Patent Description:
Power module substrate boards in which a circuit layer is bonded on one surface of an insulation layer made of a ceramic substrate board such as aluminum nitride, and a metal layer for heat dissipation is bonded on the other surface are known, and a heat sink is bonded on the metal layer.

For example, in a power module substrate board equipped with a heat sink disclosed in <CIT> related to the preamble of claim <NUM>, a circuit layer having a double structure of an aluminum layer and a copper layer is formed on one surface of an insulating layer made of a ceramic substrate board; on the other surface of the ceramic substrate board (the insulation layer), a metal layer having a double structure of an aluminum layer and a copper layer is bonded; and a heat sink made of aluminum is bonded on this copper layer of the metal layer.

In a method of manufacturing this power module substrate board equipped with a heat sink, aluminum boards are brazed on both surfaces of the ceramic substrate board at first, after that, a copper board is laminated on one side and a copper board and an aluminum board of the heat sink is laminated on the other side, and this laminate is heated with pressed in a lamination direction, so that aluminum and copper is bonded by solid phase diffusion. At this time, in <CIT>, a bonded surface of the heat sink is bonded with formed in a convex shape in accordance with warp of a surface of the metal layer of the power module substrate board occurred by a bonding temperature of the heat sink.

In this solid phase diffusion bonding, the laminate is arranged between a pair of pressing boards which are energized by a spring and given a load by bringing close the pressing boards by energizing by a fixed board fixed on a pair of guide posts provided outside of an outer peripheral of the ceramic substrate board.

However, since the guide posts cannot be arranged right on the laminate, it is difficult to add the load on the inside comparing to the outside of the ceramic substrate board. The ceramic substrate board and the aluminum board can be substantially evenly bonded in a whole surface since a liquid phase is generated by brazing; however, the aluminum layer and the copper layer are bonded by the solid phase, and a contact state thereof largely influences on bonding. By bonding using the above-described pressing boards, the load is biased on the outside of the circuit layer but is not enough on the inside, and bonding defects may occur in other parts than the outside part of the metal layer. Particularly, in a case in which the circuit layer is separated several, sufficient intermetallic composed layers are not generated at inside peripheral edge parts facing a space between adjacent copper boards for circuit layers , and the bonding defects may occur easily.

The present invention is achieved in consideration of the above circumstances, and has an object to prevent the bonding defects by adding the uniform load even on the inner edge parts facing the space between the adjacent copper boards for the circuit layers.

A method of manufacturing a bonded body for an insulation circuit substrate board of the present invention includes steps of: forming an aluminum circuit layer forming a plurality of aluminum circuit layers on one surface on a ceramic substrate board; and a step of forming a copper circuit layer, by laminating copper boards for the circuit layers respectively on the aluminum circuit layers; arranging this laminate between a pair of support boards having a convex curved surface on at least one surface and arranged to face the convex curved surfaces toward each other; and pressing the laminate in a lamination direction by moving the support boards to a facing direction and heating in this pressing state, so as to bond the copper boards on the aluminum circuit layers by solid phase diffusion. In the step of forming the copper circuit layers, the support boards are arranged so that at least one of the convex curved surfaces are in contact with a plurality of the copper boards for the circuit layers adjacent in the laminate.

According to this manufacturing method, in the step of forming copper circuit layers, the convex curved surface of the support board spans and is in contact with the adjacent copper board for circuit layers, so that a load is easy to be added as in the outer peripheral edge parts even in the edge part of the copper board for the circuit layers in a center of the ceramic substrate board where conventionally the load is not easy to be added.

A preferred aspect of the method of manufacturing a bonded body for an insulation circuit substrate board of the present invention is that the convex curved surfaces of the support boards preferably have a curvature radius not less than <NUM> and not more than <NUM>. By the curvature radius in this range, an intermetallic compound layer is formed with a sufficient thickness over the edge parts of the adjacent copper circuit layers and good bonding can be obtained.

A preferred aspect of the method of manufacturing a bonded body for an insulation circuit substrate board of the present invention is that preferably the support boards be made of a carbon material sheet. The carbon material sheet can be a laminate board of one or more carbon sheets and one or more graphite sheets.

By the carbon material sheet, it is possible to prevent the support boards and the laminate from adhering. By cushioning characteristic of the carbon material sheet, a gentle pressing gradient can be obtained in which the load is gradually increases from the outer peripheral side toward the center of the convex curved surface, so that the copper boards for the circuit layers can be pressed even uniformly over a whole surface and bonded.

In the method of manufacturing a bonded body for an insulation circuit substrate board of the present invention, the convex curved surface may be a spherical surface or may be a cylindrical surface. It is appropriate to set the shape of the convex curved surface in accordance with the number and an arrangement state of the copper boards for the circuit layers in the laminate.

In a bonded body for an insulation circuit substrate board of the present invention, in the support boards, the one surface maybe the convex curved surface and the other surface may be a flat surface. For example, among the support boards stacked with the laminates therebetween, the outermost support boards may have a flat surface which does not press the copper boards for the circuit layers; and the pressure from the pressing board can be received on the whole flat surface.

A preferred aspect of the method of manufacturing a bonded body for an insulation circuit substrate board of the present invention is that arranging a pair of the support boards between a pair of pressing boards facing in the lamination direction to each other, holding a pair of the pressing boards so as to approach or be away from each other along the lamination direction on at least two guide post provided along the lamination direction, and pressing the laminate with a pair of the support boards by approaching a pair of the pressing boards each other.

It is difficult to evenly press the laminate between a pair of the pressing boards held by the two guide posts; however, by the convex curved surface of the support boards, it is possible to add a sufficient load even on the center part of the laminates.

A bonded body for an insulation circuit substrate board of the present disclosure includes a ceramic substrate board, a plurality of aluminum circuit layers bonded on one surface of the ceramic substrate board, copper circuit layers bonded on the respective aluminum circuit layers by solid phase diffusion, and intermetallic compound layers between the aluminum circuit layers and the copper circuit layers; and in the intermetallic compound layers, a boundary is set at a position of <NUM> from an edge part beside a gap between the adjacent copper circuit layers, a thickness ratio t2/t1 is <NUM>% or more where an average thickness in a center side of the boundary is t1 and an average thickness in an edge part side of the boundary is t2.

Since the average thickness t2 of the intermetallic compound layers beside the gaps between the copper circuit layers is <NUM>% or more of the average thickness at the center side of the intermetallic compound layers, the edge parts are also adequately bonded by solid phase diffusion and a sufficient bonding state can be maintained.

In addition, this bonded body for an insulation circuit substrate board can be used in states of being used as an insulation circuit substrate board having a plurality of circuit layers as it is, or being formed into single insulation circuit substrate board by forming a scribe line on the ceramic substrate board between the adjacent copper circuit layers and splitting it.

According to the present invention, it is possible to prevent the bonding defects by adding the uniform load even on the inner edge parts facing the space between the adjacent copper boards for the circuit layers.

Hereinafter, embodiments of the present invention will be explained. <FIG> and <FIG> show a bonded body <NUM> for an insulation circuit substrate board for manufacturing a plurality of power module substrate boards (insulation circuit substrate boards) <NUM> as an example of the bonded body for the insulation circuit substrate board manufactured by a manufacturing method of the present invention. In the illustrated example, four power module substrate boards <NUM> can be manufactured.

The bonded body <NUM> for the insulation circuit substrate board has a ceramic substrate board <NUM>, a plurality of circuit layers <NUM> bonded on one surface (a top surface) of the ceramic substrate board <NUM>, and a plurality of heat radiation layers <NUM> bonded on the other surface (a bottom surface) of the ceramic substrate board <NUM>. Regarding a plane size, each of the circuit layers <NUM> is a square shape with a side <NUM> or more and <NUM> or less; and a gap "g" between the respective circuit layers <NUM> is <NUM> or more and <NUM> or less. In this embodiment, the heat radiation layers <NUM> are also arranged with the same gap "g".

The ceramic substrate board <NUM> is an insulation material preventing an electrical connection between the circuit layers <NUM> and the heat radiation layers <NUM>; e.g., it is formed by aluminum nitride (AlN), silicon nitride (Si<NUM>N<NUM>), or the like; and a board thickness thereof is <NUM> to <NUM>.

In this embodiment, scribe lines <NUM> are formed in a cross shape in planar view on the ceramic substrate board <NUM> to equally divide this into four.

The circuit layers <NUM> and the heat radiation layers <NUM> both have a double structure of an aluminum layer made of aluminum or aluminum alloy and a copper layer made of copper or copper alloy.

In this case, in the circuit layers <NUM>, for each of the sections divided by the scribe lines <NUM>, an aluminum circuit layer <NUM> and a copper circuit layer <NUM> are bonded in a laminate state; the scribe lines <NUM> are formed on the ceramic substrate board <NUM> along the gaps "g" of the adjacent circuit layers <NUM>.

The aluminum layers which will be the circuit layers <NUM> are the aluminum circuit layers <NUM> and the aluminum layers which will be the heat radiation layers <NUM> are aluminum heat radiation layers <NUM>; however, in a case of not being distinct particularly, they are called simply aluminum layers.

These aluminum layers <NUM> and <NUM> are made of aluminum or aluminum alloy: pure aluminum with purity <NUM>% by mass or more or purity <NUM>% by mass or more is preferable to reduce stress. A thickness of these aluminum layers <NUM> and <NUM> is preferably <NUM> to <NUM>. The aluminum circuit layers <NUM> and the aluminum heat radiation layers <NUM> may have the same thickness or may have different thickness.

These aluminum layers <NUM> and <NUM> are formed by brazing in which aluminum boards are laminated on both the surfaces of the ceramic substrate board <NUM> with Al-Si type brazing material therebetween, pressed in a lamination direction and heated.

Regarding copper layers which will be the circuit layers <NUM> and copper layers which will be the heat radiation layers <NUM>, similarly to the aluminum layers, the copper layers which will be the circuit layers <NUM> are the copper circuit layers <NUM> and the copper layers which will be the heat radiation layers <NUM> are copper heat radiation layers <NUM>; however, in a case of not being distinct particularly, they are called simply copper layers.

These copper layers <NUM> and <NUM> may be formed of copper or copper alloy; oxygen-free copper is appropriate. A planar size may be the same as that of the aluminum layers: in the illustrated example, they are formed to be slightly smaller than the aluminum layers. An appropriate board thickness is <NUM> or more and <NUM> or less: the copper circuit layers <NUM> and the copper heat radiation layers <NUM> may have the same thickness or may have different thickness.

The copper circuit layers <NUM> are formed by bonding copper boards by solid phase diffusion on the respective aluminum circuit layers <NUM>; and the copper heat radiation layers <NUM> are formed by bonding copper boards by solid phase diffusion on the aluminum heat radiation layers <NUM>.

Next, a method of manufacturing this bonded body <NUM> for insulation circuit substrate board will be explained. In a case of this embodiment, as shown in <FIG>, manufacture is carried out with a step of forming scribe lines (<FIG>), a step of bonding an aluminum layer (<FIG>), a step of bonding a copper layer (<FIG>), and a step of dividing (<FIG>) in order.

The scribe lines <NUM> are formed on the ceramic substrate board <NUM> for dividing it into a plurality of the power module substrate boards <NUM>. The scribe lines <NUM> can be formed by laser machining as shown in <FIG>. Specifically, the machining of the scribe lines <NUM> is carried out by emitting a laser light L such as a CO<NUM> laser, a YAG laser, a YVO<NUM> laser, and a YLF laser.

As shown in <FIG>, a plurality of aluminum boards <NUM> for the circuit layers are laminated on a top surface of the ceramic substrate board <NUM> with braze foils <NUM> therebetween and a plurality of aluminum boards <NUM> for the heat radiation layers are laminated on a bottom surface of the ceramic substrate board <NUM> with the braze foils <NUM> therebetween. The aluminum boards <NUM> for the circuit layers and the aluminum boards <NUM> for the heat radiation layers are laminated in respective forming sections separated by the scribe lines <NUM> on the ceramic substrate board <NUM>. Here, although the braze foils <NUM> are used for brazing, paste of brazing material may be applied on the surfaces of the ceramic substrate board <NUM>.

Then, a laminate of the aluminum boards <NUM> for the circuit layers, the aluminum boards <NUM> for the heat radiation layers, the ceramic substrate board <NUM>, and the braze foils <NUM> is heated to <NUM> to <NUM> in a state of pressed in the lamination direction in vacuum atmosphere so as to braze.

Thereby the aluminum circuit layers <NUM> are formed on one surface of the ceramic substrate board <NUM> and the aluminum heat radiation layers <NUM> are formed on the other surface.

As shown in <FIG>, copper boards <NUM> for the circuit layers are laminated on the respective aluminum circuit layers <NUM> bonded on the top surface of the ceramic substrate board <NUM>. Similarly, copper boards <NUM> for the heat radiation layers are laminated on the aluminum heat radiation layers <NUM> bonded on the bottom surface of the ceramic substrate board <NUM>.

The copper boards <NUM> for the circuit layers are individually laminated on the respective aluminum circuit layers <NUM>. The copper boards <NUM> for the heat radiation layers are also laminated individually on the respective aluminum heat radiation layers <NUM>.

Then, this laminate <NUM> is heated at lower than eutectic temperature of copper and aluminum in a state of pressed in the lamination direction so that the aluminum circuit layers <NUM> are bonded the copper boards <NUM> for the circuit layers and the aluminum heat radiation layers <NUM> are bonded to the copper heat radiation layers <NUM> by solid phase diffusion.

<FIG> and <FIG> show a press device <NUM> used for this solid phase diffusion bonding. This press device <NUM> is provided with a base board (a press board at a fixed side) <NUM>, guide posts <NUM> vertically mounted on a top surface of the base board <NUM>, a backup board <NUM> held on upper end parts of the guide posts <NUM> movably along the guide posts <NUM>, a pressing board (a pressing board at a movable side) <NUM> held on the guide posts <NUM> movably up and down between the base board <NUM> and the backup board <NUM>, and energizing means <NUM> energizing the pressing board <NUM> downward such as springs provided between the backup board <NUM> and the pressing board <NUM>. The backup board <NUM> and the pressing board <NUM> are arranged to be parallel with the base board <NUM>.

At least the two guide posts <NUM> are provided vertically on the top surface of the base board <NUM>. Screw parts 62a are formed on upper end of the respective guide posts <NUM> and nuts <NUM> are screwed to the screw parts 62a at the top surface of the backup board <NUM>. In the present embodiment, between the base board and the pressing board <NUM>, a plurality of the laminates <NUM> are arranged in a stacked manner. In this case, the laminates <NUM> are arranged inside the guide posts <NUM> and pressed in the lamination direction between the pressing boards <NUM> and <NUM> by screwing the nuts <NUM> on the screw parts 62a of the guide posts <NUM>.

The guide posts <NUM> are not limited to two and may be provided four, one by each of the four corners on the top surface of the base board <NUM>. Between the base board <NUM> and the pressing board <NUM>, one laminate <NUM> may be arranged. Pressing means is not limited to this structure in which the nuts <NUM> are screwed on the screw parts 62a of the guide posts <NUM>, but hot pressing or the like can also be used.

In this step, on both the surfaces of the laminates <NUM>, support boards <NUM> are disposed to act the pressure effectively on the center in a surface direction of the laminates <NUM>.

Both surfaces of the support boards <NUM> are formed to be convex curved surfaces 70a. The convex curved surfaces 70a have curved surface with a radius curvature R is <NUM> or less and <NUM> or more.

The support boards <NUM> are disposed so that the convex curved surfaces 70a (refer to <FIG>) look toward the gaps "g" of the adjacent circuit layers <NUM> and the gaps "g" between the heat radiation layers <NUM> in the laminate <NUM>. The surfaces (e.g., surfaces in contact with the base board <NUM> or the pressing board <NUM>) of the support boards <NUM> not looking toward the circuit layers <NUM> may be flat surfaces.

Since the four circuit layers <NUM> which are rectangle in planar view are arranged so that one corner of them are respectively near to each other, the convex curved surfaces 70a are formed to be a spherical surface shape so as to protrude largest at a part where the four corners are near; however, a cylindrical surface may be used other than the spherical surface in accordance with an arranged number or the like of the circuit layers <NUM>. For example, in a case in which two circuit layers are aligned and arranged, it is sufficient that the convex curved surface is formed into a cylindrical surface shape and an axis direction of the cylinder is arranged along a gap between the two circuit layers. Furthermore, the curved surface may be a surface of a spheroid or the like other than the spherical surface or the cylindrical surface. Within a range of the curvature radius R = <NUM> to <NUM>, it may be one having single radius curvature or one made of a combination of a plurality of radius curvatures: it is possible to set appropriately in accordance with the number or arrangement of the circuit layers.

The support boards <NUM> are made of carbon material sheets. As the carbon material sheets, a laminate board of carbon sheets and graphite sheets for example. For the carbon sheets, for example, G-<NUM> made by Asahi Graphite Inc. (thermal conductivity <NUM> W/mK, elastic modulus <NUM> GPa) can be used. For the graphite sheets, for example, T-<NUM> made by Asahi Graphite Inc. (thermal conductivity <NUM> W/mK, elastic modulus <NUM> GPa), graphite sheets PF made by Toyo Tanso Co. (compressibility <NUM>%, recovery <NUM>%) or the like can be used.

In the press device <NUM> structured as above described, a plurality of the laminates <NUM> are arranged with the support boards <NUM> therebetween. In this case, the support boards <NUM> are arranged so that the convex curved surfaces 70a are in contact with the copper boards <NUM> for the circuit layers and the copper boards <NUM> for the heat radiation layers of the laminates <NUM>.

By maintaining pressure of <NUM> MPa or more and <NUM> MPa or less and holding in vacuum atmosphere at heating temperature of <NUM> or more and <NUM> or less for <NUM> minutes or more and <NUM> minutes or less, the copper boards <NUM> for the circuit layers and the copper boards <NUM> for the heat radiation layers are respectively bonded on the aluminum circuit layers <NUM> and the aluminum heat radiation layers <NUM> by solid phase diffusion between copper and aluminum.

In the bonded body <NUM> for the insulation circuit substrate board manufactured as above, the aluminum circuit layers <NUM> and the copper circuit layers <NUM> are laminated in order and bonded on one surface of the ceramic substrate board <NUM>; and the aluminum heat radiation layers <NUM> and the copper heat radiation layers <NUM> are laminated in order and bonded on the other surface of the ceramic substrate board <NUM>.

Between the aluminum circuit layers <NUM> and the copper circuit layers <NUM>, and between the aluminum heat radiation layers <NUM> and the copper heat radiation layers <NUM>, intermetallic compound layers M are formed by solid phase diffusion bonding of aluminum and copper (refer to <FIG>).

In this step of bonding copper boards, by pressing the convex curved surfaces 70a of the support boards <NUM> with being in contact with the copper boards <NUM> for the circuit layers and the copper boards <NUM> for the heat radiation layers, the M are formed with substantially uniform thickness over whole surfaces between the aluminum circuit layers <NUM> and the copper circuit layers <NUM> and between the aluminum heat radiation layers <NUM> and the copper heat radiation layers <NUM>.

An average thickness of the M is <NUM> or more and <NUM> or less; an average thickness of a center side than a boundary is t1 and an average thickness of an edge part side than the boundary is t2, where the boundary is set at a position <NUM> from the edge part facing on the gaps "g" between the adjacent copper circuit layers <NUM>; and a thickness ratio t2/t1 is <NUM>% or more.

At the last, as shown in <FIG>, the ceramic substrate board <NUM> is split into a plurality of pieces along the scribe lines <NUM>.

As explained above, according to the manufacturing method of the present embodiment, by pressing the convex curved surfaces 70a of the support boards <NUM> with being in contact with the copper boards <NUM> for the circuit layers and the copper boards <NUM> for the heat radiation layers; it is possible to form the M over the whole surfaces with substantially the uniform thickness by the solid phase diffusion bonding between the aluminum circuit layers <NUM> and the copper circuit layers <NUM> and between the aluminum heat radiation layers <NUM> and the copper heat radiation layers <NUM> and it is possible to bond them firmly without bonding defects.

In this case, the curvature radius R of the convex curved surfaces 70a is too small if it is less than <NUM>, so that the load is too concentrated on the vicinity of the edge parts beside the gaps "g" of the copper circuit layers <NUM> and the copper heat radiation layers <NUM> and in contrast the load on the vicinity of the outer peripheral edge parts is not enough; as a result, the bonding defects may be occur in the outer peripheral edge parts. If the curvature radius R of the convex curved surfaces 70a is more than <NUM> it is almost a flat surface, so that an improving effect of bonding is poor in the vicinity of the edge parts beside the gaps "g" of the copper circuit layers <NUM> and the copper heat radiation layers <NUM>.

In the above embodiment, a plurality of the power module substrate boards <NUM> are manufactured by forming the scribe lines <NUM> on the ceramic substrate board <NUM>; the present invention can be applied if a plurality of the circuit layers <NUM> are separated even in a case in which one power module substrate board (an insulation circuit substrate board) <NUM> is manufactured from the ceramic substrate board <NUM> without the scribe lines <NUM> (<FIG>).

A bonded body <NUM> for an insulation circuit substrate board is formed to be a state in which the circuit layers <NUM> are separated into two on one surface of the ceramic substrate board <NUM>, in which the copper circuit layers <NUM> are bonded in a laminate state with the aluminum circuit layers <NUM> therebetween respectively. On the other surface of the ceramic substrate board <NUM>, one heat radiation layer <NUM> is formed in which one copper heat radiation layer <NUM> is laminated and bonded with one aluminum heat radiation layer <NUM> therebetween.

Also in the bonded body <NUM> for the insulation circuit substrate board, after forming the aluminum circuit layers <NUM> and the aluminum heat radiation layers <NUM> on the ceramic substrate board <NUM> by braze bonding, the copper boards <NUM> for the circuit layers are bonded on the aluminum circuit layers <NUM> and the copper board <NUM> for the heat radiation layer is bonded on the aluminum heat radiation layer <NUM> by the solid phase diffusion bonding. At this time, by pressing using the support boards <NUM> having the convex curved surfaces 70a, the vicinity of the edge parts of the copper boards <NUM> for the circuit layers beside the gaps "g" are also pressed, so that the copper circuit layers <NUM> firmly bonded on the aluminum circuit layers <NUM> can be formed.

In this case, the circuit layers <NUM> are a square of <NUM> or more and <NUM> or less; the gaps "g" of the circuit layers <NUM> are <NUM> or more and <NUM> or less.

After forming the copper circuit layers <NUM> and the copper heat radiation layers <NUM> the bonded body <NUM> for the insulation circuit substrate board is used as the power module substrate board <NUM> (the insulation circuit substrate board) as it is.

Besides, the present invention can be applied for a case in which a circuit layer having a double structure of an aluminum layer and a copper layer is formed o none surface of a ceramic substrate board, it is not necessary that a heat radiation layer having a double structure on the other surface of the ceramic substrate board as in the embodiment.

A step of bonding aluminum boards was carried out as follows: two aluminum boards (<NUM> × <NUM>, thickness <NUM>, 4N-Al) were laminated with a gap <NUM> on a surface of a ceramic substrate board (<NUM> × <NUM>, thickness <NUM>, AlN) to be an insulation layer; one aluminum board (<NUM> × <NUM>, thickness <NUM>, 4N-Al) was laminated on the other surface of the ceramic substrate board, so that aluminum layers were formed by braze bonding respectively. Al-Si brazing foils (thickness <NUM>) were used as brazing material, it was added a pressure <NUM> MPa in a lamination direction and heated at temperature <NUM> for <NUM> minutes to bond.

A step of bonding copper boards was carried out as follows: copper boards (<NUM> × <NUM>, thickness <NUM>, oxygen-free copper) were laminated to be positioned on the aluminum layers formed on the surface of the ceramic substrate board, and a copper board (<NUM> × <NUM>, thickness <NUM>, oxygen-free copper) was laminated on the aluminum layer formed on the bottom surface of the ceramic substrate board; and it was added a pressure <NUM> MPa in the lamination direction using a support board having a curvature radius shown in Table <NUM> and heated at temperature <NUM> for <NUM> minutes in vacuum atmosphere to bond by solid phase diffusion.

Samples <NUM> to <NUM> made as above were observed in a microscope at a cross section substantially perpendicular to an edge surface passing through substantially a center of a circuit layer to find an intermetallic compound layer between the aluminum layers and the copper layers. An average thickness t1 of the intermetallic compound layer in a center side of a position-of-<NUM> from an edge part beside a gap between the adjacent circuit layers and an average thickness t2 of the intermetallic compound layer in the edge part side of the position-of-<NUM> from the edge part were measured; and a thickness ratio t2/t1 was calculated.

As evaluation of bonding ability, regarding obtained Samples <NUM> to <NUM>, solder was mounted on a copper circuit layer, and the intermetallic compound layer was checked after reflowing <NUM> × <NUM> minutes by microscope observation at a cross section along the B-B line shown in <FIG> (on a line through substantially the center of the circuit layer and substantially perpendicular to the end surface). Observing with the microscope VK-X210 made by Keyence Corporation, it was evaluated "not good" if breakages (cracks) were found in the intermetallic compound layer at the edge part, or it is evaluated "good" if the cracks were not found. Results are shown in Table <NUM>.

Samples <NUM> to <NUM> in which the radius curvature of a convex surface was <NUM> to <NUM> were all "good" in the evaluation of the bonding ability. The thickness ratio of the intermetallic compound layer in these cases was <NUM>% or more: it is recognized that good result was obtained if it was <NUM>% or more.

<FIG> is a microscopy photograph along the cross section taken along the line B-B at the edge part of the aluminum layer and the copper layer of Sample <NUM> before solder reflowing. <FIG> is a microscopy photograph of Sample <NUM> before solder reflowing. In <FIG>, the intermetallic compound layer M was formed to the edge of the end part, so that the aluminum layer and the copper layer were bonded. In contrast, in <FIG>, an unbonded part was generated at the edge of the end part.

Claim 1:
A method of manufacturing a bonded body (<NUM>) for an insulation circuit substrate board (<NUM>) comprising steps of:
forming an aluminum circuit layer (<NUM>) forming a plurality of aluminum circuit layers (<NUM>) on one surface on a ceramic substrate board (<NUM>); and
a step of forming a copper circuit layer (<NUM>), by laminating copper boards (<NUM>) for the circuit layers (<NUM>) respectively on the aluminum circuit layers (<NUM>); arranging this laminate (<NUM>) between a pair of support boards (<NUM>) having a convex curved surface (70a) on at least one surface and arranged to face the convex curved surfaces (70a) toward each other; and pressing the laminate (<NUM>) in a lamination direction by moving the support boards (<NUM>) to a facing direction and heating in this pressing state, so as to bond the copper boards (<NUM>) on the aluminum circuit layers (<NUM>) by solid phase diffusion, characterized in that
in the step of forming the copper circuit layers (<NUM>), the support boards (<NUM>) are arranged so that at least one of the convex curved surfaces (70a) are in contact with a plurality of the copper boards (<NUM>) for the circuit layers (<NUM>) adjacent in the laminate (<NUM>).