JP2019149459A - 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 adhesion between a circuit layer and a resin, and also to provide a manufacturing method thereof.SOLUTION: An insulation circuit board includes: a ceramic substrate; and a circuit layer made of copper or aluminum 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. The average crystal grain size of the second circuit layer is provided larger than the crystal grain size crystal of the first circuit layer.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 surface roughness (surface roughness) of the circuit layer surface becomes small, When a module in which an element is mounted on an insulated circuit board is resin-sealed, there is a problem of reducing the adhesion between the resin and the circuit layer.

  The present invention has been made in view of such circumstances, and an insulating circuit that can ensure a good inspection accuracy of a bonding interface of each component constituting a module and can also ensure a good adhesion between a circuit layer and a resin. An object of the present invention is to provide a substrate and a manufacturing method thereof.

  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, and the average crystal grain size of the second circuit layer is the crystal grain of the first circuit layer. It is larger than the diameter crystal.

In this insulated circuit board, the circuit layer has a laminated structure including a first circuit layer bonded to the ceramic substrate and a second circuit layer bonded to the first circuit layer, and the element is mounted (mounted). The average crystal grain size of the second circuit layer is larger than the average crystal grain size of the first circuit layer. Thus, in the insulated circuit board, the surface of the circuit layer on which the element is mounted is formed by the second circuit layer by combining the first circuit layer and the second circuit layer having different average crystal grain sizes. Since the second circuit layer has a larger average crystal grain size than the first circuit layer, the surface roughness (surface roughness) of the surface of the second circuit layer is larger than that of the first circuit layer. When a module in which an element is mounted on a circuit layer (second circuit layer) is resin-sealed, stress tends to concentrate on corners formed on the periphery of the circuit layer (especially the periphery of the second circuit layer) of the mold resin. In the insulated circuit board of the present invention, since the average crystal grain size of the second circuit layer is large and the surface roughness of the surface is large, the mold resin can be firmly fixed to the peripheral edge of the second circuit layer. Good adhesion between the resin and the circuit layer can be secured.
Further, as described above, since the circuit layer is formed by the first circuit layer and the second circuit layer, the ratio of the second circuit layer to the entire circuit layer is small, that is, the entire circuit layer. The thickness of the second circuit layer can be reduced. For this reason, the ratio of the reflection of the ultrasonic wave in the second circuit layer when the bonding interface between the element and the circuit layer (second circuit layer) is inspected through the circuit layer by the ultrasonic exploration video apparatus can be greatly reduced. Therefore, the reflection of ultrasonic waves in the entire circuit layer can be greatly reduced, and the inspection accuracy 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, 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 at least the other surface of the ceramic substrate. The first metal layer may be provided with an average crystal grain size equivalent to that of the first circuit layer.

  Even in an insulated circuit board having a metal layer on the other surface of the ceramic substrate, the first metal layer constituting the metal layer is provided with an average crystal grain size equivalent to that of the first circuit layer, so that an ultrasonic exploration image is obtained. When the bonding interface between the element and the circuit layer (second circuit layer) is inspected by the apparatus through the insulating circuit board, reflection of ultrasonic waves can be reduced even in the metal layer in addition to the circuit layer. Therefore, it is possible to ensure good inspection accuracy by the ultrasonic exploration video apparatus.

  As a preferred embodiment of the insulated circuit board of the present invention, the metal layer has a laminated structure including the first metal layer and a second metal layer bonded to the surface of the first metal layer, The second metal layer may be provided with an average crystal grain size equivalent to that of the second circuit layer.

The surface of the surface of the second metal layer is formed by providing the metal layer with a laminated structure of the first metal layer and the second metal layer and providing the second metal layer with a large average crystal grain size equivalent to that of the second circuit layer. The roughness can be increased. As described above, when the surface roughness of the surface of the metal layer is increased, 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.
Moreover, since the metal layer is formed of the first metal layer and the second metal layer, the ratio of the second metal layer to the entire metal layer can be reduced. For this reason, the ratio of the reflection of the ultrasonic wave in the 2nd metal layer at the time of test | inspecting the joining interface of each component of a module by an ultrasonic survey imaging device can be reduced greatly, and the reflection of the ultrasonic wave in the whole metal layer can be reduced greatly. Therefore, good inspection accuracy can be secured.

  As a preferred embodiment of the insulated circuit board of the present invention, when the circuit layer is copper, the average crystal grain size of the first circuit layer is preferably less than 250 μm. In addition, when the circuit layer is made of aluminum, the average crystal grain size of the first circuit layer is preferably less than 375 μm.

  When the circuit layer is copper or aluminum, by adjusting the average crystal grain size of the first circuit layer within the above range, both the inspection accuracy by the ultrasonic exploration imaging device and the adhesion at the time of resin sealing are achieved. Can be secured well.

  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. A layer forming step, and among the circuit layers, as a first metal material to be the first circuit layer, a second metal material to be a second circuit layer bonded to the surface of the first circuit layer Preparing a crystal grain suppressing material in which coarsening of crystal grains due to heating is suppressed, forming a clad material in which the first metal material and the second metal material are pressure-bonded, and in the circuit layer forming step, In a state where the first metal material of the clad material is disposed on one surface of the ceramic substrate with a brazing joint interposed therebetween, heating is performed by applying pressure in the laminating direction of the ceramic substrate and the clad material. The first metal of the cladding material The ceramic substrate and by bonding, to form the circuit layer having a first circuit layer and the second circuit layer on one surface of the ceramic substrate and.

  Thus, the circuit layer provided with the first circuit layer and the second circuit layer by using the crystal grain suppressing material in which the coarsening of crystal grains due to heating is suppressed as compared with the second metal material as the first metal material. Can be formed. In addition, 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 in the circuit layer forming process, A circuit layer including one circuit layer and a 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, the adhesiveness of a circuit layer and resin can be ensured favorable.

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.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
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 (the exposed surface of the insulating circuit board 10) is pressed against the surface of a heat sink (not shown) via heat conductive grease, or via a solder material or an adhesive material. It is used in a state where it is adhered and fixed.

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 average crystal grain size of the second circuit layer 122 is set larger than the average crystal grain size of the first circuit layer 121.

  When the circuit layer 12 is copper (Cu), the average crystal grain size of the first circuit layer 121 is preferably less than 250 μm, and the average crystal grain size of the second circuit layer 122 is preferably 250 μm or more. On the other hand, when the circuit layer 12 is aluminum (Al), the average crystal grain size of the first circuit layer 121 is preferably less than 375 μm, and the average crystal grain size of the second circuit layer 122 is preferably 375 μm or more. By adjusting the average crystal grain size of the first circuit layer 121 within the above range, the reflection of ultrasonic waves in the first circuit layer 121 can be greatly reduced.

  On the other hand, since the second circuit layer 122 has an average crystal grain size larger than that of the first circuit layer 121, the surface roughness of the surface of the second circuit layer 122 (surface roughness, A large arithmetic average roughness Ra) is provided. As described above, in the insulated circuit board 10, the first circuit layer 121 and the second circuit layer 122 having different average crystal grain sizes are combined, and the surface of the circuit layer 12 on which the element 91 is mounted is the second circuit layer 122. Forming. Further, since the circuit layer 12 is formed of the first circuit layer 121 and the second circuit layer 122, the ratio of the second circuit layer 122 to the entire circuit layer 12 is small. Thus, the thickness of the second circuit layer 122 can be reduced. For this reason, when the bonding interface of each component of the power module 101 is inspected by an ultrasonic imaging apparatus (SAT) performed through the circuit layer 12, the ratio of the reflection of the ultrasonic wave in the second circuit layer 122 can be greatly reduced. . Therefore, the reflection of ultrasonic waves in the entire circuit layer 12 can be greatly reduced, and good inspection accuracy can be ensured. The thickness of the second circuit layer 122 is preferably smaller than the thickness of the first circuit layer 121.

  On the other hand, when the power module 101 in which the element 91 is mounted on the circuit layer 12 is resin-sealed, stress tends to concentrate on the corners arranged on the periphery of the circuit layer 12. However, in the insulated circuit board 10, since the surface roughness of the second circuit layer 122 disposed on the surface of the circuit layer 12 is large, the mold resin 81 can be firmly fixed to the periphery of the circuit layer 12. Therefore, it is possible to satisfactorily ensure both the inspection accuracy by the ultrasonic exploration video apparatus and the adhesion at the time of resin sealing.

  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 at least the other surface of the ceramic substrate 11, and the first metal layer 131 is connected to the first circuit layer 121. It is provided with an equivalent average crystal grain size. In the insulated circuit board 10 of the present embodiment, the metal layer 13 has a laminated structure including the first metal layer 131 and the second metal layer 132 bonded to the surface of the first metal layer 131. . The average crystal grain size of the second metal layer 132 is set to an average crystal grain size equivalent 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 preferably less than 250 μm when the circuit layer 12 is made of copper (Cu), like the first circuit layer 121, and the circuit layer 12 is made of aluminum (Al). Sometimes it is preferably less than 375 μm. Further, like the second circuit layer 122, the average crystal grain size of the second metal layer 132 is preferably 250 μm or more when the circuit layer 12 is copper, and is 375 μm or more when the circuit layer 12 is aluminum. Is preferred.

  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 and the metal layer 13 made of copper is 0.05 mm to 3.0 mm. The thickness of the first circuit layer 121 and the first metal layer 131 is 0.025 mm to 2.975 mm, and the thickness of the second circuit layer 122 and the second metal layer 132 is 0.025 mm to 2.975 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. 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.

  As the first metal material 221a, a crystal grain suppressing material in which coarsening of crystal grains due to heating is suppressed as compared with the second metal material 222a is used. If the crystal grain suppressing material is a copper material, it is possible to suitably use a material whose crystal grain size is suppressed when heated at 800 ° C. and whose average crystal grain size is less than 250 μm. Specifically, GOFC manufactured by Furukawa Electric Co., Ltd. can be used for the first metal material 221a as a crystal grain suppressing material. On the other hand, oxygen-free copper (OFC) which is a general rolled plate can be used for the second metal material 222a. When the second metal material 222a is heated at 800 ° C., the crystal grains become coarse and the average crystal grain size becomes 250 μm or more.

  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.

  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.

  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.

  As described above, as the first metal material 221a and 221b, the first circuit layer 121 and the second circuit layer 121 and the second metal material 221a and 221b can be obtained by using the crystal grain suppressing material in which the coarsening of the crystal grains due to heating is suppressed as compared with the second metal material 222a and 222b. The circuit layer 12 including the circuit layer 122 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, one heating in the circuit layer forming step and the metal layer forming step is performed. Thus, the clad members 251 and 252 and the ceramic substrate 11 are joined together to form the circuit layer 12 including the first circuit layer 121 and the second circuit layer 122, and the metal including the first metal layer 131 and the second metal layer 132. The layer 13 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. Since the surface of the second circuit layer 122 provided on the periphery of the circuit layer 12 has a surface roughness larger than that of the surface of the first circuit layer 121, the mold resin 81 is largely exposed on the surface of the circuit layer 12. The second circuit layer 122 is in close contact with the surface and firmly bonded.

  In the insulated circuit board 10 of the power module 101 configured as described above, the circuit layer 12 includes the first circuit layer 121 bonded to the ceramic substrate 11 and the second circuit layer 122 bonded to the first circuit layer 121. The average crystal grain size of the second circuit layer 122 on which the element 91 is mounted (mounted) is made larger than the average crystal grain size of the first circuit layer 121. Thus, in the insulated circuit board 10, the first circuit layer 121 and the second circuit layer 122 having different average crystal grain sizes are combined, and the surface of the circuit layer 12 on which the element 91 is mounted is formed by the second circuit layer 122. Forming. Since the second circuit layer 122 has a larger average crystal grain size than the first circuit layer 121, the surface roughness (surface roughness) of the surface of the second circuit layer 122 is larger than that of the first circuit layer 121. Become. When the power module 101 having the element 91 mounted on the circuit layer 12 (second circuit layer 122) is resin-sealed, corners formed on the periphery of the circuit layer 12 of the mold resin 81 (periphery of the second circuit layer 122). However, in the insulated circuit board 10 of the present embodiment, the average crystal grain size of the second circuit layer 122 is large and the surface roughness of the surface is large. The two circuit layers 122 can be firmly fixed to the periphery, and the adhesion between the mold resin 81 and the circuit layer 12 can be ensured satisfactorily.

  Further, as described above, since the circuit layer 12 is formed of the first circuit layer 121 and the second circuit layer 122, the ratio of the second circuit layer 122 to the entire circuit layer 12 can be reduced. For this reason, the ratio of the reflection of the ultrasonic wave in the second circuit layer 122 when the bonding interface between the element 91 and the circuit layer 12 (second circuit layer 122) is inspected through the circuit layer 12 by the ultrasonic exploration video apparatus is calculated. The reflection of ultrasonic waves in the entire circuit layer 12 can be greatly reduced. Therefore, good inspection accuracy can be secured.

  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.

  Moreover, in the insulated circuit board 10, since the 1st metal layer 131 which comprises the metal layer 13 is provided in the average crystal grain diameter equivalent to the 1st circuit layer 121, the insulated circuit board 10 is used with an ultrasonic survey imaging device. In addition, when the bonding interface between the element 91 and the circuit layer 12 is inspected, the metal layer 13 in addition to the circuit layer 12 can reduce the reflection of ultrasonic waves. Moreover, since the metal layer 13 is formed of the first metal layer 131 and the second metal layer 132, the ratio of the second metal layer 132 to the entire metal layer 13 can be reduced. For this reason, it is possible to greatly reduce the rate of reflection of ultrasonic waves in the second metal layer 132 when inspecting the bonding interface of each component of the power module 101 by the ultrasonic exploration imaging apparatus, and to reduce the reflection of ultrasonic waves in the entire metal layer 13. It can be greatly reduced. Therefore, it is possible to ensure good inspection accuracy by the ultrasonic exploration video apparatus.

  Further, as described above, the metal layer 13 has a laminated structure of the first metal layer 131 and the second metal layer 132, and the second metal layer 132 is formed with a large average crystal grain size equivalent to that of the second circuit layer 122. Therefore, the surface roughness of the surface of the second metal layer 132 can be increased. Thus, when the surface roughness of the surface of the metal layer 13 is increased, the wettability between the metal layer 13 and the solder is improved when the heat dissipation layer (heat sink) is stacked on the metal layer 13 and joined by solder or the like. For this reason, the adhesiveness and joining reliability of the metal layer 13 and a thermal radiation layer can be improved, and the thermal radiation from the metallic layer 13 to a thermal radiation layer can be performed smoothly. Moreover, also when laminating | stacking the metal layer 13 and a thermal radiation layer on both sides of heat conductive grease, by making the surface roughness of the surface of the metal layer 13 large, between the metal layer 13 and a thermal radiation layer, it is. The heat conductive grease can be retained, and the heat conductive grease can be prevented from falling outside. Therefore, since the adhesiveness between the metal layer 13 and the heat dissipation layer can be ensured satisfactorily, the thermal resistance between the metal layer 13 and the heat dissipation layer can be reduced, and the heat dissipation performance can be ensured satisfactorily.

  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 of the second embodiment shown in FIG. A configuration including only the circuit layer 12 formed on one surface without providing a metal layer on the other surface of the ceramic substrate 11 like the substrate 20 is also included in the present invention.

  In the first embodiment described above, the metal layer 13 is configured to include the first metal layer 131 and the second metal layer 132. However, like the insulated circuit board 30 of the third embodiment shown in FIG. In addition, the metal layer 33 may be composed of only the first metal layer 131. In the second embodiment and the third embodiment, common elements to those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, a various change can be added in the range which does not deviate from the meaning 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, in the said embodiment, although the circuit layer 12 and the metal layer 13 which varied the average crystal grain diameter for every area | region were formed with copper (pure copper or copper alloy), aluminum (pure aluminum or aluminum alloy) was used. Alternatively, the circuit layer 12 and the metal layer 13 can be formed by changing 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. Then, by using the rolled material with the average crystal grain size adjusted in this way, an insulated circuit board having circuit layers having different average crystal grain sizes between the first circuit layer and the second circuit layer 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 the structure shown in Tables 1 and 2 formed on one surface of a ceramic substrate was used. In Examples 1-1 to 1-3 and 2-1 to 2-3, the circuit layer was formed by increasing the average crystal grain size of the second circuit layer on which the element is mounted than the first circuit layer. . On the other hand, in Comparative Examples 1-1 to 1-2 and 2-1 to 2-2, the second circuit layer of the circuit layer was formed with an average crystal grain size smaller than that of the first circuit layer.

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. As the clad material for forming the circuit layer, a rectangular plate having a plate thickness of 1.6 mm and a plane size of 28 mm × 28 mm is used, the thickness of the first metal material portion is 1.2 mm, and the thickness of the second metal material portion is 0. 4 mm. In addition, when each metal plate serving as the 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, and the ceramic substrate and the clad material are bonded. The insulating circuit board was produced by bonding.

  The surface roughness of the upper surface of the circuit layer of each obtained insulating circuit board was measured, and the surface roughness of the surface of the circuit layer was measured. Subsequently, the element was joined to the surface of the circuit layer (second circuit layer) of each insulating circuit board with a solder material (Sn—Cu based 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 element and the insulated circuit board were resin-sealed about the obtained power module, and the adhesiveness of resin and a circuit layer was evaluated. The resin was an epoxy resin and was sealed with a transfer mold.

(Measurement of the surface roughness of the circuit layer surface)
The surface roughness Ra (μm) on the surface of the circuit layer (second circuit layer) was measured using a surf tester (SJ-410 manufactured by Mitutoyo). The results are shown in Tables 1 and 2.

(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.

(Adhesion evaluation by pudding cup test)
The adhesion between the mold resin and the insulated circuit board was evaluated by a pudding cup test. The pudding cup test was conducted in accordance with the international standard ISO19095-1 to 4 for the resin-metal bonding property evaluation test method. Specifically, a pudding cup-shaped resin was formed on the surface of the circuit layer of the insulating circuit board, and a shear peel strength test of the resin was performed. Then, when the obtained shear peel strength was 15 MPa or more, the adhesion between the mold resin and the insulating circuit board was evaluated as “good”, and when the shear peel strength was less than 15 MPa, it was evaluated as “no”. The results are shown in Tables 3 and 4.

  As can be seen from the results in Tables 3 and 4, when the circuit layer is copper, the average crystal grain size of the first circuit layer is set to less than 250 μm, so that the inspection accuracy by the ultrasonic imaging apparatus and the resin sealing Both the adhesiveness at the time can be secured satisfactorily. In addition, when the circuit layer is aluminum, by setting the average crystal grain size of the first circuit layer region to less than 375 μm, both the inspection accuracy by the ultrasonic exploration imaging apparatus and the adhesion at the time of resin sealing, It can be secured well.

10, 20, 30 Insulated circuit board 11 Ceramic substrate 12 Circuit layer 13, 33 Metal layer 81 Mold resin 91 Element 92 Bonding layer 101 Power module (module)
121 1st circuit layer 122 2nd circuit layer 131 1st metal layer 132 2nd metal layer 221a, 221b 1st metal material 222a, 222b 2nd metal material 224 Brazing joining material 251,252 Cladding material

Claims (6)

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;
An insulating circuit board, wherein an average crystal grain size of the second circuit layer is larger than a crystal grain size crystal of the first circuit layer. 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 includes at least a first metal layer bonded to the other surface of the ceramic substrate;
The insulated circuit board according to claim 1, wherein the first metal layer is provided with an average crystal grain size equivalent to that of the first circuit layer. The metal layer has a laminated structure including the first metal layer and a second metal layer bonded to the surface of the first metal layer,
The insulated circuit board according to claim 2, wherein the second metal layer is provided with an average crystal grain size equivalent to that of the second circuit layer.   4. The insulated circuit board according to claim 1, wherein when the circuit layer is copper, an average crystal grain size of the first circuit layer is less than 250 μm. 5.   4. The insulated circuit board according to claim 1, wherein when the circuit layer is made of aluminum, an average crystal grain size of the first circuit layer is less than 375 μm. 5. 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;
Among the circuit layers, as the first metal material to be the first circuit layer, the coarsening of crystal grains due to heating is larger than the second metal material to be the second circuit layer bonded to the surface of the first circuit layer. Preparing a suppressed crystal grain suppressing material, forming a clad material in which the first metal material and the second metal material are pressure-bonded;
In the circuit layer forming step, a stacking direction of the ceramic substrate and the clad material in a state in which the first metal material of the clad material is disposed on one surface of the ceramic substrate via a brazing joint material The first metal material of the clad material and the ceramic substrate are bonded to each other by heating and pressing, and the first circuit layer and the second circuit layer are provided on one surface of the ceramic substrate. A method of manufacturing an insulated circuit board, comprising forming the circuit layer.

Images