Insulating substrate and method of manufacturing the same

Abstract

To provide an insulating substrate with an excellent heat cycle characteristic under a high temperature in a state where a radiator plate of an insulating substrate is soldered.SOLUTION: An insulating substrate 1 is characterized in that one main surface of a radiation side metal plate 12 is bonded via a wax material layer 14 onto one main surface of a ceramic substrate 10, and a solder resist part 20 is formed onto at least one selected from a circumference of the other main surface of the radiation side metal plate 12, a side surface of the radiation side metal plate 12, and a front surface of the wax material layer 14. The prevention of a wraparound of a solder 31 to the wax material layer 14 by a solder resist does not generate so-called "solder corrosion of the wax material layer 14", and the generation of cracking in an inner part of the wax material layer 14 is avoided. Thus, a ceramic substrate 10 can be prevented from generating a stress concentration at a portion of an inner side from an end part of the radiation side metal plate 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an insulating substrate used in a semiconductor power module or the like, and a method for manufacturing the same. [Background technology]

[0002] For example, as shown in Patent Document 1, an insulating substrate used in a semiconductor power module or the like is configured by brazing a circuit-side metal plate and a heat-dissipating-side metal plate to both sides of a ceramic substrate made of AlN, Al2O3, Si3N4, or the like with a brazing material layer. A semiconductor chip is soldered to the circuit-side metal plate, and a Cu or Al-based heat sink plate with excellent thermal conductivity is soldered to the heat-dissipating-side metal plate to create a semiconductor power module or the like. Also, as shown in Patent Document 2, a metal-ceramic insulating substrate in which a metal plate is bonded to a ceramic substrate using a brazing material containing Ag, Cu, and an active metal is generally used as an insulating substrate.

[0003] In such insulating substrates, in order to prevent cracks from occurring in the ceramic substrate due to heat cycle load, Patent Document 3 discloses a technique for preventing cracks from occurring by oxidizing the copper plate before bonding a semiconductor chip or a heat sink. Patent Document 4 discloses a substrate for a power module with a heat sink that has low initial thermal resistance and can prevent cracks from occurring in the ceramic substrate due to heat cycle load and can also prevent an increase in thermal resistance. Furthermore, Patent Document 5 discloses a technique for improving heat cycle characteristics by forming a step at the end of the copper plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-70863 A [Patent Document 2] JP 2010-241627 A [Patent Document 3] JP 2013-211546 A [Patent Document 4] JP 2014-60216 A [Patent Document 5] Japanese Patent Application Publication No. 10-125821 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, an insulating substrate formed by bonding a metal plate such as a Cu plate to a ceramic substrate such as an AlN substrate has a circuit-side metal plate (circuit pattern) formed on one side of the ceramic substrate, and a heat-dissipating metal plate formed on the other side of the ceramic substrate. When the insulating substrate is used as a power module substrate, electronic components such as semiconductor chips and terminals are bonded to the surface of the circuit-side metal plate by soldering or the like, and a relatively thick (e.g., about 2 to 5 mm) heat-dissipating plate (base plate) made of, for example, Cu is bonded to the heat-dissipating metal plate by soldering. After bonding wiring of power semiconductors and the like is completed, a resin case is formed on the heat-dissipating plate so as to surround the insulating substrate, a gel material for sealing is filled in the case, and the lid of the case is closed, and the power module is manufactured through such processes.

[0006] In recent years, there has been an increasing demand for insulating substrates to improve their severe heat cycle characteristics at higher temperatures, both when the insulating substrate is used alone and when a heat sink is soldered to the insulating substrate. However, the ceramic insulating substrate of Patent Document 1 does not have sufficient heat cycle characteristics when used alone, and cracks may occur in the ceramic substrate after a heat cycle test. The insulating substrates of Patent Documents 2, 3, and 5 have excellent heat cycle characteristics when used alone, but it has been found that cracks occur in the ceramic substrate when a high-temperature heat cycle test is performed with a heat sink soldered to the heat-dissipating metal plate (metal plate for forming a heat sink) of the insulating substrate. In Patent Document 4, a solid-phase diffusion bond is formed between a metal layer of Cu or Cu alloy and a heat sink, and a bonding material made of Al or Al alloy, but compared to soldering, large bonding defects are more likely to occur between the two and it is difficult to control them, and there is a risk of cracks occurring at the bonded portion during a high-temperature heat cycle test.

[0007] High-temperature heat cycle properties are a requirement in recent years due to the use of SiC semiconductor chips that operate at high temperatures and the increased soldering temperatures required for the use of lead-free solder. For example, in a heat cycle test in which the heating temperature on the high-temperature side is 150°C or higher, it is required that no cracks occur in the ceramic substrate after a specified number of cycles of heat cycle testing.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide an insulating substrate that has excellent heat cycle characteristics at high temperatures when a heat sink is soldered to the insulating substrate (i.e., when the insulating substrate is incorporated into a power module). [Means for solving the problem]

[0009] The inventors have studied the causes of cracks occurring in ceramic substrates. As a result, they have inferred that the cracks are caused by the so-called "solder erosion of the brazing layer" in which solder components (e.g., Sn) erode into the brazing layer joining the heat-dissipating metal plate during the process of soldering the heat-dissipating plate to the insulating substrate and the subsequent heat cycle test, forming brittle compounds of the solder components and the brazing layer components (e.g., Ag, Cu, etc.). Therefore, in the present invention, the solder resist is used to prevent the solder erosion of the brazing layer (contact and wraparound of the solder with the brazing layer), thereby avoiding the erosion of the solder components into the brazing layer.

[0010] According to the present invention, one main surface of the heat-dissipating metal plate is joined to one main surface of the ceramic substrate via a brazing material layer, the brazing material layer protrudes from an end portion of the heat-dissipating side metal plate, An insulating substrate is provided, characterized in that a solder resist portion is formed on at least one selected from the periphery of the other main surface of the heat dissipation side metal plate, the side surface of the heat dissipation side metal plate, or the surface of the brazing material layer.

[0011] In this insulating substrate, it is preferable that one surface of a circuit-side metal plate is joined to the other main surface of the ceramic substrate via a brazing material layer, and the heat-dissipating-side metal plate is preferably a copper plate or a copper alloy plate, and the circuit-side metal plate is preferably a copper plate or a copper alloy plate. Also, it is preferable that the solder resist portion is formed to surround the soldering area on the other main surface of the heat-dissipating-side metal plate.

[0012] According to the present invention, there is also provided a method for manufacturing an insulating substrate, characterized in that the solder resist portion is formed by screen printing.

[0013] Also provided is a semiconductor module component (insulating substrate with heat sink), characterized in that a heat sink is joined via solder to the other main surface of the heat sink-side metal plate of the insulating substrate.

[0014] There is also provided a method for producing an insulating substrate with a heat sink, characterized in that a heat sink is joined to the other main surface of the heat sink side metal plate of the insulating substrate by soldering. Effect of the Invention

[0015] According to the present invention, the solder resist prevents the solder from flowing into the brazing material layer, so that the so-called "solder erosion of the brazing material layer" does not occur, and the occurrence of cracks inside the brazing material layer is avoided. This prevents stress concentration in the ceramic substrate at a location inside the end of the heat dissipation metal plate. As a result, the occurrence of cracks is also avoided in the ceramic substrate, and an insulating substrate with excellent high-temperature heat cycle characteristics can be obtained with a heat dissipation plate soldered to the insulating substrate. [Brief description of the drawings]

[0016] [Figure 1] 1 is a plan view of an insulating substrate according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view taken along the line XX in FIG. [Diagram 3] 1 is a cross-sectional view of an insulating substrate in which a heat sink plate is soldered to a heat sink-side metal plate. [Figure 4] FIG. 4 is a cross-sectional view of an insulating substrate according to another embodiment of the present invention. [Diagram 5] FIG. 4 is a cross-sectional view of an insulating substrate according to another embodiment of the present invention. [Figure 6] FIG. 4 is a cross-sectional view of an insulating substrate according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] According to the present invention, an insulating substrate is provided, characterized in that one main surface (surface) of a heat dissipation side metal plate is joined to one main surface (surface) of a ceramic substrate via a brazing material layer, and a solder resist portion is formed on at least one selected from the periphery of the other main surface (surface) of the heat dissipation side metal plate, the side surface of the heat dissipation side metal plate, or the surface of the brazing material layer. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0018] 1 and 2, an insulating substrate 1 according to an embodiment of the present invention is configured by brazing a circuit-side metal plate 11 and a heat-dissipation-side metal plate 12 made of copper, a copper alloy, aluminum, an aluminum alloy, etc., to both sides of a ceramic substrate 10 whose main components are AlN, Al2O3, Si3N4, etc., with brazing material layers 13 and 14, respectively. Note that Fig. 2 shows a state in which one main surface of the circuit-side metal plate 11 (the lower surface of the circuit-side metal plate 11 in Fig. 2) is brazed to the other main surface of the ceramic substrate 10 (the upper surface of the ceramic substrate 10 in Fig. 2) with a brazing material layer 13, and one main surface of the heat-dissipation-side metal plate 12 (the upper surface of the heat-dissipation-side metal plate 12 in Fig. 2) is brazed to one main surface of the ceramic substrate 10 (the lower surface of the ceramic substrate 10 in Fig. 2) with a brazing material layer 14. Then, a semiconductor chip is soldered to the other main surface of the circuit-side metal plate 11 (the upper surface of the circuit-side metal plate 11 in FIG. 2), and a heat sink (metal plate, base plate) made of copper, copper alloy, aluminum, aluminum alloy, or the like having excellent thermal conductivity is soldered to the other main surface of the heat-dissipating side metal plate 12 (the lower surface of the heat-dissipating side metal plate 12 in FIG. 2), to produce a component used in a semiconductor power module or the like. The part of the other main surface of the heat-dissipating side metal plate 12 where the heat sink is soldered is called the soldering area. The heat sink may have heat sink fins or heat sink pins formed on the opposite side of the ceramic substrate 10 (the surface to which the heat sink metal plate is not joined). The circuit-side metal plate 11 and the heat sink side metal plate 12 are preferably made of copper or a copper alloy. The heat-dissipating metal plate 12 is formed on one main surface of the ceramic substrate 10 excluding an area a predetermined distance (eg, about 0.3 to 2.0 mm) from the outer periphery of the ceramic substrate 10, and has a rectangular shape in FIGS. There is a demand for improving the (high temperature) heat cycle properties of insulating substrate 1 in a state where a heat sink is soldered to heat-dissipating metal plate 12 (that is, equivalent to a state where an insulating substrate is incorporated into a power module).

[0019] In such an insulating substrate 1, when the above-mentioned semiconductor chip is soldered to the circuit side copper plate 11 or to the heat dissipation side metal plate 12, and also when electricity is passed through the semiconductor chip, repeated heat generation occurs, and as a result, thermal stress is generated due to the difference in thermal expansion coefficient between the ceramic substrate 10 and the circuit side metal plate 11 and the heat dissipation side metal plate 12, and further due to heat cycle load, which may cause stress concentration on the surface of the ceramic substrate 10 at the boundaries (joint boundaries) between the ceramic substrate 10 and the ends of the circuit side metal plate 11 and the heat dissipation side metal plate 12, resulting in a risk of cracks. For this reason, for example, as shown in the insulating substrate 1 according to this embodiment, by forming the side surfaces 11a, 12a of the circuit side metal plate 11 and the heat dissipation side metal plate 12 into tapered surfaces and by exposing (protruding) the brazing material layers 13, 14 from the ends of the circuit side metal plate 11 and the heat dissipation side metal plate 12 to form fillets, measures are taken to alleviate the stress concentration occurring in the ceramic substrate 10 at the boundary between the ends of the circuit side metal plate 11 and the heat dissipation side metal plate 12. Also, as shown in Patent Document 5, a technique is known for improving heat cycle characteristics by forming a step at the end of a copper plate.

[0020] However, the inventors' investigations have revealed that in a semiconductor power module in which a semiconductor chip or a heat sink is soldered and mounted, cracks may occur on the surface of the ceramic substrate 10 at a location (bonding area) inside the end of the heat sink metal plate 12. The inventors have investigated the cause of the cracks that occur on the ceramic substrate 10 (in the plate thickness direction) at a location inside the end of the heat sink metal plate 12. As a result, it has been found that when the heat sink is soldered to the heat sink metal plate 12, if Sn in the solder corrodes (diffuses) into the brazing material layer 14, the Sn in the solder and elements such as Ag and Cu contained in the brazing material layer 14 form brittle compounds, which is called "solder erosion of the brazing material layer 14". Then, it has been observed that cracks occur (in a direction approximately parallel to the bonding interface) inside the brazing material layer 14 that has become brittle due to the formation of such compounds, which is called "solder erosion of the brazing material layer 14". Furthermore, when the cross section of the insulating substrate 1 was analyzed, it was observed that a crack had occurred in the thickness direction from one main surface (surface) of the ceramic substrate 10 at a location in the brazing material layer inside the end of the heat dissipation side metal plate 12 and at the tip of the crack in the brazing material layer 14. Furthermore, when a stress analysis was performed by simulation, it was found that when the crack exists in the brazing material layer, stress concentration occurs on the surface of the ceramic substrate 10 at the tip of the crack. As a result, it was found that a crack occurs on one main surface of the ceramic substrate 10 inside the end of the heat dissipation side metal plate 12. Therefore, in the present invention, by using a solder resist, it is possible to prevent the solder from wrapping around (diffusing) the brazing material layer 14, thereby avoiding the erosion (diffusion) of Sn and other components of the solder into the brazing material layer 14, thereby suppressing the occurrence of stress concentration and preventing the occurrence of cracks, that is, it was found that an insulating substrate 1 with excellent heat cycle characteristics can be obtained even in a state where a heat dissipation plate is soldered to the insulating substrate 1. Furthermore, by preventing cracks in the brazing material layer, deterioration of the heat dissipation properties of the insulating substrate can be suppressed. In recent years, the operating temperatures of power modules have tended to rise, and the use of high-temperature solders and lead-free solders with high Sn content has increased, which is likely to increase the occurrence of cracks in the ceramic substrate 10 due to the erosion of the brazing filler metal. However, the insulating substrate of the present invention is particularly suitable for semiconductor modules in which the heat-dissipating copper plate 12 and the heat sink are soldered using such solder containing a large amount of Sn.

[0021] In the insulating substrate 1 according to the embodiment of the present invention shown in Figs. 1 and 2, the solder resist portion 20 is provided around and on the side of the other main surface of the heat dissipation side metal plate 12, so that the solder soldered to the heat dissipation side metal plate 12 does not wrap around (does not come into contact with) the brazing material layer 14 (exposed between one main surface of the ceramic substrate 10 and one main surface of the heat dissipation side copper plate 12). That is, the surface center of the other main surface of the heat dissipation side metal plate 12 (the center of the lower surface of the heat dissipation side metal plate 12 in Fig. 2) is the soldering area 12b to which the heat dissipation plate 30 (described later) is soldered, and the solder resist portion 20 is arranged so as to surround this soldering area 12b. In other words, the soldering area 12b to which the heat dissipation plate 30 is soldered is formed in the surface center of the heat dissipation side metal plate 12, and the solder resist portion 20 is provided to surround (define) the soldering area 12b. The solder resist portion 20 isolates the soldering area 12b from the brazing material layer 14.

[0022] The solder resist portion 20 can be appropriately formed by applying a solder resist mainly composed of known resin such as an alkaline development type solder resist, a UV curing type solder resist, or a thermosetting type solder resist, arranging it so as to surround the soldering area 12b by means of a screen printing method or the like, and curing it by means of exposure, heating, etc. If the surfaces of the heat dissipation side copper plate and the brazing material are entirely plated with Ni plating, the "solder erosion of the brazing material layer" can be prevented, but the thermal shock resistance of the insulating substrate alone is not sufficient.

[0023] 3 shows the insulating substrate 1 configured as above, with the heat sink 30 soldered to the heat sink metal plate 12. The heat sink 30 is made of a base material with excellent thermal conductivity, such as Cu or Al, and is attached to the insulating substrate 1 by soldering the heat sink 30 to the soldering area 12b of the heat sink metal plate 12 with solder 31.

[0024] In the insulating substrate 1 according to the embodiment of the present invention, when the heat sink 30 is soldered to the heat dissipation side metal plate 12 with the solder 31, the solder 31 soldered to the soldering area 12b does not protrude (does not spread) from the area surrounded by the solder resist portion 20 (soldering area 12b), and the solder 31 can be prevented from reaching the brazing material layer 14. Since the solder 31 does not contact the brazing material layer 14, the erosion (diffusion) of the solder component Sn and the like into the brazing material layer 14 is prevented, and so-called "solder erosion of the brazing material layer 14" does not occur. As a result, the occurrence of cracks inside the brazing material layer 14 is prevented. Furthermore, by preventing the occurrence of cracks inside the brazing material layer 14, stress concentration is prevented from occurring in the ceramic substrate 10 at a location inside the end of the heat dissipation side metal plate 12. As a result, the occurrence of cracks is also prevented in the ceramic substrate 10, and an insulating substrate 1 with excellent heat cycle characteristics can be obtained.

[0025] 1 to 3 show an example in which the solder resist portion 20 is provided so as to extend across the side surface 12a of the heat-dissipating-side metal plate 12 and the surface of the heat-dissipating-side metal plate 12 (around the lower surface of the heat-dissipating-side metal plate 12 in FIGS. 2 and 3) (around the other main surface of the heat-dissipating-side metal plate 12), but as shown in FIG. 4, the solder resist portion 20 may be provided only on the surface of the heat-dissipating-side metal plate 12 (around the lower surface of the heat-dissipating-side metal plate 12 in FIG. 4) (around the other main surface of the heat-dissipating-side metal plate 12), or as shown in FIG. 5, the solder resist portion 20 may be provided only on the side surface 12a of the heat-dissipating-side metal plate 12. In addition, as shown in FIG. 6, the end of the brazing material layer 14 exposed from the end of the heat-dissipating-side metal plate 12, the side surface 12a of the heat-dissipating-side metal plate 12, and the periphery of the other main surface may be covered with the solder resist portion 20. The solder resist portion may be formed only on the brazing material layer 14, or may be formed on the brazing material layer 14 and the side surface 12a of the heat-dissipating side metal plate 12.

[0026] Although one embodiment of the present invention has been described above, the present invention is not limited to this example. It is clear that a person skilled in the art can think of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention.

[0027] For example, in the present invention, the solder resist may be any material that prevents the solder from spreading. For example, a method may be used in which a part of the heat-dissipating metal plate 12 is oxidized by laser irradiation or chemical treatment to form a metal oxide film on the surface. The solder resist portion may be disposed so that the solder does not come into direct contact with the brazing material layer of the insulating substrate. For example, as described above, even if the brazing material layer portion is not covered with the solder resist portion, it is sufficient that the solder is prevented from coming into contact with the brazing material layer. From the viewpoints of manufacturability and cost when forming the solder resist, it is preferable to use a paste-like solder resist containing a resin. Also, it is preferable to form the solder resist on the side surface of the heat dissipation side metal plate. EXAMPLES

[0028] Example 1 An aluminum nitride substrate measuring 46 mm x 48 mm x 0.4 mm was used as the ceramic substrate, and a paste-like active metal-containing brazing material prepared by adding 83 mass % silver, 10 mass % copper, 5 mass % tin, and 2 mass % titanium (as an active metal component) (Ag:Cu:Sn:Ti = 83:10:5:2) to a vehicle and kneading it was screen-printed to a thickness of 10 μm on almost the entire surface (area of ​​45 mm x 47 mm) of one and the other main surfaces (front and back surfaces) of the ceramic substrate to form brazing material layers. Oxygen-free copper plates measuring 46 mm x 48 mm x 0.3 mm were placed on one and the other main surfaces of the ceramic substrate so that the entire surface of the brazing material layer formed on the aluminum nitride substrate was covered, and the plate was heated to 850°C in a vacuum and then cooled to join copper plates to both sides of the aluminum nitride substrate.

[0029] Next, an ultraviolet-curing alkaline peelable etching resist in a predetermined circuit pattern shape was applied by screen printing to the surface of the copper plate that would become the circuit side, and an ultraviolet-curing alkaline peelable etching resist in the shape of a 44 mm x 46 mm rectangle (no resist was applied within a 1 mm range inward from the edges of the copper plate) was applied by screen printing to the central surface of the copper plate that would become the heat dissipation side.The etching resist was then hardened by irradiating it with ultraviolet light, and unnecessary parts of the copper plate were etched with an etching solution consisting of copper chloride, hydrochloric acid, and the remainder water.The etching resist was then removed with an aqueous sodium hydroxide solution to form the circuit side copper plate (copper circuit) and the heat dissipation side copper plate.

[0030] Next, the substrate was pickled by immersion in dilute sulfuric acid for 20 seconds, and then immersed in a chelating aqueous solution containing 1.6% by mass of EDTA·4Na, 3% by mass of ammonia water (ammonia water containing 28% by mass of ammonia), and 5% by mass of hydrogen peroxide water (hydrogen peroxide water containing 35% by mass of hydrogen peroxide) at 20°C for 20 minutes, and then immersed in a chelating aqueous solution containing 2% by mass of ethylenetriaminepentaacetic acid (DTPA)·5Na and 5% by mass of hydrogen peroxide water (hydrogen peroxide water containing 35% by mass of hydrogen peroxide) at 20°C for 52 minutes. This removed unnecessary portions of the brazing filler layer (active metal-containing brazing filler) remaining around the copper plate on the circuit side and the copper plate on the heat dissipation side on the surface of the aluminum nitride substrate, and yielded an intermediate insulating substrate product.

[0031] Next, the intermediate product was immersed in a chemical polishing solution consisting of 14% by mass sulfuric acid, 3.2% by mass hydrogen peroxide, and the remainder water at 45°C for 5 minutes to remove unnecessary parts of the copper plate on the circuit side and the copper plate on the heat dissipation side by chemical polishing, causing the brazing material layer (active metal-containing brazing material) to protrude from the side portions of the copper plate on the circuit side and the copper plate on the heat dissipation side, completing the process of forming the specified copper pattern and obtaining an insulating substrate.

[0032] Next, an ultraviolet-curable solder resist was applied by screen printing to a 0.05 mm wide area around the periphery of the surface (bottom surface (other main surface)) of the heat-dissipating copper plate and to the side surface of the heat-dissipating copper plate, and the solder resist was irradiated with ultraviolet light to harden it, forming a 15 μm thick solder resist section (solder flow prevention area) on the periphery and side surface of the other main surface of the heat-dissipating copper plate, thereby producing an insulating substrate. As shown in Figures 1 to 3, the shape of the solder resist section was an example that spanned the side surface of the heat-dissipating copper plate and the periphery of the other main surface of the heat-dissipating copper plate. The application of the solder resist to the side surface of the heat-dissipating copper plate was performed by increasing the printing pressure (squeegee pressure) in screen printing using the above-mentioned screen plate.

[0033] The insulating substrate thus fabricated was subjected to the following base plate soldering test to evaluate the presence or absence of erosion of the brazing material layer. First, a metal mask was used to apply Sn-5.0Sb flux-containing paste solder (M10, manufactured by Senju Metal Industry Co., Ltd.) to a thickness of 300 μm on the surface of a 120 mm × 60 mm × 3 mm heat sink (copper base plate) in the same shape as the insulating substrate (46 mm × 48 mm rectangle).

[0034] Next, the heat dissipation side metal plate of the aforementioned insulating substrate was placed on top of this paste solder so that the other main surface was in contact with it, and the temperature was raised to 270°C in a N2 atmosphere. After that, the temperature was maintained at 270°C and vacuum evacuation was performed for 3 minutes, and then the temperature was lowered, thereby soldering the insulating substrate to the heat sink (copper base).

[0035] For the insulating substrate with base plate thus obtained, a cross-sectional observation sample was prepared and element mapping was performed using an optical microscope and a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM / EDS) to confirm the presence or absence of contact between the brazing material layer and the solder and the occurrence of brazing material erosion. As a result, in the insulating substrate prepared in this embodiment, it was confirmed from the optical microscope image that the solder used for soldering the heat sink was inhibited from spreading by the solder resist portion, and contact between the solder and the brazing material layer of the insulating substrate was prevented. In addition, element mapping by SEM / EDS confirmed that Sn, a component of the solder, did not diffuse to the brazing material layer side of the insulating substrate, and brittle Cu-Sn compounds were not generated (brazing material erosion did not occur).

[0036] Example 2 An insulating substrate was obtained in the same manner as in Example 1, except that the solder resist applied to the heat-dissipating-side metal plate was limited to a 0.05 mm-wide range around the outer periphery of the surface (other main surface) of the heat-dissipating-side metal plate and was not formed on the side surface of the heat-dissipating-side metal plate. The shape of the solder resist portion was an example only on the surface (other main surface) of the heat-dissipating-side metal plate, as shown in FIG.

[0037] A base plate soldering test was carried out on this insulating substrate in the same manner as in Example 1. In the insulating substrate produced in this example, the solder resist prevented the solder used for base plate attachment from spreading, and it was confirmed from the optical microscope image that the solder was prevented from contacting the brazing material layer of the insulating substrate. In addition, element mapping by SEM / EDS confirmed that Sn and other components of the solder were not diffused to the brazing material layer side of the insulating substrate (no brazing material was eaten away).

[0038] Comparative Example 1 An insulating substrate was obtained in the same manner as in Example 1, except that the solder resist was not applied to the heat-dissipating metal plate.

[0039] A base plate soldering test was carried out on this insulating substrate in the same manner as in Example 1. In the insulating substrate produced in this comparative example, the solder used for base plate attachment spreads over the side of the copper plate on the heat dissipation side, and it was confirmed from an optical microscope image that the solder layer of the insulating substrate and the solder are in contact. In addition, element mapping by SEM / EDS confirmed that Sn and other components of the solder diffuse into the brazing layer of the insulating substrate, forming brittle Cu-Sn compounds (the brazing layer is being eaten away). [Industrial Applicability]

[0040] The present invention can be used for insulating substrates used in, for example, semiconductor power modules. [Explanation of symbols]

[0041] 1. Insulating substrate 10 Ceramic Substrate 11 Circuit side metal plate (copper circuit board) 12 Heat radiation side metal plate 13, 14 Brazing material layer 11a, 12a side 12b Soldering Area 20 Solder resist section 30 Heat sink (copper plate) 31 Solder

Claims

1. One main surface of a heat-dissipating metal plate is joined to one main surface of the ceramic substrate via a brazing material layer, the brazing material layer protrudes from an end portion of the heat-dissipating side metal plate, An insulating substrate, characterized in that a solder resist portion is formed on at least one selected from the periphery of the other main surface of the heat dissipation side metal plate, the side surface of the heat dissipation side metal plate, or the surface of the brazing material layer.

2. 2. The insulating substrate according to claim 1, wherein one main surface of a circuit-side metal plate is joined to the other main surface of the ceramic substrate via a brazing material layer.

3. 3. The insulating substrate according to claim 2, wherein the circuit-side metal plate is a copper plate or a copper alloy plate.

4. 4. The insulating substrate according to claim 1, wherein the heat-dissipating metal plate is a copper plate or a copper alloy plate.

5. 5. The insulating substrate according to claim 1, wherein the solder resist portion is formed to surround a soldering area on the other main surface of the heat-dissipating metal plate.

6. 6. The method for manufacturing an insulating substrate according to claim 1, wherein the solder resist portion is formed by screen printing.

7. 6. A semiconductor module component, comprising: an insulating substrate according to claim 1, and a heat sink plate joined to the other main surface of said heat sink side metal plate of said insulating substrate by means of solder.

8. 6. A method for manufacturing an insulating substrate with a heat sink, comprising the steps of: joining a heat sink to the other main surface of the heat sink-side metal plate of the insulating substrate according to claim 1 by soldering.

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