Copper-Ceramic Composite Grain Size Gradient
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Solution Overview
Problem
In high-power electronics, metal-ceramic composites face challenges with thermal shock resistance and wire bonding due to differences in thermal expansion coefficients between ceramic substrates and metal coatings, leading to potential detachment under temperature fluctuations.
Innovation Solution
A copper-ceramic composite with a copper or copper alloy coating having grain sizes between 10 μm to 300 μm, optimized grain size distribution, and shape factors to enhance adhesion and thermal shock resistance, allowing for strong wire bonding and improved mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the metal coating is firmly bonded to the ceramic substrate, then adhesion strength is improved, but wire bonding becomes difficult due to material incompatibility
Solution Approach 1:
The patent applies different grain sizes in different regions of the copper coating. The central region has finer grains (5-20 μm) for strong adhesion to ceramic, while the peripheral region has coarser grains (20-50 μm) that are more suitable for wire bonding. This local differentiation resolves the contradiction between adhesion strength and wire bonding compatibility.
2Strength
If the copper grain size is reduced to improve adhesion, then adhesive strength is improved, but thermal shock resistance deteriorates
Solution Approach 1:
The patent implements a gradient grain size distribution where the central region has finer grains (5-20 μm) for strong adhesion, while the peripheral region has coarser grains (20-50 μm) for better thermal shock resistance. This spatial variation in grain size allows both adhesion strength and thermal shock resistance to be optimized simultaneously.
Solution Approach 2:
The patent changes the grain size parameter across the copper coating thickness and lateral dimensions. By controlling grain size to vary from 5-20 μm in the center to 20-50 μm at the periphery, the material properties are optimized for different functional requirements: adhesion in the center and thermal shock resistance at the edges.
3Strength
If uniform fine grain structure is used throughout the copper coating, then adhesion to ceramic is improved, but thermal expansion mismatch stresses increase during temperature cycling
Solution Approach 1:
The patent creates a non-uniform grain structure with finer grains (5-20 μm) in the central region for strong adhesion and coarser grains (20-50 μm) in the peripheral region. This local differentiation allows the peripheral area to better accommodate thermal expansion stresses while maintaining strong central adhesion to the ceramic substrate.
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 composite exhibits improved thermal shock resistance, increased wire bonding strength, and enhanced adhesive strength, maintaining bonding integrity under prolonged temperature changes.
Implementation Method 1
the copper or the copper alloy has grain sizes in the range from 10 μm to 300 μm
Implementation Method 2
This layer reacts with the surface of the ceramic substrate, so that ceramic and metal can be firmly joined to one another
Implementation Method 3
oxygen reduces the melting point of the copper from 1083° C. to the eutectic melting point of 1065° C. A thin eutectic melt layer is formed by the oxidation of copper foils
Implementation Method 4
Ceramic circuit boards are of particular interest in the field of high-power electronics because of their high thermal conductivity
Data Source
AI summary
The invention relates to a copper-ceramic composite comprising: a ceramic substrate; and a copper or copper alloy coating on the ceramic substrate, the copper or copper alloy having grain sizes of 10 μm to 300 μm.