JP2004039159A - Method and device for measuring magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately evaluate the characteristics of a magnetic head when an electric discharge is generated. <P>SOLUTION: An MR head 1 is fixed on the upper surface of a discharge board 2 by grounding a wiring electrode. An antenna 6 is arranged just under the MR head 1. A voltage is impressed to a voltage impression pin 4 by a voltage generator 5 to approach the pin 4 to the head surface of the MR head 1 and to discharge electricity. Electromagnetic waves are radiated by a current allowed to flow into the MR head 1 by the discharge and received by the antenna 6 and the voltage or a current induced in the antenna 6 is measured with an oscilloscope 8. Consequently information such as the generation timing of a destruction phenomenon, and destruction strength of the MR head 1 when discharge is generated can be obtained in real time. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic head measuring method and a magnetic head measuring method for measuring the characteristics of a magnetic head when a discharge occurs, and more particularly to a magnetic head suitable for measuring a magnetoresistive (MR) head used for reproducing a magnetic tape. The present invention relates to a head measuring method and a measuring device.
[0002]
[Prior art]
In recent years, in a magnetic recording / reproducing apparatus which records and reproduces data using a magnetic tape, a further improvement in recording density is desired as the amount of information to be handled is increased. It is indispensable to employ an MR (Magneto Resistive) head instead of the inductive type head. An MR head is a magnetic head that reads a signal recorded on a magnetic recording medium by using a magnetoresistive effect by an MR element, and has a high signal detection sensitivity and a large reproduction output. The width can be easily reduced, and the recording density in the linear direction can be increased, so that high-density recording and reproduction can be performed.
[0003]
This MR head generally has a property that it is more susceptible to static electricity and heat than an inductive head. For example, when an MR head is applied to a system using a magnetic tape, the MR element is directly contacted with the magnetic tape without a protective film on the head sliding surface. At this time, the charge on the magnetic tape flows as a discharge current to the MR head, and there is a possibility that ESD (Electrostatic Discharge) destruction occurs in the MR element. For this reason, in the development of the MR head, it is important to measure the influence of the ESD destruction in the MR head in accordance with the actual use conditions.
[0004]
In order to evaluate the ESD breakdown characteristics of an MR head, conventionally, after applying an ESD pulse voltage directly to the MR head, the resistance and magnetic characteristics of the MR element portion of the MR head are measured, and the evaluation is made based on the change. It was common to do. In addition, there are standardized methods such as HBM (Human Body Model). According to these standardized methods, a human body, a charged object, a machine, and the like are assumed as environments in which devices are handled, and these environments are replaced with equivalent circuits to simulate and evaluate an ESD breakdown phenomenon. Even when this HBM is used, evaluation is performed by measuring the resistance, magnetic characteristics, and the like of the MR head after the discharge has occurred.
[0005]
FIG. 6 is a diagram showing a circuit configuration of an apparatus for simulating the ESD destruction phenomenon of the MR head using the HBM.
The circuit shown in FIG. 6 is an equivalent circuit for reproducing a case where a discharge phenomenon occurs in the MR head due to electric charges charged on a human body. In this circuit, a capacitor 103 having substantially the same capacitance as that of a human body and having a capacitance of 100 pF is connected in series to a voltage source 101 via a changeover switch 102, so that the voltage source 101 can accumulate charges in the capacitor 103. Has become.
[0006]
When the changeover switch 102 is switched after the capacitor 103 is charged, the MR head 105 to be measured is connected in series to the capacitor 103 via the resistor 104 of 1.5 kΩ, and the accumulated charge is grounded through the MR head 105. Discharged to potential. By measuring the resistance value and the like of the MR head 105 after this discharge, the ESD breakdown phenomenon in the MR head 105 can be evaluated in a pseudo manner.
[0007]
FIG. 7 is a graph showing an example of voltage measurement in an MR head using the above circuit. FIG. 7A shows the measurement results for an AMR (Anisotropic Magneto Resistive) head, and FIG. 7B shows the measurement results for a GMR (Giant Magneto Resistive) head.
[0008]
The graph shown in FIG. 7 shows the relationship between the voltage of the voltage source 101 and the resistance of the MR head 105 when the above circuit is used. According to these graphs, it can be seen that the resistance value greatly changes at about 230 to 240 V in the case of the AMR head and about 35 to 40 V in the case of the GMR head, and the ESD breakdown of the MR element is caused by the discharge. .
[0009]
FIG. 8 is a graph showing a measurement example of the sensitivity of the GMR head when the above circuit is used.
The graph of FIG. 8 shows the sensitivity of the GMR head after generating a discharge using the above-described circuit, as the amount of voltage change of the GMR head when a constant magnetic field is applied to the GMR head. According to this graph, it is understood that when the voltage generated by the voltage source 101 reaches about 30 V, the magnetic characteristics of the GMR head deteriorate.
[0010]
[Problems to be solved by the invention]
The conventional method for evaluating the effect of the MR head on ESD damage as described above can evaluate the effect of the MR element itself on ESD damage. However, when a discharge occurs in the MR head, a phenomenon that cannot be accurately evaluated may actually occur based on the characteristics of the MR element itself. For example, the insulating film laminated around the MR element may cause dielectric breakdown. In this case, it does not appear as a change in the resistance value of the MR element itself, and the occurrence of the destruction phenomenon of the MR head cannot be detected. Sufficient characteristics cannot be evaluated.
[0011]
In the above-described conventional measuring method, a change in characteristics of the MR head is measured after the MR head is actually discharged. For this reason, the measurement requires two steps, and cannot be measured in real time when a discharge breakdown occurs. For example, the current flowing in the MR element during discharge can be measured in real time. However, in this case, the measurement of the MR element itself is merely performed, and accurate characteristic evaluation of the MR head is impossible.
[0012]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a magnetic head measuring method capable of more accurately evaluating the characteristics of a magnetic head when a discharge occurs.
[0013]
It is another object of the present invention to provide a magnetic head measuring device capable of more accurately evaluating the characteristics of a magnetic head when a discharge occurs.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a method of measuring the characteristics of a magnetic head when a discharge occurs, comprising: disposing an antenna near a magnetic head in which a wiring electrode from a head element is grounded; A method of measuring a magnetic head, characterized in that the electrode to which the magnetic head is applied is brought into contact with or in contact with the head surface of the magnetic head to discharge, and a voltage or a current induced in the antenna by an electromagnetic wave radiated during the discharge is measured. Provided.
[0015]
In such a method for measuring a magnetic head, a discharge is generated from the electrode to the head surface by bringing the electrode to which the voltage is applied close to or in contact with the head surface of the magnetic head. An electromagnetic wave is radiated by a current flowing in the magnetic head at the time of the discharge, and an antenna disposed near the magnetic head receives the electromagnetic wave. At this time, the characteristics of the magnetic head can be evaluated by measuring the voltage or current induced in the antenna.
[0016]
Further, according to the present invention, in a magnetic head measuring apparatus for measuring characteristics of a magnetic head when a discharge occurs, a wiring electrode from a head element may be brought close to or in contact with a grounded magnetic head and a head surface of the magnetic head. A possible electrode, a voltage applying means for applying a voltage to the electrode, an antenna disposed near the magnetic head, and an electromagnetic wave radiated at the time of discharging from the electrode to the magnetic head. An electromagnetic wave measuring device for measuring induced voltage or current is provided.
[0017]
In such a magnetic head measuring device, when the electrode to which the voltage is applied by the voltage applying means approaches or comes into contact with the head surface of the magnetic head, discharge occurs from the electrode to the head surface of the magnetic head. The antenna receives the electromagnetic wave radiated by the current flowing in the magnetic head at the time of discharge by being disposed near the magnetic head. At this time, the voltage or current induced in the antenna is measured by the electromagnetic wave measuring means, so that the characteristics of the magnetic head can be evaluated.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of a measuring device according to an embodiment of the present invention.
[0019]
The measuring device shown in FIG. 1 is a device for measuring characteristics of a magnetic head at the time of discharge. In this embodiment, an MR head 1 for reading recorded data on a magnetic tape using an AMR element is particularly used as a magnetic head. Apply. This measuring device includes a discharge table 2, a lifting mechanism 3, a voltage application pin 4, a voltage generator 5, an antenna 6, an amplifier 7, and an oscilloscope 8.
[0020]
The discharge table 2 is a table for fixing the MR head 1 to be measured on the upper surface. An antenna 6 is disposed directly below the MR head 1 on the upper surface of the discharge table 2 or inside the discharge table 2 as described later. The MR head 1 is provided with two wiring electrodes (not shown) for connecting to external wiring and outputting a reproduction signal detected by the MR element, and one or both of these wiring electrodes are provided. Grounded.
[0021]
The elevating mechanism 3 is a mechanism for holding the voltage application pin 4 and elevating the same in the vertical direction. The voltage application pin 4 is a pin-shaped electrode for discharging the head surface of the MR head 1 and, when lowered by the elevating mechanism 3, approaches the head surface of the MR head 1 which is the sliding surface of the magnetic tape. It has become. Alternatively, the voltage application pin 4 may be in contact with the head surface. The voltage generator 5 is connected to the voltage application pin 4 and applies a voltage to the voltage application pin 4. The applied voltage is variable.
[0022]
An antenna 6 is provided immediately below the MR head 1 fixed on the discharge table 2. The antenna 6 is fixed so as to be parallel to the upper surface of the discharge table 2. Further, it is desirable that the antenna 6 is disposed such that the substantially central portion of the antenna 6 is located at a position facing the voltage application pin 4 with respect to the head surface of the MR head 1.
[0023]
The wiring from the antenna 6 is connected to an oscilloscope 8 via an amplifier 7. The amplifier 7 amplifies the signal received by the antenna 6 and supplies the signal to the oscilloscope 8. The oscilloscope 8 can measure the voltage or current of the signal supplied from the amplifier 7 and output a voltage waveform or a current waveform with time.
[0024]
The basic measuring procedure using this measuring device is as follows. That is, a voltage is applied to the voltage application pin 4 by the voltage generator 5, and the lifting mechanism 3 is operated to bring the voltage application pin 4 closer to the head surface of the MR head 1. Eventually, a discharge from the voltage application pin 4 to the MR head 1 occurs at a predetermined position. At this time, an electromagnetic wave is radiated by the current flowing in the MR head 1, and the electromagnetic wave is received by the antenna 6. The voltage or current induced on the antenna 6 by the electromagnetic wave is measured by the oscilloscope 8 via the amplifier 7.
[0025]
Further, for example, a predetermined voltage is applied to the voltage application pin 4 at a position sufficiently separated from the MR head 1, and the voltage application pin 4 is gradually approached to the MR head 1 to generate a discharge. The oscilloscope 8 may observe the distance between the MR head 1 and the voltage application pin 4 at that time and the voltage or current waveform at the antenna 6 according to the applied voltage. Alternatively, the voltage may be applied after bringing the voltage application pin 4 and the MR head 1 close to a certain distance, and the voltage or current waveform at the antenna 6 for each applied voltage may be observed. Further, observation may be performed when the voltage application pin 4 is brought into contact with the head surface of the MR head 1 to cause discharge.
[0026]
Next, FIG. 2 is a cross-sectional view illustrating an example of a mounting state of the antenna 6 on the discharge table 2.
As shown in FIG. 2, on the upper surface of the discharge table 2, for example, a glass epoxy substrate 21 is provided as an insulator. The antenna 6 is formed, for example, by etching a metal film such as Cu on the lower surface of the glass epoxy substrate 21. In order for the antenna 6 to detect the electromagnetic waves radiated from the MR head 1, it is desirable that the thickness of the glass epoxy substrate 21 be as small as possible, for example, about 1 mm or less. By disposing a thin insulator such as the substrate 21, it is possible to prevent the discharge from being directly generated from the voltage application pin 4 to the antenna 6.
[0027]
Next, FIG. 3 is a plan view showing an example of the shape of the antenna 6.
FIG. 3 shows an example of the shape of the antenna 6 when viewed from above the discharge table 2. FIG. 3A shows an example of a monopole antenna, and FIG. 3B shows an example of a loop antenna. In order to increase the sensitivity of these antennas and perform accurate measurement, the center of the monopole antenna and the center of the loop antenna are directly below the head surface of the MR head 1, respectively. It is desirable that they are arranged as follows.
[0028]
Next, FIG. 4 is a diagram showing an example of a current waveform observed in the above measuring device.
FIG. 4 shows an example of a current waveform observed in the oscilloscope 8 when a monopole antenna is used as the antenna 6. This waveform example shows a waveform of a current observed when a resistor is disposed at a fixed position of the MR head 1 in place of the actual MR head 1 and discharged.
[0029]
It can be seen from the current waveform of FIG. 4 that an electromagnetic wave radiated in a very short time of several nsec is detected when a discharge occurs. Since the antenna 6 induces a current in accordance with the amount of change in the current flowing in the MR head 1, it is possible to accurately know, in real time, a minute current change in the MR head 1 when a discharge occurs, by using a current waveform. Can be.
[0030]
For example, when the voltage is applied to the MR head 1 from the voltage application pin 4, the MR head 1 may be damaged not only by the MR element but also by the discharge current around the MR element. It is considered that the current waveform as described above is useful for analyzing a process in which such a breakdown phenomenon occurs.
[0031]
Here, an example will be described in which a breakdown phenomenon occurs in a part other than the MR element when a discharge occurs. FIG. 5 is a diagram illustrating a configuration example of a sliding surface of the MR head 1 with respect to a magnetic tape.
[0032]
FIG. 5 shows a configuration example when the sliding surface of the MR head 1 with respect to the magnetic tape is viewed from the magnetic tape side. The MR head 1 has a structure in which an MR element 13 and a pair of shield films 14a and 14b made of a soft magnetic material are provided between a conductive head substrate 11 and a protective substrate 12. Insulating films 15a and 15b are formed between the head substrate 11 and the protecting substrate 12 and the respective shield films 14a and 14b, and MR films are provided between the shield films 14a and 14b via the insulating films 15c and 15d. The element 13 is formed to form a reproducing magnetic head. The MR element 13 reads data recorded on a magnetic tape when power is supplied through a wiring electrode (not shown).
[0033]
Here, the head substrate 11 and the protection substrate 12 are connected to the ground through, for example, a base metal holding the MR head 1. Each of the insulating films 15a to 15d is formed as a thin film having a thickness of less than about 1 μm.
[0034]
When the impulse surface of the MR head 1 having such a structure is discharged from the voltage application pin 4, a large current flows through the MR element 13 itself to cause damage. In some cases, dielectric breakdown occurs between the shield films 14a and 14b and between the shield films 14a and 14b and the head substrate 11 and the protection substrate 12, and a discharge current flows. At the positions where such dielectric breakdown has occurred, for example, discharge marks 16a and 16b as shown in FIG. 5 are formed, and the MR head 1 cannot be used.
[0035]
When damage occurs in the insulating films 15a to 15d in this way, for example, even if the resistance value of the MR element 13 itself is measured thereafter, no change is observed, and the occurrence of damage cannot be detected. Further, for example, even when the current flowing through the MR element 13 at the time of discharge is measured, the same cannot be detected. However, the measurement device shown in FIG. 1 can detect a change in current in the entire MR head 1 by measuring a current or a voltage induced in the antenna 6, and thus the destruction phenomenon of the insulating films 15 a to 15 d as described above. Can be measured, and the degree of destruction can be estimated. Further, since a minute current change in the MR head 1 can be detected, it is possible to analyze in detail the generation process of the destruction phenomenon in the MR head 1 during discharge.
[0036]
As described above, the measuring device of the present invention measures the voltage and current induced in the antenna 6 to obtain information on the destruction phenomenon of the MR head 1 at the time of occurrence of discharge, such as the destruction strength and detailed timing thereof. Can be obtained in real time and without contact with the MR head 1. Such information cannot be obtained by a conventional measurement method such as post-measurement of a resistance value, a magnetic property, and the like of the MR element, and is useful for more accurate analysis of an ESD breakdown phenomenon.
[0037]
Further, in the conventional measuring method of measuring the resistance and the magnetic characteristics of the MR head 1 after the discharge, a discharge may be erroneously generated when the MR head 1 is handled, and the MR head 1 may be destroyed. Was. In the present invention, since the above measurement can be performed without contacting the MR head 1, it is possible to prevent the occurrence of such a discharge during handling.
[0038]
Further, since the measurement can be similarly performed on the MR head 1 in a non-contact manner, the measurement using the antenna 6 as in the present invention can be applied as an ESD destruction sensor in the production line of the MR head 1. It is.
[0039]
The above-described measuring apparatus can be applied to measurement of, for example, a magnetic head for recording and reproduction of an HDD (hard disk drive) in addition to a magnetic head for recording and reproduction of a magnetic tape. .
[0040]
【The invention's effect】
As described above, in the magnetic head measuring method of the present invention, when a discharge is generated from the electrode to which the voltage is applied to the magnetic head, the electromagnetic wave radiated by the current flowing in the magnetic head is disposed near the magnetic head. Received by the antenna. At this time, by measuring the voltage or current induced in the antenna, information such as the timing of the destruction phenomenon and the destruction strength of the magnetic head when a discharge occurs is obtained in real time, and the destruction phenomenon in the magnetic head is evaluated in more detail It becomes possible.
[0041]
Further, in the magnetic head measuring device of the present invention, when a discharge is generated from the electrode to which the voltage is applied to the magnetic head, an electromagnetic wave radiated by a current flowing in the magnetic head is received by an antenna disposed near the magnetic head. Is done. At this time, by measuring the voltage or current induced in the antenna by the electromagnetic wave measuring means, information such as the timing of the destruction phenomenon and the strength of the destruction of the magnetic head when the discharge occurs can be obtained in real time. It is possible to evaluate in more detail.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating an example of a mounting state of an antenna on a discharge table.
FIG. 3 is a plan view showing an example of the shape of an antenna.
FIG. 4 is a diagram showing an example of a current waveform observed in the measuring device according to the present invention.
FIG. 5 is a diagram showing a configuration example of a sliding surface for a magnetic tape in an MR head.
FIG. 6 is a diagram showing a circuit configuration of an apparatus for simulating an ESD breakdown phenomenon of an MR head using an HBM.
FIG. 7 is a graph showing an example of voltage measurement in an MR head using an HBM.
FIG. 8 is a graph showing a measurement example of the sensitivity of a GMR head when an HBM is used.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... MR head, 2 ... Discharge table, 3 ... Elevating mechanism, 4 ... Voltage application pin, 5 ... Voltage generator, 6 ... Antenna, 7 ... Amplifier, 8 ... Oscilloscope

Claims (7)

In a magnetic head measuring method for measuring the characteristics of a magnetic head when a discharge occurs,
An antenna is arranged near the magnetic head where the wiring electrode from the head element is grounded,
The electrode to which the voltage is applied approaches or contacts the head surface of the magnetic head and is discharged,
Measuring the voltage or current induced in the antenna by the electromagnetic waves radiated during the discharge,
A method for measuring a magnetic head, comprising: The method according to claim 1, wherein a monopole antenna is used as the antenna. The method according to claim 1, wherein a loop antenna is used as the antenna. 2. The method according to claim 1, wherein the antenna is disposed between the antenna and the magnetic head via a flat insulator. The method according to claim 1, wherein the antenna is provided at a position facing the electrode with respect to the magnetic head. 2. The method according to claim 1, wherein the magnetic head includes the head element made of a magnetoresistive element. In a magnetic head measuring device for measuring the characteristics of a magnetic head when a discharge occurs,
A magnetic head in which the wiring electrode from the head element is grounded,
An electrode capable of approaching or contacting the head surface of the magnetic head;
Voltage applying means for applying a voltage to the electrode,
An antenna disposed near the magnetic head;
Electromagnetic wave measuring means for measuring a voltage or a current induced in the antenna by an electromagnetic wave radiated at the time of discharge from the electrode to the magnetic head,
A measuring device for a magnetic head, comprising:

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