Hi Peter - The impact of the bismuth/indium elements (or others) in the solder joint would depend on what percentage of the final solder joint those elements constituted. I would recommend "processing" a statistical sample of solder joints using the proposed process and then conducting either chemical or electron microscopy analyses to determine just what you have for a solder joint makeup. Some elemental additions can alter the solder joint reliability at very low percentages and the possibility of having elemental segregation which could result in embrittlement or a low melting point alloy would be a concern. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: ASSY: Rework Method Author: [log in to unmask] at ccmgw1 Date: 6/2/97 1:18 PM ((Sent this on Friday, but it didn't appear to come through. Apologies if it repeats.)) I would be interested in TechNetters' comments about a rework system we have been asked to consider. The process involves adding a low temperature solder alloy (tin/lead/bismuth/indium/? - not sure of the %ages) to the existing solder joints at low temperature; the alloys mix and then allow the SMD to be removed at the low temperature. The lands are cleaned and then the device replaced as normal (soldering iron and conventional solder). The pros are rework at low-to-zero capital cost (maybe good for field service), and at low temperature. The cons are that it's actually about a 10 step process, and I believe takes longer than conventioanl methods. Couldn't be easily used for BGAs, best for QFPs etc where you can access the joints. My initial worry was the idea of remnants of the low temp alloy would be left in the new joint - what effect would that have on joint reliability? But, probably only a low concentration of bismuth might be introduced to new solder joint. Any other thoughts? Comments? I know that it's not a newly invented process - why isn't it used more commonly? Peter -- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: Peter Swanson Oxfordshire, England INTERTRONICS [log in to unmask] http://www.cygnetuk.demon.co.uk Suppliers of materials and consumables to the electronics & related industries ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * 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 subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * 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] * ***************************************************************************