Optical Detection of Bent Pins in a High-Density Array

This paper describes a prototype system being developed for the detection of bent pins on a high density integrated circuit module. It is a noncontact approach that relies on the detection of the specific optical diffraction patterns that result when laser light shines on a bent pin. As the module pins are passed through a fixed laser beam, the diffraction patterns are captured by an area optical array which is continuously scanned by a dedicated processor. If a bent pin is detected and the motion of the pin array is known, the approximate location of the bent pin can be determined by triangulation based on multiple passes. Information revealing the angle of bend in the scanning plane is imbedded in the diffraction pattern.