Circuit board having a heat dissipating sheet with varying metal grain size

Patent metadata

Field	Value
Publication number	US-10014237-B2
Application number	US-201515535122-A
Country	US
Kind code	B2
Filing date	Dec 14, 2015
Priority date	Dec 16, 2014
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A circuit board includes an insulating substrate; a metal circuit sheet joined to a first principal surface of the insulating substrate; and a heat dissipating sheet made of metal and joined to a second principal surface of the insulating substrate, the second principal surface being opposite the first principal surface. The thickness of the heat dissipating sheet is at least 3.75 times the thickness of the metal circuit sheet. The size of metal grains contained in the heat dissipating sheet is smaller than the size of metal grains contained in the metal circuit sheet, and decreases with increasing distance from the second principal surface of the insulating substrate.

First claim

The invention claimed is:

1. A circuit board comprising:
an insulating substrate;
a metal circuit sheet joined to a first principal surface of the insulating substrate; and
a heat dissipating sheet made of metal and joined to a second principal surface of the insulating substrate, the second principal surface being opposite the first principal surface,
wherein a thickness of the heat dissipating sheet is at least 3.75 times a thickness of the metal circuit sheet; and
a size of metal grains contained in the heat dissipating sheet is smaller than a size of metal grains contained in the metal circuit sheet, and decreases with increasing distance from the second principal surface of the insulating substrate.

2. The circuit board according to claim 1 , wherein the first principal surface of the insulating substrate and the metal circuit sheet are joined together with a first brazing material interposed therebetween, and the second principal surface of the insulating substrate and the heat dissipating sheet are joined together with a second brazing material interposed therebetween; and
the first brazing material has, at least in an outer portion thereof, a thermal expansion coefficient higher than a thermal expansion coefficient of the second brazing material.

3. The circuit board according to claim 2 , wherein the outer portion of the first brazing material is at least partly located outside an outer periphery of the metal circuit sheet.

4. The circuit board according to claim 1 , wherein the thickness of the metal circuit sheet is 0.8 mm or less, the thickness of the heat dissipating sheet is 3 mm or more, and a sum of the thickness of the metal circuit sheet and the thickness of the heat dissipating sheet is 3.4 mm or more.

5. The circuit board according to claim 4 , wherein the thickness of the heat dissipating sheet is 5 mm or less.

6. An electronic device comprising:
the circuit board according to claim 1 ; and
an electronic component mounted on the metal circuit sheet of the circuit board.

7. The circuit board according to claim 2 , wherein the thickness of the metal circuit sheet is 0.8 mm or less, the thickness of the heat dissipating sheet is 3 mm or more, and a sum of the thickness of the metal circuit sheet and the thickness of the heat dissipating sheet is 3.4 mm or more.

8. The circuit board according to claim 7 , wherein the thickness of the heat dissipating sheet is 5 mm or less.

Assignees

• Kyocera Corp

Inventors

• Kooriyama Shinichi
• Ogawa Narutoshi
• Konagai Masashi
• Ochiai Kensou
• Niino Noritaka

Classifications

• H10W90/754

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H10W90/734

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H10W72/5445

  being orthogonal to a side surface of the chip, e.g. parallel arrangements · CPC title

• H10W40/258

  Metallic materials (H10W40/254, H10W40/257, H10W40/255, H10W40/251, H10W40/253 take precedence) · CPC title

• H10W70/692

  Ceramics or glasses · CPC title