Modal Analysis of Flip Chip for Solder Bump Defect Detection

Abstract

Flip chip technology is one of the fastest growing segments of microelectronics packaging because of its ability to satisfy the increasing demands of high input/output density, package miniaturization, and reduced cost. A critical element in the successful application of flip chip technology is the reliability of solder bumps. In this paper, a nondestructive inspection method combining ultrasonic excitation with modal analysis is proposed for flip-chip solder bump defect detection. The signal generator and power amplifier are utilized to drive the capacitive air-coupled ultrasonic transducer to produce continuous ultrasonic waves for exciting the test chips. The vibration velocities of the chips are measured by the laser scanning vibrometer to extract the modal shapes and resonance frequencies. The results prove that the defective chips can be distinguished from the good chip by the modal shapes, and the resonance frequencies of the chips decrease with the increase of the open solder bumps. Therefore, this detection method may provide a new path for the improvement and innovation of flip chip on-line inspection systems.