JPS61284978A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To provide a function for fixing an MR chip to an MR chip fixing holder and a function for applying a magnetic bias to a chip in the holder by mixing magnetic powder of hard ferrite powder in the holder, molding the mixture and magnetizing it to form the holder as a permanent magnet. CONSTITUTION:A holder 6 is integrally molded with resin together with a lead frame 7. When the holder 6 is molded, the holder is formed of resin sufficiently mixed with magnetic powder such as hard ferrite powder, an MR chip 1 is, for example, placed in the holder, and integrated, and magnetized in a larger magnetic field than the coercive force of the holder 6 to form the holder 6 as a permanent magnet. When this structure is utilized, it is not necessary to mount a permanent magnet 3 in a sensor, and magnetic bias can be applied to the chip 1 by the magnetic field produced by the holder 6. The direction of the magnetic bias can be freely selected by altering the magnetizing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic sensor that utilizes the magnetoresistive effect of a ferromagnetic thin film.

<Summary of the Invention> The present invention involves molding a holder for fixing an MR chip by mixing magnetic powder such as hard ferrite powder, and magnetizing the holder in a magnetic field larger than the coercive force of the holder, thereby making the holder itself a permanent magnet. The magnetic field created by this applies a magnetic bias to the MR chip.

<Prior Art> As is well known, a ferromagnetic magnetoresistive sensor utilizes the phenomenon that spontaneous magnetization inside the sensor rotates under the action of an external magnetic field, and the sensor resistance value changes at this time.

FIG. 2 is a perspective view of a main part of a conventional magnetoresistive magnetic sensor. In FIG. 2, 1 is an MR chip, to which a flexible film substrate 2 is connected by solder bonding, welding, etc. for connection to an external circuit. Further, a permanent magnet 3 is attached to the lower surface of the MR chip 1 for applying a magnetic bias to the MR chip l.

FIG. 3 is a perspective view of main parts showing another conventional example.

The basic structure of this is the same as that in FIG. 2, and in FIG. 3, 1 is an MR chip, to which a lead wire 4 is connected for connection to an external circuit. Reference numeral 5 denotes a resin coat that is applied after the chip 1 and the lead wires 4 are connected by soldering or electric welding to improve mechanical strength and protect them from the outside. Further, on the lower surface of the chip I, a permanent magnet 3 for the purpose of magnetic bias is attached as described above.

As mentioned above, in this type of sensor, applying a magnetic bias to the MR chip l improves hysteresis or discontinuities in the sensor output. Therefore, conventionally, the magnetic sensor is placed on the bottom surface of the MR chip l.
A permanent magnet 3 for applying a magnetic bias to the R chip l was attached and integrated, and then this was further attached to a holder for fixing the MR chip (not shown) for use.

<Problems to be Solved by the Invention> However, in the conventional magnetic sensor, the permanent magnet 3 is attached to the sensor and integrated, and then fixed with a holder (not shown). The drawback is that it becomes complicated and increases costs.

Furthermore, since the thickness of the entire sensor is increased by attaching the permanent magnet 3, it is difficult to handle when incorporating the sensor into devices such as video cameras and televisions. There was a risk that it would cause problems at the top.

Means for Solving the Problems> In order to solve the above problems, the present invention molds a holder for fixing an MR chip by mixing magnetic powder such as hard ferrite powder, and magnetizes it to form the holder itself. By making the holder a permanent magnet, the holder has a function of fixing the MR chip and a function of applying a magnetic bias to the chip.

Effects> With the above configuration, the present invention eliminates the need to attach and integrate a permanent magnet to the MR chip, and by attaching the MR chip directly to a magnetized holder, the magnetic field generated by the holder applies a magnetic bias to the MR chip. We obtained the effect of being able to give .

<Example> Hereinafter, one embodiment of the present invention will be described in detail.

FIG. 1 is a perspective view of an embodiment of a magnetic sensor according to the present invention. I is an MR chip, 6 is a holder that is integrally molded with the lead frame 7 and has a magnetic bias function,
Reference numeral 5 denotes a reinforcing and protective resin that is potted into the electrode portion of the MR chip 1 and the lead frame 7 after the wire is connected between the electrode portion and the lead frame 7.

The above structure will be explained in more detail with reference to FIG.

FIG. 4 is partially cut away to facilitate understanding.

The holder 6 and the lead frame 7 are integrally molded from resin. This is well known as, for example, the transfer molding method - the lead frame to be sealed is set, the mold is closed, the resin preheated by a high-frequency preheater is poured into a pot, and the resin is pressurized with a plunger and injected into the cavity. It can be easily produced by a molding method that involves filling and curing. That is, the wire bond parts 7a, 7a, . . . of the lead frame 7
- is built into the holder 6 from the beginning.

The MR chip 1 is attached to this holder 6 with an adhesive or the like, and the wire bond parts 7a, 7a, . . Note that the wire connection may be performed by overlapping the chip electrodes 1a, 1a*, . . . and the wire bonding portions 7a, 7a, . . . of the lead frame 7 and soldering them. The resin 5 is further potted and cured for the purpose of increasing the mechanical strength and protecting this portion.

In the above embodiment, when creating the holder 6, the holder 6 is molded from a resin sufficiently mixed with magnetic powder such as hard fetolite powder, and after mounting the MR chip 1 thereon and integrating it, the holder 6 is molded. By magnetizing the holder 6 in a magnetic field larger than the coercive force of the holder 6, the holder 6 itself becomes a permanent magnet.

Note that the timing to magnetize the holder is not limited to the above, and may be before the MR chip 1 is attached to the holder 6.

Therefore, if the structure shown in FIG. 1 is used, it is not necessary to attach the permanent magnet 3 to the sensor, and it is possible to apply a magnetic bias to the MR chip 1 by the magnetic field generated by the holder 6 itself. Furthermore, the direction of the magnetic bias can be freely selected by changing the magnetization direction, and the strength of the magnetic bias can also be adjusted by controlling the amount of magnetic powder mixed into the holder 6. .

FIG. 5 is an exploded perspective view showing another embodiment.

Holder 9 that does not integrate the lead frame as shown
Also, by mixing magnetic powder into the resin and magnetizing it when making the holder, it is possible to impart a magnetic bias function to the holder 9 itself, and the same effect as in the previous embodiment can be obtained. It is something.

In addition, if the magnetic sensor according to the present invention is used, it is possible to use a holder 6 that has both the function of fixing the MR chip 1 and the function of applying a differential magnetic bias.Therefore, handling is improved and the overall thickness is reduced. Since it can be made thinner, it can be compactly stored in a smaller area, making it possible to downsize the entire device.

<Effects of the Invention> According to the present invention, it is possible to improve the yield due to easy assembly, and on the other hand, since the overall thickness of the sensor can be reduced, it is easy to incorporate the magnetic sensor into the device, which improves mechanical strength and quality. This is something that can be improved.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the magnetic sensor according to the present invention, Fig. 2 is a perspective view of main parts showing a conventional example, Fig. 3 is a perspective view of main parts showing another conventional example, and Fig. 4 1 is a partially cutaway perspective view showing FIG. 1 in detail, and FIG. 5 is an exploded perspective view showing another embodiment of the present invention. 1: MR chip, 5: resin, 6: holder, 7: lead frame. Agent Compiled by patent attorney Aihiko Fukushi (and 2 others) Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] 1. MR element formed from a ferromagnetic thin film on the substrate surface
In a magnetic sensor in which a chip is attached to a holder molded from resin, the holder itself is molded by mixing magnetic powder such as hard ferrite powder and magnetized in a magnetic field larger than the coercive force of the holder. A magnetic sensor characterized by being made into a permanent magnet.