Using laser scattering for detection of cracks on a microsolderball surface

Abstract

In this paper, a scanning laser probe has been developed to detect and measure cracks on a microsolderball surface. The technique, based on a light-scattering method that employs a low-power He-Ne laser and conventional optical components, enables the laser beam to be focused on the test surface. In the relative scanning between the test surface and laser probe, the specularly reflected light intensity acquired by a photodiode would exhibit the change of the scattered-light intensity, which can be used to determine the size of cracks on the solderball. Proof-of-concept experiments have been performed with measurement of cracks of different sizes (from 4 μm to 60 μm) on the microsolderball.