JP7147610B2 - Insulated circuit board and its manufacturing method - Google Patents

Description

The present invention relates to an insulated circuit board such as a power module board and a method for manufacturing the same.

As an insulating circuit board, a power module board is known in which a circuit layer is bonded to one surface of an insulating substrate made of a ceramic substrate such as aluminum nitride, and a metal layer is bonded to the other surface. In such a power module substrate, aluminum or copper is used for the circuit layer. Each is composed of pure copper with a purity of 99.99% or higher. Such copper is superior to aluminum in thermal and electrical properties, but has high deformation resistance. Therefore, when a thermal cycle is applied, a large thermal stress is generated between the ceramic substrate and the copper circuit layer, and cracks are likely to occur in the ceramic substrate.

In recent years, an insulating circuit board has been used in which an aluminum layer made of aluminum or an aluminum alloy is bonded to the surface of a ceramic substrate, and a copper layer made of copper or a copper alloy is solid phase diffusion bonded to the upper surface of the ceramic substrate. In 2, the circuit layer formed on one side of the insulating layer (ceramic substrate) of the power module substrate is combined with an aluminum layer provided on one side of the insulating layer and one side of this aluminum layer (insulating layer It has a double structure with a copper layer laminated on the side that is not joined to the surface), and an aluminum layer, which has a smaller deformation resistance than copper, is interposed between the insulating layer and the thermal stress. Therefore, the thickness of the copper layer can be set to, for example, 1.0 mm or more, and an insulated circuit board with low thermal resistance can be obtained. In addition, in the configuration of Patent Document 2, since the semiconductor element is mounted on the copper layer of the circuit layer, by making the circuit layer a double structure, when heat generated in the semiconductor element is transferred, It spreads in the plane direction in the copper layer and diffuses efficiently.

JP 2004-221547 A WO2013/147144

However, even if copper layers are bonded via an aluminum layer that has a stress buffering function, residual stress (tensile The ceramic substrate may crack due to warping change during heating.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an insulated circuit board and a method of manufacturing the same that can suppress cracking of a ceramic substrate.

An insulated circuit board of the present invention is an insulated circuit board in which a circuit layer is formed on one surface of a ceramics substrate and a metal layer is formed on the other surface of the ceramics substrate, wherein the circuit layer is the ceramics substrate. and a first copper layer made of copper or a copper alloy solid-phase diffusion-bonded to the first aluminum layer, wherein the ceramic substrate comprises a first The circuit layer is divided into a plurality of ceramic pieces by one dividing groove, and the circuit layer is divided into a plurality of circuit patterns by a second dividing groove, and the first dividing groove of the ceramic substrate corresponds to the second dividing groove of the circuit layer. and an independent portion formed by extending the overlapping portion to a location different from the second dividing groove, and the independent portion includes along the dividing groove The first aluminum layer is divided, and the first copper layer is disposed over the dividing grooves.

In the present invention, the single portion of the first dividing groove is formed in a portion different from the second dividing groove that divides the circuit layer into a plurality of circuit patterns, and the first aluminum layer is divided in the single portion. Even if thermal expansion and contraction occurs in a plurality of circuit patterns, thermal stress is less likely to occur in the ceramic substrate. Therefore, it is possible to suppress cracking of the ceramic substrate due to warp change during heating.

As a preferred aspect of the insulated circuit board of the present invention, the first dividing groove may be formed parallel to the sides of the ceramic substrate.

In the above aspect, since the first dividing grooves are formed in parallel with the sides of the ceramic substrate, it becomes easy to manufacture the insulated circuit substrate.

As a preferable aspect of the insulated circuit board of the present invention, the thickness of the first copper layer is preferably 0.8 mm or more and 3.0 mm or less.

If the thickness of the first copper layer is less than 0.8 mm, the thermal stress generated in the plurality of circuit patterns of the circuit layer divided by the second dividing grooves is small, so there is little need to take the above measures. On the other hand, if the thickness of the first copper layer exceeds 3.0 mm, the thermal stress generated in the plurality of circuit patterns is large. A crack may occur in the ceramic substrate at the center.

A method for manufacturing an insulated circuit board according to the present invention comprises: a first aluminum layer made of aluminum or an aluminum alloy on one side of a ceramic substrate; A second aluminum layer made of aluminum or an aluminum alloy is formed on the other surface of the ceramic substrate, and a second aluminum layer made of copper or a copper alloy is solid phase diffusion bonded to the second aluminum layer. A method for manufacturing an insulated circuit board on which a metal layer consisting of two copper layers is formed, wherein the first aluminum layer is bonded to one surface of the ceramic substrate, and the first aluminum layer is bonded to the other surface of the ceramic substrate. After bonding the two aluminum layers, the ceramic substrate is divided by the first dividing grooves to form a plurality of ceramic pieces, and the second dividing grooves are arranged to partially overlap the first dividing grooves to form the second dividing grooves. a dividing step of dividing one aluminum layer to form a plurality of patterns; The first copper layer is superimposed on the upper surface of the laminate to form a laminate, and the laminate is pressurized and heated to form the first aluminum layer and the first copper layer, and the second aluminum layer and the second a bonding step of solid-phase diffusion bonding a copper layer, wherein the first dividing groove for dividing the ceramic substrate in the dividing step includes an overlapping portion arranged to overlap with the second dividing groove; and a single portion formed by extending the overlapping portion to a location different from the dividing groove, and the first copper layer in the bonding step has a plurality of patterns that are the same as the plurality of patterns of the first aluminum layer. At least one of them is placed across the dividing groove and joined to the single portion.

In the present invention, a ceramic piece in which the first aluminum layer and the second aluminum layer divided into a plurality of patterns by the second dividing grooves are joined is arranged on the second copper layer, and the first copper layer is arranged thereon. Then, they can be integrated by a method of pressurization and heating. In this case, it is sufficient to devise only the arrangement of the dividing grooves, and the bonding process itself is the same as that for a normal two-layer laminated structure of aluminum and copper, and no special equipment is required.

According to the present invention, it is possible to suppress cracking of the ceramic substrate caused by thermal stress occurring in the circuit pattern of the circuit layer.

1 is a diagram of an insulated circuit board on which a plurality of circuit patterns are formed according to an embodiment of the present invention, viewed from the circuit layer side; FIG. 2 is a cross-sectional view of the insulated circuit board shown in FIG. 1 taken along line A1-A1. FIG. 2 is a cross-sectional view of the insulated circuit board shown in FIG. 1 taken along line B1-B1; FIG. 2 is a cross-sectional view taken along line C1-C1 of the insulated circuit board shown in FIG. 1; FIG. It is a figure which shows the manufacturing method of the insulation circuit board in the said embodiment. It is the figure which looked at the insulation circuit board in the 1st modification of the said embodiment from the circuit layer side. It is the figure which looked at the insulation circuit board in the 2nd modification of the said embodiment from the circuit layer side.

An embodiment of the present invention will be described below with reference to the drawings.

[Schematic configuration of insulated circuit board]
FIG. 1 is a plan view of an insulating circuit board 1 formed with a plurality of circuit patterns according to the present embodiment, viewed from the circuit layer 12 side, and FIG. 3 is a cross-sectional view of the insulating circuit board 1 along line B1-B1, and FIG. 4 is a cross-sectional view of the insulating circuit board 1 along line C1-C1.

As shown in FIG. 1, the insulating circuit board 1 is formed in a rectangular shape with a vertical dimension of 70 mm and a horizontal dimension of 36 mm in plan view. As shown in FIGS. 2 to 4, such an insulating circuit board 1 includes a ceramic substrate 11, a circuit layer 12 formed on one surface of the ceramic substrate 11, and a circuit layer 12 formed on the other surface of the ceramic substrate 11. and a metal layer 13 . The circuit layer 12 and the metal layer 13 are formed in rectangular plate shapes slightly smaller than the ceramic substrate 11 .

The ceramic substrate 11 is made of a ceramic material such as aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), etc., and has a thickness of 0.3 mm to 1.0 mm. . Also, the ceramic substrate 11 is formed in a rectangular plate shape in a plan view, and is slightly larger than each of the circuit layer 12 and the metal layer 13 . Also, the ceramic substrate 11 is divided into three ceramic pieces 101 to 103 by a plurality of first dividing grooves L1. These first dividing grooves L1 are formed so as to traverse along the width direction of the insulating circuit board 1, and the respective first dividing grooves L1 are formed parallel to each other.

The circuit layer 12 includes a first aluminum layer 121 made of aluminum or an aluminum alloy formed on the ceramic substrate 11, a first copper layer 122 made of copper or a copper alloy solid phase diffusion bonded to the first aluminum layer 121, have. The circuit layer 12 is divided into a plurality (three) of circuit patterns P1 to P3 by the second dividing grooves L2. For example, as shown in FIG. 1, a rectangular circuit pattern P2, a circuit pattern P1 surrounding three sides of the circuit pattern P2, and a rectangular circuit pattern P3 spaced apart from the end of the circuit pattern P1. , is divided by the second dividing groove L2.

The metal layer 13 includes a second aluminum layer 131 made of aluminum or an aluminum alloy formed on the ceramic substrate 11, a second copper layer 132 made of copper or a copper alloy solid phase diffusion bonded to the second aluminum layer 131, have. Among them, the second aluminum layer 131 is divided together with the ceramic substrate 11 by the first dividing grooves L1. On the other hand, the second copper layer 132 is not divided into either the first dividing groove L1 or the second dividing groove L2. That is, it exists as one copper plate.

The thickness of the first aluminum layer 121 and the second aluminum layer 131 is set to 0.2 mm or more and 0.6 mm or less, and the thickness of the first copper layer 122 and the second copper layer 132 is set to 0.8 mm or more. It is set to 3.0 mm or less. Among these, when the thickness of the first copper layer 122 is less than 0.8 mm, the thermal stress generated in the plurality of circuit patterns P1 to P3 of the circuit layer 12 divided by the second dividing grooves L2 is small. There is little need to take countermeasures. On the other hand, when the thickness of the first copper layer 122 exceeds 3.0 mm, the thermal stress generated in the plurality of circuit patterns P1 to P3 is large. , cracks may occur in the ceramic substrate 11 at approximately the center of each of the circuit patterns P1 to P3.

[Structure of First Divided Groove]
The first dividing groove L1 is formed parallel to the sides of the ceramic substrate 11 . This first dividing groove L1 is formed, for example, at the position indicated by the dashed line in FIG. 1, and divides the ceramic substrate 11 into three ceramic pieces 101-103. The first dividing groove L1 is arranged to overlap a part of the second dividing groove L2 that divides the circuit layer 12 into the circuit pattern P1 and the circuit pattern P2, and divides the circuit layer 12 into the circuit pattern P2 and the circuit pattern P3. It overlaps with the second dividing groove L2 that divides into two. Among them, the portion of the circuit layer 12 which overlaps with the second division groove L2 is called an overlapping portion L11, and the portion which does not overlap with the second division groove L2 is called an independent portion L12. The independent portion L12 is formed by extending the overlapping portion L11 to a location different from the second dividing groove L2. In this embodiment, as shown in FIGS. 1 to 3, a part of the second dividing groove L2 that divides the circuit layer 12 into the circuit pattern P1 and the circuit pattern P2 divides the ceramic substrate 11 into the ceramic piece 101 and the ceramic piece 101. 102, and the second dividing groove L2 dividing the circuit layer 12 into the circuit pattern P1 and the circuit pattern P3 divides the ceramic substrate 11 into the ceramic piece 102. It is arranged so as to overlap the overlapping portion L11 of the first dividing groove L1 dividing the ceramic piece 103 .

3, the first aluminum layer 121 is divided along the single portion L12 of the first dividing groove L1, and the first copper layer 122 is arranged over the dividing groove. It is That is, on the first dividing groove L1 that divides the ceramic piece 101 and the ceramic piece 102 in the ceramic substrate 11, as shown in FIG. The first copper layer 122 forming the circuit pattern P1 is not divided at the single portion L12 although it is divided by the single portion L12 of the one-dividing groove L1.

[Manufacturing method of insulated circuit board]
Next, a method for manufacturing the insulating circuit board 1 configured as described above will be described. This manufacturing method includes a dividing step of forming a scribe line 111 on a ceramic substrate 11, bonding aluminum plates 121A and 131A to the ceramic substrate 11, and then dividing into a plurality of ceramic pieces 101 to 103; A bonding step of placing the ceramic pieces 101 to 103 on the second copper plate 132A, stacking the first copper plate 122A thereon to form a laminate, and bonding the laminate by applying pressure and heat (FIG. 5 reference). Also, the joining process includes a scribe line forming process, an aluminum layer forming process, and a singulation process.
Each step will be described below in the order of steps.

[Scribing line forming process]
First, as shown in FIG. 5(a), on one side (the side on which the circuit layer 12 is formed) of the ceramic substrate 11 (70 mm long×36 mm wide), the ceramic pieces 101 to 103 are divided. of the scribe line 111 is formed. The scribe line 111 is formed by linearly removing one surface of the ceramic substrate 11 by, for example, irradiating it with a laser beam. These scribe lines 111 are grooves formed in the ceramic substrate 11 and serve as starting points for dividing the ceramic substrate 11 . The scribe line 111 can also be processed by, for example, a _CO2 laser, a YAG laser, a _YVO4 laser, a YLF laser, or the like.

[Aluminum layer forming step]
Next, a first aluminum layer 121 is formed on one surface of the ceramic substrate 11 on which the scribe lines 111 are formed, and a second aluminum layer 131 is formed on the other surface. Specifically, after cleaning the ceramics substrate 11 with a cleaning liquid or the like, a first aluminum plate 121A to be the first aluminum layer 121 is arranged, and a second aluminum plate 131A to be the second aluminum layer 131 is arranged on the other surface. After bonding via a brazing material, the laminate is sandwiched between carbon plates and heated in a vacuum while applying a load in the stacking direction, thereby bonding the ceramic substrate 11 and the aluminum plates 121A and 131A. .

[Singulation process]
Then, as shown in FIG. 5B, the ceramic substrate 11 is divided along scribe lines 111 into a plurality of ceramic pieces 101-103. Also, at this time, the first aluminum layer 121 is divided by the second dividing grooves L2 arranged to partially overlap with the first dividing grooves L1, and a plurality of patterns are formed by, for example, etching.
Although the formation of the plurality of patterns is performed by etching, the patterns may be formed by bonding the first aluminum plate 121A that has been previously divided into a plurality of patterns by the second dividing grooves L2.

[Joining process]
After the dividing step, the plurality of ceramic pieces 101 to 103 are arranged on the second copper plate 132A, which will become the second copper layer 132, at intervals, as shown in FIG. 5(c). Then, the upper surfaces of the plurality of ceramic pieces 101 to 103 are divided by the second dividing grooves L2 to form a first copper layer 122 divided into a plurality of patterns having the same shape as the plurality of patterns of the first aluminum layer 121. A copper plate 122A is placed. At this time, the first copper plate 122A is arranged over the dividing groove L1 in the independent portion L12 of the first dividing groove L1. Then, the first aluminum plate 121A and the first copper plate 122A and the second aluminum plate 131A and the second copper plate 132A are solid-phase diffusion-bonded by applying pressure and heat to this laminate, and the insulated circuit board 1 is manufactured. .

In the present embodiment, a single portion L12 of the first dividing groove L1 is formed at a location different from the second dividing groove L2 that divides the circuit layer 12 into a plurality of circuit patterns. is separated, thermal stress is less likely to occur in the ceramic substrate 11 even if thermal expansion and contraction occurs in a plurality of circuit patterns. Therefore, it is possible to suppress cracking of the ceramic substrate 11 due to warping change during heating. Further, since the first dividing grooves L1 are formed parallel to the sides of the ceramic substrate 11, the manufacturing of the insulating circuit substrate 1 is facilitated. Furthermore, since the thickness of the first copper layer is 0.8 mm or more and 3.0 mm or less, it is possible to suppress the possibility of cracks occurring in the ceramic substrate 11 .

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the above embodiment, the second dividing groove L2 divides the circuit pattern into three circuit patterns P1 to P3. FIG. 6 is a plan view of an insulated circuit board 1A according to a first modified example of the above embodiment viewed from the circuit layer 12A side.
As shown in FIG. 6, the circuit layer 12A of the insulating circuit board 1A is divided into a plurality (five) of circuit patterns P4 to P8 by the second dividing grooves L2. For example, as shown in FIG. 6, the second dividing groove L2 does not straightly cross the width direction of the insulating circuit board 1A, but bends multiple times or surrounds the circuit patterns P6 to P8 in a frame shape. It is a shape that These second dividing grooves L2 extend parallel to the sides of the circuit layer 12A (ceramic substrate 11) and are intricate. The circuit patterns P6, P7, P8 divided by the second dividing grooves L2 are formed in a rectangular shape.

The first dividing grooves L1 are arranged at the same positions as the first dividing grooves L1 of the first embodiment, and part of them overlaps the second dividing grooves L2. Specifically, a part of the second dividing groove L2 that divides the circuit layer 12A into the circuit pattern P4 and the circuit pattern P5, and a first dividing groove L1 that divides the ceramic substrate 11 into the ceramic piece 101 and the ceramic piece 102. are arranged so as to overlap with the overlapping portion L11 of . A part of the second dividing groove L2 that divides the circuit layer 12A into the circuit patterns P6, P7 and the circuit patterns P5, P8, and a first dividing groove that divides the ceramic substrate 11 into the ceramic piece 102 and the ceramic piece 103. The overlapping portion L11 of L1 is overlapped.

FIG. 7 is a plan view of an insulated circuit board 1B according to a second modification of the above embodiment, viewed from the circuit layer 12B side.
As shown in FIG. 7, the circuit layer 12B of the insulating circuit board 1B is divided into a plurality of (two) circuit patterns P9 and P10 by the second dividing grooves L2. For example, as shown in FIG. 7, an L-shaped circuit is formed on the circuit layer 12B. A second dividing groove L2 is formed to divide the pattern P9. The second dividing groove L2 extends parallel to the sides of the circuit layer 12B (ceramic substrate 11).

The first dividing groove L1 is formed in a straight line that divides the ceramic substrate 11 in the horizontal direction, and a part of the first dividing groove L1 overlaps with the second dividing groove L2. Specifically, the laterally extending portion of the second dividing groove L2 dividing the circuit layer 12B into the circuit pattern P9 and the circuit pattern P10, and the first groove dividing the ceramic substrate 11 into the ceramic piece 101B and the ceramic piece 102B. The overlapping portion L11 of the dividing groove L1 is overlapped.

In both the first modified example and the second modified example described above, the ceramic substrate 11 is divided. Since the single portion L12 of the one-divided groove L1 is formed, and the first aluminum layer 121 is divided in the single portion L12, thermal stress is generated in the ceramic substrate 11 even if thermal expansion and contraction occurs in a plurality of circuit patterns. Hateful. Therefore, it is possible to suppress cracking of the ceramic substrate 11 due to warping change during heating.

In the above embodiment, the first dividing grooves L1 are formed parallel to the sides of the ceramic substrate 11, but this is not the only option. It may be formed in a direction intersecting the sides of the ceramic substrate 11 . That is, it may be formed at any position as long as cracking of the ceramic substrate 11 can be suppressed.

In the above embodiment, the ceramic substrate 11, the first aluminum layer 121, and the second aluminum layer 131 are divided by the first dividing groove L1. It does not have to be.

1 1A 1B Insulated circuit board 11 Ceramic board 12 12A 12B Circuit layer 121 First aluminum layer 122 First copper layer 13 Metal layer 131 Second aluminum layer 132 Second aluminum layer 101 102 103 101A 102B Ceramic piece P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 Circuit pattern L1 First division groove L11 Overlapping portion L12 Single portion L2 Second division groove

Claims (4)

An insulated circuit board having a circuit layer formed on one surface of a ceramic substrate and a metal layer formed on the other surface of the ceramic substrate,
The circuit layer has a first aluminum layer made of aluminum or an aluminum alloy formed on the ceramic substrate, and a first copper layer made of copper or a copper alloy solid phase diffusion bonded to the first aluminum layer. death,
The ceramic substrate is divided into a plurality of ceramic pieces by first dividing grooves, and the circuit layer is divided into a plurality of circuit patterns by second dividing grooves,
The first dividing groove of the ceramic substrate includes an overlapping portion arranged to overlap with the second dividing groove of the circuit layer, and a single portion formed by extending the overlapping portion to a location different from the second dividing groove. and
In the isolated circuit board, the first aluminum layer is divided along the dividing groove in the independent portion, and the first copper layer is arranged over the dividing groove. 2. The insulating circuit board according to claim 1, wherein said first dividing grooves are formed parallel to sides of said ceramic substrate. 3. The insulated circuit board according to claim 1, wherein the first copper layer has a thickness of 0.8 mm or more and 3.0 mm or less. A circuit layer comprising a first aluminum layer made of aluminum or an aluminum alloy and a first copper layer made of copper or a copper alloy solid phase diffusion bonded to the first aluminum layer is formed on one surface of a ceramic substrate, A metal layer comprising a second aluminum layer made of aluminum or an aluminum alloy and a second copper layer made of copper or a copper alloy solid phase diffusion bonded to the second aluminum layer is formed on the other surface of the ceramic substrate. A method for manufacturing an insulated circuit board comprising:
After bonding the first aluminum layer to one surface of the ceramic substrate and bonding the second aluminum layer to the other surface of the ceramic substrate, the ceramic substrate is divided by first dividing grooves into a plurality of a dividing step of forming a ceramic piece and dividing the first aluminum layer by a second dividing groove arranged to overlap a part of the first dividing groove to form a plurality of patterns;
After the dividing step, each of the plurality of ceramic pieces is arranged on the second copper layer with a gap therebetween, and the first copper layer is overlapped on the upper surface of the plurality of ceramic pieces to form a laminate, a bonding step of solid-phase diffusion bonding the first aluminum layer and the first copper layer, and the second aluminum layer and the second copper layer by applying pressure and heat to the laminate,
The first dividing groove for dividing the ceramic substrate in the dividing step is formed by extending an overlapping portion arranged to overlap with the second dividing groove and extending the overlapping portion to a location different from the second dividing groove. and
The first copper layer in the bonding step is divided into a plurality of patterns that are the same as the plurality of patterns of the first aluminum layer, and at least one of the patterns is arranged across the dividing groove in the single portion. A method for manufacturing an insulated circuit board, characterized in that the substrates are joined together by

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