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|High Reliability High Melting Lead-Free Mixed BiAgX Solder Paste System|
|Keywords: high temperature solder alloy, BiAgX mixed solder paste, lead-free solder|
|Lead free soldering has been the main stream of industry since 2006, with eutectic SnPb system phased out by SnAgCu system. However, development of lead-free alternatives for high melting high lead solder alloys is still struggling, thus hampering the completion of full lead-free conversion. BiAg alloy exhibits acceptable bulk strength but very poor ductility and wetting on copper, therefore is not acceptable as an option. In this work, a novel high melting lead-free BiAgX mixed solder paste system has been developed, and the performance is compared with several representative high lead solder alloys. The mixed solder paste BiAgX had the melting temperature of ~260oC, which is verified by DSC and TMA. It also showed a highly improved wetting on Cu and Alloy 42 comparing to BiAg. Thermal aging does not bring noticeable changes of IMC thickness for the mixed solder pastes, mainly due to the controlled additives in the paste system. On the contrary, the high lead pastes show the significant increase of the IMC thickness and the IMC layer evolution upon aging. TCT ranking for the high lead pastes and the mixed solder ones show comparable performance.|
|Ning-Cheng Lee, Vice President, Technology