Fault Diagnosis of Flip Chip Using Vibration and Modal Analysis

Solder bump inspection of flip chip has gained more attention with the widely use of flip chip package technologies in microelectronics packaging industry. A non-destructive testing method using ultrasonic excitation and modal analysis was presented for the detection of solder bump missing, a typical defect occurred in flip chip. The flip chip with arrayed solder bumps is modelled, and the effect of solder bump missing on the modal frequencies is investigated. The shifting of the natural frequencies of the reference flip chips and defect flip chips are simulated and measured in the experiments. The analysis results of the theoretical calculation, simulation and experiments all reveal that the natural frequencies of defective chips are smaller than the ones of non-defective chips, which can be used for defective flip chips detection. Therefore, the modal analysis can be a useful tool for fault diagnosis of flip chip.