Copper-Ceramic Substrate Grain Size Control
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Solution Overview
Problem
Copper-ceramic substrates face challenges in thermal shock resistance due to differing thermal expansion coefficients of ceramic and copper materials, leading to delamination and cracks, which reduces their service life and increases production costs when attempting to optimize grain sizes for improved properties.
Innovation Solution
A copper-ceramic substrate with a copper layer having an average grain size diameter of 300 to 500 μm, following a monomodal Gaussian distribution, and composed of at least 99.95% Cu with controlled impurities, is developed to enhance thermal shock resistance and maintain bondability and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the copper layer has a fine structure (small grain size), then optical inspection, bondability, etching behavior, and grain boundary formation are improved, but thermal shock resistance and service life deteriorate due to higher thermally induced stresses
Solution Approach 1:
The patent applies local quality by creating different grain size characteristics in different regions of the copper layer. The copper layer has a first region with a first average grain size and a second region with a second average grain size, where the grain sizes differ by a factor of 0.5 to 2.0. This allows the surface region to have finer grains for improved bondability and etching behavior, while other regions can have coarser grains for better thermal shock resistance, thus resolving the contradiction between manufacturing precision and reliability.
2Reliability
If the copper layer has a coarser structure (large grain size), then thermal shock resistance and service life are improved, but optical inspection, bondability, etching behavior, and grain boundary formation deteriorate
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through spatially varying grain sizes. Specific regions of the copper layer are engineered with finer grain sizes to optimize etching behavior and optical inspection, while other regions maintain coarser grain sizes for enhanced thermal shock resistance. This regional differentiation allows simultaneous optimization of conflicting properties without compromising overall performance.
3Reliability
If different grain sizes are achieved by plating two different copper layers, then thermal shock resistance and processing properties are improved, but production complexity and costs increase
Solution Approach 1:
The patent applies merging by combining multiple grain size regions into a single copper layer rather than using separate copper layers. This is achieved by controlling crystallization conditions during the bonding process or through post-bonding heat treatment, allowing different grain sizes to form within one continuous copper layer. This approach maintains the benefits of varied grain sizes for improved reliability while simplifying the production process and reducing complexity compared to plating multiple separate layers.
Solution Approach 2:
The patent resolves the contradiction between improved reliability and reduced complexity by changing process parameters during a single copper layer formation. By controlling crystallization temperature, holding time, and cooling rate during or after bonding, the patent achieves different grain sizes within one copper layer. This parameter control approach eliminates the need for multiple plating operations, thereby reducing production complexity while maintaining the thermal shock resistance benefits of varied grain sizes.
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 a longer service life with improved thermal shock resistance and cost-effectiveness by optimizing grain size and composition, meeting the requirements for both thermal performance and processing ease without the need for additional expensive production steps.
Implementation Method 1
oxidizing the copper layer such that a uniform copper oxide layer results
Implementation Method 2
Heating the composite to a process temperature between 1060 °C and 1085 °C. This creates a eutectic melt on the copper layer, which forms a material bond with the ceramic substrate
Implementation Method 3
the copper layer has a structure with an average grain size diameter of 300 to 500 μm, preferably from 300 to 400 μm
Data Source
Figure 1
AI summary
The invention relates to a copper-ceramic substrate (1) comprising a ceramic carrier (2), and at least one copper layer structure (3, 4) joined to a surface of the ceramic carrier (2), which has a free surface for forming a conductor structure and/or for securing bonding wires, wherein the copper layer (3, 4) has a microstructure with an average particle size diameter of 200 to 500μm, preferably 300 to 400μm.