Solder bump inspection by evaluating focusing ratio on surface and two-dimensional features

Abstract

This paper proposes a method to inspect forms of solder bumps located on the surface of a semiconductor bare chip. The form of a solder bump is inspected by evaluating the two-dimensional features observed from the vertical view and by measuring the change of the optical focus on the surface of the solder bump when the Z-stage is moved once using the vertical coaxial illumination and the dome-typed uniform illumination. As the experimental result, the method for measuring the focus on the surface of the solder bump which evaluates the summary of differential brightness by the Prewitt operator had the best performance. Also, the detection rate of defective solder bumps reached 95.6% and the inspection time was 0.3 second to a solder bump.