Copper-Ceramic Bonded Substrate for Heat Cycle Reliability
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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 when subjected to repeated heat loads during assembly and use in power modules.
Innovation Solution
A copper-ceramic bonded substrate with a copper sheet bonded to a ceramic substrate, where the dislocation density of the copper sheet is controlled to 1.5×10^13 m^-2 or less, and specific impurity elements such as arsenic, antimony, sulfur, phosphorus, and zinc are present within certain content ranges to enhance heat cycle resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper sheet with high dislocation density is used to reduce thermal stress, then heat cycle properties are improved, but the mounting area is reduced and external size increases
Solution Approach 1:
The invention changes the material parameters of the copper sheet by controlling dislocation density to 1.5×10^13 m^-2 or less and specifying impurity element contents (As: 0.005-1.5 ppm, Sb: 0.005-0.5 ppm, S: 0.1-7 ppm, P: 0.05-2 ppm, Zn: 0.005-0.08 ppm). This parameter optimization allows the copper sheet to achieve adequate thermal stress relief without requiring stepped shapes or dimples that would reduce mounting area
Solution Approach 2:
The invention segments the approach to thermal stress relief by focusing specifically on the copper sheet's internal structure (dislocation density) rather than modifying the overall substrate geometry. This allows the mounting area to remain fully utilized while the copper sheet itself handles thermal stress through its controlled microstructure
2Reliability
If the outer size of the substrate is increased to maintain mounting area, then heat cycle properties can be improved, but the size of the power module increases
Solution Approach 1:
By optimizing the copper sheet's dislocation density and impurity content, the invention achieves adequate thermal stress relief within the existing substrate dimensions, eliminating the need to increase outer size for heat cycle improvement
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 approach allows for high heat cycle properties without increasing the substrate's outer size, reducing damage to the ceramic substrate from heat loads and improving the reliability of power modules.
Implementation Method 1
a dislocation density of the copper sheet is 1.5×10^13 m^-2 or less
Implementation Method 2
an Al metal circuit board is inferior to a Cu metal circuit board in terms of electrical conductivity and heat dissipation. On the other hand, when Cu is used as the metal circuit board, there is a problem that the reliability is inferior when a heat load is applied compared to when Al is used
Implementation Method 3
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)
Data Source
Figure 1~2
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 a dislocation density of the copper sheet is 1.5×1013 m-2 or less.