Vibration lifetime estimation of PBGA solder joints using Steinberg model

Abstract

The work studies the vibration lifetime modeling of Sn37Pb soldered plastic ball grid array (PBGA) assemblies on the basis of vibration tests, finite element analysis (FEA) and Steinberg's empirical formulation. The test vehicles for the vibration tests consist of twelve PBGA components with built-in daisy-chained circuits, which are assembled on a printed circuit board (PCB) symmetrically. First, the natural frequencies of the test vehicle were determined by modal tests. The first three natural frequencies were obtained using FEA, which were compared with those from the modal test. Then, narrow-band sinusoid vibration tests were conducted at the first natural frequency of the test vehicle using constant-amplitude excitation, and the number of failure cycles was recorded by monitoring the overall electrical resistance. FEA was performed to obtain the stress of the critical solder joints under various levels of sinusoidal vibration loadings. To construct the stress versus failure cycles (SN) curve of the solder joints, the stresses of solder joints were used in conjunction with the lifetime obtained from the sinusoidal vibration tests. The random vibration test was conducted on the test vehicle to assess the lifetime of the solder joints subjected to broad-band excitation. Random vibration analyses were performed numerically to obtain the displacement responses of the PBGA assembly. Finally, a fatigue life prediction based on Steinberg's model was deduced from all these procedures. A comparison of the lifetime between the experimental results and the prediction suggests that the methodology is valid and practicable in predicting the vibration lifetime of PBGA solder joints.