Manufacturing method of laminate

Abstract

The method for manufacturing a laminate according to the present invention is a method for manufacturing a laminate in which a coating formed using a material powder is laminated on the surface of an insulating substrate, and includes a pretreatment step of accelerating a material powder mainly composed of aluminum or an aluminum alloy together with a gas and spraying it onto the substrate surface in a solid state to form a pretreatment coating on the substrate surface, and a coating formation step of heating the pretreatment laminate with the pretreatment coating formed on the substrate surface to form a heat-treated coating with an irregularly uneven surface.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminate formed by laminating a metal coating on a substrate. [Background technology]

[0002] Conventional methods for producing laminates in which a metal coating is formed on a substrate include, for example, thermal spraying and cold spraying. Thermal spraying is a method of forming a coating by spraying a material (thermal spray material) heated to a molten or nearly molten state onto a substrate. Cold spraying is a method of forming a coating on the surface of a substrate by spraying a powder of the material from a divergent (Laval) nozzle together with an inert gas at or below its melting point or softening point and allowing the powder to impinge on the substrate in a solid state (see, for example, Patent Document 1). Cold spraying is performed at a lower temperature than thermal spraying, thereby mitigating the effects of thermal stress. This allows for the production of a metal coating that is free from phase transformation and inhibits oxidation. In particular, when the substrate and the material to be coated are both metals, plastic deformation occurs between the powder and the substrate when the powder of the metal material impinges on the substrate (or a previously formed coating), creating an anchor effect. Furthermore, the oxide coatings on both surfaces are destroyed, forming a metallic bond between the newly formed surfaces, resulting in a laminate with high adhesion strength.

[0003] Incidentally, there are cases where a metal coating has the function of dissipating heat from a substrate to the outside. It is generally known that heat can be dissipated efficiently by making the heat-dissipating surface uneven (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5548167 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-183390 Summary of the Invention [Problem to be solved by the invention]

[0005] For the reasons mentioned above, there is a demand for a technology for producing a metal coating by cold spraying that has high adhesive strength to the substrate and can efficiently dissipate heat.

[0006] The present invention has been made in view of the above, and has an object to provide a method for producing a laminate that has high adhesion strength and is capable of efficiently dissipating heat. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the method for manufacturing a laminate according to the present invention is a method for manufacturing a laminate in which a coating formed using a material powder is laminated on the surface of an insulating substrate, and is characterized by including a pretreatment step of accelerating the material powder, mainly composed of aluminum or an aluminum alloy, together with a gas and spraying it onto the surface of the substrate in a solid state to form a pretreatment coating on the surface of the substrate, and a coating formation step of heating the pretreatment laminate with the pretreatment coating formed on the surface of the substrate to form a heat-treated coating having an irregularly uneven surface.

[0008] Furthermore, the method for manufacturing a laminate according to the present invention is characterized in that, in the above invention, the material powder further contains an additive that bonds the material powder together, and the additive is a brazing material or magnesium.

[0009] Moreover, in the method for producing a laminate according to the present invention, in the above invention, the film forming step comprises heating the pretreatment film at a temperature of 300°C or higher and 650°C or lower. [Effects of the Invention]

[0010] According to the present invention, the effects of high adhesion strength and efficient heat dissipation are achieved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a laminate according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion of the laminate shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing an outline of a cold spray device used to form a metal coating on a laminate according to one embodiment of the present invention. [Figure 4] FIG. 4 is an SEM image showing an example of a laminate according to an embodiment of the present invention, and is a diagram showing an SEM image showing a cross section of this laminate. [Figure 5] FIG. 5 is an SEM image showing an example of a laminate according to an embodiment of the present invention, and is a diagram showing an SEM image showing a cross section of this laminate. [Figure 6] FIG. 6 is an SEM image showing an example of a laminate according to an embodiment of the present invention, and is a diagram showing an SEM image showing a cross section of this laminate. [Figure 7] FIG. 7 is an SEM image showing an example of a laminate according to an embodiment of the present invention, and is a diagram showing an SEM image showing a cross section of this laminate. [Figure 8] FIG. 8 is an SEM image showing an example of a laminate according to an embodiment of the present invention, and is a diagram showing an SEM image showing a cross section of this laminate. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Furthermore, the drawings referred to in the following description merely show the shape, size, and positional relationship of the components to the extent that the contents of the present invention can be understood. In other words, the present invention is not limited to only the shape, size, and positional relationship exemplified in each drawing.

[0013] Fig. 1 is a cross-sectional view showing the structure of a laminate according to one embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view of a portion of the laminate shown in Fig. 1. The laminate 1 shown in Fig. 1 includes a substrate 10 and a metal coating film 20 formed on one surface of the substrate 10.

[0014] The substrate 10 is a substantially plate-shaped member. Materials that can be used for the substrate 10 include nitride ceramics such as aluminum, aluminum nitride, and silicon nitride, oxide ceramics such as alumina, magnesia, zirconia, steatite, forsterite, mullite, titania, silica, and sialon, and resin layers containing inorganic fillers. Chips formed of semiconductor elements such as diodes, transistors, and IGBTs (insulated gate bipolar transistors) may be mounted on the substrate 10.

[0015] The metal coating 20 is mainly composed of a metal or alloy having good thermal conductivity, such as aluminum or an aluminum alloy. The metal coating 20 is formed by a cold spray method, which will be described later. The metal coating 20 transfers heat to the substrate 10 or releases heat stored in the substrate 10 to the outside.

[0016] Furthermore, because the metal coating 20 is formed at a low temperature by cold spraying, the effects of thermal stress are mitigated. This makes it possible to obtain a metal coating that does not undergo phase transformation and is also inhibited from oxidation. In particular, when the material powder collides with the substrate 10, plastic deformation occurs between the material powder and the material of the substrate 10, creating an anchor effect. Furthermore, the oxide films on both surfaces are destroyed, creating a metallic bond between the newly formed surfaces, resulting in a laminate with high adhesive strength.

[0017] 2, the surface of the metal coating 20 opposite to the side in contact with the substrate 10 has an uneven shape. This surface has irregularly repeated unevenness, and has a larger surface area than a flat surface. Specifically, the surface of the metal coating 20 is formed by irregularly stacking particles (here, the material that constitutes the metal coating 20).

[0018] Next, we will explain the method for forming the metal coating 20 in the production of the laminate 1. Figure 3 is a schematic diagram showing an overview of a cold spray device used to form the metal coating of the laminate according to one embodiment of the present invention.

[0019] First, the above-described substrate 10 is prepared. The above-described chip may be mounted on this substrate 10. When the chip is mounted, the side opposite to the mounting surface becomes the film formation surface.

[0020] Using a cold spray device 30 shown in Figure 3, powder of material for forming the metal coating 20 is accelerated together with gas and sprayed onto the surface of the substrate 10 in a solid state, depositing it to form a pretreatment coating 200 (pretreatment process).

[0021] The cold spray device 30 includes a gas heater 31 that heats compressed gas, a powder supply device 32 that stores powder of material for forming the metal coating 20 and supplies it to a spray gun 33, a gas nozzle 34 that sprays the heated compressed gas and the material powder supplied thereto onto a substrate, and valves 35 and 36 that adjust the amount of compressed gas supplied to the gas heater 31 and the powder supply device 32, respectively.

[0022] The material for forming the metal coating 20 is a powder material consisting of aluminum or an aluminum alloy, which is the main component of the metal coating 20, and an additive for bonding aluminum or aluminum alloys together. The mixing ratio of the main component to the additive (main component:additive) is 1 to 1.5, where the main component is 1. Note that the "main component of the metal coating 20" here refers to the component with the highest content among the components constituting the metal coating 20 (elements or alloys remaining after the coating is formed).

[0023] Examples of additives include materials that have a reducing effect on the aluminum oxide film and brazing filler metals. Materials with a high reducing effect include magnesium and zinc, with magnesium being preferred in terms of its high reducing effect on aluminum. Brazing filler metals that can be used include aluminum brazing filler metals that contain aluminum as the main component and also magnesium, copper, etc., and silver brazing filler metals that contain silver as the main component and also contain at least one of copper and tin, and also contain titanium, an active metal.

[0024] The compressed gas may be helium, nitrogen, air, or the like. The compressed gas supplied to gas heater 31 is heated to a temperature, for example, 50°C or higher, which is lower than the melting point of the powder of the material used to form metal coating 20, and then supplied to spray gun 33. The heating temperature of the compressed gas is preferably 300°C or higher and 650°C or lower. Meanwhile, the compressed gas supplied to powder supply device 32 supplies the powder in powder supply device 32 to spray gun 33 at a predetermined discharge rate.

[0025] The heated compressed gas is made into a supersonic flow (approximately 340 m / s or greater) by a divergent gas nozzle 34. The gas pressure of the compressed gas is preferably about 1 to 5 MPa. This is because adjusting the pressure of the compressed gas to this level can improve the adhesive strength of the metal coating 20 to the substrate 10. A pressure of about 2 to 4 MPa is more preferred, and a pressure of about 1.5 to 2.5 MPa is particularly preferred. The material powder supplied to the spray gun 33 is accelerated by being introduced into the supersonic flow of compressed gas, and collides and deposits at high speed on the substrate 10 while still in a solid state, forming the pretreatment coating 200. Note that the cold spray device 30 shown in FIG. 3 is not the only device that can form a coating by colliding the material powder in a solid state against the substrate 10.

[0026] The pretreatment coating 200 formed by the above-described cold spray apparatus 30 contains a main component (aluminum or aluminum alloy) and additives, and has gaps and minute spaces formed therein. This pretreatment coating 200 is then heat-treated to bond the main components together, the additives together, and the main component and additives together to form the metal coating 20 (coating formation process). The heat treatment temperature is 300°C or higher and 650°C or lower, preferably 500°C or higher and 600°C or lower. This increases the bonding strength of the metal coating 20. Depending on the properties of the additives and the heat treatment conditions, some of the additives in the metal coating 20 may evaporate or melt, or some may remain in the pretreatment coating 200 state. The addition of magnesium as an additive is preferable because it reduces the oxide film of the aluminum powder and promotes bonding between the aluminum powder particles.

[0027] 4 and 5 are SEM images showing an example of a laminate according to an embodiment of the present invention, and are diagrams showing SEM images showing a cross section of this laminate. FIGS. 4 and 5 show an example in which aluminum is the main component and a brazing filler metal is used as an additive. FIG. 4 shows a cross section of a pre-treatment coating 200 after film formation using a cold spray device 30. FIG. 5 shows a cross section of a metal coating (metal coating 20) formed by heat treatment after film formation. After film formation, there are many gaps and many areas where the powder particles are not bonded together (see FIG. 4). However, after heat treatment (see FIG. 5), many of the gaps are filled, and the bonding strength is improved compared to after film formation.

[0028] Furthermore, an example in which magnesium is used as an additive will be described with reference to FIGS. 6 to 8. FIGS. 6 to 8 are SEM images showing an example of a laminate according to an embodiment of the present invention, illustrating a cross section of the laminate. FIGS. 6 to 8 illustrate an example in which aluminum is the main component and magnesium is used as an additive. FIG. 6 shows a cross section of a pretreatment coating 200 after film formation using a cold spray device 30. FIG. 7 shows a cross section of a metal coating (metal coating 20) formed by heat treatment after film formation. FIG. 8 shows the surface of a metal coating after heat treatment after film formation. Similar to brazing filler metals, after film formation, there are many gaps and many areas where the powder particles are not bonded together (see FIG. 6). However, after heat treatment (see FIG. 7), many of the gaps are filled, and the bonding strength is improved compared to after film formation. Furthermore, as shown in FIG. 8, the surface after heat treatment has an irregular, uneven shape.

[0029] In the above-described embodiment, a powder of material for forming the metal coating 20, which contains a main component made of aluminum or an aluminum alloy and an additive that bonds the powder together, is accelerated together with a gas and sprayed and deposited in a solid state onto the surface of the substrate 10 to form a pretreatment coating 200 with an uneven surface, and the pretreatment coating 200 is then heat-treated to improve the bonding strength. According to the above-described embodiment, high adhesion strength and efficient heat dissipation are possible.

[0030] In the above-described embodiment, an example has been described in which the metal coating 20 is formed using a powder of a material containing a main component made of aluminum or an aluminum alloy and an additive that bonds the powder together, but the metal coating 20 may also be formed using a material powder of the main component alone.

[0031] As such, the present invention may include various embodiments not described here, and various design changes may be made within the scope of the technical idea specified by the claims. [Industrial Applicability]

[0032] As described above, the method for manufacturing a laminate according to the present invention is suitable for achieving high adhesion strength and efficient heat dissipation. [Explanation of symbols]

[0033] 1. Laminate 10 Base material 20 Metallic Film 30 Cold spray device 31 Gas heater 32 Powder feeding device 33 Spray gun 34 Gas nozzle 35, 36 valves 200 Pretreatment film

Claims

1. A method for manufacturing a laminate in which a coating formed using a material powder is laminated on the surface of an insulating substrate, the method comprising: a pretreatment step in which the material powder, which is composed of aluminum or an aluminum alloy as a main component and an additive for bonding the aluminum or the aluminum alloy together, is accelerated together with a gas and sprayed onto the substrate surface in a solid state to form a pretreatment film on the substrate surface; a coating formation step of heating the pretreated laminate having the pretreated coating formed on the surface of the substrate to form a heat-treated coating having an irregularly textured surface; Including, a mixing ratio of the main component to the additive in the material powder is 1 to 1.5, where the main component is 1; A method for producing a laminate comprising the steps of:

2. 2. The method for manufacturing a laminate according to claim 1, wherein the additive is a brazing material or magnesium.

3. 3. The method for manufacturing a laminate according to claim 1, wherein the pretreatment film is heated at a temperature of 300°C or higher and 650°C or lower in the film forming step.

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