But a newly published study 1 explored exactly that situation.

Until recently, we had no real-world, production-based data on the soldering behavior of the SnCuNi alloy near the low margin of the reflow window.

Laboratory tests have demonstrated good wetting at lower temperatures, but they’re just that – lab tests. It’s that 7-degree difference in minimum reflow temperatures that generates the fear – of cold joints, incomplete wetting, inconsistent IMC formation or other reliability issues - if the peak temperature of a solder joint falls into that questionable space between 233 and 240☌. Applying the 13-degree guideline to the SnCuNi alloy results in a minimum peak temperature recommendation of 240☌. Recommended reflow temperatures are typically at least 13☌ higher than melting temperatures hence the SAC305 peak temperature window of 233 – 255. SAC305 begins to melt at 217☌, reaching its fully liquid state at approximately 220.6☌. Fear of full compatibility with SAC reflow processes. Why has it not gained major acceptance as an SMT alloy? In large part, fear. Because it contains no silver, it is much more economical than SAC alloys containing 1, 3 or even 4 percent of the precious metal, and it produces smooth, shiny, easy-to-inspect solder joints. Nickel-modified tin-copper solder, known commercially as SN100C®, is a leading lead-free alloy for PTH soldering, rework and hot air leveled PCB final finishes. Sn/Cu/Ni soldering performance at low temperatures.