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Recently, progress of semiconductor packaging is drastic and multi-pinned devices such as Fan-out Wafer Level Packages (FOWLPs) attract much attention. For those applications, photosensitive polyimides (PSPIs) are applied as redistribution layers (RDLs) and they are required to have high level of properties such as adhesion to metal and reliability. We developed novel low-temperature curable positive-tone photosensitive polyimides (posi-PSPIs) with high elongation, strong adhesion to the copper RDLs, and high chemical resistance for establishing the multi RDLs by improving the base-polyimides and incorporating polyimides with cross-linkers and adhesion promoters.

We investigated the soft baking condition effect on residual solvent amount, decomposition of photo sensitive diazonaphthoquinone group, photosensitivity, and development loss amount of positive photosensitive polyimide, which composed of partial esterified poly(amic acid) and photosensitive diazonaphthoquinone sulfonate. After soft baking, 10-14% of solvent was remained. Below 120°C baking, the naphthoquinone group was remained more than 90%. More than 40% of the naphthoquinone group was decomposed when 130°C baking. Photosensitivity seems to be determined by development loss of photosensitive polyimide. 120°C for 4min is suitable soft baking condition in this study.

In view of published comments that the wear resistance of Ti-6Al-4V alloy bearing against ultrahigh molecular weight polyethylene (UHMWPE) was not adequate for total joint replacements, the literature was reviewed and compared with ongoing hip simulator studies. Two types of laboratory tests were contrasted: those run under “clean” conditions and those run with intentional contamination by acrylic cement particles. Wear-screening devices as well as hip simulators were involved in both types of studies, and both produced a dichotomy of viewpoints on the suitability of the Ti-6Al-4V/UHMWPE combination. However, the two most recent studies with hip simulators indicated that the Ti-6Al-4V-UHMWPE combination performed acceptably well. The published data from a major series of Ti-6Al-4V hip replacements have established excellent clinical and radiographic results. In seven surgical revisitations, the Ti-6Al-4V/UHMWPE combinations showed no sign of adverse wear phenomena. Thus, the clinical observations are supportive of the results of the two most recent hip simulator studies. It may well be that the laboratory models produced a variety of severe test conditions that compromised the performance of the Ti-6Al-4V and resulted in contradictory data. The hip simulator studies are being continued to establish the limits of the laboratory models and their validity with respect to the clinical situation.