Corner cracking is usually associated with high levels of organics in an acid copper plating bath. If however these are blind vias check the plating at the bottom of the via and see if there are folds, insufficient plating or disconnects in the plating.
 
 
Scott B. Westheimer



> Date: Tue, 10 Apr 2007 22:19:55 +0800> From: [log in to unmask]> Subject: [TN] Via hole plating corner crack> To: [log in to unmask]> > Dear Techneter:> > I recently experienced customer return of corner crack. The PCB is 50 mil> thick, 10 mil via, OSP finish and corner crack is over the 4 corners of top> and bottom> of hole. Crack is started from the bottom of external foil and crack through> > the entire plating. You can see the photo (file: crack through) of actual> failure. Plating is unusual column type crystal on the surface. In the hole> barrel, the plating crystal is regular. We also performed many in-procss WIP> > cross section (refer to the file "crack 9X IR") and we could only find the> crack after 6X IR reflow and its crack is started from external foil top> corner. I have sucessfuly duplicated similar failire with very high plating> current density of 30ASF with very low brighter (0.15cc/l), but its failure> mode is crack on ehe top of external foil not the same as customer return.> My questions are:> > 1. Are these two failre modes with the same root cause? What is the reason> one crack is started from the foil top corner and the other is from the> bottom?> 2.Is there any non-destructive method able screening the cracked plating?> > > http://tw.pg.photos.yahoo.com/ph/minalong2003/album?.dir=/5c32scd> > Thank you very much.> > ---------------------------------------------------> Technet Mail List provided as a service by IPC using LISTSERV 15.0> 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)> To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest> Search the archives of previous posts at: http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815> -----------------------------------------------------
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