Effect of Crystal Orientation on Sn Whisker-Free Sn–Ag–Cu Plating

Abstract

Mechanically induced Sn whiskers are a serious problem in the electronics industry because they can cause electrical short circuits in narrow gaps between electrodes such as fine pitch connector pins. The authors tried to prevent the formation of them by using one of the typical Pb-free solder materials, SnAgCu alloy, as a plating material on connector pins. It was found that reflowed SnAgCu plating was whiskerfree even under mechanical stress. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analyses revealed that Sn grains of reflowed SnAgCu plating were extremely larger than those of whisker-prone pure Sn or SnCu platings that have columnar structures. The notable feature was no obvious microstructural changes in reflowed SnAgCu plating even after applying mechanical stress for 38 days. The present study demonstrates that reflowed SnAgCu plating is one of the best candidates as whisker-free plating.

Characterization Techniques for Film Characteristics

“…This section presents several examples of the analysis and comparison of phase and crystal orientation on platings that do and do not tend to form mechanically induced whiskers, as shown in Figure 5.35 [40]. All of the maps in Figure 5.35 were obtained before applying mechanical stress.…”