Semiconductor packaging technology is moving towards three-dimensional packages due to the need for high speed/high performance in mobile devices. Consequently, laminate materials for the packages of today need to be thinner and thinner. However, the lower stiffness of the total substrate leads to increased warpage of packages made with the thinner materials. Therefore, in order to reduce this warpage, it is necessary to reduce the coefficient of thermal expansion (CTE) of the laminate materials. At Hitachi Chemical, we have developed laminate materials by focusing attention on polycyclic aromatic resins, and we have investigated indicators for low CTE resins using molecular simulation technology. This paper introduces (1) the features of those polycyclic aromatic resins that show low CTE and their stacking effects, and (2) the design of low CTE resins with the help of compatibilizing energy as an indicator.

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High reliability and stable bond quality are required for industrial electronic devices. In this paper, we clarify how adding tiny amounts of Ni and Ge improves the properties of Sn-Ag-Cu alloy lead-free solder and the reliability of the bonded interface by inhibiting the effect of the generation-bonded interface-reaction phase and solder oxidation.
By adding a few hundred ppm of an element, granular Cu-Sn-Ni alloy compounds, which are formed from Cu-Sn alloy compounds, are generated in the bonded interface-reaction phase. This shows that it is possible to control of the growth of the bonded interface reaction phase. Also, we confirm that, as an antioxidant, a tiny amount of Ge will not inhibit the generation of granular chemical compounds owing to the addition of Ni, and it shows better bond reliability than the currently used antioxidant, P. Sn-Ag-Cu alloy lead-free solder with added Ni or Ge has already been put to practical use. There are application records in a number of industrial electronic devices over the past 15 years or so. Furthermore, these applications and the effectiveness of adding tiny amounts of these elements are recognized and registered in international standard ISO9453, and registration in domestic JIS standard is determined as well. This article introduces some approaches to solving the technical issues in the practical realization of Sn-Ag-Cu-Ni-Ge alloy solder.

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The wire-bonding method for electrically connecting the substrate and the electrode pads is used for mounting semiconductor components on circuit boards. However, as wire pitch becomes narrower in advanced packaging, the flip chip method has drawn attention as a means of mounting the chip by direct connection to the circuit board. In general, circuits are formed by sputtering aluminum onto an organic insulating film, which is then plated using a double-zincate method. However, for aluminum electrodes on polyimide, the polyimide is attacked by the strong alkaline or acid zincate bath. In this article, a zincate-free process on aluminum and wiring pattern formation on polyimide proved the possibility of using a combined treatment of fine Ni particle formation with direct electroless NiB plating and thick electroless NiP plating.

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Downsizing and dense packaging of electronic devices such as power modules and light emitting diodes (LEDs) lead to an increase in heat generation. In order to prevent the damages caused by the thermal stresses due to the increased heat, we have developed a novel composite with high thermal conductivity and a thermal stress relaxation effect.
We designed this thermal stress relaxation structure by topology optimization and fabricated a composite roll laminated with a non-bonded graphite sheet and aluminum foil. The thermal conductivity and the stress relaxation effect of the composite were investigated on a power module structure with ceramics, metals and the composite. The non-bonded interface in the composite reduced the thermal expansion mismatch between the metal and ceramics and thereby relaxed the thermal stresses. Moreover, the composite showed high thermal conductivity owing to the oriented graphite sheet.

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We investigated a low-cost resin composite material to replace ceramic in the insulated board in a power module. In order to apply the resin composite material to the insulated board, several traits are required: high heat dissipation, high heat resistance, and high adhesion strength with metals such as copper. In this paper, we report on our efforts to improve the heat resistance and adhesion strength in the resin composite material by preparing the material with a high percentage of the boron nitride (BN) filler. A cyanate ester resin with very high heat resistance was used for the base resin of the composite material, and it was blended with a flexible phenoxy resin. Consequently, we achieved a high thermal conductivity of 19W/(m·K) in the resin composite material together with high heat resistance and high adhesion strength.

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In this article, an image processing method to extract thin surface stains on a satin finished surface is described. When the background of an image is noisy as with a satin finished surface, or has gradually changing light and dark distributions, it is difficult to accurately extract stains by applying binarization. One method to extract thin local stains is to subtract the value of pixels of interest from that of the background image to emphasize the contrast of stains. Based on this method, we present a “Local stain emphasizing spatial filter” to extract thin stains. The filter emphasizes stains smaller than the diameter of the filter. In order to emphasize stains of various sizes, the diameter of the filter (scale s) was changed and the image is refiltered. Then, images filtered at various scales are unified to extract stains of various sizes. The resulting image shows good extraction of stains of various sizes without extracting the satin finished surface texture.

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