JPH0474767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hybrid thin film integration head, and more particularly to a retrograde film integration head using a magnetoresistive element (hereinafter abbreviated as MR element).

Thin film magnetic heads have been widely adopted to increase recording density and improve frequency characteristics.

For example, this thin-film magnetic head is ideal for magnetic heads that require a large number of head elements and a high degree of integration for each head element in order to meet the demands for multi-channel use, such as in digital audio recorders. It is considered a thing.

However, when looking at playback heads, the playback voltage of the magnetic induction type thin-film magnetic head that has been widely used in the past is proportional to the relative speed between the head and the magnetic recording medium, so at low speeds, the playback output is also low. In order to accommodate this, it is necessary to increase the number of turns of the coil, from several hundreds to thousands of turns, making it practically difficult to use it as a thin film reproducing head.

On the other hand, in order to support such thin-film magnetic heads, thin-film magnetic heads (hereinafter abbreviated as MR heads) using magnetic flux-responsive magnetoresistive elements, which are unrelated to the relative speed between the head and the magnetic recording medium, have been developed. It is attracting attention.

An example of such an MR head is shown enlarged in FIG.

In FIG. 1, what is indicated by the reference numeral 1 is a substrate;
On its side, facing the magnetic recording medium side, there is an MR element 2.
is formed by a thin film deposition method or the like, and both ends of the MR element 2 are connected to conductive parts 3 formed on the substrate by a similar method.

If a constant current is supplied to the MR element 2 of the MR head having the above structure through the conductive part 3, when an external magnetic field approaches, the resistance value of the MR element 2 will change, resulting in a change in voltage. The strength of the magnetic field can be extracted. Reproduction output voltage ΔV at this time
is expressed as ΔV=ΔRI. ΔR is due to the external magnetic field
In the resistance change of the MR element, I is the value of a constant current applied to the MR element. The rate of change in resistance of the MR element 2 caused by an external magnetic field is generally
-1 to 3% for MR elements made of Fe, Ni-Co, etc.
It is.

Therefore, in order to obtain a large reproduction output, it is necessary to increase the absolute resistance value of the MR element.
The resistance value R of the MR element is generally expressed by the following equation (1).

R=ρ _MR ×l/w×t...(1) In equation (1), ρ _MR is the specific resistance value of the MR element, l
represents the length of the MR element, w represents the width, and t represents the thickness. No.
As is clear from equation (1), in order to increase the resistance value of the MR element, the length of the MR element must be increased,
It is necessary to reduce the width and thickness.

However, the thickness of the MR element cannot be made very thin because the element is created using thin film technology.
The width of the MR element cannot be made very small due to limitations in photoetching technology.

In addition, the length of the MR element corresponds to the track width of the read head, and as the recent high-density magnetic recording and playback technology requires multichannel and high integration, it is necessary to reduce the track width.
There is a need to reduce the length of elements.
As a result, as is clear from equation (1), there is a drawback that the reproduced output also becomes smaller.

Furthermore, when mounting an MR element, it is necessary to connect the conductive part with a flexible lead wire and connect it to the preamplifier circuit part to obtain a reproduced output signal.

As a result, the resistance values of the conductive parts and lead wires cannot be ignored, resulting in an output with a poor S/N ratio. Since the conductive parts and lead wires become long, when actually detecting the reproduced signal,
This causes noise to be induced in the surrounding area.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology.
The object of the present invention is to provide a thin film magnetic head using the device.

In order to achieve the above object, according to the hybrid thin film integrated head of the present invention, a plurality of head parts formed of magnetoresistive elements and conductive parts are arranged on a silicon substrate, and a plurality of head parts having dimensions larger than the silicon substrate are arranged. A silicon substrate on which the plurality of head portions are arranged is fixed on the first insulating substrate, and a portion of the magnetoresistive element on the silicon substrate is covered with a second insulating substrate, and the first An integrated circuit chip including a preamplifier circuit and a pad portion is fixed to a portion of the insulating substrate where the silicon substrate is not present, and is fixed to the conductive portion on the silicon substrate and the first insulating substrate. We adopted a configuration in which the pads of the integrated circuit chip are connected by wire bonding.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

The reference numeral 4 in FIG. 2 is an insulating substrate made of glass, quartz, alumina, ferrite, or the like.

5 is an MR head section, in which an MR element 2 and a conductive section 3 serving as an electrode are formed on an insulating substrate made of silicon, glass, alumina, ferrite, etc. by a thin film deposition method, and this insulating substrate is used as a substrate. 4 is fixed on top.

This MR head section 5 is fixed on a substrate 4, and its tip end, that is, the magnetic recording medium side, is covered with an insulating substrate 5a for protecting the MR element section. This insulating substrate 6 is also made of glass, quartz,
It consists of alumina, ferrite, etc.

On the other hand, the reference numeral 7 is a semiconductor integrated circuit chip, which has circuits such as a magnetic signal detection circuit and a preamplifier formed on a silicon substrate, and is fixed on the substrate 4. The pad portion 8 which becomes the connection terminal electrode of the semiconductor integrated circuit chip 7 and the
The MR head section 5 and the conductive section 3 are electrically connected to each other by a wire bonding method using a thin wire 9 made of aluminum, gold, or the like.

FIG. 4 shows an equivalent circuit diagram of a preamplifier circuit, which is a part of the preamplifier circuit. In FIG. 4, the portion designated by the reference numeral 10 is the MR element portion, and the portions designated by the symbols A and B at both ends thereof correspond to the pad portion 8 and the conductive portion 3 shown in FIG. 3, respectively.

The voltage change caused by the resistance change of the MR element section 11 is detected by the transistors T ₁ and T ₂ and amplified by the transistors T ₃ to _{T 5} .
It is taken out as the output OUT and sent to the external circuit.

Since this embodiment is configured as described above,
Since the MR element and the preamplifier integrated circuit section are formed extremely close to each other, the distance between them can be shortened, and the S/N ratio of the reproduced signal can be improved.

When using an MR head, noise generated by the induced magnetic field crossing the signal line connecting the MR element and preamplifier becomes a problem, but the magnitude of this noise is proportional to the cross-sectional area of the closed loop formed by the signal line. do.

For this reason, in the conventional example, the MR element and the preamplifier located at a remote location were connected by a lead wire such as a flexible lead wire, which resulted in a large cross-sectional area of the aforementioned closed loop and a large amount of noise.

On the other hand, in the thin-film magnetic head of the present invention, the MR element and preamplifier are arranged extremely close to each other, so the cross-sectional area of the closed loop formed by the signal line connecting them can be almost ignored, and the amount of noise can also be reduced. can be significantly reduced.

On the other hand, the connection from the output end of the preamplifier to the input end of the next stage will be connected with a lead wire as before.
Noise is generated in this part due to the induced magnetic field, but in the structure of the present invention, the signal component is amplified by the preamplifier, so even if the same amount of noise is generated in this part as in the conventional case, the signal is amplified in advance. The S/N ratio can be improved by that amount.

Furthermore, the resistance of the conductive part and lead wire that extracts the signal from the MR element is a source of noise, but in the conventional structure, this noise was generated at a stage where the signal voltage is small before the preamplifier, so the S/
This resulted in a decrease in the N ratio.

However, in the structure of the present invention, since the resistance of the lead wire portion is located after the preamplifier,
The noise caused by this can be ignored.

Furthermore, in the conventional structure, when using n MR elements, the number of connection terminals is 2n,
Even when connecting the MR element to the preamplifier section using flexible lead wires, 2n lead wires are required.

In contrast, in the structure of the present invention, the preamplifier circuit has one common drive voltage application terminal and one common ground terminal.
A total of n + 2 terminals (n output terminals) is sufficient. As a result, as the number of MR elements mounted increases to two or more, the number of terminals is reduced, so the structure of the present invention becomes more advantageous, and not only improves the S/N ratio mentioned above, but also reduces the size. It is measured.

As is clear from the above description, according to the hybrid thin film integrated head of the present invention, a plurality of head parts formed of magnetoresistive elements and conductive parts are arranged on a silicon substrate, and the head part has a size larger than that of the silicon substrate. A silicon substrate on which the plurality of head parts are arranged is fixed on a first insulating substrate, and a portion of the magnetoresistive element on the silicon substrate is covered with a second insulating substrate, and An integrated circuit chip including a preamplifier circuit and a pad portion is fixed to a portion of the first insulating substrate where the silicon substrate is not present, and a conductive portion on the silicon substrate and the integrated circuit chip fixed to the first insulating substrate are fixed. Since the pads of the integrated circuit chips are connected by wire bonding, noise induction can be reduced and S/
The N ratio can be improved, miniaturization is possible, and high-density packaging of multiple channels can be realized.

[Brief explanation of the drawing]

Figure 1 is a partially enlarged plan view illustrating the conventional structure;
2 to 4 illustrate one embodiment of the present invention, in which FIG. 2 is a side view of a thin film magnetic head, FIG. 3 is a partially enlarged plan view of the thin film magnetic head, and FIG. 4 is an integrated FIG. 3 is an equivalent circuit diagram of a preamplifier portion of the circuit section. 2...MR element, 3...Conductive part, 5...MR head part, 7...Semiconductor integrated circuit chip, 8...Pad part, 9...Thin wire.

Claims (1)

[Claims] 1. A plurality of head portions formed of a magnetoresistive element and a conductive portion are arranged on a silicon substrate, and the plurality of head portions are arranged on a first insulating substrate having a larger size than the silicon substrate. a silicon substrate on which the magnetoresistive element is placed is fixed, a portion of the magnetoresistive element on the silicon substrate is covered with a second insulating substrate, and a portion of the first insulating substrate where the silicon substrate is not present; An integrated circuit chip including a preamplifier circuit and a pad portion is fixed to the silicon substrate, and the conductive portion on the silicon substrate and the pad portion of the integrated circuit chip fixed on the first insulating substrate are connected by wire bonding. A hybrid thin film integration head featuring a unique configuration.