Tin Whisker Growth Inhibition in RE-Doped Sn-Zn Soldered Joints

Abstract

The tin whisker inhibition in RE-doped Sn-Zn soldered joints was investigated. The results indicated that after aging treatment at 150 • C, with the proper addition ratio of Ga and Nd, no obvious NdSn 3 phase nor tin whisker growth was observed in the soldered joints. By replacing the Sn-Nd phase with a Ga-Nd phase, the risk of tin whisker growth caused by the oxidation of RE-phase was significantly inhibited even in soldered joints with additional excessive contents of Nd. The IMC layer in soldered joints with optimal addition showed a relatively regular shape after aging treatment, making the soldered joint maintain preferable mechanical performance. The results would be available for guiding the study of tin whisker growth inhibition method.bearing rare earth Nd were investigated. The results could provide a feasible method to inhibit tin whisker growth, and the method has been successfully tested over a long time aging treatment. Experimental ProcedureAll alloys were made from pure Sn (99.95 wt.%), pure Zn (99.95 wt.%), pure Ga (99.95 wt.%), and pure Nd (99.5 wt.%). Under vacuum atmosphere (10-3 torr), Sn-5Nd master alloy ingots were prepared by melting Sn and Nd at 90 • C for 15 min. Then the master alloy was added into the melted SnZn alloy which was held for about 5 min while mechanical stirring was performed every 1 min. The melting temperature was controlled below 400 • C. The melted solder was chilled to cast and cut into solder bars of 40 mm length. The compositions of alloys were analyzed by inductively coupled plasma emission spectrometer (ICP-AES).The interfacial microstructure of soldered joints after aging treatment were observed by Su8010 field emission scanning electron microscope (FE-SEM, BSE mode, Hitachi Co., Ltd., Tykyo, Japan) equipped with energy dispersive X-ray spectroscopy (EDS). Phase composition analysis was determined through Rigaku ultima IV x-ray diffractometer (XRD) with following parameters: Cu-Kα target, working voltage 40 kV, operating current 40 mA, scanning speed 5 • /min, and scanning range 20 • to 100 • .According to the Japan Industry Standard JIS Z 3198-2 test methods for lead-free solders-Part7

Study on Soldering Alloy Structure Influence on Whiskers Germination and Grow Process in Joints Executed Using Tin Base Soldering Alloys

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