Copper Ceramic Composite Grain Size Control
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Solution Overview
Problem
In power electronics, metal-ceramic composites face challenges with thermal shock resistance and wire bonding due to differing thermal expansion coefficients between ceramic substrates and metal coatings, leading to potential detachment issues under temperature fluctuations.
Innovation Solution
A copper-ceramic composite with a copper or copper alloy coating having grain sizes between 10 µm and 300 µm, and a specific grain size distribution with a median value ratio of 0.75 to 1.10, enhancing adhesion and wire bonding while improving thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the metal coating is bonded to the ceramic substrate using conventional DCB process, then the metal coating can be attached to the ceramic surface, but the bond may detach under thermal cycling due to different thermal expansion coefficients
Solution Approach 1:
The patent applies different grain sizes in different regions of the copper coating. The edge region has larger grain sizes (50-300 μm) that provide stress relief during thermal cycling, while the center region maintains smaller grain sizes (10-50 μm) for strong wire bonding. This local differentiation resolves the contradiction between bond strength and thermal shock resistance.
Solution Approach 2:
The patent changes the grain size parameter of the copper coating to optimize both adhesion and wire bonding. By controlling grain sizes within specific ranges (10-300 μm overall, with 50-300 μm at edges and 10-50 μm in center), the coating achieves both strong bonding to ceramic and good resistance to thermal cycling, while also enabling reliable wire bonding.
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 and wire bonding properties, maintaining strong adhesion and bonding even under prolonged thermal cycling.
Implementation Method 1
the copper or the copper alloy having grain sizes in a range with a lower limit of 10 µm and an upper limit of 300 µm, and a number distribution of the grain sizes with a median value d50 and has an arithmetic mean darith and the ratio of d50 to darith (d50/darith) is in the range from 0.75 to 1.10
Implementation Method 2
The DCB process takes advantage of the fact that oxygen reduces the melting point of copper from 1083°C to the eutectic melting temperature of 1065°C. A thin eutectic melt layer is created by the oxidation of copper foils before metallization of the ceramic substrate
Implementation Method 3
In many power electronics applications, the metal-ceramic composite is subject to high thermal cycling, where significant temperature changes (e.g. in the range from -40°C to +150°C) can occur
Data Source
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AI summary
The present invention relates to a copper-ceramic composite comprising - a ceramic substrate, - a coating of copper or a copper alloy present on the ceramic substrate, wherein the copper or copper alloy has grain sizes in the range of 10 µm to 300 µm.