Yes, with that alloy combo it is possible that your joints will have an Sn/In intermetallic zone with MP around 118C and Sn/Pb/In at ~120-130C. This could limit the max service temp of those joints to <<100C (depending on the number of cycles/mechanical stresses in service etc). As mentioned by Wayne In can make undesirable intermetallics with Cu, but presumably this issue was considered when you first determined on the 80In/15Pb/5Ag. Regards Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Wednesday, March 10, 2010 10:34 PM To: [log in to unmask] Subject: Re: [TN] Low Temp Solder Paste Hi Carl - as Werner described, using a low temperature paste and a solderball that melts at a higher temperature will result in some type of metallurgical gradient with different amounts of microstructure/phase variation dependent on the actual temperature gradient experienced. The specific solder alloys will play a big role as they determine the types of phases that will be produced. And with In, Ag, Pb, and Sn in the mix with the elemental percentages you described, all sorts of "fun" things could happen. The In/Pb/Ag alloy melts around 150C so you are also going to have solder joint integrity issues in many high performance use environments. I would anticipate that the 80% In content makes the paste cost painful too. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] Carl Ray <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 03/10/2010 04:06 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to Carl Ray <[log in to unmask]> To [log in to unmask] cc Subject Re: [TN] Low Temp Solder Paste Sorry about that Werner (I really wanted you to guess :) ). The solder is 80In, 15Pb and 5Ag ________________________________ From: Werner Engelmaier [mailto:[log in to unmask]] Sent: Wednesday, March 10, 2010 3:44 PM To: [log in to unmask]; Carl Ray Subject: Re: [TN] Low Temp Solder Paste Hi Carl, You did not say what the paste is. When you have a high-melt SnPb ball and 63Sn/37Pb paste you wind up with a good solder joint having a gradient in Sn/Pb concentrations. When you have a SAC ball and 63Sn/37Pb paste, it depends how long you are above the Liquidus temperature of the SAC solder and whether you get good mixing-while it is not the ideal solution alloy, with good mixing the fatigue resistance is comparable to SAC & SnPb. In you case-well, IT DEPENDS. Werner -----Original Message----- From: Carl Ray <[log in to unmask]> To: [log in to unmask] Sent: Wed, Mar 10, 2010 4:09 pm Subject: [TN] Low Temp Solder Paste Hi Technetters!!! I have a question regarding low temp solder paste and standard 63/37 eutectic BGAs. Has anyone had any experience with this type of process? What are the pros and cons? Obviously the BGA doesn't see the temperatures needed for the balls to collapse so what type of solder joint do you end up with? Carl Ray Manufacturing Engineering Manager Teledyne Electronic Manufacturing Services 1425 Higgs Rd. Lewisburg, TN 37091 Direct: 931-270-2724 Cell: 931-637-5958 Email: [log in to unmask]<mailto:[log in to unmask] ><mailto:[log in to unmask]<mailto:[log in to unmask]>> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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