A customer of Metallic Resources (manufacturers of bar solder) assembles circuit boards. One of the many tests the boards go through is a thermal cycling test to see if thermal shock can cause failure in the circuit board. The customer's test specification is Spec Number TSC7514g, section 5.4, reference specification TSC 7010g. (We do not know what this means.) The customer cycles the circuit board from -30 degrees celcius to +80 degrees celcius. The board temperature is dropped to -30 and held for thirty minutes. The board temperature is then raised to +80 and held for thirty minutes, until the temperature is lowered again and so forth for a total of 3,500 hours. The customer is now noticing solder joint failures on this double sided board on the top, which is both through-hole and SMT (failures of solder paste joints on the top), and on the bottom, which is just through-hole (failures of bar solder joints). Solder joints, both top and bottom, show much cracking and some flux residue. The first question is: is this customer using their own test or is there an IPC test for thermal cycling of a completely assembled circuit board? The second question is: is the customer's temperature range too extreme, which is causing severe thermal shock, which is then causing joint failures due to different co-efficients of expansion and contraction (board, solder, lead)? The third question is: is the use of 3,500 hours of thermal cycling realistic and/or too long? Any comments would be appreciated. Sincerely, METALLIC RESOURCES Howard P. Stevens --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------