Hi Gaby - You are not going to like this but the cracking phenomena you are seeing has been documented and is going to be a problem! The NCMS has/is completing a VERY large study on Lead-Free solder alloy evaluation. They covered a huge amount of work - everything from cost analysis, manufacturability and several flavors of solder joint reliability investigations. I am not allowed to give out specific details but they did find that with some of the Sn/Pb/Bi alloys that on thru hole technology assemblies due to solidification physics that cracking occurs. They will be publishing a portion of this data at the TMS meeting in Orlando in February and at the IPC Expo in March. There is some really neat data (well, from a metallurgist standpoint anyway) going to be coming out of this effort. I suggest you contact Jerry Rosser at Hughes (or is it Raytheon now?) for more info. His email is [log in to unmask] . Good Luck. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Reflow Soldering of PTH Connectors Author: [log in to unmask] at ccmgw1 Date: 1/23/97 7:35 PM Hello,technetters! We perform double reflow on boards populated with SM LEDs on one side and on the other side SMCs and PTH connectors. In order to prevent the LEDs to go twice through hgh temperature profiles -the second one being even loger-we tried to use a solder paste with a lower melting point:Sn43Pb43Bi14 which is not eutectic. The cross section of the pin in hole showed some solder voids-which were present also when using Sn63 paste and are accptable from our point of view-but also cracks which originated from them along the pin or along the hole wall.Our boards are 0,1microns gold plated. Could anyone explain why it happed and give us some advice? Gaby P.S.Thanks to CONDOR and DAVE HILLMAN for their former replies! *************************************************************************** * 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. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * 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. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************