In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and so on. With this demand, contact failure caused by the fretting corrosion seems to become a serious problem in the future. In this report, three-dimensional observations using Focused Ion Beam (FIB)-SEM method have been made for tin plated fretting contacts before and after the contact resistance increase with tin plating thickness 5 µm. With these observations, the three dimensional structural transition from tin to tin oxide have been examined.

The authors previously conducted the observation of microstructures and three-dimensional SEM on fretting wear phenomena at tin-plated contacts. In this study, we report the fretting characteristics of dissimilar metal contacts by studying the relation between the contact resistance behaviors and micro structural changes of gold and tin-plated fretting contacts, through surface SEM observations and cross sectional SEM and AES analysis.

Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and low-latency in order to prolong the network lifetime while being able to quickly respond to actuation commands transmitted based on the real-time sensing data. These two requirements are in general in a relationship of trade-off when each node operates with well-known duty-cycling modes: nodes need to make their radio interfaces (IFs) frequently active in order to promptly detect the communication requests from the other nodes. One approach to break this inherent trade-off, which has been actively studied in recent literature of wireless sensor networks (WSNs), is the introduction of wake-up receiver that is installed into each node and used only for detecting the communication requests. The main radio IF in each node is woken up only when needed, i.e., in an on-demand manner, through a wake-up message received by the wake-up receiver. In this paper, we introduce radio-on-demand sensor and actuator networks (ROD-SAN) where the concept of wake-up receiver is applied to realize on-demand WSANs. We first evaluate data collection rate, packet delivery latency, and energy-efficiency of ROD-SAN and duty-cycling modes defined in IEEE 802.15.4e by computer simulations. Then, we present our test-bed implementation of ROD-SAN including all protocols from the lowest layer of wake-up signaling to the application layer offering the functionalities of information monitoring and networked control. Finally, we show experimental results obtained through our field trial in which 20 nodes are deployed in an outdoor area with the scale of 450m × 200m. The numerical results obtained by computer simulations and experiments confirm the effectiveness of ROD-SAN to realize energy-efficient and high-response WSANs.

In recent years, there have been ever-increasing demands to miniaturize automotive connectors. However, because the contact force decreases as connectors are miniaturized further, fretting corrosion, which is a typical problem occurring with low-force electric contacts, is expected to become a more serious problem in future. This time we developed a new experimental device capable of controlling the contact load, fretting amplitude, fretting frequency, contact part temperature and humidity optionally. In this report, we used the design of experiments method, and quantitatively evaluated the extent of the influence of the expected factor (in terms of load, amplitude, and plating thickness, etc.) on the fretting phenomenon, which occurs in the tin plating of the connector terminal. Moreover, based on SEM examination, we analyzed the surface and cross section of the contact parts when degradation occurs, and considered the mechanism of the degradation.

Due to the recent increase in electronic devices mounted on automobiles, a large number of connectors, especially low-cost tin plated connectors are being used. As a result, their contact reliability has become problematic. Furthermore, for the connectors which are subjected to fretting wear caused by heat cycle and vibrations, the contact resistance increases because of wear of tin and deposition of oxides, which generates problems of poor contact. This study is intended to analyze the change in contact resistance of tin plated connectors from the start of fretting wear to the end of their lifetime from the viewpoint of practical reliability, and to observe the trace and the characteristics of fretting wear microscopically. This study found that wear and oxidation of tin plated connectors start immediately with fretting wear, and thus accumulation of abrasion powder on fretting areas causes connectors to reach to the end of their useful lifetime quickly. Especially, it was demonstrated that amplitude of fretting has a considerable influence on a connector's lifetime. It is made clear that air-tightness, so-called "gas-tight" of tin in a fretting area influences fretting wear considerably.

In this report, Focused Ion Beam (FIB) -- SEM technique was applied to observe the tin plated fretting contacts. Spatial distributions of tin, tin oxide and so on have been confirmed quantitatively in two plating thickness of 1 and 5 µm.

In recent years, there has been increasing demand to miniaturize wiring harness connectors in automobiles due to the increasing volume of electronic equipment and the reduction of the installation space allocated for the electronic equipment in automobiles for the comfort of the passengers. With this demand, contact failure caused by the fretting corrosion is expected to become a serious problem. In this report, we examined micro-structural observations of fretting contacts of two different tin plating thicknesses using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) and so on. Based on the results, we compared the microstructure difference of fretting contact caused by the difference of the tin plating thickness.