I'd agree with Greg Bartlett's memo (below). I've actually performed the cross sections and have seen the damage. Also see the memo from Gerry Gagnon on this topic. We have photos showing the plugged vias bulge up and interfere with SMT components. Paul Terranova [log in to unmask] Phone: 508-467-3109 FAX: 508-467-6796 DIGITAL's Analytical and Environmental Test Services Lab Digital Equipment Corporation M/S: MRO1-3/D2 200 Forest Street Marlboro, MA 01752 From: NAME: Greg Bartlett <[log in to unmask]@PMDF@INTERNET> To: NAME: Frank Hinojos <[log in to unmask]@PMDF@INTERNET>, NAME: technet <[log in to unmask]@PMDF@INTERNET> RE>Tented Vias 6/25/97 Hi Frank, I'm not sure that there are many problems with tented vias entrapping contaminants, but I'd believe that *plugged* vias after HASL can cause trouble. My guess is that the underlying reason for this is that it can be expensive and time-consuming to perform the failure analysis on single vias which might have failed. It requires microsectioning and metallographic inspection equipment, as well as skilled analysts, that most companies don't have. In a past life, I was with a large OEM that had these capabilities, and we actually discovered some vias which had corroded through because of the presence of entrapped water soluble fluxes. I seem to remember that it only took a month or so to eat through the 1 mil of copper plating. At Mercury, we haven't plugged vias for quite some time now because of the entrapped contaminant issue, but also because we had a problem with the solder stencil sitting too far from the board. This gave us lousy printing of our BGA patterns. We don't do any ICT, and we partially cover our via pads with soldermask. This, in conjunction with a bare copper/OSP surface finish, tends to prevent bridging through the solder wave. Greg Bartlett Mercury Computer Systems Chelmsford, MA [log in to unmask] -------------------------------------- Date: 6/24/97 9:05 PM To: Greg Bartlett From: Frank Hinojos A couple of weeks ago I asked all of you about the dangers of using tented LPI vias. I received an overwhelming response that while it is good for assembly, it may be very detrimental to the boards' reliability due to chemical interaction of contaminants and uncured LPI in the via. Why then does it seem that everyone is using tented vias and why haven't we heard of problems arising due to your concerns? Frank Hinojos Watkins-Johnson Co. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************