The goal of this research is to develop a systematic, accurate and robust method for printed circuit board (PCB) positioning evaluation in the testing fixture. Theoretical analysis and experimental observation of tolerance distribution in bed-of-nails fixture were involved. Actual deformation of PCB (translation, rotation and deflection) could be obtained based upon a proposed model. The combined accuracy of the test lands positioning (false failure rate) were estimated by the Weibull distribution. All data processing was finished by MATLAB. Results will be helpful for evaluation of the minimal size of the PCB test lands and modification of the testing fixtures.

The lift-off characteristics at the interface of thermosonic bond were observed by using scanning electron microscope (JSM-6360LV). The vertical section of bonding point was produced by punching, grinding and ion-sputter thinning, and was tested by using transmission electron microscope (F30). The results show that the atomic diffusion at the bonded interface appears. The thickness of AdAI interface characterized by atomic diffusion is about 500 nm under ultrasonic and thermal energy. The fracture morphology of lift-off interface is dimples. The tensile fracture appears by pull-test not in bonded interface but in basis material, and the bonded strength at interface is enhanced by diffused atom fiom the other side.

Fiber optic sensors (FOS) for vibration monitoring of smart structures have certain advantages over conventional strain gage based sensors due to electromagnetic environment insensitivity and high response bandwidth. During the present study, a spatially integrating fiber optic sensor was used for vibration monitoring. It is based on the concept that the optimal placement of the sensing element can be sought by using a priori knowledge of the mode shapes of the structure. The applicability of this approach to polarimetric optical fibers is described. The acquired integrating FOS signal was used to sense and control the vibration of an eleetrorheological adaptive structure subjected to a random external excitation.

Fracture characterislics at the interface of ultrasonic bonds between Au and AI were characterized by SEM following pull lesting to effccl separation of the bonded joints. Vertical seclions at Ibe bonding point weir produced by ion-sputter thinning, alld were examined by TEM. Results show Ihat the Ibiekness of the Au/AI atomic diffusion intcrfacc was about 5O0mn due to combined effccts of ultrasonic and thennal energy. Ultrasonic vibration activates dislocations in tile crystallinc latliee and increases alomic diffusion. The fracture morphology on the lift off inlerface was dimpled rapture. Tensile fracture occurred during lbe pull test not al the bonded interface but in die base maleftal: the bond strength at the interlace was enbanced by the diffnsion reactions that occu~ed across the intert~cc due to tile combined ultrasonic and thermal energy