Joe, Thanks for correcting my mistake. Matthew >>> Joseph Fjelstad <[log in to unmask]> December 16, 1997 12:48 pm >>> Hi Matt! Good point... but I think you meant glass transition temperature (Tg) and not CTE (coefficient of thermal expansion). You may wish to correct your message Cheers! Joe At 12:16 PM 12/16/97 -0800, you wrote: >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 >############################################################## > > Tessera ...System Building Blocks for the Next Generation of Electronics 3099 Orchard Drive San Jose, CA 95134 Phone 408 894-0700 Fax 408 894-0768 ############################################################## 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 ##############################################################