Hi Steve, what became of your piezoelectric "microphones"? /Ingemar -----Original Message----- From: Stephen R. Gregory [mailto:[log in to unmask]] Sent: den 31 maj 2000 00:20 To: [log in to unmask] Subject: [TN] Capacitor issues... Hi All! This is a weird one. We've been building a board for a customer for quite some time now. Hadn't had a problem since until recently (after going through some ECO's). Customer thinks we've got a bad batch of capacitors. They're a ceramic 1206 that's reflowed on, the dielectric is a X7R, and is placed by a Phillips Topaz. I've looked at the cap under a microscope and don't see any evidence of fractures. The cap in question is in the center of a .031" board, and is in a scored 6-up panel. The customer says they can tell when there's a bad cap on the board, by putting it on a test fixture and putting finger pressure on the cap and watching for the value to change for the capacitor. If it changes, it's bad, if it doesn't, it's good. Does that sound like a good test? The reason I ask is because I've read on one of KEMET's web page "Knowledge Edge" articles that dielectrics such as X7R are considered ferroelectric dielectrics, and have a common characteristic of piezoelectricity, so by putting pressure on the cap it is going to change the values, won't it? Just trying to understand... -Steve Gregory- ############################################################## 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 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 1.8c ############################################################## 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 Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################