Insulating circuit board, method for manufacturing same, semiconductor module, and method for manufacturing same

Abstract

Provided is an insulating circuit board comprising: an insulating board; and a circuit metal plate joined to at least one surface of the insulating board. An Spd value, which is a peak density of a curve of a three-dimensional surface property parameter on a surface of the circuit metal plate, is between 100 mm-2 and 1000 mm-2 (both inclusive). An Sdr value, which is an expanded area ratio of an interface of a three-dimensional surface property parameter on the surface of the circuit metal plate, is between 0.05 and 0.2 (both inclusive).

Description

Insulated circuit board and method of manufacturing the same, semiconductor module and method of manufacturing the same

[0001] The present invention relates to an insulating circuit board and a manufacturing method thereof, a semiconductor module and a manufacturing method thereof.

[0002] Semiconductor devices such as power modules are used to control large amounts of power in electric vehicles, trains, machine tools, etc. These power modules and other semiconductor devices generally use an insulated circuit board as a component for mounting semiconductor elements. Such an insulated circuit board has a metal circuit plate for mounting semiconductor elements bonded to the surface of an insulating substrate made of ceramics or insulating resin.

[0003] For example, Patent Document 1 describes a metal-ceramic bonded substrate (insulated circuit board) in which a copper plate or copper alloy plate is bonded to each surface of a ceramic substrate as a metal plate (circuit metal plate and heat dissipation metal plate). Patent Document 2, for example, describes a power module using an insulated circuit board that includes a power element (semiconductor element), a metal wiring plate (circuit metal plate) on the underside of the power element via a solder layer, and a heat dissipation metal plate provided on the underside of the metal wiring plate via a resin insulating layer (insulating substrate).

[0004] In mounting a power module, semiconductor elements are mounted on the surface of a circuit metal plate of an insulating circuit board and wired by wire bonding. Therefore, the surface of the circuit metal plate of an insulating circuit board for a power module is required to have excellent wire bonding properties.

[0005] As a method for obtaining a surface with excellent wire bonding properties, a method of reducing the surface roughness by chemical polishing treatment is known, as disclosed in, for example, Patent Documents 3 and 4.

[0006] JP 2016-51778 A JP 2007-288054 A JP 2007-081217 A JP 7-147465 A

[0007] In recent years, wide bandgap semiconductors such as SiC and GaN have begun to be adopted as power semiconductor elements, replacing the conventionally used Si power semiconductors. Wide bandgap semiconductor elements have a low on-resistance, making it possible to control the same amount of power as Si semiconductors with a smaller chip than conventional Si semiconductor elements.

[0008] Accordingly, metal wires to be wired to semiconductor elements are becoming thinner from the conventionally commonly used diameter of 300 μm to thinner diameters, for example, 175 μm or less.

[0009] However, when the metal wire is thinned, as shown in Patent Documents 3 and 4, even if the roughness Ra (arithmetic mean roughness) of the circuit metal plate surface is set to 1.0 μm or less, or Rz (maximum height, Rmax in JIS B0601:1982) is set to 5.0 μm or less, there is a problem that the bonding strength between the metal wire and the surface of the metal plate is reduced.

[0010] Therefore, an object of the present invention is to provide a technique for improving the bonding strength between an insulating circuit board and a circuit metal plate even when a thin metal wire is used.

[0011] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it was found that it is difficult to determine the surface properties of the metal circuit plate of an insulated circuit board suitable for thinned metal wires (hereinafter also referred to as thin wires) using conventional two-dimensionally evaluated line roughness (e.g., Ra, Rz, Rzjis, etc.). Conventionally, the surface roughness of the metal circuit plate of an insulated circuit board for a power module has been controlled by line roughness (e.g., Ra, Rz, etc.) measured using a stylus-type roughness tester. However, measurement using line roughness is merely a two-dimensional evaluation of one cross section of the measurement surface, and is insufficient for identifying surface properties suitable for thinned wires.

[0012] Therefore, the inventors used a laser microscope to evaluate the three-dimensional surface texture parameters of the surface of the circuit metal plate of various insulated circuit boards, and investigated the relationship between the three-dimensional surface texture parameters and the bond strength between the surface of the circuit metal plate and the thin wire in the insulated circuit board.As a result, they found that by setting the three-dimensional surface texture parameters of the surface of the circuit metal plate of the insulated circuit board within a predetermined range, good bond strength between the thin wire and the metal plate surface can be maintained.

[0013] In addition, as a manufacturing method for easily obtaining a circuit metal plate surface having three-dimensional surface texture parameters within a predetermined range, a method for manufacturing a circuit metal plate surface using sulfuric acid (H ２ SO ４ ) and hydrogen peroxide (H ２ O ２ It has been found that this can be achieved by performing chemical polishing treatment twice using a chemical polishing solution containing

[0014] A first aspect of the present invention is an insulated circuit board comprising an insulating substrate and a circuit metal plate bonded to at least one surface of the insulating substrate, wherein the Spd value, which is a peak density of three-dimensional surface texture parameters on the surface of the circuit metal plate, is 100 mm －２ More than 1000mm －２ or less, and an Sdr value, which is a developed area ratio of an interface of a three-dimensional surface texture parameter on the surface of the circuit metal plate, is 0.05 or more and 0.2 or less.

[0015] A second aspect of the present invention is the first aspect, wherein the arithmetic mean roughness Ra of the surface of the circuit metal plate is 0.15 μm or more and 1.5 μm or less.

[0016] A third aspect of the present invention is the first or second aspect, wherein the standard deviation of the Spd value is 100 mm at a plurality of points on the surface of the circuit metal plate. －２ Hereinafter, the standard deviation of the Sdr value is 0.05 or less.

[0017] A fourth aspect of the present invention is any one of the first to third aspects, wherein when an Al wire having a diameter of 125 μm is bonded to the surface of the circuit metal plate, the average shear strength at a plurality of bonding locations is 300 cN or more.

[0018] A fifth aspect of the present invention is any one of the first to fourth aspects, wherein when an Al wire having a diameter of 125 μm is bonded to the surface of the circuit metal plate, the first quartile of the shear strength at a plurality of bonding locations is 250 cN or more.

[0019] A sixth aspect of the present invention is any one of the first to fifth aspects, wherein when an Al wire having a diameter of 125 μm is bonded to the surface of the circuit metal plate, the interquartile range, which is the difference between the third quartile and the first quartile of the shear strength at a plurality of bonding locations, is 90 cN or less.

[0020] A seventh aspect of the present invention is a method for manufacturing a bonded body, the method comprising: a preparation step of preparing an assembled body including an insulating substrate and a circuit metal plate joined to at least one surface of the insulating substrate; a first chemical polishing step of treating the assembled body with a first chemical polishing solution containing 1.0 mol / L to 1.6 mol / L of sulfuric acid and 0.7 mol / L to 1.2 mol / L of hydrogen peroxide; a second chemical polishing step of treating the assembled body after the first chemical polishing step with a second chemical polishing solution containing 0.04 mol / L to 0.4 mol / L of sulfuric acid and 1.0 mol / L to 3.0 mol / L of hydrogen peroxide; and an acid pickling step of pickling the assembled body after the second chemical polishing step, wherein an Spd value, which is a peak density of peaks in a three-dimensional surface texture parameter on the surface of the metal plate, is 100 mm －２ More than 1000mm －２ wherein the Sdr value, which is a developed area ratio of three-dimensional surface texture parameters on the surface of the metal plate, is 0.05 or more and 0.2 or less.

[0021] An eighth aspect of the present invention is a semiconductor module comprising: an insulating circuit board according to any one of the first to sixth aspects; and a semiconductor element connected to the circuit metal plate by a metal wire having a diameter of 175 μm or less.

[0022] A ninth aspect of the present invention is a method for manufacturing a semiconductor module, comprising connecting a semiconductor element to the circuit metal plate of the insulating circuit board of any one of the first to sixth aspects with a metal wire having a diameter of 175 μm or less.

[0023] According to the present invention, even if the wire is a thin wire, the bonding strength between the wire and the metal circuit plate in the insulating circuit board can be improved.

[0024] Fig. 1 is a flow diagram of a method for producing an insulating circuit board according to one embodiment of the present invention, and Fig. 2 is a graph showing the shear strength of Examples 1 to 3 and Reference Example 1.

[0025] <One embodiment of the present invention> An embodiment of the present invention will be described below. Fig. 1 is a flow diagram of a method for manufacturing an insulating circuit board according to one embodiment of the present invention. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits.

[0026] The insulating circuit board of the present invention includes an insulating substrate and a circuit metal plate bonded to at least one surface of the insulating substrate. In this embodiment, an insulating circuit board having a circuit metal plate on one main surface of the insulating substrate and a heat dissipation metal plate on the other main surface will be described as an example.

[0027] (Insulating Substrate) The insulating substrate is a plate-shaped member made of, for example, a ceramic material or a resin material. Ceramic materials used for the insulating substrate include oxide ceramics such as alumina, and non-oxide ceramics such as aluminum nitride, silicon nitride, silicon carbide, and boron nitride. Resin materials used for the insulating substrate include, for example, epoxy resin, polyurethane resin, polyimide resin, and insulating resins in which insulating ceramic filler particles such as alumina, aluminum nitride, silicon nitride, silicon carbide, and boron nitride are dispersed in a polymer resin material. The insulating substrate is preferably made of a ceramic material because it can achieve high levels of both insulation and heat dissipation performance. Among these, the insulating substrate is preferably made of a ceramic material such as alumina, aluminum nitride, or silicon nitride.

[0028] (Circuit metal plate) The circuit metal plate is bonded to one main surface of the insulating substrate. The circuit metal plate is produced, for example, by bonding a raw metal plate to the insulating substrate and then forming a predetermined circuit pattern on the metal plate. As described below, the circuit metal plate is configured to have a predetermined surface shape by a predetermined chemical polishing process. As the metal plate forming the circuit metal plate, a plate-shaped member made of a pure metal or an alloy can be used. From the viewpoint of improving electrical conductivity and thermal conductivity, the metal plate is preferably made of copper or a copper alloy, or aluminum or an aluminum alloy. Note that the circuit metal plate may also be bonded to the other main surface of the insulating substrate.

[0029] (Heat dissipating metal plate) The heat dissipating metal plate is bonded to the other main surface of the insulating substrate. The heat dissipating metal plate is produced, for example, by bonding a raw metal plate to the insulating substrate and then forming a predetermined heat dissipating metal pattern on the metal plate. Like the circuit metal plate, the heat dissipating metal plate may be subjected to a predetermined chemical polishing process and may be configured to have a predetermined surface shape. Note that the metal plate forming the heat dissipating metal plate may have the same composition as the metal plate forming the circuit metal plate, or may have a different composition. From the viewpoint of manufacturing efficiency, it is preferable that the respective metal plates have the same composition. By bonding the heat dissipating metal plate to the other main surface of the insulating substrate, heat generated from semiconductor elements mounted on the insulating circuit board can be efficiently dissipated, which is preferable.

[0030] (Three-dimensional surface texture parameter) In this embodiment, from the viewpoint of improving the bonding strength with the metal wire, the circuit metal plate in the insulating circuit board has a predetermined value of three-dimensional surface texture parameter obtained when its surface is measured with a laser microscope. The three-dimensional surface texture parameter is a quantification of information on the surface texture and roughness of the circuit metal plate with respect to a planar direction (two-dimensional surface) in a microscopic area. The three-dimensional surface texture parameter serves as an index for ensuring the bonding strength of the metal wire when the contact area between the surface of the circuit metal plate and the metal wire becomes smaller when the metal wire is thinned, and strict control of the contact state between the two is required. The three-dimensional surface texture parameter is measured based on ISO 25178-2:2012.

[0031] According to the investigations of the present inventors, among the three-dimensional surface texture parameters obtained when multiple locations on the surface of a circuit metal plate in an insulating circuit board are measured with a laser microscope, it has been found that the average peak density (Spd value) and the average developed area ratio (Sdr value) of the interface are parameters that have a particularly large effect on the bonding strength between the metal wire and the circuit metal plate. Here, the relationship between the surface shape of the circuit metal plate and the bonding strength will be described.

[0032] In wire bonding to a circuit metal plate in an insulated circuit board, a metal wire is brought into contact with the circuit metal plate, pressed in with a predetermined load and pressing force, and then bonded to the circuit metal plate by, for example, applying ultrasonic waves. Since the metal wire and the circuit metal plate are to be bonded in close contact, the surface roughness (uneven shape) of the circuit metal plate is important. If the surface of the circuit metal plate has many protrusions or the protrusions have a steep shape, the metal wire will ride over the protrusions, making it difficult to bond the metal wire to the metal plate. In particular, for thin wires with a diameter of 175 μm or less, the load and pressing force must be smaller than those for metal wires with a diameter of 250 μm to 500 μm in order to suppress deformation of the metal wire during bonding, making it more difficult to bond the metal wire to the circuit metal plate. Therefore, when using thin wires, the density and shape of the protrusions on the surface of the circuit metal plate become even more important.

[0033] The Spd value (peak density) indicates the number of peaks (points on the surface that are higher than the surrounding adjacent points) per unit area. The smaller the Spd value, the fewer the peaks (protrusions) on the surface of the circuit metal plate, and the larger the Spd value, the more the peaks (protrusions).

[0034] In this embodiment, from the viewpoint of increasing the bonding strength between the circuit metal plate and the metal wire, the Spd value of the circuit metal plate is 100 mm －２ More than 1000mm －２ The range is as follows: Spd value is 1000 mm －２If the Spd value exceeds 100 mm, the number of protrusions on the surface of the circuit metal plate will be excessively large. If the number of protrusions is excessively large, the metal wire may ride up on the protrusions, making it difficult to adhere the metal wire to the circuit metal plate, and high bonding strength cannot be achieved. In particular, when the metal wire is thinned and a metal wire (thin wire) having a diameter of, for example, 175 μm or less is bonded, the load and the amount of pressing may not be large compared to when a metal wire having a diameter of, for example, 250 μm to 500 μm is bonded. As a result, if there are many protrusions, the metal wire cannot crush the protrusions, and a sufficient bonding interface cannot be secured, which is thought to prevent high bonding strength from being obtained. On the other hand, if the Spd value is 100 mm －２ If the Spd value is less than 100 mm, the metal wire can be brought into close contact with the circuit metal plate, but the contact area between the circuit metal plate and the metal wire becomes excessively large, which tends to excessively reduce the surface pressure during wire bonding. If the surface pressure is low, when the metal wire is pressed into the circuit metal plate to perform wire bonding, it becomes difficult to destroy the oxide film present at the bonding interface between the metal wire and the metal plate, and high bonding strength may not be achieved. In this regard, －２ More than 1000mm －２ By setting the thickness within the following range, it is possible to form a surface shape suitable for bonding thin wires on the circuit metal plate, and to increase the bonding strength. －２ Over 800mm －２ It is preferable that the length is 180 mm or less. －２ Over 700mm －２ More preferably, the Spd value is 300 mm or less. －２ Over 400mm －２ Over 500mm －２ That's all.

[0035] The Sdr value (interface developed area ratio) indicates how much the developed area of ​​the measurement region (surface area of ​​the measured shape) has increased relative to the projected area of ​​the measurement region. The larger the Sdr value, the more protrusions there are or the shape of the protrusions is steeper, and the smaller the Sdr value, the closer the surface is to flat, the fewer protrusions there are, and the more gentle the shape of the protrusions. A perfect surface without any protrusions has an Sdr value of 0. The Sdr value is a numerical value measured, for example, in accordance with ISO 25178-2:2012. Details will be described later in the examples.

[0036] In this embodiment, from the viewpoint of increasing the bonding strength between the circuit metal plate and the metal wire, the Sdr value of the circuit metal plate is in the range of 0.05 to 0.2. If the Sdr value exceeds 0.2, the number of protrusions on the surface of the circuit metal plate will be excessively large, or the shape of the protrusions will be steep. If the number of protrusions is excessively large and the shape is steep, the metal wire may climb up on the protrusions, making it difficult to adhere the metal wire to the circuit metal plate, and high bonding strength cannot be achieved. On the other hand, if the Sdr value is less than 0.05, the surface of the circuit metal plate will be nearly flat, and the metal wire can be adhered to the circuit metal plate. However, the contact area between the circuit metal plate and the metal wire will be excessively large, reducing the surface pressure, making it difficult to destroy the oxide film present at the bonding interface, and high bonding strength may not be achieved. In this regard, if the Sdr value is in the range of 0.05 to 0.2, a surface shape suitable for bonding thin wires can be formed on the circuit metal plate, and bonding strength can be increased. The Sdr value is preferably 0.08 or more and 0.15 or less, and more preferably 0.1 or more and 0.14 or less.

[0037] (Arithmetic mean roughness) The arithmetic mean roughness Ra of the circuit metal plate of the insulating circuit board is not particularly limited as long as the Spd value and Sdr value satisfy the above ranges, but is preferably 0.15 μm or more and 1.5 μm or less, more preferably 0.3 μm or more and 1.1 μm or less, even more preferably 0.4 μm or more and 1.0 μm or less, and even more preferably 0.5 μm or more and 0.8 μm or less. When the arithmetic mean roughness Ra of the surface of the metal plate falls within the specified range, the bonding strength during wire bonding can be increased.

[0038] (Surface Distribution) In order to suppress in-plane variations in the bonding strength between the circuit metal plate and the metal wire on the surface of the circuit metal plate of the insulating circuit board, it is preferable that the in-plane variations in the Spd value and Sdr value on the surface of the circuit metal plate are small. Specifically, when multiple points on the surface of the circuit metal plate are measured with a laser microscope, the standard deviation of the Spd value is 100 mm. －２ It is preferable that the standard deviation of the Sdr value is 0.05 or less. This makes it possible to reduce the variation in the bonding strength when wire bonding is performed at multiple locations on the surface of the circuit metal plate, thereby preventing the occurrence of locations where the bonding strength is locally low. The coefficient of variation of the Spd value is preferably 12% or less, more preferably 10% or less. The coefficient of variation of the Sdr value is preferably 23% or less, more preferably 20% or less. The coefficient of variation of the Spd value is calculated using the following formula (1), and the coefficient of variation of the Sdr value is calculated using the following formula (2). Spd coefficient of variation (%) = 100 × [standard deviation σ of Spd] / [average value of Spd] (1) Sdr coefficient of variation (%) = 100 × [standard deviation σ of Sdr] / [average value of Sdr] (2)

[0039] (2) Semiconductor Module The semiconductor module is configured by connecting semiconductor elements to the circuit metal plate of the above-mentioned insulating circuit board by metal wires.

[0040] Examples of metal wires that can be used include Al wires containing aluminum, Au wires containing gold, and Cu wires containing copper. Al wires are preferred from the viewpoint of achieving both cost and moisture resistance. The diameter of the metal wire is not particularly limited, but in this embodiment, the surface of the metal plate is formed so that the Spd and Sdr values ​​are within a predetermined range. Therefore, high bonding strength can be achieved even when using thin wires with a diameter of 175 μm or less. The diameter of the thin wire is preferably 175 μm or less, and more preferably 100 μm or more and 175 μm or less.

[0041] Furthermore, in a semiconductor module using the insulating circuit board of the present invention, when a metal wire (e.g., an Al wire) having a diameter of 125 μm is bonded to the surface of the metal plate of the insulating circuit board, the shear strength at each of the bonding locations is high. Specifically, the average shear strength at the bonding locations is preferably 300 cN or more.

[0042] Furthermore, in the semiconductor module, the variation in the Spd and Sdr values ​​on the surface of the metal plate is small, so when a metal wire (e.g., an Al wire) with a diameter of 125 mm is bonded to the surface of the metal plate, the variation in shear strength at multiple bonding locations is small. Specifically, the first quartile of the shear strength at multiple bonding locations is preferably 250 cN or greater. Furthermore, the interquartile range, which is the difference between the third and first quartiles of the shear strength at multiple bonding locations, is preferably 90 cN or less.

[0043] (3) Manufacturing Method of Insulated Circuit Board Next, a manufacturing method of the above-mentioned insulated circuit board will be described. Here, as an example, a case where a metal-ceramic circuit board is manufactured, in which a circuit metal plate is bonded to one main surface of a ceramic substrate, which is an insulating substrate, and a heat dissipation metal plate is bonded to the other main surface, will be described.

[0044] (Preparation Step) First, a bonded body is prepared in which a circuit metal plate and a heat dissipation metal plate are bonded to the main surface of a ceramic substrate. The bonded body can be produced, for example, as follows.

[0045] Specifically, first, metal plates are bonded to both main surfaces of a ceramic substrate. Known bonding methods, such as direct bonding, brazing, and adhesive bonding, can be used. Brazing is particularly suitable because it reduces voids at the interface between the ceramic substrate and the metal plate and provides a bonding layer (brazing material bonding layer) formed between the ceramic substrate and the metal plate with excellent thermal cycling resistance. When brazing is used as the bonding method, a laminate is prepared in which a brazing material is disposed between the ceramic substrate and the metal plate, and the laminate is heated to a predetermined temperature, for example, a temperature at which a liquid phase is generated from the brazing material, and then cooled.

[0046] Next, a predetermined pattern is formed on each of the metal plates bonded to both main surfaces of the ceramic substrate. For example, an etching resist film having a predetermined circuit pattern is formed on the surface of the metal plate bonded to one main surface of the insulating substrate, and an etching resist film having a predetermined heat dissipation metal pattern is formed on the surface of the metal plate bonded to the other main surface. These resist films may be formed by forming a resist using a known method such as screen printing, laminating, or photomasking, and then curing it.

[0047] Next, the areas of the metal plate not covered with the resist film are removed using a known etching solution, such as cupric chloride, iron chloride, hydrofluoric acid, or a chelating agent, and then the resist film is removed. Furthermore, if the bonded body is produced by a brazing method, the unnecessary brazing material bonding layer between the patterns is removed. This results in a bonded body in which a circuit metal plate having a predetermined circuit pattern and a heat dissipation metal plate having a predetermined heat dissipation metal pattern are bonded to both main surfaces of the ceramic substrate.

[0048] (First Chemical Polishing Treatment Step) Next, the bonded body is subjected to a chemical polishing treatment using a chemical polishing solution containing sulfuric acid and hydrogen peroxide. In this embodiment, first and second chemical polishing treatments are performed using two types of first and second chemical polishing solutions having different concentrations of sulfuric acid and hydrogen peroxide. Note that in this embodiment, the first and second chemical polishing treatments are performed on the circuit metal plate and heat dissipation metal plate of the bonded body, but it is sufficient to perform the first and second chemical polishing treatments at least on the circuit metal plate to be wire-bonded.

[0049] The first chemical polishing step is performed to remove oxide layers, hydroxide layers, and scratches caused during handling that have formed on the surfaces of the circuit metal plate and the heat dissipation metal plate prior to the first chemical polishing step, and to uniformly form a surface shape suitable for the second chemical polishing step described below. In the first chemical polishing step, a first chemical polishing solution is brought into contact with the surfaces of the circuit metal plate and the heat dissipation metal plate of the bonded assembly. The first chemical polishing solution forms a metal oxide layer on the surfaces of the circuit metal plate and the heat dissipation metal plate through the oxidizing action of hydrogen peroxide, and the metal oxide layer can be dissolved by sulfuric acid. As a result, portions of the surfaces of the circuit metal plate and the heat dissipation metal plate are dissolved in the thickness direction, removing the oxide layers, hydroxide layers, and scratches that have formed on the surfaces of the circuit metal plate and the heat dissipation metal plate.

[0050] The first chemical polishing solution contains 1.0 mol / L to 1.6 mol / L of sulfuric acid and 0.7 mol / L to 1.2 mol / L of hydrogen peroxide. The first chemical polishing solution preferably contains 1.2 mol / L to 1.5 mol / L of sulfuric acid. The first chemical polishing solution also preferably contains 0.8 mol / L to 1.1 mol / L of hydrogen peroxide. Compared to the second chemical polishing solution described below, the first chemical polishing solution contains a higher concentration of sulfuric acid and a lower concentration of hydrogen peroxide. Because the first chemical polishing solution has a high dissolution and removal rate due to sulfuric acid, it preferentially dissolves and removes easily soluble portions (e.g., grain boundaries) and easily soluble crystal orientations of the metal plate. As a result, the surfaces of the circuit metal plate and the heat dissipation metal plate can be roughly polished.

[0051] In addition to sulfuric acid and hydrogen peroxide, the first chemical polishing solution may contain a stabilizer for hydrogen peroxide. The stabilizer can suppress decomposition of hydrogen peroxide, maintain the oxidizing power of hydrogen peroxide, and extend the life of the first chemical polishing solution. Examples of stabilizers that can be used include linear polyhydric alcohols such as ethylene glycol and glycerin, phenols, acetamides, and benzamides. Among these, ethylene glycol and glycerin are preferred because they are highly soluble in water, have low toxicity, and are easy to handle. The concentration of the stabilizer is not particularly limited, but is preferably 0.1 mol / L to 0.5 mol / L.

[0052] The method for bringing the first chemical polishing liquid into contact with the metal plate of the joined body can be a conventionally known method, such as an immersion treatment method in which the joined body is immersed in the first chemical polishing liquid, or a spray treatment method in which the first chemical polishing liquid is sprayed in the form of a spray or shower.

[0053] As a processing condition for the first chemical polishing, the temperature of the first chemical polishing solution is preferably 30°C to 60°C, and more preferably 40°C to 60°C. Since the lower the concentration of sulfuric acid in the first chemical polishing solution, the slower its reactivity tends to be. Therefore, it is advisable to increase the temperature according to the concentration to enhance reactivity. In this regard, by setting the temperature of the first chemical polishing solution within the above range, oxide layers, hydroxide layers, and scratches on the metal plate can be stably dissolved and removed. Furthermore, the contact time with the first chemical polishing solution (e.g., immersion time) is not particularly limited as long as it can dissolve and remove the oxide layers, hydroxide layers, and scratches formed on the surface of the metal plate. It may be adjusted appropriately depending on the thickness of the oxide layers, hydroxide layers, and the depth of scratches. Since the thickness of the oxide layers, hydroxide layers, and the depth of scratches are, for example, 10 μm to 50 μm, the contact time is preferably 270 seconds to 390 seconds when dissolving and removing such oxide layers, hydroxide layers, and scratches. When the thickness of the oxide layers, hydroxide layers, and scratches is greater than 50 μm, it is advisable to extend the contact time.

[0054] After the first chemical polishing treatment, the bonded body is preferably washed with water. This washes away the first chemical polishing solution adhering to the metal plate and stops any further reaction. The water washing method can be, for example, an immersion treatment method or a spray treatment method. The temperature of the water used for washing is preferably in the range of, for example, 4°C to 30°C, from the viewpoint of suppressing deterioration of the metal plate.

[0055] (Second Chemical Polishing Step) Next, the metal plates of the joined body that have been subjected to the first chemical polishing process are brought into contact with a second chemical polishing solution to chemically polish the surfaces of the metal plates. The second chemical polishing process allows the surface of the metal plate that has been roughly chemically polished by the first chemical polishing process to be precisely dissolved and removed. This allows the surface of the metal plate to be formed into a shape that has Spd and Sdr values ​​within a predetermined range and is suitable for joining thin wires.

[0056] The second chemical polishing liquid has a lower sulfuric acid concentration and a higher hydrogen peroxide concentration than the first chemical polishing liquid. Specifically, the second chemical polishing liquid contains 0.04 mol / L to 0.4 mol / L of sulfuric acid and 1.0 mol / L to 3.0 mol / L of hydrogen peroxide. The second chemical polishing liquid preferably contains 0.05 mol / L to 0.1 mol / L of sulfuric acid. The second chemical polishing liquid preferably contains 1.5 mol / L to 2.7 mol / L of hydrogen peroxide, more preferably 1.9 mol / L to 2.4 mol / L. The second chemical polishing liquid has a gentler dissolution and removal action than the first chemical polishing liquid because the formation of a metal oxide layer occurs more preferentially due to the oxidizing action of hydrogen peroxide. With such a second chemical polishing liquid, the diffusion rate of ions contributing to dissolution is rate-limiting, and it is presumed that dissolution of three-dimensional protrusions present on the metal plate occurs preferentially over dissolution of the surface of the metal plate. In other words, the second chemical polishing solution can preferentially dissolve the protrusions on the metal plate, making it possible to process the metal plate to be more flat.

[0057] The second chemical polishing solution may contain a stabilizer for hydrogen peroxide in addition to sulfuric acid and hydrogen peroxide, similar to the first chemical polishing solution. The stabilizer may be the same as that used in the first chemical polishing solution, and preferably at least one of ethylene glycol and glycerin. The concentration of the stabilizer is not particularly limited, but is preferably 0.1 mol / L to 0.5 mol / L.

[0058] As in the first chemical polishing treatment, the method for bringing the second chemical polishing solution into contact with the metal plate of the joined body can be a conventionally known method such as an immersion treatment method or a spray treatment method. When a spray treatment method is used, it is preferable to reduce the spray rate because the metal oxide layer produced during the reaction in the second chemical polishing treatment may fall off due to the impact of the spray.

[0059] As a processing condition for the second chemical polishing, the temperature of the second chemical polishing solution is preferably 30°C to 60°C, and more preferably 40°C to 60°C. Since the lower the concentration of sulfuric acid in the second chemical polishing solution, the slower its reactivity tends to be, it is advisable to increase the temperature according to the concentration to enhance reactivity. In this regard, by setting the temperature of the second chemical polishing solution within the above range, protrusions on the metal plate can be stably dissolved and removed, thereby achieving the desired surface condition. Furthermore, the contact time with the second chemical polishing solution (e.g., immersion time) can be appropriately adjusted so that the Spd value and Sdr value on the surface of the metal plate fall within a predetermined range. The contact time is preferably 330 seconds to 450 seconds.

[0060] (Pickling Process) Next, the bonded body after the second chemical polishing treatment is brought into contact with a pickling solution and pickled. A metal oxide layer may remain on the surface of the metal plate after the second chemical polishing treatment. For example, if the metal plate is made of copper, hydrogen peroxide may oxidize the copper during the second chemical polishing treatment, leaving a thin, sparse oxide layer mainly composed of copper (II) oxide. If the bonded body is washed with water without pickling, the metal oxide layer may fall off, resulting in a rough surface of the metal plate. In this regard, pickling can dissolve and remove the remaining metal oxide layer, for example, an oxide layer mainly composed of copper (II) oxide.

[0061] The pickling solution used for pickling is not particularly limited as long as it dissolves and removes the metal oxide layer without excessively dissolving the substrates of the circuit metal plate and the heat dissipation metal plate, but it is preferable to use dilute sulfuric acid or dilute hydrochloric acid. When dilute sulfuric acid is used as the pickling solution, it is preferable to set the sulfuric acid concentration to 0.5 mol / L to 2.0 mol / L.

[0062] As a method for contacting with the pickling solution, a conventionally known method such as an immersion treatment method or a spray treatment method can be used, as in the first chemical polishing treatment, etc. When a spray treatment method is used, it is preferable to reduce the spray rate in order to prevent the metal oxide layer from falling off due to the impact of the spray.

[0063] As a condition for pickling, the temperature of the pickling solution is preferably 4°C to 30°C from the viewpoint of suppressing deterioration of the surfaces of the surface-prepared circuit metal plate and heat dissipation metal plate underlying the metal oxide layer. The pickling treatment time is not particularly limited as long as it can dissolve and remove the remaining metal oxide layer. In the case of an immersion treatment method, the immersion time is preferably 10 to 20 seconds.

[0064] (Cleaning Step) Next, the bonded body after the second chemical polishing treatment is cleaned to remove impurities present on the surfaces of the circuit metal plate and the heat dissipation metal plate of the bonded body.

[0065] The cleaning method is preferably water washing or pure water washing, and a conventionally known method such as an immersion treatment method or a spray treatment method can be used, as in the first chemical polishing treatment step, etc. The liquid temperature for water washing or pure water washing is preferably in the range of 4°C to 30°C.

[0066] In this manner, a metal ceramic circuit substrate is obtained as the insulating circuit substrate of this embodiment.

[0067] A semiconductor module is fabricated using the above-described insulating circuit board. Specifically, first, a semiconductor element is placed on the insulating circuit board. Next, one end of a prepared metal wire is brought into close contact with an electrode of the semiconductor element, and they are wire-bonded by, for example, applying ultrasonic waves. Next, the other end of the metal wire is brought into close contact with a circuit metal plate of the insulating circuit board, and they are wire-bonded by, for example, applying ultrasonic waves. In this manner, a semiconductor module can be manufactured.

[0068] <Other embodiments of the present invention> Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0069] In the above embodiment, the first chemical polishing process and the second chemical polishing process are performed on the prepared assembly. However, other processes may be performed as needed. For example, if oil or grease adheres to the surface of the metal plate of the prepared assembly, a known degreasing process may be performed before the first chemical polishing process. Furthermore, if metal oxide scale or the like is present on the surfaces of the circuit metal plate and the heat dissipation metal plate of the prepared assembly, a known pickling process may be performed before the first chemical polishing process. Furthermore, for example, after the above pickling process, additional surface treatments may be performed to further impart functionality to the surfaces of the circuit metal plate and the heat dissipation metal plate of the insulating circuit board, as long as the three-dimensional surface properties of the metal plate are not impaired. Specifically, an anti-rust film or various plating films may be formed on the surfaces of the circuit metal plate and the heat dissipation metal plate.

[0070] In the above-described embodiment, an etching method is used to form the circuit metal plate and the heat dissipation metal plate of the insulated circuit board, but the present invention is not limited to this. For example, a metal plate may be punched into a predetermined circuit pattern shape or a heat dissipation metal pattern shape in advance, and then bonded to an insulating layer (made of insulating ceramics or insulating resin material) by a known method (such as direct bonding or brazing if the insulating layer is made of insulating ceramics, or a method of hot pressing via a thermosetting resin layer or a thermoplastic resin layer if the insulating layer is made of insulating resin material, or an adhesive bonding method using various adhesives) to form the circuit metal plate and the heat dissipation metal plate of the insulated circuit board.

[0071] In the above embodiment, the case where the chemical polishing step is performed consecutively after the metal pattern formation step by etching has been described, but the chemical polishing step can be performed at any timing as long as it does not impair the obtained three-dimensional surface texture. For example, when pattern formation is performed by the mounting method, the chemical polishing step may be performed on the punched circuit metal plate and heat dissipation metal plate before they are bonded to the insulating layer.

[0072] In the above-described embodiment, an insulating circuit board is described in which metal plates are formed on both main surfaces of a single insulating layer, but the insulating layer may be multiple layers.Furthermore, the insulating circuit board may have only a circuit metal plate and no heat dissipation metal plate.

[0073] In the above-described embodiment, the entire surfaces of both the circuit metal plate and the heat dissipation metal plate of the insulated circuit board are subjected to the chemical polishing process of the present invention, but when the insulated circuit board is mounted as a power module, the chemical polishing process does not need to be performed on areas where wire bonding is not performed (non-wire bonding areas). For example, by protecting the non-wire bonding areas with a resist film or the like before the chemical polishing process, it is possible to obtain an insulated circuit board in which the wire bonding areas have the three-dimensional surface texture of the present invention, while the other surfaces of the circuit metal plates have surface texture suitable for other mounting processes.

[0074] The present invention will be explained in more detail below with reference to Examples and Reference Examples, but the present invention is not limited to these examples in any way.

[0075] (1) Fabrication of Insulated Circuit Boards First, insulated circuit boards were fabricated. Specifically, aluminum nitride (AlN) substrates measuring 58 mm long, 50 mm wide, and 1 mm thick were prepared. Copper plates measuring 58 mm long, 50 mm wide, and 0.3 mm thick were brazed to both sides of each prepared AlN substrate using Ag-Cu-Ti brazing (Ag:Cu:Ti = 88:10:2). Next, etching resists of predetermined patterns were formed on each of the copper plates bonded to the AlN substrates by screen printing. Subsequently, unnecessary copper plate portions were etched and removed using an etching solution containing copper chloride, and the etching resist was peeled and removed using a sodium hydroxide solution. Subsequently, unnecessary brazing material bonding layers were etched and removed using an etching solution containing EDTA, and copper circuit metal plates and copper heat dissipation metal plates were formed on both sides of the AlN substrates, respectively, to fabricate a bonded assembly.

[0076] Twenty-four bonded bodies obtained in this manner before the chemical polishing treatment step were prepared, and these were randomly divided into four equal parts, to obtain four sets of bonded bodies, each consisting of six pieces.

[0077] In this example, each of the produced bonded bodies was subjected to chemical polishing treatment under the following conditions to produce an insulating circuit board.

[0078] Example 1 In Example 1, first, a chemical bath was prepared as a first chemical polishing solution, containing sulfuric acid at a concentration of 1.4 mol / L, hydrogen peroxide at a concentration of 0.9 mol / L, and ethylene glycol as a stabilizer at a concentration of 0.4 mol / L, with a liquid temperature of 45°C. As a second chemical polishing solution, a chemical bath was prepared as a second chemical polishing solution, containing sulfuric acid at a concentration of 0.06 mol / L, hydrogen peroxide at a concentration of 2.15 mol / L, and ethylene glycol as a stabilizer at a concentration of 0.2 mol / L, with a liquid temperature of 50°C. As a pickling solution, a chemical bath was prepared as a second chemical polishing solution, containing sulfuric acid at a concentration of 1.0 mol / L, with a liquid temperature of room temperature. 4 L of each chemical solution was prepared. The compositions of each chemical solution are summarized in Table 1 below.

[0079] Next, one bonded body was immersed in a first chemical polishing solution for 300 seconds, rinsed with water, immersed in a second chemical polishing solution for 400 seconds, and then immersed in a pickling solution for 15 seconds, and finally rinsed with water and pure water to produce an insulating circuit board of Example 1. The water rinsing and pure water rinsing were also performed by immersion treatment.

[0080]

[0081] Example 2 In Example 2, as shown in Table 1, a chemical bath containing sulfuric acid at a concentration of 0.055 mol / L, hydrogen peroxide at a concentration of 2.1 mol / L, and ethylene glycol at a concentration of 0.2 mol / L was used as the second chemical polishing solution, and the solution temperature was 50°C. The insulating circuit board of Example 2 was produced by carrying out the same process as in Example 1.

[0082] Example 3 In Example 3, as shown in Table 1, the second chemical polishing solution used was a chemical bath containing sulfuric acid at a concentration of 0.065 mol / L, hydrogen peroxide at a concentration of 2.2 mol / L, and ethylene glycol at a concentration of 0.2 mol / L, and the solution temperature was 50°C, and the same treatment was carried out as in Example 1 to produce an insulating circuit board of Example 3.

[0083] Reference Example 1 In Reference Example 1, an insulating circuit board was produced in the same manner as in Example 1, except that the second chemical polishing solution used was a chemical bath containing sulfuric acid at a concentration of 0.75 mol / L, hydrogen peroxide at a concentration of 0.94 mol / L, and ethylene glycol at a concentration of 0.26 mol / L, the solution temperature of which was 35°C, and the immersion time was 60 seconds, as shown in Table 1. In Reference Example 1, the second chemical polishing solution had a higher sulfuric acid concentration and a lower hydrogen peroxide concentration than in Examples 1 to 3. Therefore, if the second chemical polishing solution was treated at 50°C, as in Examples 1 to 3, an excessive amount of material would be dissolved and removed. Therefore, to suppress the dissolving and removing effect, the solution temperature in Reference Example 1 was set to 35°C.

[0084] (2) Evaluation Methods The insulating circuit boards produced in Examples 1 to 3 and Reference Example 1 obtained above were used as samples to evaluate line roughness, three-dimensional surface texture parameters, wire bonding, and shear strength. Each evaluation method is described below.

[0085] (Line Roughness Evaluation) For line roughness evaluation, surface roughness measurement was performed based on JIS B0601-2001. The measurement device used was a stylus-type roughness meter "SURFTEST SJ-210" manufactured by Mitutoyo Corporation. A stylus with a tip radius of 2 μm and a conical taper angle of 60° was used, and the measurement conditions were cutoff value λc: 0.8 mm, cutoff value λs: 2.5 μm, reference length: 0.8 mm, and evaluation length (= measurement length): 4 mm. Two types of roughness parameters were evaluated: Ra (arithmetic mean roughness) and Rz (maximum height). Measurements were performed at four randomly selected locations on the surface of the circuit metal plate per substrate. Since there were six samples in each Example and Reference Example, a total of 24 locations (6 sheets x 4 locations) were measured. Table 2 shows the average values ​​of Ra (arithmetic mean roughness) and Rz (maximum height) from the measurement results.

[0086] (Evaluation of Three-Dimensional Surface Texture Parameters) Three-dimensional surface texture parameter evaluation was performed based on ISO 25178-2:2012. The measurement device used was a laser microscope "VK-X1100" (manufactured by Keyence Corporation). Laser confocal images were captured using a 5x objective lens, and three-dimensional surface texture parameters were calculated using the analysis software "VK-X Series Multi-File Analysis Application." The captured image size was 2,784 μm x 2,088 μm (pixel count: 1024 x 768 pixels). The analysis software's measurement conditions were as follows: measurement area was the entire captured image, filter type: Gaussian, S-filter: 10 μm, F-operation: None, L-filter: 2 mm, and end effect correction: Enabled. Two types of three-dimensional surface texture parameters were measured: Spd value (peak density) and Sdr value (interface developed area ratio). Measurements were taken at four randomly selected locations on the surface of the circuit metal plate for each sample. Since there were six samples in each Example and Reference Example, measurements were taken at a total of 24 locations, six samples x four locations. The average values ​​of the measurement results are shown in Table 2.

[0087] (Wire bonding and shear strength evaluation) To evaluate the bonding strength of the metal wire, wire bonding was performed on each sample, and the bonding strength between the metal wire and the surface of the metal plate was evaluated by shear strength measurement. As the metal wire, a thin Al wire with a diameter of 125 μm, "TANW-Soft1 φ125 STD" (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was used, and as the wire bonding and shear strength measuring device, a bond tester "Model 5600-C" (manufactured by F&K Delvotec) was used. Specifically, first, a "Model 5650" was used as the bonding head of the bond tester, and the wire bonding conditions were US Time: 50 ms, US Power: 45 digits, B-Force Start: 40 cN, B-Force End: 70 cN, TD Steps: 67 μm, and the wire loop conditions were Loop Mode: No Reverse, Loop Form: Triangular, Z-Presign: 35%, Loop H-Factor: 160%, XY Loop Wire bonding was performed on the metal plate of the insulated circuit board with an H-Factor of 25% and a Z-Delay of 50% so that the distance between the first bond and the second bond was 3 mm, and two Al wire loops were formed per insulated circuit board. Next, using an "SH-5000C" as the shear strength measurement head of the bond tester, shear strength measurements were performed on the first bond and the second bond of the two Al wire loops with a test speed of 300 μm / s and a shear height of 15 μm. Four measurements were taken per sample. Here, a total of 24 locations were measured per batch (6 sheets x 4 locations). Table 3 shows the average, maximum, third quartile, median, first quartile, and minimum values ​​obtained from the shear strength measurement results for the first bond and the second bond, respectively. FIG. 2 shows a graph of the shear strength of Examples 1 to 3 and the Reference Example.

[0088]

[0089]

[0090] (3) Evaluation Results As shown in Table 2, it was confirmed that in Examples 1 to 3 and Reference Example 1, the arithmetic mean roughness Ra was in the range of 0.1 μm to 1.0 μm and the maximum height Rz was in the range of 1.0 μm to 5.0 μm. On the other hand, with regard to the three-dimensional surface texture parameters of the surface of the metal plate, in Examples 1 to 3, the average Spd value was 100 mm －２ More than 1000mm －２ On the other hand, in Reference Example 1, the average Spd value was 1723 mm －２ And 1000 mm －２ It was confirmed that the average Sdr value was greater than 0.2. Furthermore, in Examples 1 to 3, the average Sdr value was 0.05 to 0.2, while in Reference Example 1 it was 0.511, which was greater than 0.2. In other words, although Reference Example 1 had a line roughness similar to that of Example 1 and the like, the density of protrusions was higher and the shape of the protrusions was steeper than that of Example 1 and the like. From this, it was confirmed that even when the line roughness values ​​were similar, the density and shape of the protrusions differed greatly when the surface was measured three-dimensionally.

[0091] In Examples 1 to 3, chemical polishing was performed using a second chemical polishing solution with a relatively low sulfuric acid concentration of 0.06 [mol / L], 0.055 [mol / L], or 0.065 [mol / L]. This allowed the protrusions remaining during the first chemical polishing to be dissolved and removed, and it is believed that this allowed the Spd and Sdr values ​​on the surface of the metal plate to be adjusted to within the specified range. In contrast, in Reference Example 1, a second chemical polishing solution with a sulfuric acid concentration of 0.75 [mol / L], which is higher than that of Example 1, was used, and it was confirmed that the Spd and Sdr values ​​could not be adjusted to within the specified range. This is believed to be because the high reactivity of sulfuric acid caused not only the protrusions but also the flat surfaces of the metal plate to be dissolved and removed.

[0092] Furthermore, as shown in Table 2, in Reference Example 1, the standard deviation of the Spd value was 236 mm －２ The standard deviation of the Sdr value was 0.140, and it was confirmed that the density and shape of the protrusions varied widely on the surface of the metal plate and were not uniform. In contrast, in Examples 1 to 3, the standard deviation of the Spd value was 100 mm. －２Hereinafter, it was confirmed that the standard deviation of the Sdr value was 0.05 or less, and that the density and shape of the protrusions varied little on the surface of the metal plate. Furthermore, the coefficient of variation of the Spd value was 12% or less in Examples 1 to 3, while it was 13.7% in Reference Example 1, confirming that the variation of the Spd value was small in Examples 1 to 3. Similarly, the coefficient of variation of the Sdr value was 20% or less in Examples 1 to 3, while it was 27.3% in Reference Example 1, confirming that the variation of the Sdr value was small in Examples 1 to 3.

[0093] Furthermore, as shown in Table 3, the shear strengths of Examples 1 to 3 and Reference Example 1 when wire-bonded to a metal plate were measured. In Reference Example 1, the average shear strength at 24 bonding locations was 249 cN, confirming a tendency for low wire bond strength. Furthermore, the minimum shear strength at multiple bonding locations was 200 cN, and the first quartile of shear strength was 214 cN, confirming the occurrence of many locations with low bond strength. Furthermore, the interquartile range, which is the difference between the first and third quartiles, was high at 97 cN, confirming that the shear strength at multiple bonding locations varied widely, i.e., the bond strength varied widely. Specifically, as shown in FIG. 2, Reference Example 1 exhibited a large variation in shear strength. Note that FIG. 2 is a graph showing the shear strengths of Examples 1 to 3 and Reference Example 1. FIG. 2 is a box plot of the share intensity for each example, where the bottom of the whiskers indicates the minimum share intensity, the top of the whiskers indicates the maximum, the bottom of the box indicates the first quartile, the top of the box indicates the third quartile, the line inside the box indicates the median (second quartile), and the x (marked x) indicates the mean.

[0094] In contrast, in Examples 1 to 3, the Spd and Sdr values ​​on the surface of the metal plate were within the specified range, so the average shear strength was 300 cN or higher, confirming a tendency for high wire bond strength. Furthermore, as shown in Figure 2, the minimum shear strength value at multiple bonding locations was 260 cN or higher, and the first quartile of shear strength was 260 cN or higher, confirming that there were few locations where bond strength was extremely low. Furthermore, the interquartile range was 90 cN or less, confirming that the shear strength variation at multiple bonding locations was small, i.e., that there was little variation in bond strength.

[0095] As described above, by subjecting a metal plate to chemical polishing using two chemical polishing solutions with different concentrations of sulfuric acid and hydrogen peroxide, the Spd and Sdr values ​​of the metal plate of an insulating circuit board can be adjusted to fall within a predetermined range, thereby improving the bonding strength between the metal plate and the insulating circuit board even when using thin wires.

Claims

1. An insulated circuit board comprising an insulating substrate and a circuit metal plate bonded to at least one surface of the insulating substrate, wherein the Spd value, which is the peak density of the three-dimensional surface texture parameters on the surface of the circuit metal plate, is 100 mm －２ More than 1000mm －２ or less, and an Sdr value, which is a developed area ratio of an interface of a three-dimensional surface texture parameter on the surface of the circuit metal plate, is 0.05 or more and 0.2 or less.

2. The insulating circuit board according to claim 1, wherein the arithmetic mean roughness Ra of the surface of said circuit metal plate is 0.15 μm or more and 1.5 μm or less.

3. At a plurality of points on the surface of the circuit metal plate, the standard deviation of the Spd value is 100 mm －２ 3. The insulating circuit board according to claim 1, wherein the standard deviation of the Sdr values ​​is 0.05 or less.

4. An insulating circuit board according to claim 1 or 2, wherein when Al wires having a diameter of 125 μm are bonded to the surface of the circuit metal plate, the average shear strength at a plurality of bonding locations is 300 cN or more.

5. An insulating circuit board according to claim 1 or 2, wherein when Al wires having a diameter of 125 μm are bonded to the surface of the circuit metal plate, the first quartile of the shear strength at a plurality of bonding locations is 250 cN or more.

6. An insulating circuit board according to claim 1 or claim 2, wherein when an Al wire having a diameter of 125 μm is bonded to the surface of the circuit metal plate, the interquartile range, which is the difference between the third quartile and the first quartile of the shear strength at a plurality of bonding locations, is 90 cN or less.

7. A method for manufacturing a bonded assembly, comprising: a preparation step of preparing an assembly including an insulating substrate and a circuit metal plate bonded to at least one surface of the insulating substrate; a first chemical polishing step of treating the assembly with a first chemical polishing solution containing 1.0 mol / L to 1.6 mol / L of sulfuric acid and 0.7 mol / L to 1.2 mol / L of hydrogen peroxide; a second chemical polishing step of treating the assembly after the first chemical polishing step with a second chemical polishing solution containing 0.04 mol / L to 0.4 mol / L of sulfuric acid and 1.0 mol / L to 3.0 mol / L of hydrogen peroxide; and an acid pickling step of pickling the assembly after the second chemical polishing step, wherein the Spd value, which is the peak density of the peaks of the three-dimensional surface texture parameters on the surface of the metal plate, is 100 mm －２ More than 1000mm －２ wherein the Sdr value, which is a developed area ratio of three-dimensional surface texture parameters on the surface of the metal plate, is 0.05 or more and 0.2 or less.

8. A semiconductor module comprising the insulating circuit board according to claim 1 or 2 and a semiconductor element connected to the circuit metal plate by a metal wire having a diameter of 175 μm or less.

9. A method for manufacturing a semiconductor module, comprising connecting a semiconductor element to the circuit metal plate of the insulating circuit board according to claim 1 or 2 with a metal wire having a diameter of 175 μm or less.

Images