Pros/Cons of Gold immersion boards(solderability)

Wayne,

I haven't seen anything indicating that Gold Immersion is necessary for lead free...

However, it is my companies preferred finish for lead free assemblies.

We've taken this stance for the following reasons: 1. Better solder quality on through-hole parts. This was determined through personal experience, and your mileage may vary. However, we found that white-tin finishes resulted in a very large quantity of voids/blow-holes during wave soldering. Gold immersion finishes did not exhibit these issues.

2. Better over-all processing. While white-tin is cheaper, we found that the issues related with keeping the finish clean for manufacturing out weighed the cost increase of gold immersion. We were cleaning all white-tin assemblies with alchohol prior to each paste application, just to keep ahead of the poor-solder issues we encountered when we didn't clean them.

3. Better leveling from the board house. I haven't personally observed the differences in this, but my board house assures me that with gold immersion, they can produce higher quality product. This became important to us in some BGA assemblies, as well as some 0402/0201 assemblies.

cheers, ..rob

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