Restoring Immersion Sliver PCBS?

I've written before about immersion silver finished boards and some of the challenges associated with that technology. It's a popular choice for RoHS these days because it's inexpensive compared to some of the others, has a nice planar surface and, conveniently, is, in fact, RoHS compliant.

Silver_sampleIt has a somewhat high nuisance factor though, because of its proclivity to tarnish and susceptibility to fingerprint grease and other surface contaminants. All the board houses will say it doesn't have any of those issues, but it does. Immersion silver pcbs need to be kept clean, dry and dark. Even then they still have a shelf life. A silver board doesn't take solder well if it's been stored too long, poorly or mishandled. Nag, nag, nag. Okay - got that out of my system...

So, what do you do if your boards have surface issues? Do you toss them? Do you send them to a psychologist? Do you turn them into expensive cubicle art? Do you use them like a Frisbee®? One of my manufacturing engineers told me that some board houses will re-plate them for you. For a fee, of course.

Apparently, in some cases, they can dip the boards and etch the old silver surface off and then re-plate them. I don't know if all board fab shops can or will do this, but if you have a couple of hundred dollars worth of unusable PCBs, it would certainly be worth a call to your Board fab shop to see if they can re-plate them for you.

Has anyone already had silver boards replated? Drop me a comment - I'd like to hear how it worked out for you.

Duane Benson
No Tarn-X, please

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Thanks for the note. I suspect this may be one of the areas where theory and actual practice diverge, but I'll see if I can hunt down some of that information at Sandia. Any one else have any thoughts here?

Long term aging studies have been done with ImAG boards kept out in the open. They still solder well, and the visible tarnish has been tested and verified to have NO adverse impact on RF performance in sensitive weapons systems applications. Sandia National Labs has details regarding this PCB finish.

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