Pure Copper Material With Stable Grain Structure After Heat Bonding
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Solution Overview
Problem
Existing pure copper materials used in electrical and electronic components, such as heatsinks and thick copper circuits, face challenges with crystal grain coarsening and nonuniformity during heat treatment, leading to bonding defects and inspection troubles.
Innovation Solution
A pure copper material with a copper content ranging from 99.9% to 99.999% mass, featuring an average crystal grain size of 10 μm or more, and controlled strain distribution through specific processing and additive elements like Ca, Sr, and Ba, to suppress crystal grain coarsening and ensure uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pressure treatment is performed at high temperature to bond pure copper material to ceramics substrate, then bonding strength is improved, but crystal grain coarsening and nonuniformity occur
Solution Approach 1:
The patent applies preliminary cold working (rolling) to the pure copper material before bonding to create a refined crystal grain structure with specific orientation. This preliminary action prepares the material so that subsequent high-temperature bonding does not cause excessive grain coarsening, as the cold-worked structure provides a foundation that resists rapid grain growth during heat treatment.
Solution Approach 2:
The patent controls the crystal grain size to be 10 μm or more before bonding, and maintains this size after bonding by controlling the bonding temperature and time parameters. By carefully adjusting these parameters, the material achieves both strong bonding and uniform crystal grain structure, resolving the contradiction between bonding strength and grain uniformity.
2Reliability
If heat treatment is performed at high temperature to strengthen bonding, then bonding reliability is improved, but crystal grain coarsening occurs causing defects
Solution Approach 1:
The patent performs preliminary cold working to create a fine, uniform crystal grain structure before heat treatment. This preliminary refinement allows the material to undergo high-temperature bonding with minimal grain coarsening, as the cold-worked structure provides nucleation sites that control grain growth during subsequent heat treatment.
Solution Approach 2:
The patent specifies that the crystal grain size should be 10 μm or more after bonding, which is achieved by controlling the bonding temperature and time parameters. This parameter control ensures that heat treatment strengthens bonding while maintaining uniform crystal grain structure and avoiding defects.
3Quantity of substance
If pure copper material is used for high current applications, then electrical conductivity is improved, but resistance heat generation becomes a problem
Solution Approach 1:
The patent specifies copper purity of 99.9% or more to minimize electrical resistance and heat generation. By controlling the chemical composition parameter (purity) and physical structure (uniform crystal grain size of 10 μm or more), the material achieves optimal electrical conductivity for high current applications while minimizing resistive heating.
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 solution achieves a uniform and fine crystal structure in pure copper materials, reducing crystal grain size variation even after heat treatment, which enhances the material's conductivity, heat radiation, and stability in electronic devices.
Implementation Method 1
a pressure treatment is performed in a high-temperature atmosphere
Implementation Method 2
when a measurement area of 1 mm2 or more is measured by an EBSD method
Implementation Method 3
it is important to control the distribution of strains in the material
Data Source
AI summary
This pure copper material includes Cu in an amount of 99.9 mass % or more and 99.999 mass % or less, an average crystal grain size in a rolled surface is 10 μm or more, and when a measurement area of 1 mm2 or more is measured by an EBSD method at a measurement interval of 1 μm, measurement points at which a CI value obtained by an analysis using data analysis software OIM is 0.1 or less are excluded, and boundaries between adjacent pixels with a misorientation of 5° or more are regarded as crystal grain boundaries, an average of local orientation spread (LOS) is 2.00° or less.