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Ask the Experts

July 31, 2006 - Updated
July 5, 2007 - Originally Posted

Do we have to process a 2 side SMT boards within 24 hours of breaking the seal on the packaging?

The question is in regards to Immersion Silver Board Finish and it is a leaded process. Do we have to process a double side SMT board within 24 hours of breaking the seal on the board packaging. Our room is environmentally controlled.

Ray Whittier

Expert Panel Responses

Immersion silver board finishes are very susceptible atmospheric reaction but not normally form oxygen. Sulfur is the killer of immersion silver. I have been in manufacturing facilities near highway on ramps where silver will tarnish with in on shift due to the sulfur from car exhaust. If you have a clean area and low sulfur you have a wider process window than 24hrs. But it is still recommended to keep control of these boards.

Karl Seelig
Deck Street Consultants

In his 32 years of industry experience, Mr. Seelig has authored over 30 published articles on topics including lead-free assembly, no-clean technology, and process optimization. Karl holds numerous patents, including four for lead-free solder alloys, and was a key developer of no-clean technology.

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