We found the TSOPs we use have a high tin content solder plate or solder coat ( 85/15) . The appearance of the solder is reminiscent of "solder pest", allotropic tin formations at low temperatures, often encounered before the addition of antimony in the alloy was common. I wonder what the effects of the different tin alloys are where the two flow together and wonder if this causes the lines you see. These lines look like cracks beginning to form so we pull on the leads and find they are usually not cracks, just some kind of boundary. When we do encounter actual cracks, they are pretty obvious. ---------- From: TechNet-request To: technet Cc: ELOUIS Subject: Re: cracked solder joints with alloy 42 tsops Date: Wednesday, October 09, 1996 8:11AM Hi Ed - A question- you said "..had stress lines develop....after convection reflow" - is that after some type of stress testing (thermal, etc.) or literally right after the reflow process. If you are having "stressed" solder joints right out of the reflow process I suspect that you have a process problem or a board/layout design problem. The TechNet traffic has shown that there are quite a few electronic manufacturers that have/are experiencing cracking problems with Alloy 42 TSOPs as part of the stress screening. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: cracked solder joints with alloy 42 tsops Author: [log in to unmask] at ccmgw1 Date: 10/8/96 2:21 PM I would like to send or fill out over the phone a questioneer for all users of tsops having alloy 42 leads who have experienced problems with stressed or cracked solder joints on pwas. We had stress lines develop in solder joints after convection reflow when we had bulbous solder joints. Reducing stencil apertures to (19.7 mil pitch) 10 mil width with 50% length using a 6 mil thick stencil rather than an 8 mil stencil gave solder joints with heel fillets and a 50% toe fillet that survived the reflow process but they showed stress lines after wave soldering. Hand solder repair of cracked joints appeared to remedy the situation. E.Louis Lockheed Martin Corp. 11 Federal St. OPS-2C Camden,N>J> 08102 phone#:609-338-3508 fax #: 609-338-2575 *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************