Teruo Yamanaka

Electrical environmental characteristics for automotive electric systems

The electrical environment is one of the most important factors in the design of high reliability electronic systems mounted on automobiles. Studies were made of the generation mechanisms and characteristics of both transients and high-frequency conducted noise generated in automotive electrical components. The high-frequency conducted noise data were obtained in terms of amplitude-frequency through real-time statistical treatment of the acquired data. The most important transient for automotive electronic systems has been found to be the alternator load dump transient caused by battery disconnection, and the most influential high-frequency conducted noise is caused by contact breaking. The high-frequency conducted noise characteristics can be expressed in the amplitude-frequency relation in the frequency range of 100 kHz-80 MHz.

Microwave Heating of Ceramics and its Application to Joining

A new butt joining method for ceramics by microwave heating was developed. Ceramics were heated in a rectangular cavity. A klystron of maximum 3 kW at 6 GHz was used as the power amplifier. The heating system can control the iris, plunger and microwave power to keep a power efficiency up to 90% and a accuracy within ±10°C at 1800°C. Microwave ceramic-ceramic joining was tried by using this system. A bending strength of the joined alumina rod (92% purity) was 420 MPa without adhesive. This value was equal to the original strength. Silicon nitride ceramics were joined with adhesive, which was a sintered ceramic sheet having lower purity and larger dielectric loss factor than the base ceramics. The microwave energy was concentrated on the sheet, so that only the joining area was heated. The strengths of joined specimens were in excess of 70% of original strengths. The joined boundary line was not detected in microscopic observation, and there was little difference in microstructure between before and after joining. These results suggest that sintering aids in grain boundary phases were preferentially heated and melted or diffused, resulting in sound joining of ceramics.