As a way to store still images of a printed circuit board, retaining the high quality of the original images and at the same time providing a high compression ratio, we propose a new storage method that converts a series of still images into a dynamic image format. In this method, the bitmap file of the original images of a printed circuit board is converted into an audio video interleave (AVI) format. A number of enlarged shot images of the same point on the printed circuit board are collected to generate many similar images. Therefore, the original still image file can be treated as a frame image of successive dynamic images. This study evaluated the compression ratio and quality of the compressed images by conducting a compression experiment with the image files of a printed circuit board. To evaluate image quality, we compared differences between the original image and converted images at the same point and determined the average values and variation of the differences. The results of the image file compression experiment showed that while block noise occurred in the JPEG format conversion process, it was rarely found with this proposed AVI format conversion method. When the images in the AVI format files were compared with those in JPEG format files, the results confirmed that in terms of image quality the AVI files are equivalent to JPEG (Quality 100) and are superior to JPEG (Quality 50) files. In terms of compression, the AVI files have an approximately ten times higher compression ratio than JPEG (Quality 100) files and are equivalent to JPEG (Quality 50) files.

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This paper discusses the effect of irregularly grown intermetallic compounds (IMC) on tin whisker growth. Since irregular IMCs are formed along tin grain boundaries, due to diffusion between the tin finish and the substrate, the IMC network affects the local stress distribution of the tin plating layer. A microstructure-considered finite element analysis was performed to evaluate the IMC-induced stress evolution and a spontaneous whisker growth model was developed based on the local stress gradient and the IMC network. The model can qualitatively explain the fundamental behavior of whisker growth. The IMC network also affects pressure-induced tin whisker formation. IMC can prevent deformation of the plating layer, resulting in higher stress concentration. In particular, the lack of uniformity in IMC growth produces high residual stresses which can accelerate whisker growth.

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This paper describes the effect of oxygen in a nitrogen atmosphere on the wettability of lead-free solder alloys. Molten solder drops of Sn–3Ag–0.5Cu and Sn–9Zn were dropped onto Cu plates in a low oxygen atmosphere without flux, and their surface tension and contact angles were measured. Although the surface tension of Sn–9Zn was less than that of Sn–3Ag–0.5Cu, its contact angle of Sn–9Zn was larger. This is assumed to have been caused by the differences in the surface structures of the molten solder drops, which were composed of liquid metal and metal oxide.

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We have recently fabricated high-power near-ultraviolet light-emitting diodes (LED) on ceramic packages without sub-mounts, using a direct flip-chip bonding (DFCB) technique. In the ceramic packages, pad electrodes of 0.35 mm LED chips were bonded onto metalized packages using metal stud bumps. The cross-sectional microstructures of the chip/bump/ceramic of both non-degraded and degraded DFCB packages were investigated using a scanning electron microscope with energy dispersive x-ray spectroscopy. We have confirmed the presence of firm flip-chip interfaces between the stud bumps and the DFCB packages, and failure at the p-type contact layer/p-electrode interface. In addition, x-ray computed tomography (CT) and ultrasonic scanning were carried out as non-destructive inspection methods. The clacks at the interfaces of the DFCB package could be detected by ultrasonic scanning inspection, but not by x-ray CT, due to the lack of resolution.

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