AgSn-Based Solder Alloys and Solder/Conductor Interactions in Lead-Free Electronics

摘要

As lead-free alternatives to PbSn-based solders are being sought, more information is needed about the properties of the different lead-free solders and about their interactions with conductor metals or metal finishes such as Cu, Ni, Ag, Au and recently Bi. Especially in fine-pitch applications such as flip chip, where solder volumes are small, it is important to control the intermetallic reactions that occur during soldering in order to ensure good reliability. In this work, solder-conductor reactions were investigated both experimentally and theoretically by employing thermodynamic modeling. The phase transformations occurring during soldering and the resulting solder microstructures were also studied. The electronics industry has selected solders based on the SnAg system as its preferred lead-free choice with ternary and multicomponent alloying elements to optimize the microstructure and mechanical properties. Therefore, emphasis was placed on studying the SnAg solder system, with Bi, In and Cu as major alloying elements, and its reactions with Cu, Ni, and CuNi alloys as conductor metals or metal finishes.