Answer yes. Melting the object you are joining is welding. Soldering is dissolving. When you make solder joints to SN plated/coated surfaces they do not melt in the solder. The plating dissolves rapidly and goes into solution. (The usual analogy is sugar into coffee). The underlying or base metal is now exposed to solder but dissolves very slowly. Naturally we don't wait for that process to complete :). So on freezing there is a transitional zone which is neither pure solder nor base metal but a mixture. (usually referred to as intermetallic layer) Sn/2.5Bi can be regarded as a tin plating. The small amount of Bi is added to control Tin whisker growth. A smaller amount of lead has the same affect. Ceramic devices have had a tin plate - with the lead - for donkey's years without a mention for the most part. Now under Pb-free legislation some people need to know what their BoM is and the added content information is causing everyone to look into things more closely. Best Wishes Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Bogert Sent: Thursday, June 06, 2013 9:19 PM To: [log in to unmask] Subject: [TN] Soldering to SMD device wth Sn98Bi2.5 leads using Sn63Pb37 solder June 6, 2013 We have an OM who soldered surface mount Opto-couplers with Sn98/Bi2.5 leads using Sn63Pb37 solder. The reflow solder profile used was the traditional one for Sn63 solder with a measured peak temperature in the range of 209 to 215C. The actual amount of Bi by weight that wound up in the completed solder joint was calculated to be about 0.19%. Based on this, there is no issue with a low temperature alloy forming with the combination of Bi and Pb. However, since the melting point of the Sn98/Bi2.5 solder is around 223-231C, the reflow profile used will not result in melting of the solder on the part terminations. Is this an issue or will the Sn63 properly bond to the solder on the part terminations to form an acceptable solder joint? [log in to unmask] ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________