Dave, I concur in most cases but I am starting to see new RoHS lead frame material that doesn't appear to have any surface finish on it that only wet with more heat on longer soak times... Again "it depends"... Paul Paul Edwards Process/Quality Engineering Surface Art Engineering -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Wednesday, March 02, 2011 8:00 AM To: [log in to unmask] Subject: Re: [TN] Recommended Reflow Peak Temperature Using Sn63Pb37 Solder and SAC305 Finished Component Leads? Hi Dick! The introduction of lead-free soldering technology sometimes messes with everyone's thought processes and your question is one that I have seen asked multiple times by lots of folks. The typical tin/lead SMT soldering process has a maximum board reflow temperature in the 215C - 225C range (and yes, there are always exceptions). With a Sn63Pb37 solder alloy melting temperature of 183C, that means we are reflow any components with a eutectic tin/lead surface finish. However, other components with surface finishes such as gold, silver, nickel/palladium/gold and palladium/silver, the solder joint formation is the result of dissolution so we have technically been soldering a number lead-free component surface finishes for years. The industry is now seeing the introduction of tin, tin/bismuth and various other lead-free surface finishes such as the SAC alloy family you mentioned. Formation of solder joints using these lead-free surface finishes will be accomplished by dissolution in the same fashion as gold, silver, etc in a tin/lead reflow process. Depending on which lead-free surface finish you are dealing with, you may want to slightly slow down the conveyor speed or tweak the reflow temperature a few degrees higher (if possible, some components have max reflow temperatures around 225C) to allow for more complete dissolution and solder joint formation. Some of the rules of thumb we use when soldering to nickel plating can be applied here (see Werner's past TechNet responses on soldering to nickel). I have conducted a number of lead-free component and tin/lead solder process reflow trials and found minimal impact to the overall reflow profile times/temps. Having a well characterized reflow profile is the key parameter. Dave Hillman Rockwell Collins [log in to unmask] "Richard D. Krug" <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 03/02/2011 08:30 AM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to "Richard D. Krug" <[log in to unmask]> To [log in to unmask] cc Subject [TN] Recommended Reflow Peak Temperature Using Sn63Pb37 Solder and SAC305 Finished Component Leads? What should the peak reflow temperature be when using Sn63Pb37 solder paste when some component lead finishes are now an undefined Pb-free finish? Based on comments from the component manufacturer, I suspect a SAC alloy. Can I solder to SAC solder or do I need to reflow the lead finish? Dick Krug, CSMTPE SMT Process Engineer Sparton Corporation 30167 Power Line Road Brooksville, FL 34602-8299 p (352) 540-4012 (Internal Ext. 2012) [log in to unmask] ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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