JPS6265221A - Manufacture of thin film magnetic head - Google Patents

Abstract

PURPOSE:To know the end point of grinding precisely by flowing a DC bias current to a thin film magnetic head in process of polishing and checking the variation process of a decrease in impedance including the resistance variation of a head due to magnetic saturation of a core when forming a gap part in the magnetic head. CONSTITUTION:The tip parts of an upper magnetic layer and a lower magnetic layer 2 which constitute the thin film magnetic head H are coupled by a contacting part 3 and specific gap depth Gd is secured inside the contacting part 3 by grinding. For the purpose, a coil 4 is put between the layers 1 and 2, both terminals are connected to a Wheatstone bridge circuit network 6 which incorporates an inductor 5 and a capacitor 14, and the DC current source 8 to which an AC oscillator 7 and a switch 14 are connected in series is connected to the bridge circuit network in parallel. The, the switch 4 is turned on and off to saturate the head H magnetically and periodically and the output of the circuit network 6 is sent to an output device 16 through a differential amplifier 9, etc. to stop the grinding when a specific gap is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of processing a gap portion of a thin film magnetic head, and particularly to a method of manufacturing a thin film magnetic head particularly suitable for high recording density magnetic disk recording devices. .

[Background of the invention]

In recent years, thin film magnetic heads have become widely used in magnetic disk recording devices and the like.

By the way, the writing characteristics of this thin film magnetic head largely depend on the depth direction dimension (gap depth) of the magnetic gap, and therefore, this dimension must be polished to a necessary and minimum value.

For this purpose, it is necessary to accurately detect the end point of machining.
As described in Japanese Patent No. 08, a method has been proposed for detecting a sound at the end of polishing using a change in inductance of a magnetic head. In this process, first, the gap depth is ensured to be at least a predetermined size, and the upper and lower magnetic layers are brought into contact with each other at the tips of the gaps, thereby manufacturing a magnetic head having an intermediate shape in which the magneto core forms a closed magnetic circuit. This is a method of determining the end point of the machining by detecting the change in the inductance of the #g magnetic head when the magnetic core becomes an open magnetic circuit by polishing the tip of the gap part, with respect to the inductance of the magnetic head at this time. .

However, in recent years, there has been a significant demand for high-density recording in magnetic recording, and as a result, thin-film magnetic heads are also becoming more popular with smaller track widths.

However, in such a thin film magnetic head, the inductance is small, for example, 25 OnH1j degrees, and the inductance change when changing from an open magnetic circuit to an open magnetic circuit as described above is also about 10 nH79.
Because of the small size of the process, the conventional method described above has the disadvantage that it is not possible to accurately detect the end of machining, resulting in insufficient product yields and increased costs.

[Purpose of the invention]

It is an object of the present invention to eliminate the above-mentioned drawbacks of the prior art, to detect the end point of magnetic gap polishing with high precision, and to manufacture a thin film magnetic head with a high-density recording layer at a yield rate of 9. The present invention provides a method for manufacturing a thin film magnetic head.

[Summary of the Invention] In order to achieve this object, the present invention supplies a DC bias current to a thin-film magnetic head during polishing, and changes the process of decreasing the impedance of the magnetic head due to magnetic saturation of the core. ! ! Layer Pe is characterized by the fact that this allows polishing to be performed with high sensitivity at the end of the polishing process.

Note that at this time, not only the inductance changes, but also
Another feature is that it is designed to be understood as an impedance change including a resistance change, thereby achieving high sensitivity detection.

Further, in one embodiment of the present invention, a Wheatstone bridge circuit network is used to detect the impedance of the thin-film magnetic head, and the magnetic head is connected to one side of the circuit network, thereby detecting the impedance of the magnetic head in the form of an electrical signal. The feature is that the polishing process can be stopped automatically from this point.

Furthermore, in one embodiment of the present invention, the above-mentioned DC bias current is made into a rectangular wave pulse with a convenient frequency, the i-th impedance is detected in response to the change in the DC bias current, and the difference and ratio thereof are determined. This feature makes it possible to eliminate the effects of changes in the local environment, and to detect the end of processing with high accuracy.

[Embodiments of the Invention] Hereinafter, a method for manufacturing a thin film magnetic head according to the present invention will be described in detail with reference to the drawings.

Figure F1 shows one embodiment of the present invention, and in the figure, H represents a thin film magnetic head with an intermediate shape before processing the gap part, and the gap depth Gd of the predetermined dimension is secured. A contact portion 3 is provided at the tips of the upper magnetic layer 1 and the lower magnetic layer 2 by polishing, and a polishing process is performed to remove the contact portion 3 while leaving a gap depth Gd.

Furthermore, in the embodiment shown in FIG. F1, the coil 4 of the magnetic head H to be polished is shrunk to one side, and the inductor 5 and capacitor 15 for cutting the direct flow are cut into small pieces facing the core coil 4. Wheatstone bridge network with 6. #An AC oscillator 7 serving as a high frequency signal (t'yMH2-several tens of MHz) source for detecting the impedance of the magnetic head H; a DC current source 8 for generating magnetic saturation in the magnetic head H; A high frequency differential amplifier 9 for detecting the impedance of the magnetic head H from the output of the bridge circuit network 6 and detecting the end point of core processing from the change thereof.
An arithmetic unit flrl that takes in the output of the differential amplifier 9 via the transformer 12 and the AC-DC converter 10, determines impedance changes, and outputs a polishing device stop signal from the output device 16.1. It is also provided with a switch 14 for turning on and off the direct current source 8.

Next, the operation of this embodiment will be explained.

In addition, the high frequency signal from the flow generator 7 is connected to the bridge circuit network 6.
and the output of this bridge network 6 is connected to capacitor 1.
It increases through 3. After this is amplified by the differential amplifier 9, it is detected by the AC-DC converter 10 as the swing #A signal.

This amplitude is proportional to the potential difference due to the impedance imbalance of the bridge circuit network 6 caused by the impedance of the magnetic head H, and is detected as a signal corresponding to the impedance of the magnetic head H.

Here, in order to prevent the excitation of the magnetic head H from deviating from a reversible range, the high-frequency signal applied to the bridge circuit network 6 should be sufficiently high in amplitude within a range that can be measured by the AC'-DC converter 10. It shall be kept small.

Next, switch 14 is activated by a low frequency pulse (PH2~number+mH).
z) is turned on and off. This K is faster current source 8
A DC bias current is passed through the coil 4 of the magnetic head H, and excitation is repeated at regular intervals to bring the magnetic head H into periodic K1111 saturation.

While the detection is continued in this manner, as the tip of the thin film magnetic head H is polished, the impedance of the magnetic head H changes as shown in FIG. 2.

As is clear from this ν2 diagram, the output of the AC-DCI" converter 10, which represents the impedance of the magnetic head H, changes up and down kl' by turning on and off the DC bias current by the switch 14. If the output value representing the impedance when ON is a, and the output value representing the impedance when OFF is b, the difference in these output values (b-a) is approximately 10 times greater before and after polishing. It shows the wide range of changes.

Therefore, the arithmetic unit [11] sequentially detects the output values a and b,
These output values a during polishing of the magnetic head H,
Track the temporal changes in b. From this result, the time ct do when these output values atbKt appear
By determining e and f, it is possible to know the progress of machining and the end point.

Here, the output of the AC-DCI' converter 10 may include changes in device fF characteristics and the like due to changes in the surrounding environment. However, in this embodiment, the switch 14 alternately detects the impedance in two states: a state where the magnetic head H is magnetically saturated and a state where the magnetic head H is not magnetically saturated. If the fluctuation is longer than at least one period of the switch 14, by detecting the impedance in the sacral state using the impedance in one state as the base, the influence of the surrounding environment fluctuation is removed and the impedance is detected purely. It is possible to detect only changes in the impedance of the magnetic head H.

Thus, in this example, the difference in output values (ba).

Alternatively, the ratio (b/a)K allows the skin to be detected more accurately and with high sensitivity without reducing fluctuations in the surrounding environment at the end of the polishing process.

Incidentally, when mass producing the magnetic head H, it is conceivable that variations in impedance characteristics may occur. In this case, the output values a and b before the magnetic head H is polished are stored as ai and bi, and the output values when the magnetic head H is polished are stored. (for a and b, respectively, ai and bi
Standardized by a/atb//b.

By further providing a feature that allows the polishing process to be completed, it becomes possible to detect the finished product of the polishing process.

Incidentally, here, a cape fluctuation of about a few percent occurs in the above output #b, but this is due to the difference in the magnetic domain structure that falls when the magnetic head IT is released from magnetic saturation and relaxes. This can be stabilized by, for example, demagnetizing the magnetic head H at the same time as the DC bias current reaches 0FFK.

Also, as a method, turn on the DC bias current.

Instead of turning it off, you can apply two or three different levels of DC bias current in a rectangular waveform, or
A small value of DC current is constantly turned ON and OFF as described above.
The bias current may be superimposed on the bias current.

Furthermore, at this time, by changing the value of the DC bias current, the relative positions of points c, d, e, and f in Figure 2 can be adjusted, and according to this, the final point of the polishing process can be adjusted. When the magnetic head H approaches , it becomes possible to predict it in advance, and more precise polishing becomes possible.Next, the principle of the above embodiment is that the magnetic head H is excited by a DC bias current. It is sharpened by the rabbit 3 diagram or the bamboo 5 diagram. Here, 2314 is the magnetic field line distribution of the magnetic head H, and FIGS. 4 and 5 are the inductance and resistance values of the magnetic head H measured using a high frequency of 10 MHz.

By providing the contact portion 3 on the back shown in FIG. 13, the magnetic core of the magnetic head H having the closed magnetic group μ configuration shown in FIG. When the magnetic core has an open magnetic circuit configuration as shown in c), the magnetic path resistance of the magnetic core increases and the magnetic flux within the magnetic core decreases.For this reason, as shown in Figure 4, the magnetic head H A decrease in inductance (A) occurs.In addition, the conventional example
No. 5708) is a method that utilizes only (A). Also, in the upper magnetic R4P difference part) 01 of the magnetic head H, the smaller the track width, the smaller the cross-sectional area of the insulating layer, and the narrower the magnetic path. There is. Therefore, when a direct current (for example, 5 mA) is applied to the magnetic head H, the magnetic density of the upper magnetic step portion 101 increases as shown in Figure 3 (bl) of the furnace, and magnetic saturation occurs. Ru.

From this K, a decrease in inductance (B) occurs.In contrast, the magnetic head H is polished lI! When processed and the contact portion 3 is removed as shown in FIG. 3(c), the magnetic resistance of the magnetic head H increases. Therefore, rFfIT
The magnetic flux in the magnetic core caused by the ir current decreases,
The value of interface (C') is smaller than the above (P)K. In addition, Andan (N, C.

Anderson) and Jones (R,E,
Jones, Jr.
2896° (1981) (IEEE Trans,
on Mag, ) shows the relationship between the track width of the magnetic head and the applied DC current.

On the other hand, as shown in Figure 5M, the resistance value of the magnetic head H exhibits a similar trend to that of the inductance shown in Figure 4, although the overall change is small. This is presumed to be due to the effect that hysteresis loss and eddy current loss of the magnetic core of the magnetic head H are reduced due to magnetic saturation of the magnetic core.

Therefore, in the present invention, in order to detect the end of the process based on the above principle, we have adopted a method of detecting impedance, including not only the inductance of the magnetic head but also the resistance value. By simultaneously detecting the magnetically saturated impedance, it is possible to detect the end point of the process with high sensitivity and precision.

Next, the detection operation according to the embodiment shown in FIG. 21 will be explained in more detail with reference to FIGS. 6 and 7.

Until now, in the Pierre and Ming Dynasties, K, as shown in figure 6 fa),
Set the DC bias current to two values, B and C (in the case of Figure 1, C
= 0).

Therefore, in the following, an embodiment will be described in which K is used to enable more detailed detection, including the progress status of the grinding process.

In this embodiment, a three-value DC bias current having three levels A, B, and C as shown in FIG. 7(a) Ic is used.

Then, the impedance corresponding to each bias level A, B, and C changes as the processing progresses (that is, as time progresses), as shown by the curves s, t, and u in FIG. As shown in Figure 6 (b), the end point of machining was determined from the relationship between curve @1 and U.Here, the curve t rises as it approaches the end point of machining.This is due to the machining. When the tip of the head becomes thinner, the bias current B
This is because the tip becomes saturated and approaches the state of an open magnetic core in terms of octane. Therefore, when a larger bias current A is applied, the thickness at the tip of the head magnetic body becomes thicker than the embodiment shown in FIG. 6! T! At V (that is, a state where the amount of processing is small), an impedance change of about twice that of the embodiment shown in FIG. 6 is shown. As described above, by applying the third bias level A and comparing the curves 3° and U, it is possible to detect a state in which the machining amount is insufficient by a specific value. Therefore, according to this embodiment, the optimum end point of machining can be detected. It is possible to generate a warning signal before the nuclear warning signal reaches the point, and if the processing speed is reduced by the nuclear warning signal, the detection of #reverse termination #r#' can be increased with a slight increase in the processing time.Next , an example of a method and jig for polishing the magnetic head 11 will be discussed.

As shown in FIG. 8, the magnetic head is formed on a helad slider 1, and as shown in FIG. Head slider 1 from the broken line Y to the solid line Y
Polished together with 7.

The f410 diagram shows a lap sander 18 that is suitable for the above polishing process.
In this schematic diagram, for example, an inductor motor 19 is connected to a pulley 2.
The lap surface plate 21 is rotated in the direction of the arrow through the 1!
The lapping jig 22 is configured to rotate on its own axis as shown by the arrow with respect to the revolution of the lapping jig 22. Uniform polishing can be achieved by this rotational action.

FIG. 11 shows an embodiment of the wrap jig 22, in which the wrap #J
The magnetic head (2), which is attached to the bottom of the iL22, is polished by the dummy head 24 at an inclination by the rotation of the lapping jig 22. A circuit board 25 is attached to the silk, and a rabbit 1 is attached to this board 25.
Wheatstone bridge network shown in figure 6. AC oscillator7. Direct current fM8. Differential amplifier9. It is equipped with a switch 14, etc., so that the signal can be detected with 8/N accuracy. At this time, these devices are a must!
A supply line such as a power source is connected to the external KP! via a slip ring 26. On the other hand, since the output of the differential amplifier 9 is a high frequency signal of 10 MHz as described above, it is taken out to the outside by passing through the rotary transformer 12. Therefore, the rotating side 12b of the rotary transformer 12 is attached to the wrap jig 22, and the stationary side 12a is attached to the support member 28, and the center axis 23 of the wrap jig 22 is attached to the support member 28 by the pole bearing 27. It is designed to be held in

〔Effect of the invention〕

As explained above, according to the present invention, since the method B is used to detect the impedance including the resistance value of the magnetic head, the conventional method of measuring the absolute value of inductance is was 4% culm, whereas in the method of the present invention, the conversion rate is 5 to 10 times higher, and the detection and polishing of the end point of the polishing process is improved.

Furthermore, it is possible to simplify the device by employing a bridge circuit, and there is no need for expensive impedance measurement equipment.

Furthermore, while the conventional method requires accuracy and stability of the detection means within the processing time (10 minutes of counting),
In the present application, it is sufficient to have stability between the presence and absence of bias (period of about 001 to 10 Hz), and therefore, the dependence of the entire detection means on the surrounding environment can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention, Fig. #2 is a characteristic diagram for operation sharpness, Fig. 3 is *aZa of the magnetic field line distribution of the thin film magnetic head, and Fig. 4 is a clear view of inductance change. Figure 5 is a diagram of the resistance change, the white diagram is a characteristic diagram showing one method of the detection principle, Figure 7 is a characteristic diagram showing another method of the detection principle, and Figure F8 is the assembly of the thin film magnetic head. Figure, #'9 figure is l8
A partially enlarged view of the figure, Fig. F10 is a clear view of the polishing machine, and Figs. H: Thin film magnetic head, 1: Upper magnetic layer, 2: Lower magnetic layer, 3: Contact portion, 4: Coil , 5... Inductor, 6... Wheatstone bridge circuit network, 7.
...Negotiation oscillator, 8...Direct current source, 9
...Differential amplifier #I, 10...AC-D
C converter, 11... Arithmetic device, 14...
-Electronic switch, 16...output device. Figure 1 Between cape Figure 4 DC bias voltage shoulder tip (rnA) Figure 5 DC pi 1stP- (mA) Figure 6 ↑ (b) 241L via Figure 8 Figure 1O

Claims (1)

[Claims] 1. By depositing at least a magnetic thin film, an electrically insulating film, and an electrically conductive film in a predetermined order in the thickness direction, first an intermediate layer having a magnetic short circuit portion at the tip of a magnetic gap regulating film of a predetermined length is formed. In a thin film magnetic head in which a thin film magnetic head having a shape is formed and then the tip of the thin film magnetic head is polished to a predetermined gap depth dimension, the winding of the thin film magnetic head during the polishing process is a detection means for measuring the impedance exhibited by the winding while supplying a DC bias current of a predetermined value including a zero value; 1. A method for manufacturing a thin film magnetic head, comprising: determining means for detecting a decrease in the ratio and generating a control signal, and using the control signal to control the end of the polishing process. 2. In claim 1, the change in the DC bias current according to the predetermined mode is such that a first predetermined current value including zero is the lowest value, and a second predetermined current value larger than the first predetermined value A method for manufacturing a thin-film magnetic head characterized by a step-like change with a maximum value of . 3. In claim 1, the change in the DC bias current according to the predetermined mode is such that a first predetermined current value including zero is the lowest value, and a second predetermined value larger than the first predetermined value is the lowest value. A method for manufacturing a thin-film magnetic head, characterized in that the change is step-like over three stages, with the maximum value being an intermediate value and a third predetermined value larger than the second predetermined value. 4. A method of manufacturing a thin film magnetic head according to claim 1, wherein the detection means includes an AC Wheatstone bridge network, and the winding is connected to one side of the network. 5. In claim 1, the polishing process is a lapping process, and at least a part of the detecting means is attached to a lapping jig for attaching the thin-film magnetic head to be polished. A method for manufacturing a thin film magnetic head.