Research On BGA Snpb Solder Joints Reliability Under Various Impact Interface

Portable electronic products often suffer the impact behavior such as accident fall or hitted by the hard surfaces in the transport and use process, which can cause internal failure of the solder joints. BGA chip packages were studied in this paper. In order to find the failure rule and mechanism of BGA tin-lead solder joints on the different hardness collision interface, a series of experimental studies and theoretical analysis about the influence of different collision interface on reliability of BGA tin-lead solder joints have been taken under the drop condition, and different collision interface has different hardness value. Moreover, the Cox proportional hazards model which is widely used in the engineering was cited to analyze the service life and reliability of solder joints. The main work of this paper is summarized as following aspects:1、Height was adjusted and chosen to meet the JEDEC-B standard conditions, and when H=650mm, the peak acceleration value is1500g and the pulse duration of half sine pulse standard curve is0.5ms, both of which can meet standard conditions. Repeatability showed the feasibility of experiment process.2、For different fixed boundary conditions, the influence of pre-tightening force on the PCB substrate bending was analyzed, and further analysis about the impact reliability of BGA components was also taken. The results showed that the micro-strain of the substrate under the4bolts boundary was much larger than that of the6bolt boundary conditions. In the two types of boundary conditions, the difference between micro-strain mean value of board width was300με, and that of board length was400με, the number of falling that before the failure happened was different more than two times. It was clear that different boundary conditions have obvious effects on the BGA components reliability.3、When the falling height was constant, the failure law and failure mechanisms of BGA solder joints under different collision contact surfaces were analyzed, and other conditions kept same. Combined with corresponding relation of dynamic voltage and crack growth in the chain of chrysanthemum, it showed that solder crack experienced crack growth, damage accumulation and the fast growth in the process of crack propagation; comparing the failure morphology of solder joints that caused by various collision surfaces which have different hardness values, the results showed that the failure mode of solder joints is mainly welding plate fracture failure on low hardness (e.g. wood) contact surface. Unlike these result, the failure mode of solder joints is mainly intermetallic fatigue failure that between solder ball and welding plate on high hardness (e.g. steel and stone) contact surface. Therefore, it was clear that the failure modes of solder joints that caused by different hardness collision interface were not the same.4、Based on statistical analysis methods, acceleration (g) and strain amplitudes of base board (ε1and ε2)that acquired in the various hardness collision interface were considered as the covariate, the proportional hazards model was established to predict service life of solders joints, the results showed that the greater the acceleration was, the faster solder joint failure was and the lower the reliability was; in other words, the higher the collision interface hardness was, the easier the solder BGA components failure was.