Harmonic vibration test for accelerated reliability assessment of board level packaging

Board level package reliability under mechanical shock has always been a great concern for mobile electronic products. As a result of “short to market” demand for new electronic products, a great effort has always been made towards developing more efficient methods for reliability assessments. This paper presents a board level mechanical reliability test method based on harmonic vibration. Numerical simulation was used to determine the relationship between vibrating conditions and the sample responses. Strain gauges were used to measure the PCB deformation and verify the modeling. Failure detection system was constructed to collect the interconnects failure data of vibration tests. Results show that besides acceleration level, vibration amplitude is highly dependent on vibration frequency. Compared with very high pulse height and short pulse width of the acceleration in a drop impact, continuously vibration loading can achieve gradually increased vibration amplitudes until the balance of vibration loading and damping. A large amplitude vibration can be obtained using relatively low acceleration level at lowest resonance frequency, which produces similar strain amplitude in a drop impact test. Synchronal measurements of board strain and solder failure correlates loading condition with failure behavior. Failure data indicates the whole failure process can be divided into four stages. The loading cycle number to failure in vibration test is much more than those in drop impact tests. While vibration test takes much less testing time and performs much more effectively.