Bob, Was electrical monitoring performed in-situ? If you only monitor before and after exposure (or only during dwells), you are often missing bad solder joints, especially in ball grid arrays. Craig -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Perkins Sent: Tuesday, March 20, 2001 5:10 PM To: [log in to unmask] Subject: [TN] BGA Thermal Cycling and cold spray Hi all, I have a question regarding thermal cycling, a good pcb that has passed all pretests and post tests with a typical thermal cycle. A few PCBs were then hit with a cold spray of -30c and then tested again, after this test a fall out of 20%. Are we introducing a crack by the severe thermal shock of the cold spray or is it revealing a bad solder joint. Thanks in advance, Bob Perkins SMT Process Manufacturing, Automation Technician Aimtronics-Delta ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------