Thanks all for the responses. The reason for my interest, we were having numerous units returned from the field. Analysis revealed cracked solder joints on the board. It was learned the units were occasionaly being subjected to a 20C per minute thermal cycle out in the field. The field failure was also subsequently verified by lab testing. The units are encapsulated for vibration protection so our thoughts were to get as robust a solder joint as possible and make sure the CTE and modulus at the temperature extremes were as benign as possible. I remember when we had real components on the board (poke through) and the module had to encapsulated with a hard polymer a buffer coating was applied (possibly silicone) before encapsulation to help reduce the forces on the components, is this technique still in packaging folks play book? Dale Hart UTC ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/ContentPage.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------