The photonic devices used for optical communication and optical storage media such as DVDs and BDs have been joined without the use of flux using a Au–Sn solder with a melting point of 278°C. However, the characteristics of the photonic device might deteriorate because of the residual stress after joining. Thus, a solder that can decrease the residual stress by joining at lower temperatures was developed. In this study, we report on a Sn/Ag/Au solder in which Ag and Au layers are formed on the Sn to prevent the surface of the Sn (melting point: 232°C) from being oxidized. The thickness of each layer was adjusted to produce a composition with a low melting point (206°C). It was shown that the solder could join parts without the use of flux, and excellent wettability and connection reliability was achieved.

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A means of inspecting the height of minute balls using an optical system with two cameras and a lighting system is described. The two cameras detect the minute balls from a vertical direction and from an oblique direction. In the images produced, bright highlights can be observed on the balls. When the height of the minute balls is changed, the position of the bright spots in the oblique image shifts laterally. In order to measure the amount of shift in the image, it is necessary to match the two images to compare the position of the spots. In this study, a method of correcting the distortion of the images is proposed. The method uses a standard pattern in which black circle patterns are regularly arranged to measure distortion. The method can be applied to correcting the asymmetric curve distortion of images. Using this technique, the position error between the two images was corrected to within 0.027809 pixels. The result of an experiment using steel balls with a height change of 100 μm is shown. The result shows that the height change can be detected as a spot shift of approximately 10 pixels.

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Because wireless devices are getting smaller and achieving higher sensitivity, higher spatial resolution and sensitivity of magnetic near-field measurement is required for the design of such devices in order to avoid electromagnetic self-interference. In this paper, the sensitivity to magnetic and electric near-fields for two types of square loop probes, shielded and unshielded, is first prototyped and evaluated. Results measured from the probes indicate that the induced voltage by the electric near-field at frequencies from 2 GHz to 9 GHz for the shielded type was 6 dB lower than that for the non-shielded type. We provide the equivalent circuits for probes having the same difference of sensitivity as the measurement results between probes, the element values of which were derived from the structure, position, and direction of the probes. Second, we propose a method to improve spatial resolution by subtracting the induced voltage between the original and slightly shifted position. As the measured results show, the proposed method improved the spatial resolution by 40% using a shielded square loop probe 1 mm on a side with 30 μm shift, which is an equivalent spatial resolution to a square loop probe 30 μm on a side.

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The possibility of a novel high heat-resistant thermosetting resin was investigated, with the reaction of a phenolic hydroxyl group generated by ring opening polymerization of benzoxazine with an epoxy group. First of all, 3,3′-(methylene-1,4-diphenylene) bis (3,4-dihydro-2H-1,3-benzoxazine) (P-d type benzoxazine) was selected for its thermal properties. Using P-d type benzoxazine and bisphenol-A-based epoxy resin (DGEBA), epoxy resins modified polybenzoxazines were prepared. The thermal stabilities were improved remarkably and the thermoplastic property of polybenzoxazine to soften at temperatures of more than 200°C was improved. In addition, an improvement of the thermal properties by reducing equivalent ratio of epoxy group to hydroxyl group of phenol was confirmed. PdBA (0.3), whose ratio of epoxy group to hydroxyl group was 0.3, showed a Tg of 206°C and a CTE of 47 ppm/K. In addition, by using a liquid crystal type epoxy resin or a polyaromatic type epoxy resin instead of DGEBA, further improvement of the thermal and mechanical properties was suggested. Moreover, by the addition of BF₃ (NH₂Et), the curing reaction was accelerated, maintaining the thermal properties of the cured resins.

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Today's trend towards ever smaller electronic products, such as cellular phones, demands the evolution of smaller printed wiring boards (PWBs). Along with this requirement for smaller PWBs, new pattern designs and mounting techniques must also be developed, and the importance of accurate positioning has increased. Because of the growing tendency towards the integration of multi-stratified PWB designs, the widths of flexible substrates have decreased to 25 μm. The objective of this research project is to address automatic measurement techniques for PWBs by offering an alternative. As an improvement upon current complicated measurement techniques, such as image processing inspection by pattern matching or optic microscope inspection systems, a capacitance line-width measurement system with a novel measurement probe design has been developed. In this report, we showed the correction systems required to improve the accuracy and a probe shape suitable for measurement. Using the correction systems, we are able to measure the defects of a PWB model (150 μm) with accuracy within 5%.

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