Development of amorphous wire type MI sensors for automobile use

Amorphous wire type MI sensors have a high sensitivity compared to thin film MI sensors, but there have been reliability problems in developing an amorphous wire type MI sensor for automobile application because of the wide range of operating temperatures. It was difficult to achieve sufficient soldering strength between the amorphous wire and the electrode of the MI chip. In addition, stress is induced in the amorphous wire during soldering thus lowering the temperature stability characteristics. Therefore, we developed a new method for soldering the amorphous wire and a new method for assembly of the MI chip. Together with the redesign of the electronic circuit, these developments have yielded an MI sensor suitable for automobile application. This MI sensor has a sensitivity of 250 mV/Oe, has stable temperature characteristics between -40degreesC and 85degreesC and easily passed the thermal shock test, the most stringent durability test for automobile electronic parts. Two different types of products are under development; one is a standard type whose output is linear to the external magnetic field, and the other is a switch type whose output is ON or OFF relative to a threshold magnetic field. Future applications include an ABS sensor, an electronic compass, an automatic tracking system for automobiles and so on. (C) 2002 Published by Elsevier Science B.V.