I must have missed it but what are the parts w/cracked solder joints and how large are they? John Maxwell On Mon, 28 Mar 2011 15:46:16 -0400, Joyce Koo <[log in to unmask]> wrote: > You have other problem: may be your PWB Tg is not suitable for the > application. Let me guess: it should be polyimide board and got > changed to FR4 for lower cost? > -------------------------- > Sent using BlackBerry > > > ----- Original Message ----- > From: Dale Hart [mailto:[log in to unmask]] > Sent: Monday, March 28, 2011 03:01 PM > To: [log in to unmask] <[log in to unmask]> > Subject: [TN] Solder joint height control > > 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 > > ______________________________________________________________________ > T ______________________________________________________________________ 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 -----------------------------------------------------