Thank you to all of those who responded (fractured solder joints). I appreciate all the varied responses, I have been out of town but am back to continue work on this problem. I am looking for a manufacturer/vendor for the mentioned water soluble standoffs. Please let me know if you can help. Thank you in advance, Patti Volkman Electrical Engineer CSI Electronics ----Original Message Follows---- From: [log in to unmask] To: "TechNet E-Mail Forum." <[log in to unmask]>, Patricia Volkman <[log in to unmask]> Subject: Re: [TN] fractured solder joints Date: Wed, 26 Jun 2002 08:44:23 +0800 Hi, Patti, PLCC's are a bit notorious (though not as bad as CLCC's) for their rigidity when it comes to resisting creep fatigue and vibration. Solder joints frequently crack in military operating conditions if care is not taken with them. Hand soldering is a somewhat variable process unless you have a very skilled and conscientious operator doing the soldering, so some high stress points may be being built in to start with. I'm kinda reading between the lines here and get the impression that you're dealing with already assembled boards, rather than building them from scratch. Can you not screen print and mount these suckers using a rework station? It might produce more consistant results. Depending on which aircraft and where in the aircraft the boards are mounted, temperature cycling and vibration levels could be almost anything. Do you have any specs for the temperature ranges and rates of change, and vibration profile that the boards are experiencing? It's possible that the spring rate of the mounting mechanism may be contributing to an enhancement of the vibration levels, depending on the spring's natural frequency, especially as the boards seem to be long and narrow (and thin?). I wouldn't normally be comfortable with spring-mounting a board in a piece of military gear unless I was very sure of the harmonics involved, but for all I know, that portion is out of your hands. As for a cure - well, I've had some success in the past with using water soluble stand-offs under such components to create a bit of a space between the component leads and the board and increasing the solder joint height slightly. If assembly was being done using solder paste stencils to deposit paste, I would be using something like a 10 mils thick stencil, but you can try experimenting with solder joint heights as long as the solder fillet form complies with IPC-A-610 or similar. I've never tried using any of them, but there are "Fatigue Resistant Solders" about, the best known of which is "Maxon" from AMT, produced by Howard Electronic Instruments, I think, or one of their subsidiaries. It's a fairly specalised solder with a particularly fine grain structure and contains some extra dopants. The soldering temperature is slightly lower than eutectic solder at around 180 deg C, but there are higher melting point FRS's and lead-free ones as well. There is info available on the www for these if you want to surf. Hope this helps a bit. Peter Patricia Volkman <[log in to unmask]> 26/06/2002 05:18 AM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to Patricia Volkman To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: [TN] fractured solder joints Fractured Solder Joints My company has been doing hand assembly/soldering on a driver IC board for a display that is used on a military airplane. The board uses 8 Holt ICs - HI-8010SM-32 - http://www.holtic.com/ProPDFs/8010.C.pdf The boards we provide have been in use for between 1 year and 8 years, the actual time is unknown, but it is likely that they have been in place for a long period of time. The IC is a 44 pin PLCC J-lead with 0.050 center spacing on the leads. Our customer has recently found fractured solder joints associated with these ICs (identical to those in photo - IPC-A-610C page 12-85 ) It is assumed that the fractured solder joints occured after leaving our facilities, caused by airplace stress cycles or ??? I am looking for any information on why these fractures would occur, the boards are spring mounted on the plane, the boards measure about 1.5" x 5". Most importantly, I am looking for a solution to this problem. These board do not reflow well, so they are all hand soldered. The solder used in the past was Kester SN60PB40. I can also change the assembly process if that is determined to be the root cause (all hand soldered) thanks for any information you can provide. Patti Volkman (1-800-823-5588) _________________________________________________________________ Send and receive Hotmail on your mobile device: http://mobile.msn.com --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------