Hi, Jason, I could not see the pictures, there is an error. Please, could you send them again? Gaby "Jason Larson, AScT" wrote: > Hi Technet, well for once I can post some information instead of asking!!! > > Awhile back I posted some questions regarding the failure of a glass zener > diode, wanting to know what the failure was. Well after some research and > money, I came up with the root cause, thought I would share my findings. > > Some pictures of the diodes can be viewed at > http://www.driveway.com/web/catalogView.jsp?dwSession=vapp03-36a84655aeb859b > c > (thanks Steve) > > The module is used in an harsh environment, exposed to various thermal > cycles, and moisture. A polyurethane compound encapsulates the components > and a nylon-glass case houses the package. > The zener is used in the circuit for clamping transient voltage levels, the > failure mode of the zener is a short. Modules were being returned exhibiting > high current draw, following some circuit troubleshooting I determined that > the zener diode was the fault, after removing the potting compound the > observed diode conditions were noted, (see photos) > Removal of the nylon case revealed evidence of moisture ingress, white > residue, the diode being located on the edge of the board was visible > through the compound. The presence of moisture and voltage, as well as > contamination (board level, salt water from road) caused cathodic reduction. > which in turn created a leakage path through the diode. > > This leads me to one question, what is the minimum distance > components and signal tracks should be placed from the edge of the board,? > (through hole components) > > Hope the information is interesting > > Jason Larson > > ############################################################## > 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 ##############################################################