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topic 9295

Cracking of plated copper alloy parts during bending



I'm having a problem with copper alloy parts with small diameters (0.6mm) being bent at a 90 degree angle, with a bend radius of 0.6mm. The plating is copper flash, low stress nickel sulphamate, then pure gold on top (99.7%). The parts sometimes crack, and sometimes break right off. Other times, they look great. I know that the MIL specs suggest deforming before plating, but that is not an option in some cases because of the product hierarchy and assembly issues.

Any suggestions?

Paul Cabana
- Hudson, Mass, USA

First of two simultaneous responses -- (2001)

My guess would be that you might not have an equal thickness of nickel plating on all the parts. The parts which the thicker plating, would be the ones that have cracked plating. The ones with thinner nickel layer might be the ones that remained ok. I would check on these lines.

Mark Camilleri
- Malta

Second of two simultaneous responses -- (2001)

Is the plating coming off, or is the parent metal breaking? If the metal is breaking, lower the hardness or anneal after plate at a suitable temp/time for the metal and plating. This will take a higher temp than the conventional 375F used for de-embrittlement.

James Watts
- Navarre, Florida

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