JPH07249210A - Mr head testing method - Google Patents

Abstract

PURPOSE:To simplify a testing equipment by making an observation means observe reproduced data generated by a transmission means based on internal resistance values changed by a magneto-resistance effect element in accordance with the intensity of an external magnetic field. CONSTITUTION:A magnetic flux generated at the recording head of a magnetic head 2 by a current flowing in a coil 6 and corresponding to writing data becomes a leakage flux to be actuated on a magneto-resistance effect element 7 and changes the internal resistance value of the magneto-resistance effect element 7. Then, waveforms obtained according to writing data can be observed by observing the output signal of a transmission means 9 detecting changes of resistance values of the magneto-resistance effect element 7 with an observation means 10. Since waveforms are the same as waveforms in a state where data written on a recording medium are read out. the normal/defective condition of an B head while including the recording head can be decided. Thus, the normal/defective condition of the magnetic head 2 can be decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MR head testing apparatus using a magnetoresistive effect element, and more particularly to a magnetoresistive effect element without using a recording medium when the MR head is mounted on a carriage. The present invention relates to an MR head test method capable of testing the quality up to a head IC circuit that amplifies a signal read by the magnetoresistive element, including a lead wire.

In recent years, the size and capacity of magnetic recording / reproducing devices have been increasing, and since the magnetic head can also have a higher recording density than a thin film head, an MR head using a magnetoresistive effect element for data reproduction is used. Came to be used.

This is because by using the MR head, a reproduction output independent of the relative speed with respect to the recording medium can be obtained, so that the running speed of the recording medium can be lowered and the recording density can be increased.

By the way, since the MR head, which is a reproducing head of the magnetic head, uses a magnetoresistive effect element that changes the internal resistance value in response to the change of the external magnetic field, it is necessary to judge whether the MR head is good or bad. Although it is necessary to apply a magnetic field that changes from the outside to the magnetoresistive effect element, it is desired to eliminate the need for a recording medium for this purpose.

[0005]

2. Description of the Related Art FIG. 5 is a diagram for explaining an example of a conventional technique. The magnetic head 2 attached to the tip of the arm 4 of the carriage 5 via a spring is positioned on the data recording surface of the disk medium 1 as the carriage 5 moves.

The disk medium 1 is rotated by the spindle motor 3, and the write data is sent to the recording head of the magnetic head 2 to write the data on the data surface of the disk medium 1.

When data is written on the disk medium 1,
The reproducing head of the magnetic head 2, that is, the magnetoresistive effect element, is written on the disk medium 1 by changing the internal resistance value and changing the sense current due to the changing external magnetic field applied from the disk medium 1. Data is read.

Therefore, the recording head of the magnetic head 2 is supplied with a current which is turned on or off in synchronization with a clock to write data to the disk medium 1, and the magnetoresistive effect element reads the data to make an oscilloscope or the like. By observing the waveform of the read data, the quality of the magnetic head 2 can be determined.

As described above, the data is written on the disk medium 1 and read by the magnetoresistive effect element because the magnetoresistive effect element changes the internal resistance value in response to the change in the external magnetic field. It is necessary to apply a sense current to the effect element to extract the change in the internal resistance value, and whether it is good or bad cannot be confirmed by a continuity check, etc., and the operating point moves due to the sense current value, and the positive side of the reproduced waveform is detected. This is because the waveform of and the waveform on the negative electrode side are asymmetrical, and therefore it is necessary to observe the waveform of the data read by the magnetoresistive effect element.

[0010]

As described above, the MR head cannot be tested in the state where the magnetic head 2 is mounted on the carriage 5 as described above. It is necessary to write data to the MR head and then read the data from the MR head.

Therefore, it is necessary to prepare a disk motor 1 in which the number of disk media 1 corresponding to the number of the magnetic heads 2 are attached to the spindle motor 3, so that the test equipment becomes complicated and the number of test steps increases. There is a problem of doing.

In view of the above problems, the present invention has a recording head of the magnetic head 2 which is an inductive type head, and a magnetic flux generated by passing a write current through the coil leaks to the outside of the magnetoresistive effect element. Utilizing that it acts as a magnetic field,
The purpose of the MR head test is to simplify the MR head test by making the disk medium 1 and the spindle motor 3 unnecessary.

[0013]

FIG. 1 is a block diagram for explaining the principle of the present invention. In the MR head testing apparatus, the write means 8 for supplying write data to the coil 6 of the recording head of the magnetic head 2 and the magnetoresistive effect element 7 constituting the reproducing head of the magnetic head 2 are set to the strength of the external magnetic field. It is composed of a sending means 9 for sending the reproduced data by detecting an internal resistance value which changes correspondingly, and an observing means 10 for observing the reproduced data sent by the sending means 9.

Then, based on the internal resistance value changed by the magnetoresistive effect element 7 in accordance with the strength of the external magnetic field formed by the magnetic flux leaking from the recording head, the reproduction generated by the sending means 9 is performed. The data is observed by the observation means 10.

[0015]

With the above structure, the magnetic head 2 is driven by the current corresponding to the write data flowing in the coil 6.
Magnetic flux generated in the recording head of the magnetoresistive effect element 7
Acts as a leakage magnetic flux for the magnetoresistive effect element 7
Change the internal resistance of.

Therefore, the output signal of the sending means 9 for detecting the change in the resistance value of the magnetoresistive effect element 7 is observed by the observing means 10.
By observing at, the waveform obtained corresponding to the write data can be observed.

Since this waveform is similar to the state in which the data written in the recording medium is read, it is possible to judge the quality of the MR head including the recording head. Therefore, the magnetic head 2
The quality of can be judged.

[0018]

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention, FIG. 3 is a diagram for explaining a configuration example of a magnetic head, and FIG. 4 is a waveform diagram for explaining the operation of FIG.

The write circuit 11 shown in FIG. 2 supplies a current whose flow direction is reversed in a predetermined cycle to the coil 6 of the magnetic head 2 as shown by the write current in FIG. On the other hand, since the base of the transistor 16 is connected to 0V, the current supplied from the power source + Vs to the transistor 16 via the resistor 14 operates to sense the current from the collector to the magnetoresistive element 18 via the emitter. It flows as an electric current and returns to the power supply −Vs via the current source 20.

The current supplied from the power supply + Vs to the transistor 17 through the resistor 15 is connected to the base of the transistor 17 at 0V. Therefore, the transistor 17 operates and the collector-emitter passes through the magnetoresistive element. 19 flows as a sense current, and returns to the power supply −Vs via the current source 20.

Transistors 16 and 17 have resistors 14 and 1
5 and the current source 20 constitute a differential amplifier, and this differential amplifier corresponds to the sending means 9 shown in FIG. Since the magnetoresistive effect elements 18 and 19 having current polarities depending on the increase and decrease of the internal resistance value are connected so as to have opposite polarities with respect to the direction of flowing current, the When the internal resistance values of the resistance effect elements 18 and 19 change, this change amount is added and amplified.

Therefore, on the input side of the amplifier circuit 12, a change in voltage due to a change in internal resistance of the magnetoresistive elements 18 and 19 due to a change in magnetic field, that is, a change in amplitude corresponding to a change in magnetic field. The signal to do comes in.

The signal amplified by the amplifier circuit 12 is sent to the oscilloscope 13 and its waveform is observed. By the way, the magnetic head 2 has a structure as shown in FIG. 3, and shows a case where the magnetic head 2 is formed by a thin film technique.

FIG. 3A is a perspective view, and the recording head is shown with a part cut away. The upper magnetic layer 25 and the lower magnetic layer 24 guide the magnetic flux formed by the current flowing through the coil 6 to the gap, and perform magnetic recording corresponding to the data applied to the track 26 formed on the magnetic recording medium.

The reproducing head has a magnetoresistive effect element 18
And 19 are used, and one ends of the magnetoresistive effect elements 18 and 19 are connected to leads 21 and 22, respectively,
The other ends are connected to leads (not shown).
Then, in response to the change in the magnetic field of the track 26 recorded by the recording head, the magnetoresistive effect elements 18 and 1 are connected as described above.
9 changes the internal resistance value, respectively.

The permalloy 23 is used as a magnetic shield for the magnetoresistive effect elements 18 and 19. FIG. 3B is a sectional view of the slider, in which the permalloy 23 is formed on the substrate 32, the magnetoresistive effect elements 18 and 19 are formed between the permalloy 23 and 28, and they are fixed by the protective film 27.

A protective film 29 is formed on the permalloy 28, a lower magnetic layer 24 is formed on the protective film 29, a coil 6 is subsequently formed, an insulating layer 30 is subsequently formed, and an upper magnetic layer is subsequently formed. Layer 25 is formed and finally protective film 3
1 is formed.

As described with reference to FIG. 3, the magnetoresistive effect element 1
8 and 19 are magnetically shielded from the magnetic flux generated in the upper magnetic layer 25 and the lower magnetic layer 24 by the current flowing through the coil 6 by the permalloy 28, but are not completely magnetically shielded from the leakage magnetic flux. The internal resistance value is changed by the leakage magnetic flux as described above.

Therefore, as shown in the read waveform of FIG.
A waveform that changes corresponding to the waveform of the write current is obtained.
That is, if the waveform of the write current is a rectangular wave, the read waveform is also a rectangular wave, and as shown in the figure, the waveform corresponds to the waveform of the write current and has an amplitude of A on the positive electrode side around 0 V, for example. , A waveform having an amplitude of B on the negative electrode side is displayed on the oscilloscope 13.

If A and B are within the predetermined range, the magnetic head 2 is determined to be a good product, and the A or B is outside the predetermined range, or the output of the amplifier circuit 12 is noisy. If it is sent only, it is determined to be defective.

Normally, when the magnetic head 2 is attached to the carriage 5 shown in FIG. 5, the resistors 14 and 15, the transistors 16 and 17, the current source 20 and the amplifier circuit 12 are connected to the head I.
Since it is built in the C circuit, the recording head of the magnetic head 2, the magnetic head 2 including the magnetoresistive effect elements 18 and 19, the head IC circuit, and the lead wire can be included to judge the quality. .

Although the two magnetoresistive effect elements 18 and 19 are used in this embodiment, it is needless to say that the same test can be performed when one magnetoresistive effect element is used.

[0033]

As described above, according to the present invention, since it is not necessary to observe the read waveform of the magnetoresistive effect element in combination with the disk medium, the test equipment can be simplified and the number of test steps can be reduced.

Therefore, the test of the magnetic head using the magnetoresistive effect element can be economically carried out.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram of a circuit showing an embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration example of a magnetic head.

FIG. 4 is a waveform diagram illustrating the operation of FIG.

FIG. 5 is a diagram illustrating an example of a conventional technique.

[Explanation of symbols]

 1 Disk Medium 2 Magnetic Head 3 Spindle Motor 4 Arm 5 Carriage 6 Coil 7, 18, 19 Magnetoresistive Effect Element 8 Writing Means 9 Sending Means 10 Observing Means 11 Writing Circuit 12 Amplifying Circuit 13 Oscilloscope 14, 15 Resistors 16, 17 Transistors 20 Current source 21, 22 Lead 23, 28 Permalloy 24 Lower magnetic layer 25 Upper magnetic layer 26 Tracks 27, 29, 31 Protective film 30 Insulating layer

Claims (1)

[Claims] 1. A coil for a recording head of a magnetic head (2)
A writing means (8) for supplying write data to (6) and an internal resistance which the magnetoresistive effect element (7) constituting the reproducing head of the magnetic head (2) changes in accordance with the strength of the external magnetic field. Transmitting means (9) for detecting the value and transmitting the reproduced data, and observing means for observing the reproduced data transmitted by the transmitting means (9)
In an MR head test apparatus comprising (10), based on an internal resistance value changed by the magnetoresistive effect element (7) in accordance with the strength of an external magnetic field formed by a magnetic flux leaking from the recording head. An MR head test method characterized in that the reproducing data generated by the transmitting means (9) is observed by the observing means (10).