Dear Doug: Thank you very much for your reply. Where can I get a copy of Bellcore 332? Is it for free? Best regards Kang >From: Doug <[log in to unmask]> >Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>, Doug <[log in to unmask]> >To: [log in to unmask] >Subject: Re: [TN] Reliability Prediction Methods >Date: Mon, 12 Jun 2000 23:32:10 -0700 > >Kang Zhang wrote: > > > > Hello all > > > > Two questions: > > > > 1. Is there any big difference in reliability prediction results between > > using MIL-HDBK-217F notice2 and using Bellcore? I just try MIL. Using > > Bellcore can get "better" MTBF or "worse"? > > > > 2. Except the above two, are there any other methods to predict the > > reliability of electronic components, such as FET, Bipolar? > > > > Any inputs are very welcome. Thanks in advance! > > > > Kang > >For #1 ... >My opinion only, I've no experience with the MIL-217 >(what I'm comparing Bellcore with MIL-217 is what a > colleague I saw go through with 217), but I've been >working with Bellcore 332 for a couple of years now. > >Bellcore will give you better "numbers". The assumption >with Bellcore 332 is 50% electrical stress and uniform >temp stress on the part (usually 40 degrees C). That's >a global assumption, i.e. all parts throughout the entire >system. The guy I knew who worked extensively with 217 >made individual electrical and temp stress measurements >for the MIL contracts he worked on. Very tedious work. >I'm not sure if that's really necessary for 217, but >that's what the guy I knew did. > >For #2 ... >Yes. The reliability numbers the semiconductor >industry produces comes from using the Arrhenius >equation in conjunction with accelerated temp >testing of the chip. Emailed back and forth with >one of the reliability engineers over at Intel >about it a couple of years ago. Since, they use >so many different types of material in the making >of a chip, the activation energy (which is needed >for the Arrhenius equation) is guessed at. But >this is all used for the accelerated temp testing >they do for chips. But the bottom line is that >they develop a lot of empirical data over time. >So they're pretty accurate. > >Just an aside. I was corrected by a vendor once rather >sternly for using MTBF for a part. They were adamant >that "MTBF" was to be used for something that was to >be repaired such as a printed circuit board. The correct >acronym for a part is MTTF or Mean Time To Failure. The >key words being "Between" versus "To". You don't >"repair" a chip or a fuse. It's from this type of >database and field repair reports the come into Bellcore >that the FITs (Failure In Time) data tables in the back >of 332 are generated. I believe 332 edition 4 had >some corrections to some FITs values in edition 5 >to make them more realistic. > >Regards, Doug McKean > >############################################################## >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 >############################################################## ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ############################################################## 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 ##############################################################