Solder Joint Reliability and Paste Stability Performance of Resin Reinforced Low Temperature Solder PasteAuthors: Atsushi Yamaguchi, Ph.D., Andy Behr, Yasuo Fukuhara, Hirohisa Hino, Yasuhiro Suzuki, Naomichi Ohashi
Company: Panasonic Corporation, Electronic Materials Business Division
Date Published: 9/17/2017 Conference: SMTA International
This situation prompted us to develop a solder paste material that combines specialized epoxy resins and other organic components with SnBi solder particles to form a low temperature joint reinforced solder paste or JRP. This approach enables the concurrent formation of SiBn solder joints and a reinforcing polymer collar via a one pass reflow process. This paper describes the solder joint properties and reliability of the initial material developed by us, as well as the characteristics of an iterative formulation designed to improve reworkability and paste stability.
We evaluated the influence of the epoxy resin component in the first material (JRP1) on solder joint reliability. We compared the joint properties of samples made SAC305 solder paste, unreinforced SnBiAg solder paste and JRP1 solder paste. The evaluation revealed that the JRP technology alleviates issues the associated with the brittleness of SnBi solder by encasing the weakest region of the solder joints in a fully cured epoxy resin. Ball joint shear testing, BGA solder joint strength testing, temperature cycle testing, and drop shock testing revealed that low temperature JRP solder paste demonstrated equivalent or better joint properties than those made with SAC305 solder paste.
While the initial formulation exhibited the desired reliability performance, it was noted that this material was somewhat difficult to rework and the -20ºC storage requirement was also undesirable. The next iteration (JRP2) incorporated a modified resin system. The new material exhibited improved reworkability, refrigerated storage (5ºC) stability and better drop shock reliability, including a 2X improvement in characteristic life performance (number of drops to 63.2% failure) compared to SAC305 solder paste. Key words: low temperature solder; SnBi solder paste; solder joint reliability; resin coverage; temperature cycling test; drop shock test; low temperature joint reinforced solder paste; JRP; reworkability; refrigerated storage life.
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