We are currently seeing strange component failures in the PLL circuit of one of our assemblies. The components are as follows: 1) BB619 Tuning diode SOD-23, defective 2) 1500 pF NPO Nickel Barr .080 X .05 Cap, becomes resistive? 3) BAV99 Dual Diode SOT-23, PN junction damaged All of the parts are surface mount an contained within the walls of a SMT RF shield with just the fence installed during reflow. The dimensions of the fence is 1.75" square at a height of .5". We use a very similar circuit on another assembly that does not have any of these problems nor does it have a SMT RF shield. I believe the damage to the components is heat related? One theory I have is during reflow, the shield fence acts as a large heat conductor and transfers the heat , through the ground, to the components causing heat related damage? All but the tuning diode has one pin connected to ground. I have never heard of a case where something like this has happened. Could it be heat radiated off the four walls of the fence, creating a oven within the area of the walls? Does anyone have any other ideas or have seen similar problems? Any help would be appreciated! Thank you. Best Regards, Mike Forrester LeCroy Corp. [log in to unmask] ############################################################## 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 ##############################################################