I would ask Dr. Laura Turbini at Georgia Tech. She has done some work on filament corrosion on pwb's and this sounds very similar. Suzanne _______________________________________________________________________________ To: Nachbor Suzanne; Savage Bill From: Seppanen Gordy on Fri, Mar 29, 1996 11:10 AM Subject: FW: Military Polyimide Board Failures FYI for the IPC Technet service. Please forward to anyone else you know. Gordy _______________________________________________________________________________ To: [log in to unmask] From: TED JONES on Fri, Mar 29, 1996 10:30 AM Subject: Military Polyimide Board Failures The Navy has recently experienced field failures (shorts) on three 7-layer polyimide PWBs. The boards had operated for 300 hours in a sealed chamber. The chamber is maintained at 50C, with constant humidity. The shorts (about 8 ohms of resistance) developed between a PTH and ground plane on layer 5. There is a voltage potential of 30 volts (+15/-15) between the PTH and plane. The clearance between the PTH's pad and the plane is 10 mils. Horizontal microsections of the failed areas do not show any obvious migration path. The only anomaly noted on the failed pad is that it demonstrates much more pink ring than pads on adjacent PTHs. We're looking for ideas on the most likely cause of the shorts. Have there been any studies done that indicate pink ring will or will not contribute to this type of failure? Has anyone seen similar failures?