Dear All, I am only an occasional subscriber to the Technet but I have found it very useful in the past when I have a technical query. I am using multi-layer boards in aerospace applications and I am having to weed out latent PCB defects by stress screening the bare boards. My current stress screening in a HALT chamber uses a temperature range of -40 deg C to +125 deg C, 35 deg C / min ramp rate, for 5 cycles. The board supplier then performs continuity tests and this confirms hard faults on 0% to 20% of boards. I am concerned that I may not be precipitating all latent faults and I am interested to know if I could use a wider range of temperature extremes. Can anyone tell me if FR4 boards may experience damage in the region -40 to -70 deg C or above +125 deg C? Best regards Terry Exell BAE SYSTEMS Plymouth, UK ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** --------------------------------------------------------------------------------- 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------