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Printed Circuit Board (PCB) to Stainless Steel in Spa Environment

 

I'm trying to determine the best material combination to use in a chlorine/bromine environment. The device will not be in direct contact, but the air around will be very humid with those chemicals. (It's a Pool/Spa application) I have to make a connection between a Printed Circuit Board (PCB) and a Stainless Steel contact arm. This connection has to withstand 100,000 operations. I am assuming if I gold plate both the PCB and the contact that would be best. But for a cheaper solution, I'm wonder if plating neither or just one might work. Is the Soldermask over Copper finish of a standard PCB good enough to withstand this? What about the Stainless Steel (304, I believe). The important factor is the contact intergity, it cannot corrode and not make good electrical contact.

Jon Cusack
TruHeat - Allegan, Michigan

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A switch made of 304 stainless and solder in a humid wet spa for 100,000 cycles. No, I think you should use an enclosed switch. Given the fatal accidents concerning the location of emergency shutoff switches, and the new electrical code that followed the accidents, it would be better to have a reliable connection.

  
Tom Pullizzi
Falls Township, Pennsylvania

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It depends on a number of things including the voltage and current that the contact will carry. If you look at a cell phone, for example, you'll see electroless nickel is usually sufficient for the charging circuit, but gold is used for the lower current signal contacts. Circuit board fingers used to frequently be tin in the days of bigger components and larger currents, but are usually gold these days unless the insertion is very infrequent and has a good high pressure basis. In a spa environment, anything short of gold is begging for reliability trouble I think.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey