Diffractive Optic Based Pitch, Roll and Z Axis Displacement Sensor

摘要

Flip chip bonding of integrated circuits to chip carrier packaging requires ultra precise placement. Maintaining the parallelism of the IC chip's ball grid array interconnect to the carrier packaging bond pads is of most concern. The bonding tool vacuum pick and place tip which carries the IC, must guarantee that the solder balls that form the interconnect ball grid array are flat and parallel to the mating pads on the carrier. During assembly operations where thousands of IC's are assembled per hour, continuous measurement must be fed back to small motion actuators which can adjust the position of the IC before bonding. This paper describes the design and implementation of a diffractive beam shaper optic into a displacement measurement sensing device. Testing of various beam shapes and conditions allowed for improvements in sensing resolution and dynamic range. A prototype was constructed to allow real time feedback of micro displacements of an IC surface including Z Axis offset, pitch and roll. The sensor assembly design, prototype performance and resulting test data will be presented. Test data includes measurement data, diffractive beam shaper design and its impact on sensor measurement resolution and range.