In this paper, a half-sized unbalanced dipole antenna with fan-shaped and trapezoidal radiators is proposed. In addition, the VSWR, input impedance characteristics, and radiation patterns of the proposed antenna were investigated. It was found that the antenna has a maximum bandwidth when the radius of the fan-shaped element is 12 mm, the length of the upper base is 12 mm, the length of the lower base is 20 mm, the height of the trapezoidal element is 22 mm, the distance between the fan-shaped and trapezoidal elements is 0.4 mm, and the thickness of the antenna elements is 1.6 mm. In spite of the radiator area being 60% that of an unbalanced dipole antenna with semicircular and trapezoidal radiators, VSWR characteristics less than 2.0 and a relative bandwidth of 133% over the frequency band of 3.0 to 15 GHz were obtained.

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Demand for metallized polymer films for use in various electronics applications is growing rapidly. Polyimide film has been widely used up to now for such applications as a low-k substrate due to its chemical and thermal stability, and its excellent dielectric properties. Here we report on the use of ion-doped precursors for fabrication of metallic patterns on a polyimide substrate. The process relies on the following steps to enable the fabrication of metallic patterns with a ca. 30 μm line width. First, the surface of the polyimide is modified by an alkaline treatment, then doped with metallic ions. Next, coating and photopatterning of PMMA resist is followed by reduction of the doped ions using aqueous sodium tetrahydroborate. The nanogranular structures are fabricated at the metal/polymer interface after the reduction treatment, which can contribute to relatively high adhesion of the deposited metal thin films on the polyimide substrate. This approach is an etching-free process and provides an effective methodology toward lower-cost and higher-throughput microfabrication.

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Recently, the problem of electromigration failure in flip-chip solder joints has become a critical issue because of miniaturization of the solder joint structure. In this paper, we report on a newly developed method of predicting the electromigration failure of a solder joint. This method was based on the atomic flux divergence (AFD) method and could predict the behaviors of voids and hillock growth in a micro solder joint. We compared the electromigration failure lives of two solder joint structures using our method. One structure was a conventional solder ball joint and another was a Cu-cored solder ball joint. We found that the Cu-cored solder ball joint had a longer life because crack growth near the center of the Cu-cored joint was prevented because of its geometric feature. Moreover, we measured the failure lives and observed void shapes using synchrotron radiation X-ray microtomography. Accordingly, we could find that the results predicted by our method corresponded to actual results.

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Embedding active device technology is a very effective means of downsizing printed wiring boards, because of its large occupied area. Since a bare die is preferred in order to achieve a thin substrate, the flip chip mounting technique is inevitably used. In this case, resin is used to under-fill the gap between the bare die and the inner layer of substrate. In our evaluation using TEG chips, delamination at this part was found depending on the substrate structure, conductive pattern, and bare die size. Regarding these phenomena, thermal deformation analyses and actual deformation measurements were performed, and these results suggested the possibility of failure prediction even by elastic analysis. In addition, we found that thermal deformation could be reduced by adjusting the copper conductive pattern.

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This paper reports on a novel fabrication process and the characterization of an electrical contact structure made of a conductive polymer and elastomer for application to woven flexible sheet device technology. The structure can be fabricated by reel-to-reel continuous fiber processing because it is formed using just die-coating and dispensing techniques. The height of the structure can be easily controlled by changing the emulsion volume that drops onto the cable. The resistance between the structure and a PEDOT : PSS coated PET ribbon remained nearly unchanged until 1.2×10⁵ times load repetitions with a force of 4 N (∼100 MPa). From the resistance measurements in the bending radius range of 1 to 10 cm using flexible sheets formed by weaving a PET ribbon cable, the structure enhances the durability, flexibility, and stability of the electrical contacts in the woven-sheet devices better than those of the ribbons without it.

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