After some problems here with cracked solder joints on Alloy 42 leaded TSOP devices, our stress analysis expert did some calcxulations And found that the stress were above yield strength for the SN63 solder but not by much. We sent some of the devices back to the manufacturer for their testing and they found solder joint pull forces necessary to break the lead/solder bond to be between 0.33 Kg and 0.78 Kg. The former is 0.726 lbs and the latter is 1.716 lbs. We are talking about fine pitch 19 mil. Some one in the assembly business said that between 1.0 and 1.5 lbs pull is expected. These alloy 42 leads had a tin/lead (high lead composition) plating which was not reflowed. My experience shows has been that tin/lead plating has to be reflowed in order to be a protective film. This type of plating is very porous and the lead oxidizes easily. I hear reports from some quarters that alloy 42 TSOPs are used successfully and others say never use alloy 42 TSOPs they don't work. We encountered a manufacturer who used identical TSOPs as we used but did not complain about any problems. The difference was that they assembled the parts as soon as they arrived. We did not. Our solder joints showed cracks at the heal hours after soldering. Reflow of our stressed joints manually, using RMA flux, alleviated the problem. I am thinking here that the alloy 42 TSOP problem is caused partly by solderability and partly by coefficient of expansion mismatch. I have heard that some people are changing to palladium or palladium/silver plating to overcome solderability problems. Can some one tell me where to learn about these platings and are they worthwhile pursuing. ############################################################## 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 ##############################################################