KR920003481B1 - Magnetic head manufacturing method - Google Patents

Abstract

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Description

Method of manufacturing thin film magnetic head

1 is an explanatory diagram of one embodiment of the present invention.

2A and 2B are diagrams showing pulse current waveforms output from the pulse oscillator of FIG. 1 and impedance output waveforms from the AC-DC converter of FIG.

FIG. 3 shows that when the bias current of the computing device of FIG. 1 is zero, I ₁ and I ₂ , and the corresponding impedance values are Z ₀ , Z ₁ and Z ₂ , respectively, Z ₁ -Z ₀ │ / │Z ₂ -Z ₀ Characteristic diagram showing the relationship between the value of │ and the value of OW.

4 is an explanatory diagram of magnetic flux flow in a magnetic head of the present invention.

5 is a characteristic diagram showing the relationship between bias current and impedance when the gap depth of the magnetic head is different.

6 is a magnetic head configuration diagram when a gap depth such as Gd (A) and Gd (B) in FIG. 5 is changed.

7 is a characteristic diagram showing the relationship between bias current and impedance when the full length of the magnetic head is different.

8 is a diagram showing the configuration of the magnetic head when the pull length is changed, such as P ₁ (A) and P ₁ (B) in FIG.

9 is a magnetic head configuration diagram in which magnetic layers are magnetically contacted at their tip portions.

* Explanation of symbols for main parts of the drawings

1: upper magnetic layer 2: lower magnetic layer

3: tip of magnetic core 4: conductor winding

5: magnetic head 6: coil

7: bridge circuit 8: AC oscillator

9: pulse oscillator 10: differential amplifier

11: AC-DC converter 12, 13: condenser

14: computing device

The present invention relates to a method of manufacturing a thin film magnetic head.

When the magnetic disk device writes new data, it writes new data on the old data which becomes unnecessary on the magnetic disk which is a magnetic recording medium. This erases the old data and records the new data. Therefore, the magnetic field generated from the magnetic head for recording new data should be at least strong enough to write data over the entire thickness of the recording medium.

If the magnetic field generated from the magnetic head is so weak that new data cannot be written in the entire thickness of the recording medium, the old data is not erased and is duplicated with the newly recorded data. For this reason, the strength of the magnetic field generated in the magnetic head used in the magnetic disk apparatus is evaluated by the redundant recording characteristics.

The redundant recording characteristic is expressed as the ratio of the reproduction output of new data to the reproduction output of old data which cannot be erased on the magnetic disk.

In practice, since the redundant recording characteristics are checked during the manufacturing process of the magnetic head and evaluated in the worst case, the data written as the lowest frequency of the modulated signal used in the magnetic disk device is used as the old data, and the other data written as the highest frequency is used. Used as new data to erase data. The current value of the signal exciting the magnetic head is the same in both the old data and the new data.

If the reproducing output value is ΔE ₁ f according to the residual data of the old data written at the lowest frequency and the other reproducing output value of the new data written at the highest frequency is E ₂ f, the redundant recording characteristic value is decibel of these ratios as follows. It is represented by the characteristic.

OW = -20log E ₂ f / △ E ₁ f (dB)

The redundant recording characteristic of the magnetic head used as the product is about -25 dB. In recent years, thin film magnetic heads are indispensable for increasing the recording density of recording media and obtaining the storage capacity in magnetic disk devices.

In thin film magnetic heads, the strength of the generated magnetic field depends on the shape of the tip of the magnetic core, and in particular on the magnetic gap depth.

In the past, many ideas have been envisioned and implemented on the method of adjusting the magnetic gap depth in order to obtain a thin film magnetic head having recording characteristics in such a manner as to obtain the required OW value. For example, the ideas of FIGS. 1 and 2 described in Japanese Patent Application Laid-Open No. 60-254404, published on December 16, 1985 under the name of "Manufacturing Method of Thin Film Magnetic Head".

However, in manufacturing the thin film magnetic head, the truck width Tw and the pole lengths P ₁ and P ₂ (thickness of the magnetic layer forming the magnetic gap portion) and the magnetic gap depth G ₁ (non-magnetic portion forming the magnetic gap portion) Tend to reduce the thickness of the strata). In this case, the recording characteristics cannot be determined only by forming the magnetic gap depth to a predetermined size. In other words, the recording characteristics are influenced by the overall shape of the tip portion of the magnetic core.

In the thin film magnetic head, when the magnetic gap depth is reduced to 0.3 [mu] m, for example, as in the case of the truck width or the like, the tip of the magnetic core of the magnetic head cannot be measured by the optical method.

Therefore, whether or not the recording characteristics of the manufactured thin film magnetic head are good should be performed by assembling the manufactured thin film magnetic head in a magnetic disk device and measuring the OW value after performing the recording and reproducing operation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method in which the pass and fail of an inspection concerning the recording characteristics of a thin film magnetic head can be easily determined, thereby manufacturing the magnetic head with high precision.

The present invention applies a DC bias current to the thin film magnetic head to be inspected, measures the impedance degradation caused by saturation of the magnetic core of the magnetic head, thereby detecting the recording characteristics of the magnetic head to manufacture the magnetic head with high precision. It relates to a manufacturing method.

The thin film magnetic head is most saturable at the tip of the magnetic core. The state of magnetic saturation depends on the shape of the tip of the magnetic core.

The recording characteristics of the thin film magnetic head also depend on the shape of the tip of the magnetic core. Therefore, there is a strong correlation between the above described impedance drop and the recording characteristics. By using the correlation, the recording characteristic can be detected based on the impedance drop value.

Referring to FIG. 1, a magnetic head 5 including an embodiment of the present invention includes an upper magnetic layer 1, a lower magnetic layer 2, a conductor winding 4, and an electrical insulation layer 15. By photo lithography, for example, as shown in FIG. 4B, the layers are stacked in a predetermined order, and a magnetic gap is formed at the distal end portion 3 of the magnetic core including the upper magnetic layer 1 and the lower magnetic layer 2. .

The redundant recording characteristic of the magnetic head 5 is detected according to the impedance of the magnetic head 5 as described later.

As an apparatus for measuring impedance in the embodiment, as shown in FIG. 1, the magnetic head 5 is connected to one branch of the bridge circuit 7 and the coil has an inductance almost the same as that of the magnetic head 5. (6) and a condenser 12 for blocking the DC current are arranged on the opposite side of the magnetic head 5 of the bridge circuit 7. An AC oscillator 8 as a high frequency signal source (a few MHz to several tens of MHz) and a pulse oscillator 9 as a bias current source for generating magnetic saturation of the magnetic head 5 and the magnetic core are connected to an input terminal of the bridge circuit 7. Connected.

The high frequency differential amplifier 10 and the AC-DC converter 11 and the computing device 14 for amplifying the output of the bridge circuit 7 are connected to the output terminal of the bridge circuit 7. Gd is the gap depth, P ₂ is the pole length of the lower magnetic layer 2, and Tw is the truck width of the tip 3, respectively.

Next, the operation of the above embodiment will be described.

A high frequency signal from the AC oscillator 8 is input to the bridge circuit 7 and an output of the bridge circuit 7 is generated through the capacitor 13. After the output of the bridge circuit is amplified by the differential amplifier 10, its amplitude is detected by the AC-DC converter.

The magnitude of the amplitude is proportional to the potential difference due to the impedance imbalance of the bridge circuit 7 generated by the impedance of the magnetic head 5 and is detected as a signal corresponding to the impedance of the magnetic head 5.

Here, the high frequency signal applied to the bridge circuit 7 is made small enough to measure the amplitude of the high frequency signal in such a way that the excitation of the magnetic head 5 is reversible.

In addition to the high frequency signal, the current generated by the pulse oscillator 9 flows into the conductor winding 4 of the magnetic head 5 as a bias current, so that the magnetic head 5 is periodically saturated.

For example, as shown in FIG. 2A, if a pulse current that periodically repeats with O, I ₁ and I ₂ occurs from the pulse oscillator 9, the inductance value output from the AC-DC converter is shown in FIG. 2B. It is as follows.

The calculation unit 14 calculates impedance conversion values of Z ₁ -Z ₀ and Z ₂ -Z ₀ when the bias currents are I ₁ and I ₂ based on the impedance value Z ₀ when the bias current is zero. Calculate and output the ratio | Z ₁ -Z ₀ | / │Z ₂ -Z ₀ |. This output value is a value characterized by the state of magnetic saturation of the magnetic head 5 generated by the bias current. The correlation between the values of Z ₁ -Z ₀ / Z ₂ -Z ₀ and the redundant recording characteristics of the magnetic head 5 is shown in FIG.

This data is a measurement result that takes into account the shape and manufacturing conditions when the same thin film magnetic head is manufactured when dozens of magnetic heads are selected and measured. The recording signal frequencies used in the measurement of the redundant recording characteristics are 2.3 MHz and 9 MHz, respectively, and the bias currents I ₁ and I ₂ are 7.5 mA and 15 mA, respectively.

As shown in FIG. 3, a value characterized by the supersaturation characteristic and the magnetic saturation state of the magnetic head 5 due to the bias current, │Z ₁ -Z ₀ │ / │Z ₂ -Z ₀ │ is a straight line in FIG. As shown by (L), it has a linear functional relationship.

For this reason, as shown in FIG. 3, the correlation diagram is tabulated and stored in the computing unit 14 to pass and fail the duplicate recording characteristic. The value of │Z ₁ -Z ₀ │ / │Z ₂ -Z ₀ │ It can be determined based on the criteria. This is because the duplicated recording value with the magnetic head can be determined from the ratio of | Z ₁ -Z ₀ | / │Z ₂ -Z ₀ | as can be seen in FIG.

Hereinafter, the principle of the present invention will be described with reference to FIGS. 4 to 6. This is based on the magnetic saturation of the magnetic core of the magnetic head 5.

4A is a front view of the magnetic head 5 viewed from the outside of the upper magnetic layer. 4B is a cross-sectional view taken from 4B-4B 'of FIG. 4A. 4C is an equivalent circuit diagram for showing the magnetic flux flow of the magnetic head shown in FIGS. 4A and 4B, which are considered as magnetic circuits.

As shown in FIGS. 4A and 4B, the magnetic core of the magnetic head 5 has a narrow track width at the tip 3 of the magnetic core. This is to strengthen the magnetic field generated from the magnetic head 5 by concentrating the magnetic flux caused by the current flowing from the distal end portion 3 of the magnetic core to the conductor winding 4 to flow through the interior of the magnetic core.

The current flowing through the conductor windings 4 generates magnetic force.

The magnetic resistance values of the upper magnetic body 1 and the lower magnetic body 2 are separated from the distal end portion 3 of the magnetic core in the upper magnetic layer 1 and the lower magnetic layer 2, respectively, and Rg ₁ , R ₁ and Rg ₂ , respectively. , R ₂ . Then, the magnetic resistance to the magnetic flux leaked between the upper magnetic layer 1 and the lower magnetic layer 2 is divided into different parts from the distal end of the magnetic core so that the magnetic resistance at the distal end part 3 is Rg, and the magnetic resistance at the other part is R1. This is called.

The magnetoresistance to the magnetic field generated in the magnetic head 5 is referred to as R.

Only the magnetic flux passing through the magnetoresistance R after passing through the magnetoresistances R1, R ₁ , Rg ₁ , R ₂ , and Rg ₂ with respect to the magnetomotive force generated by the current flowing through the conductor winding 4 It becomes a magnetic field in the head 5. In general, Rg _1, Rg ₂ magnetic resistance is larger than the magnetic resistance of the R _1, R _2, because the character of Rg _1, Rg ₂ is at a premium. Since the magnetic path of the resistor Rg is short, the magnetic resistance of Rg is smaller than that of R1. Therefore, the magnetoresistances Rg ₁ , Rg ₂ , and Rg included in the tip 3 of the magnetic core determine the amount of magnetic flux flowing through the resistor R.

The resistance value of Rg depends on the shape of the magnetic gap formed by the upper magnetic layer 1 and the lower magnetic layer 2 at the tip 3 of the magnetic core.

As the magnetic gap depth Gd of the magnetic head increases, the resistance of Rg decreases. At this time, the amount of magnetic flux passing through the magnetic gap increases and the amount of magnetic flux passing through the resistor R decreases.

In a magnetic head having a small truck width Tw, a pole length P, and a large magnetic gap depth Gd, the values of the resistors Rg ₁ and Rg ₂ become large and the amount of magnetic flux passing through the resistor R becomes small.

Therefore, the strength of the magnetic field depends on the shape of the tip 3 of the magnetic core.

The tip 3 of the magnetic core is configured to concentrate the magnetic flux as described above. Therefore, where the magnetic saturation occurs first when the magnetic flux passing through the magnetic core is increased, the tip portion 3 of the magnetic core. If the magnetic core is made of the same magnetic material, the first magnetic saturation occurs in the part having a large magnetoresistance.

When magnetic saturation occurs at the tip 3 of the magnetic core, the magnetic resistance at that portion becomes larger. For this reason, magnetic saturation occurs even with a small magnetic flux in a part having a large magnetoresistance.

The increase in the magnetoresistance is detected as increasing the magnetoresistance of all the magnetic cores and decreasing the inductance of the magnetic head 5.

Hereinafter, with reference to FIG. 5 and FIG. 6, the characteristic in the case where a gap depth is Gd (A) and Gd (B) is demonstrated. In the case where the gap depth Gd is as narrow as Gd (A) as shown in FIG. 6 or as deep as Gd (B), the inductance value is equal to the common bias current I ₀ (OmA), Z ₀ (A), Z ₁ (A), Z ₂ (A) or Z ₀ (B), Z ₁ (B), Z ₂ (B corresponding to I ₁ (7.5 mA), I ₂ (15 mA)) ).

In other words, if the gap depth is Gd (B), the inductance value is reduced by less bias current than Gd (A). This phenomenon is described below with reference to the magnetic head equivalent circuit shown in FIG. 4C. When the gap depth is as deep as Gd (B), the resistance value of Rg is smaller than the narrow gap depth Gd (A), and flows through the resistances Rg ₁ and Rg ₂ at the deep gap depth Gd (B). The magnetic flux becomes larger for the same bias current compared to that at the narrow gap depth Gd (A), so that when the gap depth is as deep as Gd (B), it saturates with less bias current at the resistors Rg ₁ and Rg ₂ . is generated, and the inductance is reduced. If the resistance value Rg smaller, since they do not have sufficient magnetic flux flowing through the resistor (R) the magnetic flux generated in the magnetic head is reduced. setting the bias current and │Z ₁ -Z ₀ By obtaining the value of Z ₂ -Z ₀ , Gd (A) and Gd (B) indicated by small circles are obtained as shown in Fig. 3. When magnetic saturation occurs in the magnetic head due to a small bias current The value of | Z ₁ -Z ₀ | / | Z ₂ -Z ₀ | is increased.

The next to the pole length will be described with reference to Figure 7 and 8 is also the characteristics of other cases, such as _{P 1 (A), P 1} (B).

If the pole length P ₁ is as thick as P ₁ (A) or goes as P ₁ (B) as shown in FIG. 8, the inductance value is the common bias current I ₀ as shown in FIG. 7. Z ₀ (A), Z ₁ (A), Z ₂ (A), or Z ₀ (B), Z ₁ (B), corresponding to (OmA), I ₁ (7.5mA), I ₂ (15mA)) , Z ₂ (B). That is, when the pole length is P ₁ (B), the inductance value is reduced by less bias current compared to P ₁ (A).

This phenomenon is explained below by adding the magnetic head equivalent circuit shown in FIG. 4C. When the pole length is as thin as P ₁ (B), the resistance value of Pg ₁ becomes larger than the thick pole length (P ₁ (A)).

In other words, the magnetic field corresponding to the resistor Rg ₁ becomes narrow.

For this reason, when the pole length becomes as thin as P ₁ (B), magnetic saturation occurs due to a small bias current in the resistor Rg ₁ , and the inductance of the magnetic head is reduced. When magnetic saturation occurs in the resistor Rg ₁ , the magnetic flux flowing through the resistor R is insufficient and the magnetic field generated in the magnetic head is reduced.

By setting the bias current and obtaining the value of Z ₁ -Z ₀ / Z ₂ -Z ₀ |, P ₁ (A) and P ₂ (B) represented by fewer triangles are shown in FIG. Is obtained together.

Even when the pole length of the lower magnetic layer 2 is changed, similarly to the case where the pole length P ₁ of the upper magnetic layer 3 is changed, between the bias current and │Z ₁ -Z ₀ │ / │Z ₂ -Z ₀ │ A characteristic diagram of can be obtained.

When the magnetic gap length is deep or the water length is thin, magnetic saturation occurs due to a small bias current in the magnetic head.

Therefore, the magnetic core of the magnetic head where magnetic saturation occurs due to a small bias current has a large value of Z ₁ -Z ₀ / Z ₂ -Z ₀ |, and thus the magnetic field generated in the magnetic head is reduced.

In order to know that the magnetoresistances of Rg ₁ , Rg ₂ and Rg are appropriate magnetoresistance, it is necessary to know the inductance lowering state.

To create a variable that characterizes the state of inductance degradation, it is necessary to measure the change in inductance at least at two points with different bias current values and to calculate the rate of change. However, the inductance value of the thin film magnetic head is about 200nH to 300nH and the inductance drop is 20 to 30nH.

Therefore, since sufficient precision cannot be obtained with normal impedance meta, it is necessary to measure inductance by the apparatus shown in FIG.

When the resistance of the conductor winding 4 of the magnetic head 5 is measured as a signal of several MHz to several tens of MHz, the same effect as the aforementioned inductance decrease occurs. That is, the resistance value decreases when the bias current increases as in the case of FIGS. 5 and 7 where the inductance value decreases when the bias current increases. This is because phase delay occurs due to hysteresis loss and eddy current loss of the magnetic core.

The detection sensitivity can be increased by detecting the impedance drop based on the inductance drop and the resistance drop.

When the resistance value of the conductor group wire 4 becomes large by miniaturizing the conductor winding 4 of the magnetic head 5, the impedance drop is reduced due to the heating effect of the conductor winding 4 by the bias current. This is because the resistance increases with increasing temperature of the conductor winding 4. In this case, it is better to carry out the method of the present invention only by the inductance which removes the resistance value from the change in impedance. The measurement of inductance is performed by comparing the output of the differential amplifier 10 with the signals of the AC oscillator 8 and further configuring a device for detecting the phase difference therebetween, and measuring the inductance based on the obtained phase difference and impedance.

In addition, the impedance measuring method of the present invention includes the steps of forming the magnetic gap depth of the thin film magnetic head more than a predetermined length, and polishing the tip 3 of the magnetic core to form a magnetic gap portion. It can be used together during the polishing process of the above-mentioned manufacturing method.

In this case, according to the embodiment of the present invention, the thin film magnetic head having advantageous recording characteristics can be produced by detecting the redundant recording characteristics that have reached a predetermined value, determining the pass / fail of the magnetic heads, and terminating the polishing process.

In addition, as shown in FIG. 9, in the case of the magnetic head in which the upper magnetic layer 1 and the lower magnetic layer 2 of the tip portion 3 of the magnetic head are in magnetic contact, the impedance measuring method of the present invention is small. By detecting the overlapping recording characteristic that has reached the stationary, it can be used in the polishing process of the tip 3 and at the finishing of the polishing process of the magnetic head, and thus a thin film magnetic head having advantageous recording characteristics can be manufactured. In the magnetic head equivalent circuit shown in FIG. 9, the resistance Rg is formed of a magnetic material, and the value of the resistance Rg is very small in FIG.

When the magnetic head shown in FIG. 9 is compared with the magnetic head shown in FIG. 6, the deficit is the same in that the gap depth Gd is very deep. In the magnetic head shown in FIG. 9, when the impedance of the magnetic head is measured and the tip of the magnetic head is for example as in the case of FIG. _3, Z ₁ -Z ₀ | / | Z ₂ -Z ₀ | In the case of being a basis for detecting the value of, the contact portion of the tip of the magnetic head is removed and at the same time the gap depth seems to narrow suddenly, and the overlapping characteristic is detected to reach a predetermined value.

According to an embodiment of the present invention, the recording characteristic is measured by using a magnetic saturation phenomenon which depends on the overall shape of the leading end of the magnetic core of the magnetic head, whereby a direct correlation with the recording characteristic of the magnetic head is obtained and the recording characteristic is recorded. Detected without actually measuring the characteristic

The recording characteristics can be easily detected by measuring the impedance and simply connecting the appropriate apparatus and the magnetic head using a lead wire or probe.

Claims (6)

A method of manufacturing a thin film magnetic head, comprising the steps of: laminating a magnetic layer, an electric dissipation layer, and a conductor winding in a predetermined order in a thickness direction thereof, and performing lapping treatment at the tip of the layer to form the magnetic head at a neck height; When the conductor winding has a DC bias current (I ₀ ) with a magnitude including the zero value applied to the conductor windings, the impedance value is Z ₀ and at least two DC bias currents (I ₁ , I) applied to the conductor windings. ₂ ) the ratio of each deviation (Z ₁ -Z ₀ ) and (Z ₂ -Z ₀ ) of the impedance (Z ₀ ) to a predetermined value of Z ₁ and Z ₂ , respectively, when the conductor winding has

Detecting the redundant recording characteristics of the magnetic head so that the value is lower, and when the non- | Z | Z ₁ -Z ₀ | / | Z ₂ -Z ₀ | A method of making a thin film magnetic head comprising determining access. 2. The lapping process of claim 1, wherein the lapping process measures the redundant recording characteristics of the magnetic head on the basis of the ratio, and the magnetic head reaches the required value when the neck height formed by the lapping process of the tip portion has a neck height larger than a predetermined value. The method is completed by detecting the defect. The method of claim 2, wherein the leading end of the magnetic layer is formed to have a predetermined neck length. The method of claim 2, wherein the leading ends of the magnetic layers are spaced apart from each other. The method of claim 2, wherein the leading ends of the magnetic layers are arranged to be in contact with each other. The method according to claim 1, wherein DC pulses (0), (I ₁ ), and (I ₂ ) are repeatedly applied to the conductor windings from the pulse generator, and the ratio | Z ₁ -Z ₀ | / | Z ₂ -Z ₀ | A method characterized in that it is calculated by a calculator based on impedance (Z ₀ ), (Z ₁ ), (Z ₂ ) according to DC pulses (0), (1), (2).

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