Copper-Ceramic Bonded Substrate Hardness Control for Heat Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing copper-ceramic bonded substrates face challenges in maintaining good heat cycle properties without increasing the outer size of the substrate, particularly when subjected to repeated heat loads that can cause thermal stress and damage to the ceramic substrate.
Innovation Solution
A copper-ceramic bonded substrate is developed with a copper sheet that has 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 and thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a copper sheet is used as the metal circuit board, then electrical conductivity and heat dissipation are improved, but reliability deteriorates when heat load is applied
Solution Approach 1:
The invention changes the physical parameter of copper sheet hardness by controlling its Vickers hardness to be 42.5 HV or less through specific compositional control (limiting impurity elements like Mg, Ni, Se, Sn, Te, and Bi). This parameter change allows the copper sheet to maintain good electrical conductivity and heat dissipation while improving reliability under heat load by enabling appropriate plastic deformation to relieve thermal stress.
2Reliability
If a stepped shape or dimples are provided on the metal sheet to alleviate thermal stress, then thermal stress resistance is improved, but mounting area is reduced
Solution Approach 1:
Instead of changing the geometric shape (stepped structure or dimples) of the metal sheet, the invention changes the material parameter (Vickers hardness) of the copper sheet to 42.5 HV or less. This allows the copper sheet itself to relieve thermal stress through plastic deformation, maintaining a flat surface with full mounting area while achieving thermal stress resistance.
3Reliability
If the Vickers hardness of the copper sheet is reduced to 42.5 HV or less, then heat cycle properties are improved, but manufacturing precision may be affected
Solution Approach 1:
The invention achieves the target Vickers hardness of 42.5 HV or less not by changing the copper sheet thickness or geometry, but by precisely controlling the compositional parameters (limiting impurity elements). This compositional control approach maintains manufacturing precision while achieving the desired hardness for improved heat cycle properties.
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 outer size, reducing thermal stress on the ceramic substrate, and suppressing work hardening of the copper sheet, thereby enhancing the durability and reliability of the power module.
Implementation Method 1
a thermal stress caused by a difference in thermal expansion between the ceramic substrate and the metal circuit board can be alleviated by a plastic deformation of the aluminum
Implementation Method 2
an increase in Vickers hardness due to a heat load
Data Source
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.