Copper-Ceramic Substrate Grain Structure for Thermal Shock Resistance
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Solution Overview
Problem
Copper-ceramic substrates face challenges with thermal shock resistance due to differing thermal expansion coefficients of ceramic and copper materials, leading to delamination and cracks, which affects the service life of power modules.
Innovation Solution
A copper layer with distinct grain sizes on either side, where the side facing the ceramic has a coarser grain size for improved thermal shock resistance and the exposed side has a finer grain size for increased hardness and machinability, achieved through targeted temperature treatment or use of different copper materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the copper layer has a fine grain size to improve hardness and machinability, then the thermal shock resistance deteriorates
Solution Approach 1:
The copper layer is designed with different grain sizes in different regions: a first region with fine grain size (5-50 μm) for high hardness and machinability, and a second region with coarse grain size (100-1000 μm) for high thermal shock resistance. This local differentiation allows each region to optimize its properties for specific functional requirements.
Solution Approach 2:
The copper layer is segmented into multiple regions with distinct grain structures. The first region (fine grains) and second region (coarse grains) are separated by a grain boundary region, creating a gradient structure that transitions from fine to coarse grains, thereby combining the advantages of both grain sizes.
2Reliability
If the copper layer has a coarse grain size to improve thermal shock resistance, then the machinability and hardness deteriorate
Solution Approach 1:
The copper layer is designed with different grain sizes in different regions: a first region with fine grain size (5-50 μm) for high hardness and machinability, and a second region with coarse grain size (100-1000 μm) for high thermal shock resistance. This local differentiation allows each region to optimize its properties for specific functional requirements.
3Device complexity
If a single grain size is used in the copper layer, then the manufacturing process is simplified, but the ability to meet multiple conflicting requirements deteriorates
Solution Approach 1:
The copper layer is designed with different grain sizes in different regions: a first region with fine grain size (5-50 μm) for high hardness and machinability, and a second region with coarse grain size (100-1000 μm) for high thermal shock resistance. This local differentiation allows each region to optimize its properties for specific functional requirements.
Solution Approach 2:
The grain size parameter is varied across different regions of the copper layer. By controlling the grain size to be 5-50 μm in the first region and 100-1000 μm in the second region, the patent optimizes mechanical and thermal properties for different functional requirements.
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
Enhances thermal shock resistance, reduces delamination and crack formation, and improves machinability and bonding wire connection quality, allowing for optimized copper layer properties without compromising other requirements.
Implementation Method 1
achieved through targeted temperature treatment or use of different copper materials
Implementation Method 2
Due to the different thermal expansion coefficients of the ceramic and copper materials used, mechanical stresses are thermally induced during use in the copper-ceramic substrate
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a copper-ceramic substrate (1) comprising - a ceramic support (2) and - a copper layer (3, 4) joined to a surface of the ceramic support (2), where - the copper layer (3, 4) has at least one first layer (5, 6) which faces the ceramic support and has an averaged first particle size, and a second layer (7, 8) disposed on the side of the copper layer (3, 4) that faces away from the ceramic support (2), and having an averaged second particle size, where - the second particle size is smaller than the first particle size. The first layer (5, 6) has on average a particle size of greater than 100 μm, preferably about 250 to 1000 μm, and - the second layer (7, 8) has on average a particle size of less than 100 μm, preferably about 50 μm, or - the first layer (5, 6) has on average a particle size of greater than 150 pm, preferably about 250 to 2000 μm, and the - second layer (7, 8) has on average a particle size of less than 150 pm, preferably about 50 pm. Preference is given to using Cu-ETP and Cu-OF or Cu-OFE.