Title :
Imaging flaws in soldered joints of integrated circuits using an ultrasound electronic scanning technique
Author :
Kubota, J. ; Musha, Y. ; Takahashi, M.
Author_Institution :
Hitachi Ltd., Japan
Abstract :
An electronic scanning c-scopic 25-MHz ultrasonic imaging system has been developed for high-speed precise testing of electronic parts such as ICs. Two-dimensional scanning is performed, one axis being electronic and the other mechanical. A focused beam is formed so as to be a longitudinal wave in solid samples. Voids equal to or larger than 0.2 mm in diameter in the solder are accurately detected and their sizing data agree within 0.1 mm with those measured visually through an optical microscope after destruction. The imaging performance was examined for fatigue cracks in soldered joints. In 1000 heat cycles between -55 and +150 degrees C, cracks resulted in the soldered joints of most samples, and their growth was clearly visible. By comparing the images with those observed by a scanning electron microscope, minimum cracks of 1- mu m separation were found to be detectable. The c-scan imaging of a 14*14 mm area of the joints was completed in 1.2 s by the system.<>
Keywords :
acoustic imaging; crack detection; flaw detection; integrated circuit testing; soldering; thermal stress cracking; ultrasonic materials testing; voids (solid); -55 to 150 degC; 1.2 s; 25 MHz; 2D scanning; c-scan imaging; fatigue cracks; flaw imaging; focused beam; heat cycles; high-speed precise testing; integrated circuits; longitudinal wave; soldered joints; ultrasonic imaging system; ultrasound electronic scanning technique; void detection; Circuit testing; Electron optics; Electronic equipment testing; Focusing; Optical imaging; Optical microscopy; Size measurement; Solids; System testing; Ultrasonic imaging;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on