Abstract
We have developed a 3-6μm thin-film pressure sensor using the piezo-resistive effect of Cu-Mn-Ni alloys in order to measure the oil-film pressure in the plane bearing of the internal combustion engine. This sensor can be deposited 3-6μm in thickness directly on the bearing surface using the PVD (RF magnetron sputtering) method without changing the shape of the sliding surface or reducing the rigidity of bearing housing, caused by making a hole for sensor installation in the bearing housing. On the other hand, one of the problems with this sensor is low durability. In order to improve the sensor durability, we have deposited and evaluated the diamond-like carbon (DLC) as the material for the insulation and protection films of the sensor. Although we succeeded in fabricating a DLC film of high insulation resistance by using DC magnetron sputtering, the DLC film showed low adhesion strength on the sensor alloys such as Cu alloys and Ni-Cr alloys. In the next step, we tried to deposit the aluminum oxide film by using the RF magnetron sputtering method enhanced with inductivity-coupled plasma. As the result of scratch test, the thin-film, deposited by above new sputtering method, showed a high critical load (Lc), compared with the films deposited by the conventional RF magnetron sputtering. This film provided a sufficiently high adhesive strength to the sensor alloys.
