# US 8,785,787 B2 · Metal-based circuit board

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- Number: US 8,785,787 B2
- Document ID: US8785787B2
- Status: Granted
- Kind: B2
- Application number: 13/407,585
- Filed: 2012-02-28
- Published: 2012-08-30
- Granted: 2014-07-22
- Earliest claimed: 2011-02-28
- Assignees: Koa Corporation
- Applicants: Souhei Kouda; Toshiharu Takayama
- Inventors: Souhei Kouda; Toshiharu Takayama
- Web page: https://patentgrep.com/patent/US8785787B2

## CPC

- H05K 1/053: {the metal substrate being covered by an inorganic insulating layer}
- H10W 70/6875: {being on a metallic substrate, e.g. insulated metal substrates [IMS]}
- H10W 70/69: Insulating materials thereof
- H05K 3/4685: {Manufacturing of cross-over conductors}
- H05K 2201/017: Glass ceramic coating, e.g. formed on inorganic substrate
- H05K 2201/068: wherein the coefficient of thermal expansion is important
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## Abstract

A metal-based circuit board, which reduces the influence of thermal expansion, is provided having a structure where an insulating layer A having a large coefficient of thermal expansion is sandwiched between insulating layers B having a small coefficient of thermal expansion. Such a structure allows the insulating layers B to contract and expand so as to suppress contraction and expansion of the insulating layer A and thereby reduce the stress in the direction of negating the stress. As a result, while warpage or distortion is suppressed to be minimal, the bonding strength of the upper and the lower layer is maintained, and degree of freedom for circuit design is not impaired, thereby providing a highly reliable circuit structure.

## Claims

### Claim 1

A metal-based circuit board comprising a first conductor layer formed on a substrate made of a metal material via an insulating layer, and a second conductor layer formed on the first conductor layer via an insulating layer; wherein the insulating layer between the first and the second conductor layer comprises a first intermediate insulating layer and second intermediate insulating layers, and has a structure of the first intermediate insulating layer sandwiched between the second intermediate insulating layers; wherein coefficient of thermal expansion of the first intermediate insulating layer is larger than that of the second intermediate insulating layers.

### Claim 2 (depends on 1)

The metal-based circuit board according to claim 1, wherein the first and the second conductor layer do not come in direct contact with the first intermediate insulating layer.

### Claim 3 (depends on 2)

The metal-based circuit board according to claim 2, wherein the insulating layer between the first and the second conductor layer has a structure where the first intermediate insulating layer is completely wrapped by the second intermediate insulating layers.

### Claim 4 (depends on 3)

The metal-based circuit board according to claim 3, wherein coefficient of thermal expansion of the first intermediate insulating layer and that of the second intermediate insulating layers are smaller than that of the substrate, and larger than those of the first and the second conductor layer.

### Claim 5 (depends on 1)

The metal-based circuit board according to claim 1, wherein the insulating layer between the substrate and the first conductor layer has a structure where a first insulating layer is formed on the surface of the substrate, a second insulating layer having a smaller coefficient of thermal expansion than that of the first insulating layer is formed on the first insulating layer, and the first conductor layer is formed on the second insulating layer.

### Claim 6 (depends on 5)

The metal-based circuit board according to claim 5, wherein an insulating layer is formed on the rear side of the substrate.