I have studied the effect of PCB flexure on the cracking of MLCs. This failure mechanism is widespread throughout the industry and can lead to latent failures. For normal case sizes in the worst orientation, a microstrains of about 1300 are in the danger zone for cracking the ceramic body (not the solder joint). Trying to apply this number is problematic since predicting how much flexure the PCB will see is difficult. Check out Murata's application note on this subject. Bob Veale Rockwell Automation Breton Flemming writes "I am involved in a project with the objective of understanding effects of PCB surface strain (due to flexure) on component reliability. Throughout my research, I have encountered studies surrounding global effects of warpage and flexure on product reliability, but have not found values indicating maximum stress/strain thresholds for individual surface mount components. The advantage of such information would be to give general ideas about component placement issues on any board, not just one particular size or geometry. Any direction as to possible sources of information relating to individual component stress/strain thresholds (studies, books, articles, etc.) would be greatly appreciated along with any thoughts or comments. Any surface mount components are of interest for any one of the following failure mechanisms: yield, creep, fatigue." ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################