Pure Copper Sheet Composition for Uniform Grain Growth During Joining
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Solution Overview
Problem
Conventional pure copper sheets used in electrical and electronic components face issues with nonuniform coarsening of crystal grains during high-temperature joining, leading to poor joining and appearance defects, and the addition of sulfur to suppress grain growth deteriorates hot workability.
Innovation Solution
A pure copper sheet composition with specific impurity elements (P, Pb, Se, Te, Ag, Fe, S, and others) and controlled grain boundaries to suppress crystal grain coarsening and ensure uniformity, maintaining hot workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sulfur content is increased to suppress crystal grain coarsening, then crystal grain growth is suppressed, but hot workability significantly deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by precisely controlling multiple impurity elements (P: 0.01-3.00 mass ppm, Pb+Se+Te: ≤10.0 mass ppm, Ag+Fe: ≥3.0 mass ppm, S: 0.01-5.00 mass ppm) rather than simply increasing sulfur content, achieving grain boundary strengthening without sacrificing hot workability
Solution Approach 2:
The patent creates a composite effect by combining multiple impurity elements that work synergistically: P, Pb, Se, and Te segregate to grain boundaries to suppress grain growth, while Ag and Fe form solid solutions in the matrix, achieving both grain refinement and maintained workability
2Strength
If pressure heat treatment is performed at high temperature for joining, then joining strength is improved, but crystal grains become coarse and nonuniform
Solution Approach 1:
The patent performs preliminary grain boundary strengthening through controlled impurity segregation before the pressure heat treatment process, so that when high-temperature joining is performed, the grain boundaries are already fortified and resist grain coarsening during the subsequent heat treatment
Solution Approach 2:
The patent modifies the material's chemical composition parameters to create a more stable microstructure that is resistant to grain coarsening during high-temperature processing, enabling the material to withstand pressure heat treatment without significant grain growth
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 effectively prevents crystal grain coarsening and nonuniformity after pressure heat treatment, ensuring excellent hot workability and suitable appearance for electrical and electronic components.
Implementation Method 1
0.01 mass ppm or more and 3.00 mass ppm or less of P, 10.0 mass ppm or less of a total content of Pb, Se, and Te... in which an average crystal grain size of crystal grains on a rolled surface is 10 μm or more
Implementation Method 2
there is an element having a crystal grain growth-suppressing effect of suppressing the coarsening of crystal grains by being present at crystal grain boundaries
Implementation Method 3
3.0 mass ppm or more of a total content of Ag and Fe... the content of Ag and Fe is 3.0 mass ppm or more
Implementation Method 4
a heat treatment is performed at a high temperature in a state where the ceramic substrate and the copper sheet are pressurized at a relatively high pressure (for example, 0.1 MPa or more) in the stacking direction
Data Source
AI summary
A pure copper sheet of the present invention has a composition including 99.96 mass % or more of Cu, 0.01 mass ppm or more and 3.00 mass ppm or less of P, 10.0 mass ppm or less of a total content of Pb, Se, and Te, 3.0 mass ppm or more of a total content of Ag and Fe, and inevitable impurities as a balance, in which an average crystal grain size of crystal grains on a rolled surface is 10 μm or more, an aspect ratio of the crystal grain on the rolled surface is set to 2.0 or less, and a length percentage of the small tilt grain boundary and the subgrain boundary with respect to all grain boundaries is set to 80% or less in terms of partition fraction.