Polysilsesquioxane (PSQ) is a typical organic-inorganic hybrid material with various characteristics which depend on the organic functional groups. The appropriate organic functional groups can immobilize the metal nanoparticles in PSQ thin films. In order to disperse the metal nanoparticles uniformly in the PSQ thin films, a protecting group which prevents aggregation of the nanoparticles and a reducing agent for the metal ions are necessary. As metal nanoparticles can be easily prepared in the PSQ thin film, it is possible to provide the function on the surface of a glass substrate by coating it with PSQ. In this study, the ternary PSQ was prepared by a sol-gel reaction using a trialkoxysilane with both reducing and protecting groups. Palladium nanoparticles were generated in these PSQ thin films. It was confirmed that these palladium nanoparticles on the PSQ thin films had the proper activity for the electroless copper plating. We also studied how to improve the adhesion of copper thin films.

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Electronic plastic packages often show hysteresis of warpage during a thermal cycle. We used finite element analysis (FEM) to analyze the thermal hysteresis of the bottom package of a package-on-package (PoP) system considering the changes in the viscoelastic material properties of the resin due to the thermal history. For the sake of ease, we first analyzed a two-layered test package consisting of a Si chip and underfill (UF) resin, which is epoxy resin containing silica particles. Before analysis, we measured the actual viscoelastic material properties and coefficient of thermal expansion of the UF resin before and after thermal loading using a dynamic mechanical analyzer (DMA) and a thermo-mechanical analyzer (TMA). We changed the viscoelastic material properties during the analysis. We could accurately analyze the thermal hysteresis of the two-layered test chip. Then, we analyzed a test package that imitates the bottom package of a PoP system. We assumed the substrate to be a multi-layered material made of the core material, prepreg, solder-resist resin and a copper layer. In this analysis, the calculated warpage did correspond quantitatively with the measured warpage.

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Electroless plating has not been applied to FPC production processes as a method of metallization on PI and PEN surfaces because of the adhesion deterioration problem after heat load. This problem could be a result of the necessary pretreatment surface modification required for electroless plating. This study focused on reducing the modification layer thickness to solve this problem. With a modification layer on a PI film of approximately 10 nm, the peeling strength dropped from 0.58 kN/m to 0.22 kN/m after heat load. However, when the modification layer was reduced to several nm, the peeling strength rose from 0.39 kN/m to 0.55 kN/m. In the case of PEN film, the rise of peeling strength was observed while the modification conditions were weak. Based on the analysis of the stripped interface, it can be concluded that the resin deteriorates due to the heat load when there is a large amount of modification. On the other hand, no deterioration is observed, which can therefore improve the adhesion interface.

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We have been developing a new type of interposer based on a copper-filled aluminum oxide (Cu-AAO) film and SOV (Sea Of Via) design concept for application to high-density 3-D packaging. The Cu-AAO contains numerous through-copper filaments regularly positioned on a submicron pitch. By using Cu-AAO as a core substrate, it is possible to form free-shape through-packaging vias (TPVs) in any position.
In this study, we first evaluated the insulation properties of the Cu-AAO substrate. Then, we formed the interposer including the fine-pitch coaxial TPVs that were developed utilizing the unique features of Cu-AAO. Furthermore, we demonstrated 3-D shortest connection between the chips by attaching a TEG (Test Element Group) chip on both sides of the interposer.

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