Study On Impactand Drop Properties Of Low Silver Content Snagcu Lead-free Solder Joint

Due to the increasing demand on smaller, thinner and lighter electronic products, packaging density has been increased as well as the joint size is decreased. The service conditions of solder joints are more and more complex, which has brought forward increasingly serious challenges to reliability of solder joints in electronic packaging. In the process of transport, storage and use, they are more vulnerable to unexpected vibration, impact, thereby causing the electronic device failure. Therefore, it is necessary to study the reliability of the electronic device under the conditions of the drop impact.Effects of silver content on drop property of SnAgCu based lead-free solder joint were studied. Results show that with the decreasing of silver content in SnAgCu solder, under the significance testing at99%probability, the drop property of solder joint can be improved significantly. The solder joint with a preset gap has a shorter drop lifetime. During drop test, failures occur at the interface layer between copper base metal and solder material for all solder joints. The brittle fracture characteristic exists in the appearance of failure position. It is found that the interface layer is getting thinner continuously with the decreasing of silver content, which might be the main cause to improve the drop property of solder joint.In order to clarify the influence mechanism of the silver content on drop property of solder joint, the failure process of solder joints of different silver content on one time impact load, repeated impact load and different tensile rate were studied. Results show that with the silver content increasing, the tensile strength of solder joint is improved, the fractograph show ductile fracture. With the silver content increasing, the repeatedly impact property of SnAgCu based lead-free solder joint is decreased. Under impacting load, all the fracture surfaces are relatively bright and smooth, that suggests that the fracture of solder joints is brittle. Thus effects of strain rate on destruction process of solder joint were studied. The tensile strength of the joint increase with the increasing of strain rate at low strain rate range (≤3.33/s). The joints would fractured in the solder alloy, that suggests that the fracture of solder joints is toughness. However, tensile strength of the different silver content joints were difference when increaseing of strain rate. In this time the joints would fractured at the interface between the solder alloy and intermetallic compounds, that suggests that the fracture of solder joints is brittle.