Hi Michael! Turkeyday in Iowa was only 70F but we didn't' complain! The answer to your question is pretty simple: you will get a solder alloy which lies somewhere between the two alloy compositions you start with. The tin content will be in the 63% - 90% range and you Pb content will be in the 10%-37% range provided the soldering operation allows for the normal diffusion/mixing mechanisms to take place. Some folks consider this a problem because finding or understanding the reliability characteristics of this "new" solder alloy can be difficult. Other folks just evaluate the two alloys (the Sn63 and Sn90) for their reliability characteristics/merits and if both alloy data sets fit their use environment then they assume the "new" alloy won't cause them any issues. The use/combination of different solder alloys for solder joints can be a pretty involved topic - I don't know of a lot of published information on the subject. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] "Alderete, Michael" <[log in to unmask]> on 11/25/98 04:55:05 PM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to "Alderete, Michael" <[log in to unmask]> To: [log in to unmask] cc: Subject: [TN] ASSY:mixing of high and low-temp PbSn alloys Dave Hillman, et al... 1st, Happy Thanksgiving to all on TechNet. QUESTION: at "normal" soldering iron temperatures, what happens when you melt a eutectic solder preform (p/o clip lead) together with hi-temp, 90 to 94% Sn (bal=Pb) solder? Will the two solders alloy, or just form a mixture? Please provide as metallurgically correct an answer as possible. Thanks in advance Michael Alderete Aerojet, Azusa (So.) CA ...it's going to be about 80F here tomorrow. Hope you'll still answer this question on solder mixtures. ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################