Advanced packaging demands higher performance, smaller size, and lower energy consumption. Thus, a wide variety of materials have been used and the writing layer has become denser. Against this background, the performance of plasma technology is required for advanced packaging in order to support miniaturization, a wide variety of materials, and various substrate shapes. This paper introduces a dry ashing process in redistribution layer production and a ULVAC dry-ashing system, called "NA-series". Ashing treatment has applications such as descum, controlling the surface shape, and surface modification. In the near future, plasma technology will be attracting increased attention due to the complexity and miniaturization of advanced packaging products.

Maintaining the water content in the human body is necessary to prevent heatstroke on construction sites in the hot sun. As such, determining levels of perspiration for the entire body is important. This study focused on helmets (or hard hats), which are mandatory on construction sites, to develop a wearable helmet device that can measure the amount of perspiration while completing various activities. The results of our experiments indicate the feasibility of measuring whole-body perspiration levels using this device. In addition, we show that the estimated perspiration rate can potentially be used as an index for the earlier identification of heatstroke occurrence compared with the traditional indicator, i.e., a rise in core body temperature.

Motor drive systems with three-phase inverter circuits are becoming common in order to meet demands of high controllability and lower power consumption. Adequate thermal design is vital to allow integration of the motor drive system with lightweight, small inverters. To realize adequate thermal design, we must understand the heat transfer structure of the system. In this paper, we propose a methodology to obtain a thermal impedance distribution along the heat transfer path, as the heat transfer structure. Firstly, the thermal impedance distribution expression utilizing a Cauer thermal network is explained. Secondly, two types of test boards with a MOSFET sample are prepared and are measured to obtain the transient junction temperatures. After that, the thermal impedance distributions are extracted from the measurement results and these results are discussed.

Thermal fatigue of wire-bonding and die-attach materials is a critical factor in the structural integrity of power modules. A power-cycling test, a temperature-cycling test and a mechanical-fatigue test are utilized to evaluate the expected lifetime of power modules. Moreover, lifetime evaluation in the design phase is considered to be important for power modules incorporated into mass-produced commodities such as automobiles and home appliances, because in-service condition monitoring is difficult for power modules used in such commodities. In this paper, we consider a power-cycling test and a temperature-cycling test, and discuss the applicability of the lifetime evaluation formulae obtained from these tests to evaluating the lifetime of power modules in the design phase. In addition, we discuss a mechanical-fatigue test as a substitute for a temperature-cycling test.

In order to mechanically and electrically connect a sensor chip and a flexible printed circuit (FPC) board, we evaluated a caulked connecting method where the stud-bumps formed on the sensor chip are pushed into blind-via-holes (BVHs). The stud-bumps and the BVHs can be easily fabricated with conventional manufacturing technologies. The results of the caulked connection experiment confirm that mechanically fixed electrical connections with an electric resistance of 0.057 Ω can be achieved by making the diameter of the bump larger than the inner diameter of the BVH. Observing the connecting parts using a Scanning Transmission Electron Microscope (STEM), showed that the interfaces between the Au electrodes of the BVH side wall and the Au material of the bumps were bonding. Thus, it is clear that this caulking method is able to connect sensor chips and FPC-boards.

Previously, Sn-Pb plating was widely used in the electronics field, due to its good solderability. Recently however, lead-free plating has been developed because of concerns about the effects of lead on the environment. It is widely known that whisker defects sometimes occur in pure tin plating so we investigated a method for the suppression of whisker defects. We found that Periodic Reverse (PR) electrolysis suppresses whisker defects in tin plating and the orientation of the deposited Sn showed a decrease of preferred crystal orientation. In this paper, we discuss the suppression mechanism of PR electrolysis. In addition, we discuss the relationship between the decrease of preferred crystal orientation and whisker growth.

This paper evaluates the insulation capability of a gate-insulating layer used in organic thin-film transistors (OTFTs) under mechanical loading. For this evaluation, a novel specimen structure which has a "semiconductor-less" structure is proposed; in the proposed structure, the semiconductor layer is removed from the conventional OTFT structure. The evaluation results demonstrate that the insulation capability of the gate-insulating layer is deteriorated starting from 1.0~1.5% strain of the specimen. Additionally, the degradation of the insulation capability is saturated around the yield stress (3.0~4.0% strain) of the specimen substrate (PEN). The evaluation results of the leakage current represent that the leakage path is the source-gate-drain electrode via the gate electrode. The laser-microscope observation results show that the plastic deformation (mechanical damage) is observed in the insulation layer in the degradation range of the insulation capability.

In this paper, the intensity of a singular stress field (ISSF) is focused and newly analyzed for a stepped-lap joint, and the adhesive strength is considered in terms of the ISSF. In this problem, it is necessary to analyze the two different singular stress fields at the interface end point A and each interface corner point B_i (i = 1,2…Ns-1, Ns = the number of steps) on the adhesive surface. Therefore, two different reference solutions are used in this study. The reference problem for point A is a butt joint having the same adhesive layer thickness as the stepped-lap joint. The reference problem for point B_i is chosen as a single rectangular fiber in an infinite plate under remote tension. In order to investigate the effect of the number of steps, Ns, on the ISSF of the stepped lap joint, four models with different numbers of steps are calculated. By comparing the stress distributions, we found that the ISSF at point A is larger than that at point B_i. Moreover, we also show that the ISSF at point A decreases with an increasing number of steps, Ns, but there is almost no change of the ISSF at point B_i.

Solder electromigration (EM) is recognized as a potential reliability problem in power modules and high performance processors. Power modules are getting smaller in size and higher in power, which causes the solder joints inside to operate at higher temperatures with higher current densities. The addition of Sb to a Sn-rich solder is known to be an effective way to allow high temperature operation up to 175°C. This study investigates the fundamental EM phenomena of a Cu/Ni-P/Sn-0.7Cu/Ni-P/Cu joint and a Cu/Ni-P/Sn-5Sb-0.7Cu/Ni-P/Cu joint to understand the effect of Sb addition on EM under the condition of 175°C and 50 A/mm². The EM failure occurred at the cathode after disappearance of the initial intermetallic compound (IMC) layer in both cases. The Sb addition can delay the decrease in thickness of the IMC layer; therefore it has the effect of extending the EM lifetime.