Gary, In my past I have experienced similar "popcorning" of .020" pitch, 100 pin TQFP's (thin plastic). The original evaluations of the package assembly process demonstrated excellent processing capabilities, then when assembling components with die enclosed, we encountered "tombstoning" of the QFP's. One corner was lifted. When looking closely, the component appeared to be warped. Further investigations (C-SAM) clearly demonstrated popcorning on the underside of the die. The only resolution for the popcorning we found to work was to prebake the parts prior to assembly. You are correct that there are some other measures you can take to temporarily resolve the issue, but popcorning is a long term field reliability issue. Methods like C-SAM and Sonoscan are ways to non-destructively verify delamination. The equipment is costly though. I have encountered other issues where the component characteristics change over temperature. When exposed to cold environments (and sometimes ambient), the component reset. When heated it returned to a normal state. This appeared to be die related. This is probably unlikely in your case, but it is one alternative. Regards, Allen Hertz Racal-Datacom (954) 846-5829 [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: ASSY: GEN: Popcorning during reflow Author: [log in to unmask] at ftl03 Date: 10/30/96 09:27 PM Has anyone else observed the following? We have a CMOS PQFP that was "popcorned" during reflow soldering. Cross sectioning clearly shows that the die, along with its mounting epoxy, has separated from the leadframe by approximately .002" (2-mils). There were no visible cracks in the plastic overmold material at 500X magnification. The problem is...some parts don't fail until after a few thermal cycles of 0 to 50 degrees C during live circuit testing at-speed. And...we can make them recover after failing by merely baking the entire board from 1.5 to 24 hours at 125 degrees C. The baking fix is not permanent and the parts eventually fail again. Some parts don't work initially but do work after the above baking treatment (we discovered, quite by accident, that baking "fixes" the parts). My question is...is the popcorning likely to be the only problem with these parts? Has anyone else been able to anneal a part so that it will recover from popcorning? Doesn't sound likely to me! Gary P. --- Gary D. Peterson _/_/_/ _/ _/ _/ SANDIA NATIONAL LABORATORIES _/_/_/ _/ _/_/ _/ _/ P.O. Box 5800, M/S 0503 _/_/ _/_/_/ _/ _/ _/ _/ Albuquerque, NM 87185-0503 _/_/_/_/_/_/ _/ _/ _/_/ _/ Phone: (505)844-6980 _/ _/_/ _/ _/_/_/ _/ _/ _/_/_/_/ FAX: (505)844-2925 _/ _/_/ _/ E-Mail: [log in to unmask] _/_/_/ *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************