We have experienced several failures of multilayer chip capacitors in 120Vrms AC applications. These are 500V and 1000V DC rated, X7R, .01uF multilayer ceramic chip capacitors. After some investigation, we see that some supplier's parts survive and another supplier's devices have a high failure rate. We have ruled out causes such as flexure cracks and thermal cracks. It appears that the dielectric is degrading and breaking down under AC conditions but is OK under DC conditions. The peak-to-peak AC voltage is well within the DC rating of the part. Has anyone observed MLC failures with AC line voltage but not DC voltage? Is there any selection guidelines or other know-how for choosing a ceramic capacitor for AC across-the-line applications? Bob Veale Rockwell Automation Cleveland Ohio ############################################################## 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 ##############################################################