Magnetic resistance element, method for preparing the same and m

Details Magnetic resistance element, method for preparing the same and m Magnetic resistance element, method for preparing the same and m

1993-06-17

1996-07-23

Lateef, Marvin M.

Electrical resistors

Resistance value responsive to a condition

Magnetic field or compass

32420721, 324252, 428694TP, H01L 4300

Patent

active

055393721

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a magnetic resistance element, a method for preparing the same and a magnetic sensor using the same, more specifically to a magnetic resistance element for a magnetic encoder covered with a protective film, a method for preparing the same and a magnetic sensor using the same.


BACKGROUND ART

In the prior art, a magnetic resistance element has a structure shown in FIG. 2. That is, a ferromagnetic thin film 2 comprising a Ni--Fe alloy, a Ni--Co alloy, etc. is formed on a substrate such as glass, ceramics of alumina, etc., and a protective film 3 is formed on the ferromagnetic thin film 2. As the protective film 3, there has been generally used a silicon oxide layer with a film thickness of 10 to 30 .mu.m formed from silicon oxide by a CVD method, sputtering, etc. or a thin layer with a film thickness of 5 to 10 .mu.m comprising a non-water permeable resin such as a polyimide resin, an epoxy resin or a polyamide resin, etc. A lead wire 5 is connected with the end portion of the ferromagnetic thin film 2 by means of solder 4. A mounting portion by the solder 4 is covered with a resin 6.
However, in the protective film 3 comprising silicon oxide, fine cracks and pinholes exist so that water is penetrated through these cracks and pinholes, whereby there involves a problems that the ferromagnetic thin film 2 comprising a Ni--Co alloy, etc. is corroded. For this reason, in the prior art, the film thickness of the protective film 3 has been made as thick as 10 to 30 .mu.m to decrease fine cracks and pinholes, whereby moisture resistance is improved. However, it is impossible to prevent cracks and pinholes completely, and there still involves a problem that the ferromagnetic thin film 2 is corroded by water.
Further, when the film thickness of the protective film 3 is made thick, there involve problems that a distance between the ferromagnetic thin film 2 and a magnetic material to be detected is broadened so that detection output is lowered, and cracks are easily formed on the substrate and the protective film 3 by thermal shock since thermal expansion rate of the ferromagnetic thin film 2 comprising a metal is greatly different from those of the substrate 1 comprising ceramics and the protective film 3.
Also, when the protective film 3 comprising a non-water permeable resin such as a polyimide resin, an epoxy resin or a polyamide resin, etc. is formed on the ferromagnetic thin film 2, there involve a problem that a resin is coated in the air so that molecules of water adsorbed on the ferromagnetic thin film 2 are encapsulated by the resin, and the ferromagnetic thin film 2 is corroded by the molecules of water or a minute amount of water contained in the resin.
An object of the present invention is to solve the above problems, and to provide a magnetic resistance element in which moisture resistance is excellent, detected output is enlarged by making the film thickness of a protective film thinner and no crack is formed by thermal shock, and a method for preparing the same.


DISCLOSURE OF THE INVENTION

The magnetic resistance element of the present invention comprises a substrate, a ferromagnetic thin film formed on said substrate, a first protective film comprising silicon oxide (SiO.sub.x wherein 0.5.ltoreq.x.ltoreq.2) formed on said ferromagnetic thin film and a second protective film comprising a synthetic resin formed on said first protective film.
The method for preparing the magnetic resistance element of the present invention comprises a first step of heating a substrate on which a ferromagnetic thin film is formed under vacuum at 150.degree. to 350.degree. C., a second step of forming a first protective film of silicon oxide (SiO.sub.x wherein 0.5.ltoreq.x.ltoreq.2) on said ferromagnetic thin film on said substrate, and a third step of forming a second protective film comprising a synthetic resin on said first protective film.
Further, the magnetic sensor of the present invention is a magnetic resistance effective type element sensor which comprises a synthet

REFERENCES:
patent: 4309482 (1982-01-01), Suzuki et al.
patent: 5061562 (1991-10-01), Yamanaka et al.
patent: 5073460 (1991-12-01), Futamoto et al.
patent: 5132173 (1992-07-01), Hashimoto et al.
Patent Abstracts of Japan, vol. 12, No. 246 (1988) of JP-A-63 033 880.

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