Abstract
Soldering is the most important of joining technologies and there are numerous solder joints in modern electronic products. The phases and microstructures of solder joints are critical to their properties. Various remarkable phenomena caused by phase transformation and microstructural evolution in solder joints have been reported. The phenomena include ripening, layer detachment, liquation, cruciform pattern formation, solid-state amorphization, alternating layer formation, shift of reaction paths, and the effects of electromigration.