(A) study on the magnetic dispersion and vertical stacking of conductive particles for fine pitch semiconductor test socket interposer

Abstract

In the semiconductor industry, the demand for higher number of Input/output (I/O) counts and smaller size is increasing, and to meet the needs, the semiconductor packaging technology is heading to finer pitch and higher integration. Accordingly, the new testing techniques are required for the semiconductor packages with finer pitch. A test socket interposer is the key element in the testing process, which interconnects the device under the test and the test board. However, the conventional interposer is not applicable for fine pitch under 300um due to its structural limitations. In this study, a fine pitch interposer technology is newly introduced with magnetically dispersed and vertically stacked conductive particles in the composite polymer structure, which is composed of polyvinyl fluoride (PVDF) and Non-Conductive Film (NCF). The factors that affect the dispersion and stacking behavior were studied to fabricate the interposer, and its electrical and mechanical properties were characterized. In Chapter 2, the effect of the magnetic field on the dispersion rate of conductive particles was studied. The conductive particle dispersion was enhanced with increasing magnetic field strength and longer exposure time under the magnetic field. In Chapter 3, the effect of the surface properties of the underlying NCF on the dispersion and vertical stacking of conductive particle was investigated. The tackiness, surface energy and surface roughness of NCF were optimized by the controlling the curing degree of NCF and the amount of residual solvent in the PVDF, which resulted in the better movement of the conductive particles on the NCF. In Chapter 4, a bilayer interposer was fabricated with the optimized conditions and its daisy chain resistance and durability were evaluated. The interposer had 35um pitch in average and showed a stable interconnection with the fine pitch test vehicles up to 1000 repetitive cycles.