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February 1999

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Subject:
Galvanic reactions
From:
doug smith <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 18 Feb 1999 09:48:59 -0800
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In PCB fabrication process SnPb is used as an etch resist. On some boards gold is selectively plated, for example on a BGA pattern. In this case both the SnPb and the Au are being used as the etch resist.

The etch process removes unwanted copper leaving the plated circuits and component lands.

Can copper staining on gold be the result of a galvanic cell that is formed when the nickel/gold and tin/lead are used as an etch resist?

Doug Smith
Technical Support Engineer
Yamamoto Mfg. (USA), Inc.

(408)944-8308
[log in to unmask]

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