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Soldering to brass?

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Soldering to brass? | 7 August, 2007

General soldering question not related to SMT.

Is it OK to solder a wire to a brass terminal? It seems OK but I'm unsure about the long term reliability.

Application is a high reliability electronic utility meter.

Thanks Steve

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Soldering to brass? | 7 August, 2007

Zinc from the brass diffuses into the solder and reacts with tin causing dezincification.

Dezincification is a specific type of de-alloying, or selective, leaching corrosion of brass fittings. This type of corrosion selectively removes zinc from the brass alloy, leaving behind a porous, copper-rich structure that has little mechanical strength. This weakens the integrity of the brass fitting. [2nd paragraph excerpted from and editing of a USEPA report]

So, you need a barrier plate between the brass and the tin of the solder. Use a flash of copper or nickel-plating as a barrier between the brass and tin. Nickel has a longer shelf life, but difficult to solder. Copper is easier to control and solder. So, we suggest that you use copper.

IPC-HDBK-001, 5.1.2 Barrier Layers: Brass is an alloy consisting mainly of copper and zinc. Without a barrier layer of copper or nickel over the brass, the zinc will dissolve into the molten solder during soldering, zinc contamination of the solder joint is evident by a rough, grainy, frosty, porous surface with a high dendritic structure. Also, solder wetting to the terminal would be inhibited.

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Soldering to brass? | 8 August, 2007


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