1. Field of the Invention
The present invention relates to a magnetic sensor, and more particularly, to a magnetic sensor that is employed as a rotation sensor for providing control to an automobile engine or ABS control in an automobile brake system.
2. Description of the Related Art
FIG. 10A is a cross-sectional view of the configuration of a magnetic sensor disclosed in Japanese Patent Laid-Open Publication No. Hei 91-79865 (19971), while FIG. 10B is a cross-sectional view of a modified example of FIG. 10A. As shown in FIG. 10A, a magnetic sensor 50 is fabricated in a manner such that a magnetic sensor chip 51 having a magneto-resistance element (MRE) and mounted on a lead frame 52 is packaged by molding in a molded material 53 of an epoxy-based thermosetting resin. Additionally, using an adhesive material 54, a bias magnet 55 is fixedly bonded into a recessed portion on a surface of the molded package as opposed to the magnetic sensor chip 51 mounted on the lead frame 52. A modified example shown in FIG. 10B is adapted to include the bias magnet 55 fixed onto the lead frame 52 in the molded package.
However, the conventional technique shown in FIG. 10A provides the bias magnet 55 outside the molded package, raising a problem that the magnetic sensor 50 is increased in size by the dimensions of the bias magnet 55. Furthermore, the detection accuracy of the magnetic sensor 50 depends on the positional relationship between the bias magnet 55 and the magnetic sensor chip 51. In aligning and bonding the bias magnet 55 using the adhesive material 54, the bias magnet 55 may be dislocated while the adhesive material 54 is being hardened, thereby raising another problem of providing reduced detection accuracy.
On the other hand, the bias magnet 55 may also be provided in the molded package as shown in the modified example illustrated in FIG. 10B. In this case, the magnetic sensor 50 can be reduced in size; however, the bias magnet 55 needs to be aligned with and then fixed to the lead frame 52. This raised still another problem of complicating the fabrication process as well as increasing the number of components required.