JP7342371B2 - Insulated circuit board and method for manufacturing an insulated circuit board - Google Patents

Description

The present invention includes a metal substrate, an insulating resin layer formed on one surface of the metal substrate, and a circuit layer having a circuit pattern formed on a surface of the insulating resin layer opposite to the metal substrate. The present invention relates to an insulated circuit board comprising: and a method for manufacturing the insulated circuit board.

Power modules, LED modules, and thermoelectric modules have a structure in which power semiconductor elements, LED elements, and thermoelectric elements are bonded to an insulated circuit board that has a circuit layer made of a conductive material formed on one side of an insulating layer. .
As the above-mentioned insulated circuit board, for example, a metal base circuit board described in Patent Document 1 has been proposed.

In the metal base circuit board described in Patent Document 1, an insulating resin layer is formed on a metal substrate, and a circuit layer having a circuit pattern is formed on this insulating resin layer. Here, the insulating resin layer is made of epoxy resin, which is a thermosetting resin, and the circuit layer is made of copper foil, and the copper foil placed on the insulating resin layer is etched. The circuit pattern is formed by

In the metal-based circuit board described in Patent Document 1, various elements and the like are bonded onto the circuit layer via a solder layer to form the various modules described above.
Here, the circuit layer and insulating resin layer made of copper foil have a large coefficient of thermal expansion, so when the various modules mentioned above are subjected to a thermal cycle, there is a risk that cracks may occur in the solder layer due to thermal stress. there were.

Therefore, for example, Patent Documents 2 and 3 propose techniques for suppressing the occurrence of cracks in the solder layer due to thermal stress during thermal cycle loads.
Patent Document 2 proposes a technique for alleviating thermal stress acting on a solder layer by forming a low elasticity resin layer that does not contain filler.
Patent Document 3 proposes a technique for alleviating thermal stress acting on a solder layer by reducing the elasticity of the entire insulating resin layer.

Japanese Patent Application Publication No. 2015-207666 Japanese Patent Application Publication No. 2012-129445 Japanese Patent Application Publication No. 2007-149870

Incidentally, recently, there has been a tendency for the amount of heat generated from various elements to increase, and an insulated circuit board with excellent heat dissipation characteristics is required more than ever.
Here, in the above-mentioned Patent Document 2, since the filler was not included, the thermal conductivity was low and the heat dissipation characteristics were insufficient.
Further, in Patent Document 3, although a filler is contained, the thermal conductivity is still low, for example, 5 W/(m·K) or less, and the heat dissipation characteristics are insufficient.

This invention was made in view of the above-mentioned circumstances, and even when various elements are bonded to a circuit layer via a solder layer, it is possible to suppress the occurrence of cracks in the solder layer due to thermal stress. Another object of the present invention is to provide an insulated circuit board with excellent heat dissipation characteristics, and a method for manufacturing this insulated circuit board.

In order to solve the above problems, the insulated circuit board of the present invention includes a metal substrate, an insulating resin layer formed on one side of the metal substrate, and an insulating resin layer formed on the opposite side of the metal substrate. an insulated circuit board comprising: a circuit layer having a circuit pattern formed on a surface; the insulating resin layer has a thermal conductivity of 10 W/(m·K) or more; has a copper layer disposed on the insulating resin layer side and an aluminum layer laminated on the copper layer, and the aluminum layer is made of aluminum having an elastic modulus of less than 100 MPa in a plastic deformation region. The thickness ta of the copper layer is within the range of 0.25 mm or more and 5.0 mm or less, the thickness tb of the aluminum layer is within the range of 0.02 mm or more and 0.3 mm or less; The ratio ta/tb between the layer thickness ta and the aluminum layer thickness tb is within the range of 2.5 or more and 15 or less, and the bonding interface between the copper layer and the aluminum layer contains Cu and An intermetallic compound layer made of an intermetallic compound of Al is formed, and this intermetallic compound layer is characterized by a structure in which intermetallic compounds of a plurality of phases are laminated.

According to the insulated circuit board having this configuration, the insulating resin layer is made of a resin having a thermal conductivity of 10 W/(m·K) or more, and the insulating resin layer has excellent thermal conductivity. Further, the circuit layer has a copper layer disposed on the side of the insulating resin layer, and the copper layer with high thermal conductivity allows heat to spread in the plane direction. Therefore, the insulated circuit board has particularly excellent heat dissipation characteristics.
Further, the circuit layer has an aluminum layer laminated on the copper layer, and a solder layer is formed on this aluminum layer. Since the above-mentioned aluminum layer is made of aluminum having an elastic modulus of less than 100 MPa in the plastic deformation region, the aluminum layer can relieve thermal stress acting on the solder layer during thermal cycle loads.
Therefore, even if a thermal cycle is applied, it is possible to suppress the occurrence of cracks in the solder layer.

Here, in the insulated circuit board of the present invention, it is preferable that the ratio ta/tb of the thickness ta of the copper layer to the thickness tb of the aluminum layer is 10 or less.
In this case, the ratio ta/tb of the thickness ta of the copper layer and the thickness tb of the aluminum layer is set to 10 or less, and the aluminum layer is formed to have a sufficient thickness with respect to the copper layer. In the solder layer, it is possible to reliably relieve the thermal stress that acts on the solder layer during thermal cycle loads.

Further, in the insulated circuit board of the present invention, it is preferable that the thickness ta of the copper layer is 0.3 mm or more.
In this case, the thickness ta of the copper layer is set to 0.3 mm or more, and the thickness of the copper layer is ensured, so that heat can be efficiently spread in the plane direction in the copper layer, and the heat dissipation characteristics are improved. It can definitely be improved.

The method for manufacturing an insulated circuit board of the present invention is a method for manufacturing an insulated circuit board for manufacturing the above-described insulated circuit board, in which a laminated copper plate and an aluminum plate are pressurized in the lamination direction and heated. a laminate forming step in which a laminate of copper and aluminum is formed by solid phase diffusion bonding with an aluminum plate; a metal piece forming step in which the laminate is processed to form a metal piece constituting the circuit layer; a resin composition disposing step of disposing a resin composition on one surface of the metal substrate; disposing the metal pieces in a pattern on one surface of the resin composition; and a metal piece disposing a pressing member. and a pressing member arranging step, pressurizing the metal substrate, the resin composition, the metal piece, and the pressing member in the stacking direction and heating them to cure the resin composition and form the insulating resin layer, The method is characterized by comprising a resin curing step for joining the metal substrate, the insulating resin layer, and the insulating resin layer to the metal piece.

As described above, the method for manufacturing an insulated circuit board having this configuration includes a laminate forming step of forming a laminate of copper and aluminum, a metal piece forming step of forming metal pieces constituting the circuit layer, and a resin a resin composition arranging step of arranging the composition; a metal piece and pressing member arranging step of arranging a metal piece and a pressing member on one side of the resin composition; and a resin curing step of curing the resin composition. , it is possible to manufacture an insulated circuit board having the above configuration.
Further, the circuit pattern is formed without etching, and even if the circuit layer is composed of a laminate of a copper layer and an aluminum layer, the circuit pattern can be formed with high precision.
Furthermore, since the metal substrate, the resin composition, the metal piece, and the pressing member are pressurized in the lamination direction, the resin composition can be sufficiently pressurized and the resin composition can be reliably cured. The insulation properties of the insulating resin layer can be ensured.

According to the present invention, even when various elements are bonded to the circuit layer via the solder layer, the occurrence of cracks in the solder layer due to thermal stress can be suppressed, and the insulated circuit board has excellent heat dissipation characteristics. Furthermore, it is possible to provide a method for manufacturing this insulated circuit board.

FIG. 1 is a schematic explanatory diagram of a power module including an insulated circuit board according to an embodiment of the present invention. FIG. 1 is a schematic explanatory diagram of an insulated circuit board according to an embodiment of the present invention. FIG. 2 is a flow diagram illustrating a method for manufacturing an insulated circuit board according to an embodiment of the present invention. FIG. 1 is a schematic explanatory diagram of a method for manufacturing an insulated circuit board according to an embodiment of the present invention. FIG. 1 is a schematic explanatory diagram of a method for manufacturing an insulated circuit board according to an embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the attached drawings.
FIG. 1 shows an insulated circuit board 10 according to an embodiment of the present invention and a power module 1 using this insulated circuit board 10.

The power module 1 shown in FIG. 1 includes an insulated circuit board 10, a semiconductor element 3 bonded to one surface (upper surface in FIG. 1) of the insulated circuit board 10 via a first solder layer 2, and an insulated circuit board 10. 10 (lower side in FIG. 1) is provided with a heat sink 31 bonded to the other side (lower side in FIG. 1) via a second solder layer 32.

The semiconductor element 3 is an electronic component including a semiconductor, and various semiconductor elements are selected depending on the required function.
Here, the insulated circuit board 10 and the semiconductor element 3 are bonded via the first solder layer 2. This first solder layer 2 is made of, for example, a Sn-Ag-based, Sn-Cu-based, Sn-In-based, or Sn-Ag-Cu-based solder material (a so-called lead-free solder material).

The heat sink 31 is for dissipating heat on the insulated circuit board 10 side. The heat sink 31 is made of copper, copper alloy, aluminum, aluminum alloy, or the like, which has good thermal conductivity. In this embodiment, the heat sink is made of oxygen-free copper. Note that the thickness of the heat sink 31 is set within a range of 3 mm or more and 10 mm or less.
Here, the insulated circuit board 10 and the heat sink 31 are bonded via the second solder layer 32. Like the solder layer 2 described above, this second solder layer 32 is made of Sn-Ag-based, Sn-Cu-based, Sn-In-based, or Sn-Ag-Cu-based solder material (so-called lead-free solder material). Can be configured.

As shown in FIGS. 1 and 2, the insulated circuit board 10 of this embodiment includes a metal substrate 11 and an insulating resin formed on one surface (the upper surface in FIGS. 1 and 2) of the metal substrate 11. layer 12, and a circuit layer 15 formed on one surface (the upper surface in FIGS. 1 and 2) of the insulating resin layer 12.

The metal substrate 11 has the effect of improving heat dissipation characteristics by spreading the heat generated in the semiconductor element 3 mounted on the insulated circuit board 10 in the surface direction. Therefore, the metal substrate 11 is made of a metal with excellent thermal conductivity, such as copper or a copper alloy, aluminum or an aluminum alloy. In this embodiment, it is made of a rolled plate of oxygen-free copper.
Further, the thickness of the metal substrate 11 is set within a range of 0.05 mm or more and 3 mm or less, and in this embodiment, it is set to 0.3 mm.

The insulating resin layer 12 prevents electrical connection between the circuit layer 15 and the metal substrate 11, and is made of an insulating thermosetting resin. This insulating resin layer 12 has a thermal conductivity of 10 W/(m·K) or more.
In this embodiment, in order to ensure the strength and thermal conductivity of the insulating resin layer 12, a thermosetting resin containing a filler is used.
Here, as the filler, for example, alumina, boron nitride, aluminum nitride, etc. can be used. Furthermore, as the thermosetting resin, epoxy resin or the like can be used. In this embodiment, the insulating resin layer 12 is made of epoxy resin containing alumina as a filler.
Further, the thickness of the insulating resin layer 12 is within a range of 20 μm or more and 250 μm or less, and in this embodiment, it is 60 μm.

As shown in FIGS. 1 and 2, the circuit layer 15 has a laminated structure including a copper layer 15a disposed on the insulating resin layer 12 side and an aluminum layer 15b laminated on the copper layer 15a. There is. That is, the semiconductor element 3 is mounted on the aluminum layer 15b via the first solder layer 2.
The copper layer 15a is made of copper or a copper alloy, and in this embodiment is a rolled plate of oxygen-free copper.
The aluminum layer 15b is made of aluminum with an elastic modulus of less than 100 MPa in the plastic deformation region, and in this embodiment is made of 4N aluminum (the above-mentioned elastic modulus of 38 MPa) with a purity of 99.99 mass% or more.
The elastic modulus of the aluminum layer 15a in the plastic deformation region is the slope from 0.2% yield strength to the maximum tensile strength in the stress strain diagram.

Here, the thickness ta of the copper layer 15a is preferably within the range of 0.25 mm or more and 5.0 mm or less.
Note that the lower limit of the thickness ta of the copper layer 15a is preferably 0.3 mm or more, and more preferably 0.5 mm or more. On the other hand, the upper limit of the thickness ta of the copper layer 15a is preferably 2.0 mm or less, more preferably 1.5 mm or less.

Moreover, it is preferable that the thickness tb of the aluminum layer 15b is within the range of 0.02 mm or more and 0.3 mm or less.
Note that the lower limit of the thickness tb of the aluminum layer 15b is preferably 0.05 mm or more, and more preferably 0.1 mm or more. On the other hand, the upper limit of the thickness tb of the aluminum layer 15b is preferably 0.2 mm or less, more preferably 0.15 mm or less.

Further, the ratio ta/tb between the thickness ta of the copper layer 15a and the thickness tb of the aluminum layer 15b is preferably in the range of 2.5 or more and 15 or less.
Note that the lower limit of the above-mentioned thickness ratio ta/tb is preferably 3 or more, and more preferably 5 or more. On the other hand, the upper limit of the thickness ratio ta/tb is preferably 12.5 or less, more preferably 10 or less.

In this embodiment, the copper layer 15a and the aluminum layer 15b constituting the circuit layer 15 are bonded by solid phase diffusion bonding, and the bonding interface between the copper layer 15a and the aluminum layer 15b contains Cu and Al. An intermetallic compound layer (not shown) made of an intermetallic compound is formed. Note that this intermetallic compound layer is composed of intermetallic compounds of multiple phases, and specifically, it has a structure in which η ₂ phase, ζ ₂ phase, δ phase, γ ₂ phase, etc. are laminated. .

Moreover, as shown in FIG. 5, this circuit layer 15 is a laminated layer in which a copper layer 25a and an aluminum layer 25b are laminated on one surface (the upper surface in FIG. 5) of the insulating resin layer 12 (resin composition 22). It is formed by joining the metal pieces 25 of the structure.
In this circuit layer 15, a circuit pattern is formed by arranging the metal pieces 25 described above in a pattern.

Next, a method for manufacturing the insulated circuit board 10 according to this embodiment will be described with reference to FIGS. 3 to 5.

(Laminated board forming process S01)
First, as shown in FIGS. 3 and 4, a copper plate 35a made of oxygen-free copper and an aluminum plate 35b made of 4N aluminum are laminated and bonded to form a laminate 35.
In this embodiment, the laminated plate 35 is formed by solid-phase diffusion bonding the copper plate 35a and the aluminum plate 35b.

In this laminate forming step S01, an aluminum plate 35b is laminated on the copper plate 35a. At this time, it is preferable that the bonding surfaces of the copper plate 35a and the aluminum plate 35b are smoothed by removing scratches on the surfaces in advance.
Then, the laminated copper plate 35a and aluminum plate 35b are pressurized (0.1 MPa or more and 3.5 MPa or less) in the lamination direction and heated to solid phase diffusion bond the copper plate 35a and aluminum plate 35b. get.
Here, the bonding conditions for solid-phase diffusion bonding are preferably such that the heating temperature is 400° C. or more and less than 548° C., and the holding time at the heating temperature is 5 minutes or more and 240 minutes or less.

(Metal piece forming step S02)
Next, the metal piece 25 that will become the circuit layer 15 is formed by punching the laminate 35 described above.
In this embodiment, as shown in FIG. 4, a metal piece 25 having a predetermined shape is punched out from the laminate plate 35 by sandwiching and shearing the laminate plate 35 using a convex die 52 and a concave die 53 of a punching machine 51. Thereby, a metal piece 25 having a laminated structure of a copper layer 25a and an aluminum layer 25b is obtained.

(Resin composition placement step S03)
Next, as shown in FIGS. 3 and 5, a resin composition 22 containing a filler, a thermosetting resin, and a curing agent is applied to one surface (the upper surface in FIG. 5) of the metal substrate 11. Place the sheet material. At this time, the thickness t0 of the resin composition 22 is within the range of 40 μm or more and 500 μm or less.
Furthermore, in this embodiment, alumina and boron nitride are used as fillers. Furthermore, epoxy resin is used as the thermosetting resin.

(Metal piece and pressing member arrangement step S04)
Next, a plurality of metal pieces 25 are arranged in a circuit pattern on one surface (the upper surface in FIG. 5) of the resin composition 22 described above, and a pressing member 40 is arranged in an area other than the metal pieces 25.
The pressing member 40 is designed to have the same thickness as the metal piece 25, and specifically, the thickness tolerance between the pressing member 40 and the metal piece 25 is within 0.03 mm.

(Resin curing step S05)
Next, the metal substrate 11, the resin composition 22, the metal piece 25, and the pressing member 40 are pressed and heated in the stacking direction to harden the resin composition 22 to form the insulating resin layer 12, and the metal substrate 11 and the insulating resin layer 12, and the insulating resin layer 12 and the metal piece 25 are bonded.
In this resin curing step S05, the heating temperature is within the range of 120°C or more and 250°C or less, and the holding time at the heating temperature is within the range of 10 minutes or more and 180 minutes or less. Further, the pressure load in the stacking direction is within a range of 1 MPa or more and 5 MPa or less.
Here, in this resin curing step S05, the ratio t1/t0 of the thickness t0 of the resin composition 22 before curing to the thickness t1 of the insulating resin layer 12 after curing is 0.8 or less. It is preferable to press the metal substrate 11, the resin composition 22, the metal piece 25, and the pressing member 40 in the stacking direction.

In the manner described above, the insulated circuit board 10 of this embodiment is manufactured.

(Heat sink bonding process S06)
Next, the metal substrate 11 and the heat sink 31 are laminated with a solder material interposed therebetween, and they are soldered together in a reduction furnace.

(Semiconductor element bonding process S07)
Next, the semiconductor element 3 is laminated on the circuit layer 15 via a solder material, and the semiconductor element 3 is soldered in a reducing furnace.
The power module 1 of this embodiment is manufactured as described above.

According to the insulated circuit board 10 according to the present embodiment configured as above, the insulating resin layer 12 is made of a resin having a thermal conductivity of 10 W/(m·K) or more. The layer 12 has excellent thermal conductivity. Furthermore, since the circuit layer 15 includes the copper layer 15a, the heat from the semiconductor element 3 can be efficiently spread in the plane direction by the copper layer 15a. Therefore, it is possible to provide an insulated circuit board 10 with excellent heat dissipation characteristics.

In the insulated circuit board 10 according to the present embodiment, the circuit layer 15 includes a copper layer 15a disposed on the insulating resin layer 12 side, and an aluminum layer 15b laminated on the copper layer 15a. The semiconductor element 3 is bonded to the layer 15b via the first solder layer 2, and since the aluminum layer 15b is made of aluminum having an elastic modulus of less than 100 MPa in the plastic deformation region, the first Thermal stress acting on the solder layer 2 can be sufficiently alleviated by this aluminum layer 15b. Therefore, even if a thermal cycle is applied, the occurrence of cracks in the first solder layer 2 can be suppressed.

Furthermore, in the present embodiment, if the ratio ta/tb between the thickness ta of the copper layer 15a and the thickness tb of the aluminum layer 15b is 10 or less, a sufficient thickness is provided for the copper layer 15a. This means that the aluminum layer 15b is formed, and the thermal stress acting on the first solder layer 2 can be reliably alleviated in the aluminum layer 15b.

Further, in this embodiment, when the thickness ta of the copper layer 15a is set to 0.3 mm or more, the thickness of the copper layer 15a is ensured, and the copper layer 15a is efficiently heated. can be expanded in the plane direction, and the heat dissipation characteristics can be reliably improved.

Furthermore, according to the method for manufacturing an insulated circuit board according to the present embodiment, a laminate forming step S01 in which a laminate 35 is formed by solid-phase diffusion bonding of a copper plate 35a and an aluminum plate 35b, and a metal plate forming the circuit layer 15 are performed. A metal piece forming step S03 in which the piece 25 is formed, a resin composition placement step S03 in which the resin composition 22 is placed, and a metal piece and pressing step in which the metal piece 25 and the pressing member 40 are placed on one side of the resin composition 22. Since it includes the member arrangement step S04 and the resin curing step S05 of curing the resin composition 22 to form the insulating resin layer 12, it is possible to manufacture the above-mentioned insulated circuit board 10.

Further, the circuit pattern is formed without etching, and even if the circuit layer 15 is composed of a laminate of the copper layer 15a and the aluminum layer 15b, the circuit pattern can be formed with high precision. Become.
Furthermore, since the metal substrate 11, the resin composition 22, the metal piece 25, and the pressing member 40 are pressurized in the lamination direction, the resin composition 22 can be reliably cured by sufficiently pressurizing the resin composition 22. Therefore, the insulation properties of the insulating resin layer 12 can be ensured.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical idea of the invention.
Although the present embodiment has been described as a power module configured by mounting a semiconductor element on an insulated circuit board, the present invention is not limited to this. For example, an LED module may be constructed by mounting an LED element on a circuit layer of an insulated circuit board, or a thermoelectric module may be constructed by mounting a thermoelectric element on a circuit layer of an insulated circuit board.

Further, in this embodiment, the metal substrate is described as being made of copper or a copper alloy, but it is not limited to this, and may be made of other metals such as aluminum or aluminum alloy. You can. Alternatively, it may have a structure in which a plurality of metals are laminated.

Further, in this embodiment, the resin composition constituting the insulating resin layer is described as using an epoxy resin containing alumina and boron nitride as inorganic fillers, but the insulating resin layer is not limited to this. Any material may be used as long as the layer has a thermal conductivity of 10 W/(m·K) or more and can insulate the circuit layer and the metal substrate.

Further, in this embodiment, the aluminum layer is made of 4N aluminum with a purity of 99.99 mass% or more, but the aluminum layer is not limited to this, and may be made of aluminum with an elastic modulus of less than 100 MPa in the plastic deformation region. Bye.
Further, in this embodiment, the copper layer is described as being made of oxygen-free copper, but the copper layer is not limited to this, and may be made of other copper or copper alloy such as tough pitch copper.

Furthermore, in this embodiment, a metal piece and a pressing member having approximately the same height as the metal piece are arranged on one side of the resin composition, and the resin composition is pressed in the stacking direction. However, the method is not limited to this, and other methods may be used as long as they can uniformly press the entire surface of the resin composition.

Below, the results of a confirmation experiment conducted to confirm the effects of the present invention will be explained.

According to the method for manufacturing an insulated circuit board according to the present embodiment described above, an insulating resin layer shown in Table 1 is formed on one side of a metal substrate made of a rolled plate of oxygen-free copper (40 mm x 40 mm, thickness 2.0 mm). An insulated circuit board was manufactured in which a circuit layer (37 mm x 37 mm, thickness shown in Table 2) shown in Table 2 was formed on this insulating resin layer. Note that the resin curing step was carried out under the conditions shown in Table 3.
The thermal conductivity of the insulating resin layer was determined by measuring the thermal diffusivity using the laser flash method in an air atmosphere at room temperature (25°C), measuring the specific heat using DSC, and measuring the density using the Archimedes method. Calculated from.
Note that the elastic modulus (elastic modulus in the plastic deformation region) of the second layer (aluminum layer) was calculated as the slope from 0.2% proof stress to the maximum tensile strength by creating a stress strain diagram.

A semiconductor element (6 mm x 6 mm) was soldered onto the circuit layer of the obtained insulated circuit board using a solder material (Eco Solder Pellet SM725 manufactured by Senju Metal Industry Co., Ltd.). Note that the thickness of the solder layer was 1.5 mm.
The soldering conditions were such that the atmosphere was a mixed atmosphere of nitrogen and hydrogen (nitrogen:hydrogen = 1:3 in volume ratio), the temperature was raised from room temperature and held at 210°C for 10 minutes, and then held at 310°C for 5 minutes. Note that the temperature increase rate was 10° C./min.

Then, the heat dissipation characteristics of the insulated circuit board were evaluated using the ΔVF method. The ΔVf method evaluates heat dissipation characteristics using the temperature dependence of the rising voltage Vf of a semiconductor element from the forward direction, and measures the change in Vf (ΔVf) before and after power is applied for a certain period of time. If this ΔVf is small, the temperature rise of the element will be small, and the heat dissipation characteristics of the insulated circuit board will be good. The evaluation results are shown in Table 3.

Furthermore, the insulated circuit board to which the semiconductor element was bonded was subjected to 2000 cycles of a cooling/heating cycle of -40°C x 5.5 minutes←→150°C x 4.0 minutes. Thereafter, the solder layer was observed using transmitted X-rays, and the bonding rate was calculated from the following formula. Here, the initial bonding area is defined as the area to be bonded before bonding, that is, the area of the solder layer. Note that if there are many cracks in the solder layer, the bonding rate will decrease. The evaluation results are shown in Table 3.
Bonding rate (%) = {(Initial bonding area) - (Peeling area)}/(Initial bonding area) x 100

In Comparative Example 1 in which the circuit layer was composed of only a copper layer, many cracks were observed in the solder layer after the thermal cycle load, and the bonding rate was significantly reduced.
In Comparative Examples 2 and 3, in which the circuit layer had a laminated structure of a copper layer and an aluminum layer, and the elastic modulus of the aluminum layer in the plastic deformation region was 100 MPa or more, many cracks were observed in the solder layer after thermal cycle loading. The bonding rate decreased significantly. It is presumed that this is because the aluminum layer was not able to sufficiently alleviate thermal stress.

In Comparative Example 4 in which the circuit layer was composed of only an aluminum layer, the heat dissipation characteristics were insufficient. It is presumed that this was because the heat could not be sufficiently spread in the plane direction.
In Comparative Example 5, in which the thermal conductivity of the insulating resin layer was less than 10 W/(m·K), the heat dissipation properties were insufficient. It is presumed that this is because the insulating resin layer has a thermal resistance.

In contrast, the circuit layer has a laminated structure of a copper layer and an aluminum layer, and the elastic modulus of the aluminum layer in the plastic deformation region is less than 100 MPa, and the thermal conductivity of the insulating resin layer is 10 W/(m・K) or more. In Examples 1 to 7 of the present invention, there were few cracks in the solder layer after the thermal cycle load, and the bonding rate was sufficiently maintained. Moreover, the heat dissipation properties were sufficiently excellent.
In addition, in Examples 1-5 and 7 of the present invention in which the ratio ta/tb between the thickness ta of the copper layer and the thickness tb of the aluminum layer was set to 10 or less, cracks in the solder layer did not occur after the thermal cycle load. It was further suppressed, and the bonding rate became even higher.
Furthermore, in Examples 1 to 6 of the present invention in which the thickness ta of the copper layer was 0.3 mm or more, the heat dissipation characteristics were even more excellent.

From the above, according to the example of the present invention, even when various elements are bonded to a circuit layer via a solder layer, cracks in the solder layer due to thermal stress can be suppressed, and the heat dissipation properties can be improved. It has been confirmed that it is possible to provide an excellent insulated circuit board and a method for manufacturing this insulated circuit board.

10 Insulated circuit board 11 Metal substrate 12 Insulating resin layer 15 Circuit layer 15a Copper layer 15b Aluminum layer 22 Resin composition 25 Metal piece 35 Laminated plate 40 Pressing member

Claims (4)

A metal substrate, an insulating resin layer formed on one side of the metal substrate, and a circuit layer having a circuit pattern formed on a side of the insulating resin layer opposite to the metal substrate. An insulated circuit board,
The insulating resin layer has a thermal conductivity of 10 W/(m·K) or more,
The circuit layer includes a copper layer disposed on the insulating resin layer side and an aluminum layer laminated on the copper layer, and the aluminum layer has an elastic modulus of less than 100 MPa in a plastic deformation region. Constructed of aluminum
The thickness ta of the copper layer is within the range of 0.25 mm or more and 5.0 mm or less, the thickness tb of the aluminum layer is within the range of 0.02 mm or more and 0.3 mm or less, and the thickness of the copper layer is The ratio ta/tb of ta to the thickness tb of the aluminum layer is within a range of 2.5 or more and 15 or less,
An intermetallic compound layer made of an intermetallic compound of Cu and Al is formed at the bonding interface between the copper layer and the aluminum layer. An insulated circuit board characterized by having the following configuration . The insulated circuit board according to claim 1, wherein the ratio ta/tb of the thickness ta of the copper layer and the thickness tb of the aluminum layer is 10 or less. 3. The insulated circuit board according to claim 1, wherein the copper layer has a thickness ta of 0.3 mm or more. A method for manufacturing an insulated circuit board for manufacturing the insulated circuit board according to any one of claims 1 to 3, comprising:
A laminate forming step in which the laminated copper plate and aluminum plate are pressurized in the lamination direction and heated to solid phase diffusion bond the copper plate and the aluminum plate to form a copper and aluminum laminate;
a metal piece forming step of processing the laminate to form metal pieces constituting the circuit layer;
a resin composition placement step of placing a resin composition on one surface of the metal substrate;
a metal piece and pressing member arranging step of arranging the metal pieces in a pattern on one surface of the resin composition and arranging a pressing member;
The metal substrate, the resin composition, the metal piece, and the pressing member are pressed and heated in the stacking direction to harden the resin composition to form the insulating resin layer, and the metal substrate and the insulating resin are heated. a resin curing step of joining the insulating resin layer and the metal piece;
A method for manufacturing an insulated circuit board, comprising:

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