Richard, A fairly good paper on the subject is one by Luis Torres. It is dated 1984, but gives tha basic formulas and reasonings along with some test data. It is IPC-TP-510 "Thermally Induced Strain in Plated Through Holes" and is available fron the IPC order desk. Phil Hinton ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################