Since this topic is very hot in Technet, I'd like to drop few cents of my own. All we, boneheads know board design and fabrication processes are contributing factors for flatness of boards. Hope we all realize that CTE of FR4 material is approx. 130'c. When the material goes above this temp during board fabrication, reflow or wavesoldering processes, it expands, shrinks, warp, bows, and do all kinds of bad things to itself. So why not a mad chemist invents a board material with CTE of 250'c or higher?... Using OSP or Ni/Au surface finish boards provides consistent flatness because they are not subjected to thermal stress during board fabrication process, unlike HASL process. regards Matthew Park Automation Engineer Norsat International Inc. BC. ############################################################## 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 ##############################################################