Hi Phil, I can only comment on the last of your questions from a laboratory failure analysis viewpoint. We have one customer whose PCB assemblies exhibited the "black pad" separations on a BGA component. They thought that underfilling the BGA would help hold the solder balls onto the board, but cross-sections after the underfill process showed that the balls separated anyway. I don't know if would happen with every type of underfill process, but it did not seem to have a positve effect for this customer. Wade McFaddin Nextek Inc. > -----Original Message----- > From: phil bavaro [SMTP:[log in to unmask]] > Sent: Friday, February 22, 2002 11:34 AM > To: [log in to unmask] > Subject: [TN] ENIG black pad issues > > We have used ENIG as our primary BGA board finish for many many, many > boards built for cellular communications without issues regarding this > problem. > > We have a major PWB fabricator telling us that they cannot control what > appears to be a "black pad" problem and that we should be changing to > Entek's OSP combined with a selective gold process for our standard > finish. > > I cannot say that we have never had this problem before but usually it was > more a case of unrinsed soldermask on a pad rather than corroded nickel > plating beneath the gold finish. > > I did the cross sectioning myself and took some great pictures of the > contaminated pad surfaces that were yielding when subjected to drop > testing. > > I am convinced that ENIG is a solid finish but I know that it can be > susceptible to nickel wetting problems. I have three questions: > > 1) What kind of frequency are the rest of you finding "black pad" to > occur > on ENIG boards? > 2) What finish do you use for high density BGA/CSP double sided boards > that have surface contact (gold) plating requirements? > 3) Are any of you using underfill to hopefully negate the solder joint > brittleness that the black pad surface inherently creates? > > -------------------------------------------------------------------------- > ------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt delivery of Technet send e-mail to [log in to unmask]: > SET Technet NOMAIL > To receive ONE mailing per day of all the posts: send e-mail to > [log in to unmask]: SET Technet Digest > Search previous postings at: www.ipc.org > On-Line Resources & Databases > > E-mail Archives > Please visit IPC web site http://www.ipc.org/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > -------------------------------------------------------------------------- > ------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------