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Undercutting of Silver Braze on Brass after Silver-Plating Process

November 6, 2012

Q. Any help is appreciated as this problem has not been resolved over a year now. We are a manufacturer of small electronic devices that sometimes use brass sheets (0.015") that are folded over to form a box enclosure. The sides are brazed with wire braze 560 AWS BAg-7 (0.015" CD-Free Silver). Due to the design requirement, the parts are sent to the plating house to be plated with 0.0003" minimum of Silver over 0.0002" of copper. We constantly get parts back that have undercutting around the braze and brass. The braze / brass interface area is smooth when we send them to the plater. We have even sandblasted on some occasions to see if it makes a difference. We suspect some type of chemical etching of the zinc in either the brass / braze interface during the activation of the parts before the plating. We have sent the parts to 2 different plating houses and have similar results. They cannot tell us what is happening. The problem with this undercut is that some part of the silver braze will become very thin as to act like a flake and possibly fall off if touched. We are trying to obtain some Silvatech B60T BAg-18 (it doesn't contain Zinc) in hope that it will not undercut. Any suggestion as to possible cause or solution. Thank you.

Trung Lively
- Orlando, Florida