PCBA Tech - Auxiliary welding during PCBA processing

Auxiliary welding during PCBA processing
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During PCBA processing, some materials are sometimes difficult to solder. In some cases, special flux must be used for auxiliary soldering.
PCBA processing is difficult to weld aluminum and its alloys due to the formation of the passivation layer of aluminum oxide. The flux must be able to destroy this layer and be able to fully wet the solder. Some metal salts or organic compounds can be added to the flux, and the salt must be able to penetrate the cracks in the oxide layer. Metal ions are more expensive than aluminum and then undergo a redox reaction, dissolving the surface layer of aluminum and forming deposits in it. The intermediate layer of another metal can then be wetted with solder.

For example, a combination of triethanolamine, fluoroboric acid, and cadmium fluoroborate. More than 1% of magnesium in the alloy will impair the effectiveness of the flux because the magnesium oxide layer is more resistant to fire. Another possibility is an inorganic flux composed of zinc chloride or tin(II) chloride, ammonium chloride and fluoride. The presence of silicon in the alloy will impair the effectiveness of the flux, because silicon does not undergo an exchange reaction with aluminum.

1. Magnesium alloys. The flux for welding these alloys at low temperatures is molten acetamide. Acetamide can dissolve the surface oxides of both aluminum and magnesium.

2. Stainless steel is a difficult-to-weld material due to its stable self-healing surface oxide layer and low thermal conductivity. A solution of zinc chloride in hydrochloric acid is a common flux for stainless steel; however, it needs to be removed completely because it can cause pitting corrosion. Another high-efficiency flux is phosphoric acid; but the tendency to polymerize at higher temperatures limits its application. iPCB is happy to be your business partner. Our business goal is to become the most professional prototyping PCB manufacturer in the world. With more than ten years of experience in this field, we are committed to meeting the needs of customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requirements. As one of the most experienced PCB manufacturers and SMT assemblers in China, we are proud to be your best business partner and good friend in all aspects of your PCB needs. We strive to make your research and development work easy and worry-free.
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