Experimental analysis of thermal displacement and strain distributions in a small outline J-leaded electronic package by using wedged-glass phase-shifting moire interferometry

摘要

To evaluate the influence of a printed wiring board (PWB) with a high coefficients of thermal expansion (CTE) on the thermal deformation of a small outline J-leaded electronic package (SOJ), a newly developed phase-shifting method was applied to moire interferometry. This phase-shifting moire interferometry method uses a wedged glass plate as a phase shifter to obtain displacement fields with a sensitivity of100 nm/line. This technique also enabled the quantitative determination of strain distributions in all observation areas. Thermal loading was applied from room temperature (25℃) to an elevated temperature (100℃), and then the thermal strains of SOJ with and without the PWB were compared. The results showed that the concentrations of the longitudinal strains ε_(xx) and ε_(yy) became increasingly prominent when mounted on the PWB, and the shear strains γ_(xy) were concentrated at the corners of the silicon chip. The values of these strains increased by about 50% when the SOJ was mounted on the PWB.