Aluminum Solder Composite Surface for Flux-Free Joining
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Solution Overview
Problem
Existing composite materials with exposed silicon particles on the surface cause increased tool wear during mechanical separation processes due to high surface roughness, which is abrasive and leads to poor solderability and dimensional accuracy in flux-free soldering.
Innovation Solution
The composite material is modified by ensuring that silicon particles partially exposed on the surface do not protrude beyond the aluminum matrix, achieved by incorporating at least 0.1 wt% bismuth in the aluminum solder alloy and using a pickling treatment before the final cold rolling pass to embed the silicon particles within the matrix, reducing surface roughness and maintaining flux-free solderability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkaline pickling is performed after cold rolling to expose silicon particles on the surface, then flux-free solderability is improved, but surface roughness increases and tool wear increases
Solution Approach 1:
The patent applies preliminary pickling treatment before the final cold rolling pass instead of after. This timing ensures silicon particles are exposed and embedded in the aluminum matrix before rolling, achieving flux-free solderability while the subsequent rolling process reduces surface roughness and prevents excessive tool wear during mechanical separation
Solution Approach 2:
The patent changes the timing parameter of the pickling process from post-rolling to pre-rolling, and controls the cold rolling conditions to achieve optimal surface finish. By adjusting the rolling pass sequence and pickling timing, the process achieves both solderability and low tool wear
2Reliability
If silicon particles are exposed on the surface to enable flux-free soldering, then solderability is improved, but surface roughness increases leading to poor dimensional accuracy
Solution Approach 1:
Pickling is performed before the final cold rolling pass to expose silicon particles, then the rolling process embeds them in the matrix and smooths the surface. This preliminary timing ensures both solderability and dimensional accuracy are achieved
Solution Approach 2:
The cold rolling process that could potentially increase surface roughness is instead used beneficially to embed the exposed silicon particles into the aluminum matrix, smoothing the surface while maintaining the silicon exposure needed for solderability
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 results in low-wear mechanical processing and improved solderability, allowing for flux-free soldering with reduced tool wear and enhanced dimensional accuracy, while maintaining the soldering quality.
Implementation Method 1
the solder layer of the finished composite material is alkaline pickled after cold rolling
Implementation Method 2
the solder layer of the finished composite material is alkaline pickled after cold rolling
Data Source
AI summary
A composite material and method for producing said composite material are disclosed, with a support layer composed of a wrought aluminum alloy and with an external solder layer composed of an aluminum solder alloy provided on one or both flat sides of the support layer, wherein the solder layer has partially exposed silicon particles on its surface, which constitute a first area fraction of the total area of the surface of the solder layer. In order to reliably ensure flux-free solderability, it is proposed for the solder layer to have a rolled surface and for its aluminum solder alloy to contain at least 0.1 wt % bismuth (Bi), wherein the first area fraction is greater than 2.5%.