JP2019149460A - Insulation circuit board and manufacturing method thereof - Google Patents

Abstract

To provide an insulation circuit board capable of excellently ensuring inspection accuracy of the junction interface of respective components configuring a module and excellently securing junction reliability between a circuit layer and a ceramic substrate, and also to provide a manufacturing method thereof.SOLUTION: An insulation circuit board includes: a ceramic substrate; and a circuit layer made of aluminum or copper and formed on one face of the ceramic substrate. The circuit layer is formed in a laminated structure having a first circuit layer joined to one face of the ceramic substrate and a second layer joined to the surface of the first circuit layer, and the thickness of the first circuit layer is 20% or less of the total value of the thickness of the first circuit layer and the thickness of the second circuit layer. When the circuit layer is copper, the average crystal grain size of the first circuit layer is 250 μm or more, and the average crystal grain size of the second circuit layer is less than 250 μm. When the circuit layer is aluminum, the average crystal grain size of the first circuit layer is 375 μm or more, and the average crystal grain size of the second circuit layer is less than 375 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an insulating circuit board on which elements such as a power element, an LED element, and a thermoelectric element are mounted, and a manufacturing method thereof.

As an insulating circuit substrate formed by joining a metal member and a ceramic member, for example, a ceramic substrate such as AlN (aluminum nitride), Al ₂ O ₃ (alumina), Si ₃ N ₄ (silicon nitride), and one of the ceramic substrates And a circuit layer made of a metal having excellent conductivity, such as aluminum (Al) and copper (Cu), which are bonded to the surface, are known. In addition, in this type of insulated circuit board, for example, a power module substrate on which a power element is mounted, a metal layer made of a metal having excellent thermal conductivity is formed on the other surface of the ceramic substrate, Bonding a heat dissipation layer (heat sink) through a metal layer is also performed.

  For example, Patent Document 1 discloses a circuit board (insulating circuit board) in which a copper circuit is formed on the surface of a ceramic substrate (ceramic substrate) or a heat dissipation copper plate is formed on the back surface of the ceramic substrate together with the copper circuit. Yes.

  Various modules are manufactured by soldering (mounting) elements such as power elements, LED elements, and thermoelectric elements to the surface (upper surface) of the circuit layer of the insulating circuit board configured as described above. In addition, the module on which the element is mounted is also sealed with potting resin or molding resin from the viewpoint of ensuring insulation and protecting the wiring.

Japanese Patent No. 3211856

By the way, the inspection of the bonding interface between the circuit layer and the element and the bonding interface between the circuit layer and the ceramic substrate in various modules is performed using an ultrasonic exploration imaging device (SAT). It is known to be performed via each layer of the substrate.
However, when a circuit layer is formed by bonding a metal such as copper to a ceramic substrate, for example, when a copper (Cu) plate serving as a circuit layer is bonded to a ceramic substrate, it is usually active such as Ag-Cu-Ti. It is necessary to heat at a temperature of 800 ° C. or higher using a metal brazing material. When heated in such a temperature range, the copper crystal grains become coarser than before heating. For this reason, when inspecting the bonding interface (solder joint) between the circuit layer and the element via the insulating circuit board (circuit layer) with an ultrasonic exploration imaging apparatus, the reflection of the ultrasonic wave at the circuit layer becomes large, Decreasing inspection accuracy is a problem.

  On the other hand, as a countermeasure, it is conceivable to use a material for the circuit layer that is difficult to coarsen the crystal grains even when high heat is applied. In this case, the hardness of the circuit layer increases, so that the circuit layer and the ceramic substrate The stress difference at the bonding interface increases, and the insulating circuit board is likely to warp. Also, from the viewpoint of electrical transmission performance and heat dissipation performance, it is desirable to make the thickness of the circuit layer relatively large (thick), but if the thickness of the circuit layer is increased, the warpage generated in the insulated circuit board increases and the ceramic substrate breaks. There is a fear. For this reason, it becomes a problem to reduce the bonding reliability between the circuit layer and the ceramic substrate.

  The present invention has been made in view of such circumstances, and it is possible to satisfactorily secure the inspection accuracy of the joining interface of each component constituting the module and to secure the joining reliability between the circuit layer and the ceramic substrate. An object of the present invention is to provide an insulated circuit board and a method for manufacturing the same.

  The insulated circuit board of the present invention includes a ceramic substrate and a circuit layer made of copper or aluminum formed on one surface of the ceramic substrate, and the circuit layer is bonded to one surface of the ceramic substrate. A first circuit layer and a second circuit layer bonded to the surface of the first circuit layer. The thickness of the first circuit layer is equal to the thickness of the first circuit layer and the second circuit layer. When the circuit layer is copper, the average crystal grain size of the first circuit layer is 250 μm or more, and the average crystal grain size of the second circuit layer is 250 μm. When the circuit layer is made of aluminum, the average crystal grain size of the first circuit layer is 375 μm or more, and the average crystal grain size of the second circuit layer is less than 375 μm.

In this insulated circuit board, the circuit layer has a laminated structure having a first circuit layer and a second circuit layer, and the average crystal grain size of the first circuit layer to be bonded to the ceramic substrate is 250 μm or more in the case of copper, aluminum In this case, the hardness of the first circuit layer is set low by providing a relatively large thickness of 375 μm or more. Thereby, the thermal stress applied to the ceramic substrate when the insulating circuit substrate is heated can be reduced, and the ceramic substrate can be prevented from cracking. Therefore, it is possible to satisfactorily secure the bonding reliability between the circuit layer and the ceramic substrate during the element mounting process and in the usage environment.
In the circuit layer, the thickness of the first circuit layer is set to 20% or less of the total thickness of the first circuit layer and the second circuit layer, and the ratio of the first circuit layer to the circuit layer is small. In contrast, the thickness of the first circuit layer is reduced. As described above, the average crystal grain size of the first circuit layer is relatively large, but the ratio of the first circuit layer to the circuit layer is reduced. For this reason, when inspecting the bonding interface between the element and the circuit layer (second circuit layer) via the insulated circuit board by the ultrasonic exploration imaging apparatus, the ratio of ultrasonic reflection in the first circuit layer is greatly reduced. It is possible to ensure good inspection accuracy.
Thus, by adjusting the thickness of the first circuit layer and the average crystal grain size of the first circuit layer and the second circuit layer within the above range, the inspection accuracy by the ultrasonic exploration imaging apparatus and the circuit layer ( Both the first circuit layer) and the bonding reliability between the ceramic substrate can be secured satisfactorily. In addition, as a whole circuit layer, a sufficient thickness can be secured by combining the first circuit layer and the second circuit layer. Therefore, it is possible to satisfactorily ensure the electric transmission performance and heat dissipation performance, which are functions required for the circuit layer.

  As a preferred embodiment of the insulated circuit board of the present invention, the circuit layer includes the first circuit layer, the second circuit layer, and a third circuit layer bonded to the surface of the second circuit layer. A three-layer structure having a thickness of the third circuit layer equivalent to the thickness of the first circuit layer, and the third circuit layer having an average crystal grain size equivalent to that of the first circuit layer. Good.

The surface of the circuit layer on which the element is mounted (mounted) is formed by the third circuit layer, and the average crystal grain size of the third circuit layer is set to a large average crystal grain size equivalent to that of the first circuit layer. The surface roughness (surface roughness) of the surface of the circuit layer can also be made relatively large. When a module in which an element is mounted on a circuit layer (third circuit layer) is resin-sealed, stress tends to concentrate on corner portions formed on the periphery of the circuit layer (particularly the periphery of the third circuit layer) of the mold resin. In the insulated circuit board of the present invention, since the average crystal grain size of the third circuit layer is large and the surface roughness of the surface is large, the mold resin can be firmly fixed to the periphery of the third circuit layer, The adhesion between the mold resin and the circuit layer can be improved.
Further, the thickness of the third circuit layer is made equal to the thickness of the first circuit layer, and the thickness of the third circuit layer is made thin. For this reason, the ratio of the reflection of the ultrasonic wave in the 3rd circuit layer at the time of test | inspecting the joining interface of each component of a module with an ultrasonic survey imaging device can be reduced significantly. Therefore, the reflection of ultrasonic waves in the entire circuit layer can be greatly reduced, and the inspection accuracy can be secured satisfactorily.

  As a preferred embodiment of the insulated circuit board of the present invention, a metal layer made of the same metal as the circuit layer is provided on the other surface of the ceramic substrate, and the metal layer is bonded to the other surface of the ceramic substrate. A first metal layer and a second metal layer bonded to the surface of the first metal layer, wherein the thickness of the first metal layer is equal to the thickness of the first metal layer. The total thickness of the two metal layers is 20% or less, the first metal layer is provided with an average crystal grain size equivalent to that of the first circuit layer, and the second metal layer is the second circuit layer. It is good to be provided with an average crystal grain size equivalent to.

The metal layer has a laminated structure including a first metal layer and a second metal layer, and the first metal layer is provided with a large average crystal grain size equivalent to that of the first circuit layer. The hardness of one metal layer can be provided low. For this reason, the thermal stress applied to the ceramic substrate when the insulating circuit substrate is heated can be reduced, and the ceramic substrate can be prevented from cracking. Therefore, not only the reliability of bonding between the circuit layer of the insulating circuit board and the ceramic substrate but also the reliability of bonding between the metal layer and the ceramic substrate can be ensured in the element mounting process and in the usage environment.
Also in the metal layer, the thickness of the first metal layer is set to 20% or less of the total thickness of the first metal layer and the second metal layer, and the ratio of the first metal layer to the metal layer is small, that is, the metal The first metal layer is formed thinner than the layer. For this reason, when inspecting the bonding interface between the element and the circuit layer (second circuit layer) via the insulating circuit board by the ultrasonic flaw detection imaging apparatus, the ratio of the reflection of the ultrasonic wave in the first metal layer can be greatly reduced. . Therefore, the reflection of ultrasonic waves can be reduced even in the metal layer in addition to the circuit layer, and the inspection accuracy by the ultrasonic exploration video apparatus can be ensured satisfactorily.

  As a preferred embodiment of the insulated circuit board of the present invention, the metal layer includes the first metal layer, the second metal layer, and a third metal layer bonded to the surface of the second metal layer. When the third metal layer has a three-layer structure, the thickness of the third metal layer is equivalent to the thickness of the first metal layer, and the third metal layer has an average crystal grain size equivalent to that of the first metal layer. Good.

The surface of the third metal layer is formed by forming the surface of the metal layer with the third metal layer and setting the average crystal grain size of the third metal layer to a large average crystal grain size equivalent to that of the first metal layer. A large surface roughness can be provided. Thus, by increasing the surface roughness of the surface of the metal layer, the wettability between the metal layer and the solder is improved when the heat dissipation layer (heat sink) is overlapped on the metal layer and joined by solder or the like. . For this reason, the adhesiveness and joining reliability of a metal layer and a thermal radiation layer can be improved, and the thermal radiation from a metallic layer to a thermal radiation layer can be performed smoothly. In addition, when laminating a metal layer and a heat dissipation layer with heat conductive grease, increasing the surface roughness of the surface of the metal layer increases the thermal conductivity between the metal layer and the heat dissipation layer. The grease can be retained, and the heat conductive grease can be prevented from falling outside. Therefore, since the adhesion between the metal layer and the heat dissipation layer can be ensured satisfactorily, the thermal resistance between the metal layer and the heat dissipation layer can be reduced, and the heat dissipation performance can be ensured favorably.
Further, the thickness of the third metal layer is made equal to the thickness of the first metal layer, and the thickness of the third metal layer is made thin. For this reason, the ratio of the reflection of the ultrasonic wave in the 3rd metal layer at the time of test | inspecting the joining interface of each component of a module with an ultrasonic survey imaging device can be reduced significantly. Therefore, the reflection of the ultrasonic wave in the whole metal layer can be greatly reduced, and the inspection accuracy can be secured satisfactorily.

  A method for manufacturing an insulated circuit board according to the present invention is a circuit that forms a circuit layer having a first circuit layer bonded to one surface of a ceramic substrate and a second circuit layer bonded to the surface of the first circuit layer. An average crystal grain size after heating at a bonding temperature between the circuit layer and the ceramic substrate as the first metal material to be the first circuit layer out of the circuit layers. If the layer is copper, a metal material of 250 μm or more is prepared, and if the circuit layer is aluminum, a metal material of 375 μm or more is prepared. As the second metal material to be the second circuit layer, average crystal grains after heating at the bonding temperature A metal material having a diameter of less than 250 μm if the circuit layer is copper and less than 375 μm if the circuit layer is aluminum is prepared, and the thickness of the first metal material is equal to the thickness of the first metal material and the second metal material. Match the thickness of the metal And forming a clad material in which the first metal material and the second metal material are pressure-bonded to each other, and in the circuit layer forming step, brazing the one surface of the ceramic substrate. In a state where the first metal material of the clad material is disposed so as to overlap with a bonding material, by pressing in the laminating direction of the ceramic substrate and the clad material and heating at the bonding temperature, The first metal material and the ceramic substrate are joined to form the circuit layer having the first circuit layer and the second circuit layer on one surface of the ceramic substrate.

  By forming a clad material in which the first metal material and the second metal material are pressure-bonded in advance, the clad material and the ceramic substrate are joined by one heating at the joining temperature in the circuit layer forming step. The circuit layer including the first circuit layer and the second circuit layer can be easily formed. Therefore, the manufacturing process of the insulated circuit board can be simplified.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the test | inspection precision of the joining interface of each component which comprises a module favorable, it can ensure favorable joining reliability of a circuit layer and a ceramic substrate.

It is the longitudinal cross-sectional view which represented typically the power module using the insulated circuit board of 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the insulated circuit board shown in FIG. It is a longitudinal cross-sectional view which shows the manufacturing method of the insulated circuit board shown in FIG. 2 in order of a process. It is the longitudinal cross-sectional view which represented typically the insulated circuit board of 2nd Embodiment of this invention. It is the longitudinal cross-sectional view which represented typically the insulated circuit board of 3rd Embodiment of this invention. It is the longitudinal cross-sectional view which represented typically the insulated circuit board of 4th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 shows a power module 101 using an insulating circuit board (power module board) 10 manufactured by the method for manufacturing an insulating circuit board according to the first embodiment of the present invention. This power module 101 includes an insulated circuit board 10 and an element 91 mounted on the surface of the insulated circuit board 10, and the element 91 and the insulated circuit board 10 are resin-sealed with a mold resin 81 made of epoxy resin or the like. It is a thing. Note that reference numeral 92 in FIG. 1 indicates a bonding layer such as a solder material to which the element 91 is fixed. In the power module 101, the exposed surface of the power module 101 (exposed surface of the insulating circuit board 10) is pressed against the surface of the heat dissipation layer (heat sink) 71 or the like via thermal conductive grease, or a solder material or an adhesive material is applied. It is used in a state where it is bonded and fixed via.

As shown in FIG. 2, the insulated circuit board 10 includes a ceramic substrate 11, a circuit layer 12 formed on one surface of the ceramic substrate 11, a metal layer 13 formed on the other surface of the ceramic substrate 11, It has. The ceramic substrate 11 is formed of a ceramic material such as AlN (aluminum nitride), Al ₂ O ₃ (alumina), Si ₃ N ₄ (silicon nitride).

  The circuit layer 12 is formed of copper (pure copper or copper alloy) or aluminum (pure aluminum or aluminum alloy), and a metal plate made of these metals is formed on one surface of the ceramic substrate 11 with Ag—Cu—Ti or Al—. It is formed by bonding with a brazing bonding material such as Si. The circuit layer 12 includes a first circuit layer 121 bonded to one surface of the ceramic substrate 11 and a second circuit bonded to the surface of the first circuit layer 121, as shown in FIGS. The element 91 is mounted on the surface of the second circuit layer 122 arranged on the surface of the circuit layer 12.

  The thickness t11 of the first circuit layer 121 is 20% or less of the total value (t11 + t12) of the thickness t11 of the first circuit layer 121 and the thickness t12 of the second circuit layer 122. When the circuit layer 12 is copper (Cu), the average crystal grain size of the first circuit layer 121 is 250 μm or more, and the average crystal grain size of the second circuit layer 122 is less than 250 μm. On the other hand, when the circuit layer 12 is aluminum (Al), the average crystal grain size of the first circuit layer 121 is set to 375 μm or more, and the average crystal grain size of the second circuit layer 122 is set to less than 375 μm. In any case, the average crystal grain size of the first circuit layer 121 is set larger than the average crystal grain size of the first circuit layer 121.

  The metal layer 13 is made of the same metal as the circuit layer 12, and is formed by bonding a metal plate to the other surface of the ceramic substrate 11 with a brazing joint material, like the circuit layer 12. As shown in FIGS. 1 and 2, the metal layer 13 includes a first metal layer 131 bonded to the other surface of the ceramic substrate 11 and a second metal bonded to the surface of the first metal layer 131. A stacked structure including the layer 132. The thickness t21 of the first metal layer 131 is set to 20% or less of the total value (t21 + t22) of the thickness t21 of the first metal layer 131 and the thickness t22 of the second metal layer 132. Further, the first metal layer 131 is provided with an average crystal grain size similar to that of the first circuit layer 121, and the second metal layer 132 is provided with an average crystal grain size similar to that of the second circuit layer 122.

  The average crystal grain size of the first circuit layer 121 is equivalent to the average crystal grain size of the first metal layer 131. The average crystal grain size of the first circuit layer 121 is based on the average crystal grain size of the first metal layer 131. This includes not only the case where the diameter exactly matches the diameter but also the case where there is a difference of ± 20%. Similarly, the average crystal grain size of the second circuit layer 122 is equivalent to the average crystal grain size of the second metal layer 132 is that the average crystal grain size of the second metal layer 132 is the reference. This includes not only the case where the average crystal grain size exactly matches but also the case where there is a difference of ± 20%. The average crystal grain size of the first metal layer 131 is 250 μm or more when the circuit layer 12 is copper (Cu), and 375 μm or more when the circuit layer 12 is aluminum (Al), like the first circuit layer 121. It is said. Similarly to the second circuit layer 122, the average crystal grain size of the second metal layer 132 is less than 250 μm when the circuit layer 12 is copper, and less than 375 μm when the circuit layer 12 is aluminum.

  In FIG. 1 and the like, the metal layer 13 is formed with the same plane area as the circuit layer 12, but the metal layer 13 may be formed with a plane area different from that of the circuit layer 12.

The average crystal grain sizes of the first circuit layer 121, the second circuit layer 122, the first metal layer 131, and the second metal layer 132 are measured using, for example, an optical microscope. In this embodiment, the average crystal grain size of the first circuit layer 121 and the second circuit layer 122 of the circuit layer 12 is determined by polishing the circuit layer 12 in the thickness direction, and the plane of the second circuit layer 122 and the first circuit layer 121. Were sequentially exposed, and the crystal grains in the planes of the layers 122 and 121 were measured using an optical microscope. Similarly, the average crystal grain size of the first metal layer 131 and the second metal layer 132 of the metal layer 13 is determined by polishing the metal layer 13 in the thickness direction, and the plane of the second metal layer 132 and the first metal layer 131. Were sequentially exposed, and crystal grains in the planes of the respective layers 132 and 131 were measured using an optical microscope. And the number of crystal grains completely included in the measurement range of a known area (for example, 5000 mm ² ) observed by an optical microscope, the number of half of the number of crystal grains cut around the measurement range, The circle equivalent diameter (the diameter of a circle having the same area as the unit area of metal particles) is calculated from the area obtained by adding the number to the total number of crystal grains and the area of the measurement range divided by the total number of crystal grains. The equivalent diameter was defined as each average crystal grain size.

As an example of the dimensions of the insulating circuit substrate 10 configured as described above, the thickness (plate thickness) of the ceramic substrate 11 made of Si ₃ N ₄ (silicon nitride) is 0.1 mm to 1.5 mm, Cu ( The thickness of the circuit layer 12 made of copper and the thickness of the metal layer 13 are 0.8 mm to 3.0 mm. The thickness t11 of the first circuit layer 121 and the thickness t21 of the first metal layer 131 are 0.01 mm to 0.6 mm, the thickness t12 of the second circuit layer 122 and the thickness t22 of the second metal layer 132 are 0.79 mm to 2.4 mm. However, these dimensions are not limited to the above numerical range.

  The element 91 is an electronic component including a semiconductor, and an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Transistor), a FWD (eld of various types), and FWD (ellow wire) according to a required function. A semiconductor element is selected. In this case, although not shown, the element 91 is provided with an upper electrode part at the upper part and a lower electrode part at the lower part, and the lower electrode part is provided on the upper surface of the circuit layer 12 (second circuit layer 122). The element 91 is mounted on the upper surface of the circuit layer 12 by being joined by soldering or the like. The upper electrode portion of the element 91 is connected to the circuit electrode portion and the like of the circuit layer 12 via a lead frame (not shown) and the like.

Further, the power module 101 is integrated by sealing the element 91 and the insulating circuit substrate 10 with a mold resin 81 except for the back surface side of the metal layer 13. As the mold resin 81, for example, an epoxy resin containing a SiO ₂ filler can be used, and for example, it is molded by transfer molding.

Next, a method for manufacturing the insulating circuit board 10 will be described in the order of steps with reference to FIG.
As shown in FIGS. 1 and 2, for an insulating circuit board 10 having a circuit layer 12 and a metal layer 13 on both surfaces of a ceramic substrate 11, a circuit layer forming step for forming the circuit layer 12, The metal layer formation process to form can be performed simultaneously. In the circuit layer forming step, a metal plate (cladding material) that becomes the circuit layer 12 is bonded to one surface of the ceramic substrate 11, and the first circuit layer 121 bonded to one surface of the ceramic substrate 11 and the first circuit layer 121. The circuit layer 12 having the second circuit layer 122 bonded to the surface of the circuit layer 121 is formed. Further, in the metal layer forming step, a metal plate (cladding material) that becomes the metal layer 13 is bonded to the other surface of the ceramic substrate 11, and the first metal layer 131 bonded to the other surface of the ceramic substrate 11 and its A metal layer 13 having a second metal layer 132 bonded to the surface of the first metal layer 131 is formed.

  As shown in FIG. 3A, the first metal material 221 a that becomes the first circuit layer 121 and the second metal material 222 a that becomes the second circuit layer 122 are pressure-bonded as the metal plate that becomes the circuit layer 12. A clad material 251 is formed. In addition, the thickness of the first metal material 221a of the clad material 251 is set to 20% or less of the total value of the thickness of the first metal material 221a and the thickness of the second metal material 222a. Since the thickness t11 of the first circuit layer 121 and the thickness of the first metal material 221a are substantially the same, the thickness of the first metal material 221a that becomes the first circuit layer 121 in FIG. Is denoted by the same symbol t11 as the thickness t11 of the first circuit layer 121. In addition, since the thickness t12 of the second circuit layer 122 and the thickness of the second metal material 222a are substantially the same, the thickness of the second metal material 222a that becomes the second circuit layer 122 in FIG. Is indicated by the same symbol as the thickness t12 of the second circuit layer 122. The clad material 251 can be formed, for example, by stacking the base material of the first metal material 221a and the base material of the second metal material 222a and rolling with a roll or the like. The clad material 251 is formed in a desired outer shape by punching a plate material by press working.

  The first metal material 221a has an average crystal grain size after heating at a bonding temperature between the circuit layer 12 and the ceramic substrate 11 of 250 μm or more when the circuit layer 12 is copper (Cu), and the circuit layer 12 is made of aluminum (Al ), A metal material having a thickness of 375 μm or more is used. For example, when the circuit layer 12 is copper, oxygen-free copper (OFC) of a general rolled plate can be used for the first metal material 221a. In this case, when the first metal material 221a is heated at the bonding temperature (800 ° C.) between the circuit layer 12 made of copper and the ceramic substrate 11, the crystal grains become coarse and the average crystal grain size becomes 250 μm or more.

  On the other hand, the second metal material 222a has an average grain size after heating at the bonding temperature between the circuit layer 12 and the ceramic substrate 11 of less than 250 μm if the circuit layer 12 is copper, and the circuit layer 12 is aluminum (Al). If so, use a metal material of less than 375 μm. For example, when the circuit layer 12 is copper, the second metal material 222a is a crystal in which the coarsening of crystal grains is suppressed and the average crystal grain size is less than 250 μm when heated at the bonding temperature (800 ° C.). A grain suppressing material can be used suitably. Specifically, GOFC manufactured by Furukawa Electric Co., Ltd. can be used for the second metal material 222a as a crystal grain suppressing material.

  Moreover, in this embodiment, the metal plate used as the metal layer 13 is formed by the same structure as the metal materials 221a and 222a used as the circuit layer 12. That is, the clad material 252 in which the first metal material 221b having the same configuration as the first metal material 221a and the second metal material 222b having the same configuration as the second metal material 222a are pressure-bonded as the metal plate to be the metal layer 13 is used. Use. The clad material 252 is provided so that the thickness of the first metal material 221b is 20% or less of the total value of the thickness of the first metal material 221b and the thickness of the second metal material 222b. Since the thickness t21 of the first metal layer 131 and the thickness of the first metal material 221b are substantially the same, in FIG. 3A, the thickness of the first metal material 221b that becomes the first metal layer 131 is shown. Is indicated by the same symbol t21 as the thickness t21 of the first metal layer 131. In addition, since the thickness t22 of the second metal layer 132 and the thickness of the second metal material 222b are substantially the same, the thickness of the second metal material 222b that becomes the second metal layer 132 in FIG. Is indicated by the same symbol as the thickness t32 of the second metal layer 132.

  As the brazing material 224 for joining the clad materials 251 and 252 and the ceramic substrate 11, for example, an Ag—Cu—Ti brazing material can be used. In this case, the brazing joint material 224 can be easily handled by applying to the joint surface of the clad material 251 and the joint surface of the clad material 252 in advance. In FIG.3 (b), the brazing joining material 224 is previously apply | coated to the lower surface of the 1st metal material 221a, and the upper surface of the 1st metal material 221b.

  As shown in FIG. 3C, the clad material 251 forming the circuit layer 12 is disposed so as to overlap one surface of the ceramic substrate 11 with the brazing material 224 interposed therebetween. Similarly, on the other surface of the ceramic substrate 11, a clad material 252 for forming the metal layer 13 is disposed so as to overlap with the same brazing material 224. In this state, as shown by a white arrow in FIG. 3C, pressure is applied in the stacking direction of the ceramic substrate 11 and the clad materials 251 and 252 and heating is performed at a bonding temperature (800 ° C.).

  Thereby, the first metal material 221a of the clad material 251 to be the circuit layer 12 and the ceramic substrate 11 are bonded. At this time, the clad material 251 is heated, whereby the metal of the first metal material 221a and the metal of the second metal material 222a are atomically bonded and firmly bonded. As a result, the circuit layer 12 having the first circuit layer 121 and the second circuit layer 122 is formed on one surface of the ceramic substrate 11. At the same time, the first metal material 221b of the clad material 252 to be the metal layer 13 and the ceramic substrate 11 are bonded together, and the first metal material 221b and the second metal material 222b are firmly bonded to each other. The metal layer 13 having the first metal layer 131 and the second metal layer 132 is formed on the other surface. Thereby, as shown in FIG.3 (d), the insulated circuit board 10 with which the metal layer 13, the ceramic substrate 11, and the circuit layer 12 were laminated | stacked in order is manufactured.

  The first circuit layer 121 and the second circuit layer 122 having different average crystal grain sizes are used as the second metal materials 222a and 222b by using a crystal grain suppressing material in which coarsening of crystal grains is suppressed by heating at the bonding temperature. And the metal layer 13 including the first metal layer 131 and the second metal layer 132 can be formed. In addition, by forming the clad materials 251 and 252 in which the first metal materials 221a and 221b and the second metal materials 222a and 222b are pressure-bonded in advance, at the junction temperature in the circuit layer forming step and the metal layer forming step. The clad materials 251 and 252 and the ceramic substrate 11 are joined by heating once, and the circuit layer 12 including the first circuit layer 121 and the second circuit layer 122, the first metal layer 131, and the second metal layer 132. Can be easily formed. Therefore, the manufacturing process of the insulated circuit board 10 can be simplified.

  As shown in FIG. 1, the element 91 is mounted on the insulated circuit board 10 manufactured as described above. The element 91 is bonded to the upper surface of the second circuit layer 122 of the circuit layer 12 via a bonding layer 92 made of, for example, silver sintered or solder bonding material. Although not shown, the power module 101 is manufactured by connecting necessary wirings to the element 91 and electrically connecting the circuit layer 12 and the element 91. Thereafter, the entire power module 101 excluding the lower surface of the metal layer 13 is sealed with a mold resin 81.

  In the insulated circuit board 10 of the power module 101 configured as described above, the first circuit layer 121 bonded to the ceramic substrate 11 is provided with a relatively large average crystal grain size as compared with the second circuit layer 122. Therefore, the hardness is provided low. For this reason, the thermal stress applied to the ceramic substrate 11 when the insulating circuit substrate 10 is heated can be reduced, and the ceramic substrate 11 can be prevented from cracking. Therefore, the bonding reliability between the circuit layer 12 and the ceramic substrate 11 can be satisfactorily ensured during the mounting process of the element 91 and in the usage environment of the power module 101.

  Further, when the second circuit layer 122 is made of copper, the average crystal grain size is less than 250 μm, and when the second circuit layer 122 is made of aluminum, the average crystal grain size is made less than 375 μm. Can significantly reduce the reflection of ultrasonic waves. As described above, the first circuit layer 121 has an average crystal grain size of 250 μm or more when copper is used, and an average crystal grain size of 375 μm or more when aluminum is used, and easily reflects ultrasonic waves in the ultrasonic exploration imaging apparatus. ing. However, in the insulated circuit board 10, as described above, the thickness t11 of the first circuit layer 121 is 20% of the total value (t11 + t12) of the thickness t11 of the first circuit layer 121 and the thickness t12 of the second circuit layer 122. The ratio of the first circuit layer 121 to the circuit layer 12 is small, that is, the thickness t11 of the first circuit layer 121 is sufficiently thin with respect to the circuit layer 12. As described above, the average crystal grain size of the first circuit layer 121 is set to be relatively large. However, since the ratio of the first circuit layer 121 to the circuit layer 12 is small, the ratio of ultrasonic reflection in the ultrasonic imaging apparatus is greatly reduced. it can.

  Therefore, in the insulated circuit board 10, by adjusting the thickness t11 of the first circuit layer 121 and the average crystal grain size of the first circuit layer 121 and the second circuit layer 122, the inspection accuracy by the ultrasonic exploration imaging apparatus can be improved. Both the circuit layer 12 (first circuit layer 121) and the bonding reliability between the ceramic substrate 11 can be ensured satisfactorily. Further, the circuit layer 12 as a whole can secure a sufficient thickness by combining the first circuit layer 121 and the second circuit layer 122. Therefore, it is possible to satisfactorily ensure the electric transmission performance and heat dissipation performance, which are functions required for the circuit layer 12.

  In the insulated circuit board 10, the metal layer 13 has a laminated structure of the first metal layer 131 and the second metal layer 132, and the first metal layer 131 is provided with an average crystal grain size equivalent to that of the first circuit layer 121. Therefore, the hardness of the 1st metal layer 131 joined with the ceramic substrate 11 can also be provided low. For this reason, the thermal stress applied to the ceramic substrate 11 when the insulating circuit substrate 10 is heated can be reduced, and the ceramic substrate 11 can be prevented from cracking. Therefore, not only the bonding reliability between the circuit layer 12 of the insulating circuit substrate 10 and the ceramic substrate 11 but also the bonding reliability between the metal layer 13 and the ceramic substrate 11 is ensured satisfactorily during the mounting process of the element 91 and the usage environment. it can.

  Also in the metal layer 13, the thickness t 21 of the first metal layer 131 is set to 20% or less of the total value of the thickness t 21 of the first metal layer 131 and the second metal layer 132, and the first metal layer 131 is the metal layer 13. In other words, the thickness t21 of the first metal layer 131 is made thinner than the metal layer 13. For this reason, when the bonding interface between the element 91 and the circuit layer 12 (second circuit layer 122) is inspected via the insulating circuit board 10 by the ultrasonic flaw detection video apparatus, the reflection of the ultrasonic waves on the first metal layer 131 is not detected. The ratio can be greatly reduced. Therefore, the reflection of ultrasonic waves can be reduced by using the metal layer 13 in addition to the circuit layer 12, and the inspection accuracy by the ultrasonic exploration imaging apparatus can be ensured satisfactorily.

[Other Embodiments]
FIG. 4 shows an insulated circuit board 20 according to the second embodiment of the present invention. In the first embodiment described above, the insulating circuit board 10 is configured to include the metal layer 13 formed on the other surface of the ceramic substrate 11, but the insulating circuit board 20 of the second embodiment shown in FIG. As described above, a configuration including only the circuit layer 12 formed on one surface without providing the metal layer 13 on the other surface of the ceramic substrate 11 is also included in the present invention. Note that in the second embodiment, common elements to those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 shows an insulated circuit board 30 and a power module 103 according to the third embodiment of the present invention. In 3rd Embodiment, the same code | symbol is attached | subjected to 1st Embodiment and 2nd Embodiment, and description is abbreviate | omitted.
In the first embodiment described above, the circuit layer 12 has a two-layer structure including the first circuit layer 121 and the second circuit layer 122 as shown in FIG. 2, but the insulating circuit board 30 shown in FIG. As described above, the circuit layer 32 may have a three-layer structure including the first circuit layer 121, the second circuit layer 122, and the third circuit layer 123 bonded to the surface of the second circuit layer 122. The thickness t13 of the third circuit layer 123 is equal to the thickness t11 of the first circuit layer 121, and the total value of the thickness t11 of the first circuit layer 121 and the thickness t12 of the second circuit layer 122 (t11 + t12) is 20. % Or less. The third circuit layer 123 has an average crystal grain size equivalent to that of the first circuit layer 121. When the circuit layer 32 is copper, the average crystal grain size of the third circuit layer 123 is 250 μm or more. When is an aluminum, the average crystal grain size of the third circuit layer 123 is less than 375 μm.

  The insulated circuit board 30 having the circuit layer 32 having the three-layer structure can be easily manufactured in the same manner as the insulated circuit board 10 of the first embodiment having the circuit layer 12 having the two-layer structure. Specifically, although illustration is omitted, by using a clad material having a three-layer structure in which three metal materials to be the respective layers 121, 122, and 123 of the circuit layer 32 are pressure-bonded, the bonding temperature at the circuit layer forming step can be reduced. The clad material and the ceramic substrate 11 are joined by heating once, and the circuit layer 32 including the first circuit layer 121, the second circuit layer 122, and the third circuit layer 123 can be easily formed.

  In the insulated circuit board 30 of the third embodiment, the surface of the circuit layer 32 on which the element 91 is mounted is formed by the third circuit layer 123, and the average crystal grain size of the third circuit layer 123 is the same as that of the first circuit layer 121. Since the same large average grain size is provided, the surface roughness of the surface of the circuit layer 32 can be made relatively large. As shown in FIG. 5, when the power module 103 in which the element 91 is mounted on the circuit layer 32 (third circuit layer 123) is resin-sealed, the periphery of the circuit layer 32 of the mold resin 81 (the third circuit layer 123 of the third circuit layer 123). Stress tends to concentrate on the corners formed on the periphery. However, in the insulated circuit board 30 of the third embodiment, since the average crystal grain size of the third circuit layer 123 is large and the surface roughness of the surface is large, the mold resin 81 is made of the third circuit layer 123. Can be firmly fixed to the periphery. Therefore, the adhesion between the mold resin 81 and the circuit layer 32 can be improved.

  Further, the thickness t13 of the third circuit layer 123 is made equal to the thickness t11 of the first circuit layer 121, and the thickness t13 of the third circuit layer 123 is made thin. For this reason, the ratio of the reflection of the ultrasonic wave in the 3rd circuit layer 123 at the time of test | inspecting the joining interface of each component of the power module 103 with an ultrasonic survey imaging device can be reduced significantly. Therefore, reflection of ultrasonic waves in the entire circuit layer 32 can be greatly reduced, and good inspection accuracy can be secured.

  FIG. 6 shows an insulated circuit board 40 and a power module 104 according to the fourth embodiment of the present invention. Note that in the fourth embodiment, common elements to the first to third embodiments are denoted by the same reference numerals and description thereof is omitted. In the first embodiment and the like described above, the metal layer 13 has a two-layer structure including the first metal layer 131 and the second metal layer 132. However, like the insulated circuit board 40 shown in FIG. 34 may have a three-layer structure including the first metal layer 131, the second metal layer 132, and the third circuit layer 133 bonded to the surface of the second metal layer 132. The thickness t23 of the third metal layer 133 is equal to the thickness t21 of the first metal layer 131, and the total value of the thickness t21 of the first metal layer 131 and the thickness t22 of the second metal layer 132 (t21 + t22) is 20. % Or less. The third metal layer 133 has an average crystal grain size equivalent to that of the first metal layer 131. When the circuit layer 32 and the metal layer 34 are copper, the average crystal grain size of the third metal layer 133 is 250 μm or more. When the circuit layer 32 and the metal layer 34 are aluminum, the average crystal grain size of the third metal layer 133 is 375 μm or more.

  Like the insulated circuit board 40 of the fourth embodiment, the surface of the metal layer 34 is formed by the third metal layer 133, and the average crystal grain size of the third metal layer 133 is as large as the first metal layer 131. By providing the crystal grain size, the surface roughness of the surface of the third metal layer 133 can be increased. Thus, by increasing the surface roughness of the surface of the metal layer 34, when the heat dissipation layer (heat sink) 71 is stacked on the metal layer 34 and joined by solder or the like, the metal layer 34 and the solder are wetted. Improves. For this reason, the adhesiveness and joining reliability of the metal layer 34 and the thermal radiation layer 71 can be improved, and the thermal radiation from the metallic layer 34 to the thermal radiation layer 71 can be performed smoothly. Further, when the metal layer 34 and the heat dissipation layer 71 are laminated with the heat conductive grease interposed therebetween, by increasing the surface roughness of the surface of the metal layer 34, the metal layer 34 and the heat dissipation layer 71 can be separated. The heat conductive grease can be kept between them, and the heat conductive grease can be prevented from coming outside. Therefore, since the adhesion between the metal layer 34 and the heat dissipation layer 71 can be ensured satisfactorily, the thermal resistance between the metal layer 34 and the heat dissipation layer 71 can be reduced, and the heat dissipation performance can be ensured favorably.

  Further, the thickness t23 of the third metal layer 133 is made equal to the thickness t21 of the first metal layer 131, and the third metal layer 133 is formed thin. For this reason, the ratio of the reflection of the ultrasonic wave in the 3rd metal layer 133 at the time of test | inspecting the joining interface of each component of the power module 104 by an ultrasonic survey imaging device can be reduced significantly. Therefore, the reflection of ultrasonic waves in the entire metal layer 34 can be greatly reduced, and the inspection accuracy can be secured satisfactorily.

In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, it is possible to add a various change in the range which does not deviate from resin of this invention.
For example, in the above embodiment, one side (lower electrode portion) of the element 91 is mounted on the circuit layer 12 of the insulated circuit board 10, but the insulated circuit board 10 is disposed on both sides of the element 91. A double-sided cooling structure is also possible.

Moreover, although the said embodiment demonstrated the example which formed the circuit layer and metal layer which varied the average crystal grain diameter for every area | region with copper (pure copper or copper alloy), aluminum (pure aluminum or aluminum alloy) was demonstrated. Even if it is used, the circuit layer and the metal layer can be formed by varying the average crystal grain size for each region.
For example, the average crystal grain size can be controlled by adjusting the rolling reduction per pass in the rolling process of rolling an aluminum ingot to a desired plate thickness. Specifically, when the rolling reduction per pass is increased, the average crystal grain size can be increased. And the insulated circuit which has a circuit layer from which an average crystal grain diameter differs in a 1st circuit layer, a 2nd circuit layer, and also a 3rd circuit layer by using the rolling material in which the average crystal grain diameter was adjusted in this way The substrate can be easily manufactured.

  Hereinafter, although the effect of the present invention is explained in detail using an example, the present invention is not limited to the following example.

  As shown in Tables 1 and 2, Examples 1-1 to 1-3, 2-1 to 2-3, and Comparative Examples 1-1 to 1-3 of power modules in which elements and insulating circuit boards are joined 2-1 to 2-3 were produced. As the insulating circuit board, one having a circuit layer having a configuration (thickness, average crystal grain size) shown in Table 1 and Table 2 formed on one surface of a ceramic substrate was used. In Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3, the circuit layer of the insulating circuit board was formed of copper. On the other hand, in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3, the circuit layer of the insulating circuit board was formed of aluminum.

As the ceramic substrate, a rectangular plate made of Si ₃ N ₄ (silicon nitride) having a plate thickness of 0.32 mm and a planar size of 30 mm × 30 mm was used. The clad material for forming the circuit layer has a thickness (plate thickness) of 3.0 mm when the circuit layer is copper, and a thickness (plate thickness) of 3.0 mm when the circuit layer is aluminum. A rectangular plate of 28 mm × 28 mm was used. Further, the thickness t11 of the first metal material (first circuit layer) portion and the thickness t12 of the second metal material (second circuit layer) portion were formed with the thicknesses shown in Tables 1 and 2. The “ratio of t11” shown in Table 1 and Table 2 is the ratio of the thickness t11 of the first circuit layer to the total value (t11 + t12) of the thickness t11 of the first circuit layer and the thickness t12 of the second circuit layer {t11 / (T11 + t12)} × 100 [%].

  In addition, when each clad plate serving as a circuit layer is copper, an Ag-Cu-Ti brazing joint material is used, and when aluminum is used, an Al-Si brazing joint material is used. The insulating circuit board was produced by bonding.

  The element was joined to the surface of the circuit layer (second circuit layer) of each of the obtained insulating circuit boards with a solder material (Sn—Cu solder material) to manufacture a power module. And about the obtained power module, the solder joint layer was inspected from both the element side not through the circuit layer and the insulating circuit board side through the circuit layer, and the void area ratio in the solder joint layer was measured. . Moreover, the thermal cycle test was implemented about each insulated circuit board, and the joining rate of the ceramic substrate and circuit layer after a thermal cycle test was measured.

(Measuring method of void diameter in solder joint layer)
With respect to the obtained power module, the bonding interface (solder bonding layer) between the circuit layer and the element was observed using an ultrasonic exploration video apparatus (SAT, manufactured by Hitachi Engineering & Service Co., Ltd. ES5000). The interface between the circuit layer and the element is observed from both the insulating circuit board side through the circuit layer and the element side not through the circuit layer. Measured from the direction. As for the diameter of the void, the diameter of a circle having the same area was calculated from the observed area of the void, and this equivalent circle diameter was taken as the diameter of the void. In addition, when there existed several void in one joining interface, the average value (average diameter) of the diameter of each void was computed. Further, a ratio (D1 / D2) × 100 [%] of the average diameter D1 of the void when observed from the element side and the average diameter D2 of the void when observed from the insulating circuit board side was calculated.

  The smaller the ratio value obtained, the smaller the difference between the average diameter of voids when observed from the element side and the average diameter of voids when observed from the insulated circuit board side, and better inspection accuracy can be obtained. . In this case, the test accuracy is evaluated as “good” if the ratio value is less than ± 10% (ratio exceeds 90% and less than 110%), and ± 10% or more (ratio is 90% or less or 110%). The above case was evaluated as “No”. The results are shown in Tables 3 and 4.

(Joint reliability between ceramic substrate and circuit layer after thermal cycle test)
N = 5 pieces of each insulated circuit board were prepared, and after 1000 liquid bath cooling / heating cycles of −40 ° C. × 5 minutes and 150 ° C. × 5 minutes were performed, the ceramic substrate and the circuit layer were bonded to each insulated circuit board. The interface was observed to determine whether the ceramic substrate was cracked. The thermal cycle test was performed using a liquid tank thermal shock device TSB-51 manufactured by Espec. Observation of the bonding interface between the ceramic substrate and the circuit layer was performed from the ceramic substrate side through the ceramic substrate using an ultrasonic exploration video apparatus (ES5000 manufactured by Hitachi Engineering & Service Co., Ltd.). For N = 5 insulated circuit boards, the ratio (A / N) × 100 [%] of the number A of ceramic substrate cracks was calculated. The smaller the value of the ratio obtained, the smaller the number of cracks in the ceramic substrate, and the higher the bonding reliability between the ceramic substrate and the circuit layer. In this case, the evaluation of the bonding reliability between the ceramic substrate and the circuit layer was evaluated as “Good” when the ratio value was less than 10%, and “No” when the ratio was 10% or more. The results are shown in Tables 3 and 4.

  As can be seen from the results of Tables 3 and 4, when the circuit layer is copper, the ratio of the thickness t11 of the first circuit layer is 20% or less, the average crystal grain size of the first circuit layer is 250 μm or more, the second By setting the average crystal grain size of the circuit layer to less than 250 μm, it is possible to satisfactorily ensure both the inspection accuracy by the ultrasonic exploration imaging apparatus and the bonding reliability between the ceramic substrate and the circuit layer. When the circuit layer is aluminum, the ratio of the thickness t11 of the first circuit layer is 20% or less, the average crystal grain size of the first circuit layer is 375 μm or more, and the average crystal grain size of the second circuit layer is less than 375 μm. By doing so, it is possible to satisfactorily ensure both the inspection accuracy by the ultrasonic exploration imaging apparatus and the bonding reliability between the ceramic substrate and the circuit layer.

10, 20, 30, 40 Insulated circuit board 11 Ceramic substrate 12, 32 Circuit layer 13, 34 Metal layer 81 Mold resin 91 Element 92 Bonding layer 101, 103, 104 Power module (module)
121 1st circuit layer 122 2nd circuit layer 123 3rd circuit layer 131 1st metal layer 132 2nd metal layer 133 3rd metal layers 221a and 221b 1st metal material 222a and 222b 2nd metal material 224 Brazing joining material 251 252 Clad material

Claims (5)

A ceramic substrate, and a circuit layer made of copper or aluminum formed on one surface of the ceramic substrate,
The circuit layer has a laminated structure having a first circuit layer bonded to one surface of the ceramic substrate and a second circuit layer bonded to the surface of the first circuit layer;
The thickness of the first circuit layer is 20% or less of the total value of the thickness of the first circuit layer and the thickness of the second circuit layer,
When the circuit layer is copper, the average crystal grain size of the first circuit layer is 250 μm or more, the average crystal grain size of the second circuit layer is less than 250 μm,
An insulating circuit board, wherein when the circuit layer is aluminum, the average crystal grain size of the first circuit layer is 375 μm or more, and the average crystal grain size of the second circuit layer is less than 375 μm. The circuit layer has a three-layer structure including the first circuit layer, the second circuit layer, and a third circuit layer bonded to a surface of the second circuit layer.
2. The thickness of the third circuit layer is equal to the thickness of the first circuit layer, and the third circuit layer has an average grain size equal to that of the first circuit layer. 2. Insulated circuit board. A metal layer made of the same metal as the circuit layer is provided on the other surface of the ceramic substrate,
The metal layer has a laminated structure having a first metal layer bonded to the other surface of the ceramic substrate and a second metal layer bonded to the surface of the first metal layer,
The thickness of the first metal layer is 20% or less of the sum of the thickness of the first metal layer and the thickness of the second metal layer,
The first metal layer is provided with an average crystal grain size equivalent to that of the first circuit layer, and the second metal layer is provided with an average crystal grain size equivalent to that of the second circuit layer. The insulated circuit board according to claim 1 or 2. The metal layer has a three-layer structure including the first metal layer, the second metal layer, and a third metal layer bonded to a surface of the second metal layer,
4. The thickness of the third metal layer is made equal to the thickness of the first metal layer, and the third metal layer has an average crystal grain size equivalent to that of the first metal layer. 2. Insulated circuit board. A circuit layer forming step of forming a circuit layer having a first circuit layer bonded to one surface of the ceramic substrate and a second circuit layer bonded to the surface of the first circuit layer;
Of the circuit layers, as the first metal material to be the first circuit layer, the average crystal grain size after heating at the bonding temperature between the circuit layer and the ceramic substrate is 250 μm or more if the circuit layer is copper, If the circuit layer is aluminum, prepare a metal material of 375 μm or more,
As the second metal material to be the second circuit layer, a metal material having an average crystal grain size after heating at the bonding temperature of less than 250 μm if the circuit layer is copper and less than 375 μm if the circuit layer is aluminum Prepare
The thickness of the first metal material is set to 20% or less of the total value of the thickness of the first metal material and the thickness of the second metal material, and the first metal material and the second metal material are pressure bonded. Formed clad material,
In the circuit layer forming step, in a state in which the first metal material of the clad material is disposed on one surface of the ceramic substrate with a brazing bonding material overlapped, in the stacking direction of the ceramic substrate and the clad material By pressurizing and heating at the joining temperature, the first metal material of the clad material and the ceramic substrate are joined, and the first circuit layer and the second circuit layer are formed on one surface of the ceramic substrate. A method of manufacturing an insulating circuit board, comprising: forming the circuit layer having:

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