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How to prevent immersion gold depositing on stainless steel

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I am working on ENIG finishing bond pads which are build on the stainless steel substrate. But I am incapable of covering steel substrate due to the complicated structure and pattern. Can you tell how to prevent gold deposition on stainless steel during ENIG finish? Thanks.

Zhenwei Hou
Electronic Assembly - Minneapolis, Minnesota

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Which type of gold are you using? If soft you can add a small amount of cyanide just before plating. Your supplier will tell you whether to use sodium or potassium. If hard gold you should try to passivate the stainless steel but that will not be easy especially as you will have to activate the areas to be plated.
I frequently suffer immersion gold deposits on stainless steel and I remove them with gold stripper and a paint brush.

Nick Clatworthy
- Whitstable, Kent, UK

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