the concave direction is subjected to surface grinding to expose the aluminum-silicon carbide composite,
(3) By performing heat treatment at a temperature of 500 to 560 ° C. for 1 minute or longer, the creep deformation at the time of warping is removed,
A method for producing an aluminum-silicon carbide based composite comprising forming a convex warp on a surface where the aluminum-silicon carbide based composite is exposed. 2. The method for producing an aluminum-silicon carbide composite according to claim 1, wherein the aluminum-silicon carbide composite is produced by a high-pressure forging method.

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