No problem we had several cases with copper dendrites between interconnects or vias to ground that grew in the field below conformal coatings or soldermasks. By EDX we confirmed that the dendrites are copper.
Tell me where to send the pics and I'll post them.

Best regards

Günter Grossmann
Scientist
Empa
Swiss Federal Laboratories for Materials Science and Technology
Überlandstrasse 129
8600 Dübendorf
Switzerland
Tel +41 58 765  4279
Fax +41 58 765 4054
[log in to unmask]
www.empa.ch


>-----Ursprüngliche Nachricht-----
>Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Paul Reid
>Gesendet: Donnerstag, 5. Juli 2012 20:58
>An: [log in to unmask]
>Betreff: Re: [TN] Copper Dendrites
>
>I doubt that this was copper dendrites.
>
>Sincerely,
>
>
>
>Paul Reid
>
>Program Coordinator
>
>PWB Interconnect Solutions Inc.
>235 Stafford Rd., West, Unit 103
>Nepean, Ontario Canada, K2H 9C1
>
>613 596 4244 ext. 229
>
>Skype paul_reid_pwb
>[log in to unmask]
>
>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Neil Atkinson
>Sent: July 5, 2012 2:51 PM
>To: [log in to unmask]
>Subject: Re: [TN] Copper Dendrites
>
>Thanks everyone for comments so far - haven't been on Technet for a
>while so it was good to get such good responses.
>
>Really miss Werner for questions like this...
>
>Actually we have never seen a failure for dendrites; however, we have a
>customer who has a past problem with another supplier due to dendrites
>on PCBs and as a result wants us to cover vias with solder resist or
>conformal coating.
>
>Tha,
>
>Neil
>
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