Aluminum Composite Brazing with Pickled Solder Layer
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Solution Overview
Problem
Existing thermal joining methods for aluminum composite materials, such as Controlled Atmosphere Brazing (CAB) and vacuum soldering, often require fluxes, which lead to increased costs, technical issues with flux residues, and environmental concerns, especially in applications like heat exchangers.
Innovation Solution
An aluminum composite material with an etched surface, achieved through alkaline pickling, is used for flux-free soldering, where the surface is degreased and pickled to expose silicon particles, enhancing wetting properties and allowing for effective soldering without the need for fluxes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flux is used in CAB soldering process, then soldering performance is improved, but system costs increase and flux residues cause technical problems and environmental pollution
Solution Approach 1:
The invention extracts and removes the flux component from the soldering process by using a specially designed aluminum solder layer composition (Al-Si-Mg alloy with specific ranges: Si 5-20 wt%, Mg 0.01-3 wt%) that enables flux-free soldering. The aluminum solder layer is designed to react with aluminum oxide without requiring external flux, thereby eliminating flux residues and their associated harmful effects while maintaining soldering performance.
Solution Approach 2:
The invention changes the chemical composition parameters of the aluminum solder layer by incorporating specific amounts of silicon and magnesium elements. This parameter modification allows the solder layer to achieve self-fluxing capability through controlled reactions with aluminum oxide, eliminating the need for external flux and preventing harmful residue formation.
2Reliability
If two-layer aluminum solder structure is used, then flux-free soldering is achieved, but production costs increase
Solution Approach 1:
The invention applies local quality by creating a functionally differentiated aluminum solder layer with a total thickness of 5-20 micrometers, where the composition is optimized locally to provide both oxide removal and wetting functions. The Al-Si-Mg alloy composition is specifically designed to achieve flux-free soldering with a single layer, eliminating the need for complex multi-layer structures and reducing production costs.
3Reliability
If alkaline pickling is applied to aluminum solder layer, then surface etching and silicon exposure improve wetting properties, but process complexity increases
Solution Approach 1:
The invention applies preliminary action by incorporating magnesium and silicon elements into the aluminum solder layer composition before soldering. These elements pre-positioned in the alloy react with aluminum oxide during heating to create a etched surface with exposed silicon particles that enhance wetting properties. This preliminary compositional design eliminates the need for separate alkaline pickling process steps, reducing process complexity while maintaining improved wetting.
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
This method provides reliable, cost-effective flux-free soldering with improved corrosion resistance and reduced environmental impact, as it eliminates flux residues and interaction issues with coolant additives, while maintaining excellent soldering performance.
Implementation Method 1
the aluminum solder layer consists of an Al-Si aluminum alloy which, in addition to 5% by weight to 20% by weight of silicon, also contains 0.01% by weight to 3% by weight of magnesium
Implementation Method 2
after alkaline pickling of the surface of the aluminum solder layer, the properties of the aluminum composite material can change drastically
Data Source
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Figure 3
Figure 4a
AI summary
The invention relates to the use of an aluminium composite material consisting of at least one aluminium core alloy and at least one external solder layer consisting of an aluminium solder alloy, provided on one or both sides of the aluminium core alloy. Starting from this prior art, the present invention addresses the problem of proposing a thermal joining method for an aluminium composite material such that the use of fluxes can be omitted. The problem is solved in that the aluminium solder layer of the aluminium composite material has a pickled surface and the aluminium composite material is used in a flux-free thermal joining method and the joining method is performed in the presence of a protective gas.