Copper-Ceramic Bonded Substrate Using Low-Hardness Copper

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Solution Overview

Problem

Existing copper-ceramic bonded substrates face challenges in achieving good heat cycle properties without increasing the outer size of the substrate, particularly due to thermal stress caused by heat loads during assembly and usage.

Innovation Solution

A copper-ceramic bonded substrate is developed with a copper sheet having a Vickers hardness of 42.5 HV or less, controlled impurity elements such as magnesium, nickel, selenium, tin, tellurium, and bismuth within specific ranges, and a brazing bonded layer to enhance bonding reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If stepped shape or dimples are provided on the metal sheet to alleviate thermal stress, then heat cycle properties are improved, but mounting area is reduced and external size increases

Engineering Contradiction:

Improveheat cycle propertiesVSAvoidmounting area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

Instead of changing the geometric shape of the metal sheet, the invention changes the material parameter by controlling the Vickers hardness of the copper sheet to be 42.5 HV or less through impurity element control. This allows thermal stress to be alleviated through material properties rather than geometric modifications, thereby maintaining the full mounting area and avoiding external size increase while still achieving good heat cycle properties

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The substrate achieves improved heat cycle resistance without increasing the substrate's outer size, reducing thermal stress on the ceramic substrate and preventing microcracks, while maintaining high electrical conductivity and heat dissipation properties.

Implementation Method 1

there is a method in which a brazing material made of a mixture of active metal, Ag, and Cu (Ag-Cu active metal brazing) material is interposed between a metal sheet and a ceramic plate by heat treatment (active metal brazing method)

Methodology Applied

Scientific EffectBrazing: Brazing

Implementation Method 2

the copper sheet is heated to 380°C, held for 10 minutes, and then cooled to 40°C, and this heat cycle is repeated 20 times

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Implementation Method 3

a thermal stress caused by a difference in thermal expansion between the ceramic substrate and the metal circuit board can be alleviated

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4495087A1Copper/ceramic bonded substrate and production method therefor

Publication Date: 2025.01.22 DOWA METALTECH CO LTD

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Figure 3

AI summary

There is provided a copper-ceramic bonded substrate, including: a ceramic substrate; and a copper sheet bonded to at least one surface of the ceramic substrate, wherein the copper sheet has a Vickers hardness of 42.5 HV or less, and the copper sheet has a magnesium content of 1 ppm or less, a nickel content of 2.5 ppm or less, a tin content of 0.05 ppm or less, a selenium content of 0.3 ppm or less, a tellurium content of 0.07 ppm or less, and a bismuth content of 0.2 ppm or less.