Lead-Free Wave Defects

Hello Amol, I continue to be amazed at the surprise engineers have on discovering that a non-eutectic alloy such as SAC305 displays micro-cracking and rough joints in a soldering process. There was a reason the electronics industry chose to use eutectic alloys such as Sn63 and Sn62 for automated soldering and not cheaper higher lead content non-eutectic alloys. To consider a non-eutectic alloy such as SAC305 (4C paste range) or X0307 (11C paste range) goes against over 30 years of standardized use of a eutectic alloy in over 95% of the automated soldering processes in the world. This illustrates the strength of marketing over merit. You are correct in that the SN100C alloy does not display these characteristics as it is a eutectic alloy and has proven that it does not have the micro-cracking issue and produces a smooth, shiny joint due to the nickel addition. The evidence from over 1400 machines in use and over 400 tons per month sold of SN100C illustrates that a true eutectic lead free alloy will be the alloy of choice for replacing Sn63 eutectic eventually. As further evidence, please refer to an article authored by the Japanese patent holder for SAC305- Senju Metal Industry. They published a paper confirming exactly what you are experiencing and confirmed that switching to the eutectic alloy Sn/4Ag/0.9Cu would reduce the micro-cracking and appearance issue. The paper was presented at the 11th Symposium on Microjoining and Assembly Technology in Electronics in Feb. 3 2005, and authored by Mr. Minoru Ueshima titled � Mechanism of Shrinkage Cavities and Method for Restricting Them in SnAgCu Alloy Family�. His conclusion stated that SAC305 would produce shrinkage cavities and if the desire was to reduce the possibility of this, use an alloy closer to the eutectic such as Sn/4Ag/0.9Cu. So you have the patent holder admitting that the alloy they have developed is not the ideal lead free choice as it is NOT eutectic. If you are interested in considering SN100C, I am happy to supply you a cd with the reliability test results and assist you in converting your equipment to SN100C at no expense. Please contact me at: bgilbert@fctassembly.com

Regards, Bob Gilbert 970-988-6243

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