Method for manufacturing insulated circuit board with heat sink

Abstract

To easily manufacture an insulated circuit board with a heat sink excellent in the insulation property and the reliability.SOLUTION: There is provided a method for manufacturing an insulated circuit board including: a heat sink having a top plate part and a fin for heat dissipation; an insulating layer; and a circuit layer, and the method sequentially includes: a first joining step of fabricating the top plate part separately from the fin, laminating the top plate part on one surface side of the insulating layer, laminating a metal plate for the circuit layer on the other surface side of the insulating layer, and joining the top plate part and the metal plate together; and a second joining step of joining the fins to a surface of the top plate part opposite to a joining surface with the insulating layer of the top plate part after the first joining step. After the first joining step, the metal plate for the circuit layer is etched so that a circuit layer is formed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an insulated circuit board with a heat sink, which includes a heat sink with fins for heat dissipation, an insulating layer provided on the top plate side of the heat sink, and a circuit layer provided on this insulating layer.

[0002] 2. Description of the Related Art In order to improve the heat dissipation properties of insulating circuit boards, development has been underway of insulating circuit boards with heat sinks provided on insulating layers. The heat sink provided on such an insulated circuit board may have heat dissipation fins on the top plate thereof, and an insulating layer is provided on the top plate of the heat sink with the fins, with a circuit layer provided on the opposite side of the insulating layer from the top plate, thereby forming an insulated circuit board.

[0003] As a method for manufacturing this type of insulating circuit board, for example, a method for manufacturing a power module is disclosed in Patent Document 1. In this manufacturing method, a heat sink integrally formed with heat dissipation fins and a circuit layer are bonded together via an insulating resin layer containing ceramics. Patent Document 2 proposes a manufacturing method for a wiring board with a heat sink, in which a separately manufactured top plate portion and heat dissipation fins are sandwiched with solder material and stacked on a wiring metal plate and an insulating substrate, and the top plate portion of the heat sink and the heat dissipation fins are joined at the same time as the substrates are joined.

[0004] Furthermore, Patent Document 3 discloses a method for manufacturing a heat sink-integrated insulating circuit board in which the gaps between the heat dissipation fins are filled with a water-soluble or organic solvent-soluble polymer, and the heat sink and the insulating resin layer are directly bonded together. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-204700 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-298136 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-28421 Summary of the Invention [Problem to be solved by the invention]

[0006] When using the manufacturing methods described in Patent Documents 1 and 2, an insulating layer is bonded to the top plate of a heat sink with fins, but because the bonding is performed under high pressure and thermal history, there is a risk of plastic deformation of the outer fins. Furthermore, when bonding to the insulating resin layer, the entire fin section oxidizes and discolors during heat treatment under atmospheric pressure, requiring surface treatment. However, achieving uniform surface treatment across the complex gaps between the fins is difficult. Furthermore, an insulating layer is bonded to the top plate of a heat sink with fins formed on it, but since the fins are formed on the side of the heat sink opposite the side to which the insulating layer is bonded, there is a risk that the fins will tilt or fall over when bonding the heat sink and the insulating layer, and the number of stacking layers will increase, resulting in poor productivity.

[0007] Furthermore, heat sinks typically have areas with fins and areas without, and the height of the fins varies, which can cause uneven pressure when applying pressure to the insulating layer and the top plate, leading to poor bonding and the formation of voids within the resin that forms the insulating layer. Such uneven pressure can, for example, worsen the bonding at the interface, making it more likely to cause delamination when mounting semiconductor elements. Furthermore, if the insulating layer is made of resin, voids within the resin can cause poor dielectric strength.

[0008] In the case of Patent Document 3, an attempt is made to achieve uniform bonding, but since the process of filling the fins with the fin-filling polymer and the process of removing it are required, the number of steps required to manufacture the insulating circuit board increases, making it more time-consuming and reducing productivity.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to easily manufacture an insulating circuit board with a heat sink that has excellent insulation properties and reliability. [Means for solving the problem]

[0010] The method for manufacturing an insulated circuit board with a heatsink of the present invention includes a heatsink having a top plate portion and fins for heat dissipation, an insulating layer, and a circuit layer, and the method includes a first joining step in which the top plate portion is manufactured separately from the fins, and the top plate portion is laminated on one side of the insulating layer and a metal plate for the circuit layer is laminated on the other side of the insulating layer to join them together, and a second joining step in which the fins are joined to the surface of the top plate portion opposite to the surface to be joined with the insulating layer after the first joining step.

[0011] By providing the top plate and fins separately, in the first step, the top plate is stacked on one side of the insulating layer and a metal plate for the circuit layer is stacked on the other side, and then they are joined together, allowing for uniform pressure to be applied to the entire surface. This prevents uneven pressure from occurring at the joint between the insulating layer and the top plate, resulting in a good joint. This makes it possible to provide an insulated circuit board with a heat sink that has excellent insulation and reliability, and allows semiconductor elements to be mounted stably and with high precision on the circuit layer. In addition, the second step, in which the fins are joined to the top plate at a final stage, improves process fluidity, reduces manufacturing man-hours, and improves workability.

[0012] In the present invention, after the first joining step, the circuit layer metal plate may be subjected to an etching treatment to form the circuit layer.

[0013] Even if the circuit layer has a complex circuit pattern, the first bonding step bonds the flat metal plate for the circuit layer to the insulating layer, so that the entire surface of the metal plate for the circuit layer can be bonded uniformly. Therefore, the circuit layer after the etching process is also firmly bonded to the insulating layer, and peeling and other problems can be prevented.

[0014] In the present invention, the fins may be pin-shaped or plate-shaped. This allows these pin-shaped or plate-shaped fins to be joined accurately and easily to predetermined positions on the top plate, and by ensuring the required surface area, the heat dissipation properties of the insulating circuit board are improved.

[0015] Furthermore, in the present invention, the fins may be bonded by any one of diffusion bonding, ultrasonic bonding, and sinter bonding.

[0016] The fins can be easily and reliably bonded to the top plate using either diffusion bonding, ultrasonic bonding, or sinter bonding. In any case, the entire surface of the insulating layer can be uniformly bonded in the first bonding process, resulting in a solid, integrated heat sink and a high-quality insulating circuit board with excellent insulation properties that also suppresses a decrease in breakdown voltage.

[0017] The insulating layer may be made of a thermosetting resin. As mentioned above, in the first bonding step, the entire surface of the insulating layer can be bonded with uniform pressure, preventing the occurrence of voids inside the insulating layer and ensuring a good bond without unevenness. In addition, because the insulating layer is made of resin, deformation such as warping is prevented, making it possible to keep the defect rate low and consistently produce high-quality insulated circuit boards. [Effects of the Invention]

[0018] According to the present invention, the first bonding step bonds the flat metal plate for the circuit layer, the insulating layer, and the top plate portion, so that uniform pressure can be applied to the entire surface to obtain a good bonded state. Even when the insulating layer is made of a thermosetting resin, the occurrence of internal voids can be suppressed, and an extremely good insulated circuit board with a heat sink that has excellent insulation properties and reliability can be easily manufactured. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing an insulating circuit board with a heat sink in a manufacturing method of the present invention. [Figure 2] 1 is a flowchart showing a method for manufacturing an insulating circuit board with a heat sink according to the present invention. [Figure 3] 1 is a perspective view showing a first bonding step, in which (a) shows the state before bonding and (b) shows the state after bonding. [Figure 4] 10 is a perspective view showing a second bonding step, in which (a) shows the state before bonding and (b) shows the state after bonding. [Figure 5] 1A to 1C are front views showing various bonding methods in the second bonding step, where (a) shows diffusion bonding, (b) shows ultrasonic bonding, and (c) shows sinter bonding. [Figure 6] FIG. 10 is a front view of a cross section of a top plate portion showing an example in which recesses are formed on the outer peripheral surface of a fin. [Figure 7] FIG. 10 is a perspective view showing an embodiment of an insulating circuit board with a heat sink in which the fins are plate-shaped. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the method for manufacturing an insulating circuit board with a heat sink according to the present invention will be described with reference to the drawings. An insulating circuit board 1 with a heat sink manufactured by the manufacturing method of this embodiment includes a heat sink 2, an insulating layer 3, and a circuit layer 4, as shown in FIG.

[0021] The heat sink 2 is intended to dissipate heat on the insulating layer 3 and circuit layer 4 sides, and has a flat top plate 10 that serves as a heat sink, and heat dissipation fins 11 that are joined to the top plate 10. The heat sink 2 is made of copper or a copper alloy, aluminum or an aluminum alloy, or the like, which have good thermal conductivity. In this embodiment, the top plate 10 and the fins 11 are both made of copper (oxygen-free copper), and are joined together to form an integrated heat sink 2.

[0022] The top plate portion 10 is formed to a thickness of, for example, 3 mm or more and 10 mm or less, and is joined to one surface side of the insulating layer 3 (the lower surface side in FIG. 1). On the other hand, the fins 11 are pin-shaped, such as cylindrical or rectangular, or plate-shaped. In this embodiment, the fins 11 are cylindrical pin-shaped, all formed to the same length, and are provided on the underside of the top plate portion 10 (the side opposite to the bonding surface with the insulating layer 3).

[0023] The insulating layer 3 is provided to prevent electrical connection between the circuit layer 4 and the heat sink 2, and is made of an insulating material such as an insulating resin or ceramics. In this embodiment, the insulating layer 3 is made of an insulating thermosetting resin.

[0024] In particular, in this embodiment, a thermosetting resin containing a filler is used for the insulating layer 3 to ensure strength and thermal conductivity. Here, examples of the filler that can be used include alumina, boron nitride, and aluminum nitride. Also, examples of the thermosetting resin that can be used include epoxy resin. For example, the insulating layer 3 is made of a resin composition containing alumina as the filler, epoxy resin as the thermosetting resin, and a curing agent. The thickness of the insulating layer 3 is, for example, within a range of 20 μm to 250 μm, and is 60 μm in this embodiment.

[0025] The circuit layer 4 is formed by bonding a circuit layer metal plate 12 made of a metal with excellent conductivity to the side of the insulating layer 3 opposite to the bonding surface of the top plate portion 10 (the upper surface side in FIG. 1). The circuit layer metal plate 12 may be a rolled plate of copper or a copper alloy, aluminum or an aluminum alloy, or the like. In this embodiment, a rolled plate of oxygen-free copper is used as the circuit layer metal plate 12.

[0026] As will be described later, the circuit layer 4 is formed into a predetermined circuit pattern by etching the circuit layer metal plate 12 bonded to the upper surface of the insulating layer 3. The upper surface of the circuit layer 4 serves as a mounting surface on which the semiconductor element 13 is mounted, and the semiconductor element 13 is mounted by solder or the like. Here, the thickness of the circuit layer 4 (circuit layer metal plate 12) is formed to be, for example, 0.3 mm or more and 3 mm or less, and is formed to be 0.5 mm in this embodiment.

[0027] Next, a method for manufacturing the insulating circuit board 1 with a heat sink configured as described above will be described. Fig. 2 shows a flowchart of the method for manufacturing the insulating circuit board with a heat sink of the present invention, which includes a material forming step, a first bonding step, an etching step, and a second bonding step. The steps will be described in order below.

[0028] (Material formation process) The top plate portion 10 and fins 11 of the heat sink 2, the insulating layer 3, and the metal plate 12 for the circuit layer are each formed to a predetermined shape and size. The top plate portion 10 and the multiple fins 11 of the heat sink 2 are manufactured separately. In this embodiment, the top plate portion 10, the insulating layer 3, and the metal plate 12 for the circuit layer are formed to the same shape and size. It is desirable that the top plate portion 10 and the metal plate 12 for the circuit layer are each a single flat plate. Furthermore, if the top plate portion 10 is smaller than the insulating layer 3 in plan view in the stacking direction, it is desirable that the metal plate 12 for the circuit layer be equal to or larger than the size of the top plate portion 10, and it is even more desirable that they be the same size. Alternatively, if the top plate portion 10 is equal to or larger than the insulating layer 3, it is desirable that the metal plate 12 for the circuit layer be equal to or larger than the insulating layer 3. In other words, it is desirable that the size of the joint surface between the top plate portion 10 and the insulating layer 3 is the same as the size of the joint surface between the metal plate 12 for the circuit layer and the insulating layer 3, and it is desirable that the positions of the joint surfaces when viewed in the stacking direction overlap when stacked.

[0029] The fins 11 are all cylindrical with the same length and diameter, and an appropriate number are produced depending on the area of ​​the joining surface of the top plate 10 and the installation intervals, taking heat dissipation efficiency into consideration. For example, the cylindrical fins are formed with a diameter of 0.5 mm to 6.0 mm and a length of 1.0 mm to 10 mm, with the spacing between fins 11 being 0.5 mm to 4.0 mm. In this embodiment, the diameter and length of the fins 11 are 2 mm and 6 mm, respectively, and the spacing between fins 11 is 1 mm. The material of the insulating layer 3 is formed from a sheet made of a resin composition containing alumina, epoxy resin, and a curing agent. The metal plate 12 for circuit layers is formed by punching out a rolled plate.

[0030] (1st joining process) A top plate portion 10 is disposed on one side (the bottom side in Figure 3) of the insulating layer 3 (a sheet of resin composition), and a metal plate 12 for a circuit layer is disposed on the other side (the top side in Figure 3) of the insulating layer 3, and these are stacked together. As a result, as shown in FIG. 3(b), the top plate portion 10, the insulating layer 3 (a sheet of a resin composition), and the metal plate 12 for a circuit layer are laminated in this order.

[0031] This laminate of the top plate portion 10, insulating layer 3, and metal plate 12 for the circuit layer is pressurized and heated in the stacking direction to harden the insulating layer 3 (an insulating sheet made of a resin composition), and the top plate portion 10 and the insulating layer 3, and the insulating layer 3 and the metal plate 12 for the circuit layer are bonded together by thermocompression. The conditions for pressure bonding are preferably a heating temperature in the range of 150°C to 200°C, a holding time at this heating temperature in the range of 30 minutes to 90 minutes, and a pressure in the lamination direction in the range of 50 MPa to 200 MPa.

[0032] When the insulating layer 3 is made of ceramics, the ceramics can be bonded by applying a predetermined brazing filler metal between the circuit layer metal plate 12 and the top plate portion 10 and then pressurizing and heating them. When the circuit layer metal plate 12 and the top plate portion 10 are made of copper or a copper alloy, a brazing filler metal such as Ag-Cu-Ti is used as the brazing filler metal.

[0033] (etching process) After the first bonding step, the metal plate 12 for circuit layer bonded to the upper surface of the insulating layer 3 is subjected to an etching process to form the circuit layer 4. In this case, a resist layer corresponding to the circuit pattern is formed on the metal plate 12 for circuit layer, and by immersing the metal plate 12 in this state in an etching solution, the portions not covered by the resist layer are removed, and the circuit layer 4 having the predetermined circuit pattern is formed.

[0034] (Second joining process) 4(a) and 4(b), in the second joining step, the fins 11 are joined to the surface of the top plate portion 10 opposite to the surface joined to the insulating layer 3. This forms the heat sink 2 in which the top plate portion 10 and the fins 11 are integrated. The fins 11 may be bonded by any of diffusion bonding, ultrasonic bonding, and sinter bonding. In this embodiment, a case where cylindrical fins 11 are bonded will be described, but the same bonding method can also be used when bonding fins other than cylindrical fins such as prismatic fins or plate-like fins.

[0035] FIG. 5(a) shows a case where the fins 11 are joined to the top plate portion 10 by diffusion bonding. In diffusion bonding, the bonding surfaces (end faces) of each fin 11 are brought into close contact with the top plate 10, and pressure is applied to minimize plastic deformation at a temperature below the melting point of the copper (oxygen-free copper) that makes them up, and the bonding is achieved by utilizing atomic diffusion that occurs between the bonding surfaces. In this way, the fins 11 are integrated with the top plate 10 to form the heat sink 2.

[0036] FIG. 5(b) shows a case where the fins 11 are joined to the top plate portion 10 by ultrasonic joining. Ultrasonic bonding uses an ultrasonic bonding machine (not shown) equipped with an ultrasonic oscillator, ultrasonic vibrator, and horn. High-frequency current generated by the ultrasonic oscillator of the ultrasonic bonding machine is supplied to the ultrasonic vibrator as electrical energy, and then transmitted from the ultrasonic vibrator to the horn as ultrasonic energy, which then vibrates the horn ultrasonically. By applying ultrasonic vibrations to the fin 11 and the top plate 10 through the fin 11 that the horn abuts, oxide films and deposits present at the bonding interface are destroyed and dispersed. The fin 11 and the top plate 10 are pressed together while undergoing plastic deformation in this state, and atomic forces act to bond them together.

[0037] FIG. 5(c) shows a case where the fins 11 are joined to the top plate portion 10 by sinter bonding. In sinter bonding, bonding is performed using a bonding paste 17 containing copper particles, a solvent, and an additive. After being applied to the top plate portion 10, the bonding paste 17 is preheated at a temperature of 50°C to 150°C for 1 minute to 30 minutes to volatilize the solvent contained in the bonding paste 17.

[0038] The tip surface of the fin 11 is placed in contact with the top plate 10 on which the bonding paste 17 has been applied and dried, and the fin 11 is then heated, for example, in a non-reducing atmosphere at a temperature of 200°C to 300°C for approximately 1 minute to 10 minutes while applying a pressure of 0.5 MPa to 10 MPa. A non-reducing atmosphere refers to a state in which the atmosphere is filled with a non-reducing gas, such as nitrogen or a rare gas such as argon. By performing sintering bonding under these conditions, the copper particles are sintered, bonding the fin 11 and the top plate 10 together.

[0039] According to the manufacturing method of the insulated circuit board 1 with a heat sink in the above embodiment of the present invention, the flat top plate portion 10 is manufactured separately from the fins 11, and in the first joining step, the insulating layer 3, the top plate portion 10, and the metal plate 12 for the circuit layer are stacked and joined together, so that pressure can be applied uniformly in the surface direction between the top plate portion 10 and the insulating layer 3 to reliably join them together.

[0040] Then, after an etching step, in the second bonding step, the fins 11 are bonded to the top plate portion 10 by either diffusion bonding, ultrasonic bonding, or sinter bonding. In this case, in either case, the entire surface of the insulating layer 3 can be uniformly bonded in the first bonding step, so that a firmly integrated heat sink 2 can be formed, and a reduction in breakdown voltage can be suppressed, making it possible to provide a high-quality insulating circuit board 1 with a heat sink that has excellent insulation properties.

[0041] Furthermore, even if it becomes necessary to re-bond the fins 11 due to a defect, they can be detached from the top plate portion 10 by applying a shear force to the fins 11, allowing new fins 11 to be re-fixed, and repairability is also good. In this case, ultrasonic bonding and sinter bonding are superior to diffusion bonding in that they make it easier to detach the fins 11 by shearing and are therefore more suitable for repair.

[0042] In the above embodiment, the fins 11 are formed on the outer peripheral surface of a cylindrical or prismatic column, but they may also be formed with projections and recesses. The fin 15 shown in Fig. 6 shows an example in which a large number of dimple-shaped recesses 15a are formed on the outer peripheral surface. This increases the surface area of ​​the fin 15 compared to when the outer peripheral surface is cylindrical, thereby improving heat dissipation. Instead of the recesses 15a, projections may be formed.

[0043] Furthermore, while pin-shaped fins have been shown as an example of a heat sink, plate-shaped (plate-like) fins are also possible. FIG. 7 shows an example of a heat sink 20 having plate-shaped fins 21. The fins 21 are arranged parallel to one another so that a refrigerant can flow between them. In this case, the fins are formed in a flat plate shape, but they may also be formed in a corrugated plate shape. Furthermore, recesses or protrusions may be formed on the surface of the fins as shown in FIG. 6. [Example]

[0044] The following describes the test results for evaluating the performance of the heatsink-equipped insulating circuit board 1 manufactured by the manufacturing method of the present invention. The tests carried out included a bondability test and an insulation test.

[0045] The heat sink and the metal plate for the circuit layer were made of oxygen-free copper, and the insulating layer was made of a resin composition formed into a sheet shape containing alumina as a filler, epoxy resin as a thermosetting resin, and a curing agent, all of which were formed to the same plane area. The top plate of the heat sink, the insulating layer, and the metal plate for the circuit layer were bonded at a heating temperature of 180°C for 60 minutes under a pressure of 100 MPa. After bonding the top plate, insulating layer, and metal plate for the circuit layer, fins were bonded to the top plate by the method shown in Table 1. As a comparative example, a finned heat sink in which fins were previously formed integrally by forging was used, and this finned heat sink was joined to an insulating layer and a circuit layer.

[0046] (Conjugation test) The bonding state between the circuit layer 4 and the insulating layer 3 was observed using an ultrasonic flaw detector (FineSAT200 manufactured by Hitachi Power Solutions Co., Ltd.) and the incidence of voids was measured. Voids are shown as white areas in the ultrasonic flaw detector image, so those whose area of ​​the white area was less than 5% of the bonding area were rated as "good" (passed), and those whose area was 5% or more were rated as "failed."

[0047] (Insulation test) A partial discharge tester manufactured by Mitsubishi Electric Wire Corporation was used as the measuring device, and electrodes were placed in contact with the surface of the circuit layer 4 and the surface (underside) of the top plate portion 10, and an AC voltage was applied between the two electrodes to measure the breakdown voltage. The voltage was increased in steps of 0.5 kV from 0 kV (holding time 30 seconds), and the voltage at which breakdown occurred (the voltage at which the leakage voltage became 10 mA or more) was taken as the breakdown voltage. The evaluation criteria for the insulation test were as follows: if the proportion of samples with a breakdown voltage of less than 4 kV among all the samples was less than 10%, it was rated as "good" (passed); if it was 10% or more, it was rated as "bad."

[0048] The evaluation results of the above tests are shown in Table 1.

[0049] [Table 1]

[0050] In the comparative example, when the finned heat sink and the circuit layer were bonded via an insulating layer, both the bondability and the insulation were judged to be "poor" (failed).

[0051] On the other hand, when the top plate portion 10, insulating layer 3, and metal plate 12 for the circuit layer were stacked and bonded separately from the fin 11 as in the examples, both the bondability and the insulation were judged to be "good" (passed) regardless of whether the bonding with the fin 11 was by diffusion bonding (Example 1), ultrasonic bonding (Example 2), or sinter bonding (Example 3).

[0052] From the above test results, it was confirmed that the manufacturing method of the present invention provides good bonding between the circuit layer 4 and the top plate portion 10 of the heat sink 2 and the insulating layer 3, with little void generation and excellent insulation, making it possible to manufacture an insulated circuit board 1 with a heat sink of stable quality.

[0053] The present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0054] The present invention does not preclude bonding a metal plate for a circuit layer that has been formed into a circuit pattern in advance onto the insulating layer 3. This method is also possible when the circuit pattern is not complicated or when there is no significant difference in area with the insulating layer 3, and a metal plate for a circuit layer that has been punched into the shape of the circuit pattern by press working is used. Furthermore, the joining of the fins 11 to the top plate portion 10 is not limited to the above three types of joining, and brazing material or adhesive may also be used. [Explanation of symbols]

[0055] 1. Insulated circuit board with heat sink 2,20 Heatsink 3. Insulation layer (insulation sheet) 4 circuit layers 10 Top plate 11,15,21 Fins 15a Recess 12 Metal plate for circuit layer 17 Bonding paste

Claims

1. 1. A method for manufacturing an insulated circuit board with a heatsink, comprising: a heatsink having a top plate portion and fins for heat dissipation, an insulating layer, and a circuit layer, the method comprising: a first bonding step in which the top plate portion is manufactured separately from the fins, and a metal plate for a circuit layer is laminated on one side of the insulating layer and on the other side of the insulating layer to bond them together; and a second bonding step in which, after the first bonding step, the fins are bonded to a surface of the top plate portion opposite to the surface to be bonded to the insulating layer.

2. 2. The method for manufacturing an insulating circuit board with a heat sink according to claim 1, wherein after the first bonding step, the circuit layer metal plate is subjected to an etching treatment to form the circuit layer.

3. 3. The method for manufacturing an insulating circuit board with a heat sink according to claim 1, wherein the fins are pin-shaped or plate-shaped.

4. 4. The method for manufacturing an insulating circuit board with a heat sink according to claim 3, wherein the fins are bonded to the top plate by any one of diffusion bonding, ultrasonic bonding, and sinter bonding.

5. 3. The method for manufacturing an insulating circuit board with a heat sink according to claim 1, wherein the insulating layer is made of a thermosetting resin.

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