Copper Alloy Plate Surface Finish for Soldering
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Solution Overview
Problem
Existing Co-Si based copper alloys face issues with incomplete removal of oxide films and foreign matter, leading to pinholes during soldering, which degrades solder wettability and increases imperfections in soldered areas, especially when acid pickling and grinding are not adequately performed before final rolling.
Innovation Solution
Conducting multiple rounds of acid pickling with a fine-textured buff after final heat treatment to ensure complete oxide film and foreign matter removal, achieving a smooth surface with specific anisotropy and reduced pinholes, while maintaining excellent solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid pickling and grinding are conducted before final rolling, then oxide film removal is improved, but pin holes are generated during soldering
Solution Approach 1:
The patent applies preliminary action by conducting acid pickling and buffing with fine-textured grinding grains BEFORE final rolling to remove oxide films and foreign matters. This preliminary surface treatment ensures that when final rolling occurs, the surface is already clean and smooth, preventing pin hole formation during subsequent soldering processes.
Solution Approach 2:
The patent changes the parameter of surface roughness by specifying Ra ≤ 0.2 μm and Rt ≤ 2 μm after the acid pickling and buffing process. This parameter control ensures the surface is smooth enough to prevent pin holes while maintaining adequate oxide film removal, resolving the contradiction between complete oxide removal and preventing soldering defects.
2Productivity
If buffing with acid pickling is conducted insufficiently, then productivity is improved, but solder wettability is degraded
Solution Approach 1:
The patent changes the parameter of surface roughness to Ra ≤ 0.2 μm and Rt ≤ 2 μm, which provides optimal solder wettability. By controlling these parameters through buffing with fine-textured grinding grains, the patent achieves good soldering quality without requiring excessive processing steps, thus maintaining productivity while improving reliability.
3Shape
If oxide film is not completely removed, then surface smoothness is maintained, but pin holes are generated during soldering
Solution Approach 1:
The patent simultaneously controls surface roughness parameters (Ra ≤ 0.2 μm, Rt ≤ 2 μm) and oxide film removal completeness through the acid pickling and buffing process. This dual parameter control ensures the surface is both smooth and free of oxide films that would cause pin holes, resolving the contradiction between maintaining surface smoothness and ensuring soldering quality.
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 process significantly reduces pinholes and enhances solder wettability by ensuring a smooth surface with controlled surface roughness and specular gloss differences, improving the overall quality of soldered joints.
Implementation Method 1
acid pickling is conducted after a final heat treatment, and the oxide film is dissolved and further removed
Implementation Method 2
buffing with acid pickling for a sufficient number of times using a relatively fine textured buff (grinding grains) after the final heat treatment such that the oxide film on the surface of the material and the foreign matters pushed by the rolling are removed
Data Source
Figure 1(a)~2
Figure 3
AI summary
A Co-Si based copper alloy plate, comprising: Co: 0.5 to 3.0% by mass, Si: 0.1 to 1.0% by mass and the balance Cu with inevitable impurities, wherein the Co-Si based copper alloy plate satisfies the relationship {(60 degree specular gloss G(RD) in a rolling direction) - (60 degree specular gloss G(TD) in a direction transverse to rolling direction)} => 90%.