JPS5931769B2 - Manufacturing method of thin film magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thin film magnetic head, and provides a method for effectively manufacturing a thin film magnetic head that is efficient as a magnetic head and provides good recording characteristics. be.

FIG. 1 shows an example of a cross section of a conventional one-turn type thin film magnetic head with a bias line.

In such a magnetic head, a metal layer is formed by depositing a highly conductive metal on a ferromagnetic substrate 101 that forms part of the magnetic circuit of the magnetic head using a method such as vapor deposition, electrodeposition, or sputtering. A necessary pattern is formed by forming and etching using a photo-etching technique. The conductor layer 104 formed in this way is used as a bias coil.
03 is used for each signal coil. Further, an upper magnetic layer 102 made of permalloy or the like is formed using methods such as vapor deposition, electrodeposition, sputtering, and photo-etching technology so as to partially cover the conductive layers 103 and 104 via the insulating layer 105. to configure a magnetic head. In this thin film magnetic head, the ferromagnetic substrate 101 and the upper magnetic body 102 approach each other between the conductive layers 104 and 103. Therefore, most of the magnetic flux generated by the current flowing through the signal coil 103 leaks between the ferromagnetic substrate 101 and the upper magnetic body 102 at this portion 106, and the contact surface 10T with the recording medium is leaked. The amount reached will decrease. For this reason, in a head with this configuration, the efficiency during signal recording is poor, and unless a large current is passed through the signal coil,
Difficult to record. As a way to solve this problem,
A configuration shown in FIG. 2 can be considered.

That is, the main difference from the configuration shown in FIG.
Conductors 104 and 103 are disposed on top of the conductor 9 .

According to this configuration, leakage of magnetic flux at the portion 106 between the conductor layers 104 and 103 described above is eliminated.

The present invention relates to the formation of the grooves 108 in the ferromagnetic substrate 101 in such a configuration.

To provide the grooves 108 in the substrate 101, a mirror-polished magnetic substrate 1 made of ferrite or the like is used as shown in FIG. 3a.
Then, a resist is uniformly applied and exposed and developed to obtain a resist mask 12 (FIG. 3b). Ni--Zn ferrite, which has a relatively high resistivity, can be etched with a sulfuric acid-based electrolytic etching solution. After the etching is completed, the resist is removed (FIG. 3c), and a magnetic substrate 1 such as ferrite is placed on the groove 13 formed by electrolytic etching.
Non-magnetic insulating material 14 such as glass with the same coefficient of thermal expansion as
(FIG. 3 d) and heated to fill the grooves 13 with the non-magnetic insulating material 14 (FIG. 3 e) This substrate 11 is wrapped again to separate the non-magnetic insulating material 14 and the magnetic material. A plane 15 is formed so that it is flush with the substrate (FIG. 3 f)
). At this time, the lap surface of the substrate 1 in step a and the flat surface 15 are polished so as to be substantially parallel to each other. On the ferromagnetic substrate 101 thus formed, as shown in FIG. 2, a non-magnetic conductive layer of aluminum, gold, copper, etc.
The bias coil 104 and the signal coil 10 are deposited using a method such as sputtering and selectively removed using a method such as photo etching or sputter etching.
form 3.

Both coils 104 and 103 are formed using a molded layer 10 formed by filling the groove with a non-magnetic insulating material as described above.
It is formed so that it is located almost above 9. Next, both coils 10
4, 103 and to form a gap G, SiO. An insulator layer 105 such as SiO2,
It is formed using a method such as vapor deposition or sputtering. A magnetic layer 102 made of permalloy or the like covers a part of both coils 104 and 103 insulated in this way and reaches the gap G.
is coated using a method such as vapor deposition, electrodeposition, or sputtering,
It is etched into the required shape using a method such as photo etching. Finally, a protective layer 111 for protecting the formed magnetic head is formed using a method such as vapor deposition sputtering. Next, we will discuss the problems in the groove machining process for the magnetic head formed in this way. I will explain.

The characteristics of the substrate required at the completion stage of wrapping finishing as shown in FIG.

At this time, the finishing accuracy of the groove width and groove pitch must be several microns or less. Under the above conditions, in the current manufacturing process, variations in board thickness, twisting, waviness, etc. directly affect the finished state. First, in FIG. 3a, the mirror-polished substrate 1 is 20 m long.
The plate thickness varies by about ±10 microns within an m square substrate, and the average plate thickness among the substrates within 10 spots of the mirror polishing process also varies by about ±5 microns.

Further, the twist and waviness of the substrate also vary by about ±5 microns. Next, when this substrate 1 is etched in the step shown in FIG.

In addition, when the substrate 1 is attached to the lap surface plate in step f, the twist and parallelism of the substrate due to attachment deteriorate by ±3 microns within the substrate. In addition, the lap surface plate also has an undulation of ±2 microns, and during the entire process, the lap surface on the lap surface plate and the substrate is ±2 microns.
There is a parallelism error of 30 microns. This parallelism error is
Since the lap surface plate and the lap surface are almost parallel with each other due to the latching, the variation in groove depth within the board is reduced by ±2.
5 microns, and the groove depth between the substrates is ±3
It will vary by as much as 0 micron. If the required groove depth is 5 microns or more, leakage of magnetic flux through the recess 106 between the conductive layers can be ignored, so the problem is how to reduce the above-mentioned parallelism error. Generally, in etching, the maximum inclination angle of the etched end face is considered to be around 60° in electrolytic etching unless a method such as plasma etching or sputter etching is used.

Due to the slope of the etched end face, if the groove depth varies by 30 microns, the groove width varies by ±17 microns and the groove pitch also shifts by ±17 microns. Such large variations cannot be tolerated in the next step, which is the photo-etching step of the conductor layer. The present invention attempts to improve the above-mentioned variations in groove width and groove pitch by selecting the material of the substrate. FIG. 4 shows a cross-sectional view of a groove formed by material selection according to the invention.

Does this board 21 have a specific resistance of 104Ω? This is NiZn ferrite, and this is a cross section of electrolytic etching in this case. As shown in FIG. 4, the arc centered on the end 25 of the opening 23 of the resist 22 almost matches the shape of the etched cross section. When the etched cross section becomes a nearly circular arc in this way, the angle between this circular arc and the substrate surface is approximately 90 degrees, and even if the groove depth of the substrate fluctuates by ±30 microns due to polishing, this can be absorbed. .
In other words, if the depth of the groove is c, the change in groove width due to variation can be written as C(1-J1-(÷)2) (where Δ is variation).Now, if the groove depth C is 100 microns, and the variation is If it is 30 microns, the change in groove width is ±4.6.
The variation is - compared to the case of general etching. That is, when the cross-sectional shape of the etched groove approaches a circular arc, variations in groove width and groove pitch due to variations in groove depth can be absorbed. The fact that the cross-sectional shape of the electrolytically etched groove approaches a circular arc is related to the specific resistance of the substrate, and as shown in Figure 5, in MnZn ferrite with a specific resistance of several Ω,
The etched end face is inclined at around 60 degrees, but it is 20c.
TnΩ is approximately 80 ends and 104Ω? It becomes almost an arc.

Also, 108Ω? In this case, a large voltage is required to obtain the current necessary for electrolytic etching, which causes dielectric breakdown of the resist 12, making it impractical. When the angle between the etched end face and the substrate surface is 80 or more, the change in groove width and groove pitch due to the amount of polishing becomes small, and the above-mentioned variations can be sufficiently absorbed. in this way,
Is the specific resistance 20Ω? From 107Ω? By adopting a method in which grooves are formed in the ferromagnetic ferrite substrate 12 by electric field etching during the process and then the top surface of the substrate is polished, even if there are slight variations in the ferromagnetic ferrite substrate, the requirements can be met at the completion stage shown in Figure 3 f. The above properties (1) and (2) can be satisfied.

FIG. 6 is a cross-sectional view of another embodiment of a thin film magnetic head utilizing grooves formed according to the present invention.

The difference between the embodiment in FIG. 2 and the embodiment in FIG. 6 is that in FIG. 2, a conductive layer 104 used as a bias coil and a conductive layer 103 used as a signal coil are used.
A conductive layer 104 is formed in the groove provided in the ferromagnetic substrate 101, and a conductive layer 104 is formed on an insulating layer 108 made of glass or the like that fills the groove. The conductive layer 103 buried under the body layer 108 and used for the signal coil is arranged in the groove shape described above. Otherwise, as in the embodiment shown in FIG. 2, a ferromagnetic layer 102 such as permalloy is deposited via an insulating layer 105 such as SiO or SiO2 to form a gap portion G. A protective layer 109 is formed thereon, and a sliding substrate 110 made of glass or the like is bonded with an adhesive layer 111 made of resin or the like. When the conductor layer 104 used for the bias coil is buried in the groove as shown in FIG. 6, the cross-sectional area of the coil can be made 100 times larger than that shown in FIG.

That is, for example, the shape of a bias conductive layer used in a multi-element magnetic head for recording an audio magnetic tape with a width of about 6 mm (-inch) is, in the case of FIG. 2, a width of 20 μm, a film thickness of 1 μm, The length is 10 mT, and the material of the conductor layer is Al. ．． Au. ．． If Cu or the like is used, the specific resistance is about 2 μΩ, so the resistance value of the bias conductor layer is about 10Ω. On the other hand, since a bias current of about 1 A is required, the power consumed by the bias conductor layer is several watts, and the conductor layer generates Joule heat. In the case of FIG. 6, the device cross-sectional area of the bias conductor layer 104 can be set to be as large as 30×200μ, so that the resistance value of the conductor layer is 0.1Ω or less. Therefore, power consumption in the bias conductor layer is small, and no heat is generated even when a bias current is passed. In this embodiment as well, the above discussion regarding the parallelism error between the substrate surface and the lap surface plate holds true. However, in the case of this embodiment, since the conductor layer is embedded in the groove, it is more susceptible to parallelism errors than the embodiment shown in FIG. , waviness, etc. must be reduced. Also, in particular, the specific resistance is 102Ω? If you use the following board, it will be possible to
As shown in the figure, if the bias conductor layer and signal conductor layer are formed directly on the substrate, the electrode extraction parts of both coils will be directly attached to the substrate, so multiple channels can be connected to the same substrate. In the case of a thin-film magnetic head held in
After depositing the insulating layer on the substrate 101, a conductive layer must be formed.

Also, in the case of FIG. 6, an insulating layer must be deposited on the substrate 101 as well. However, the resistivity of the substrate is 1
03Ω? In this case, there will be no interference between the channels, and there will be no problem even if the conductor layer is directly applied to the substrate without an insulating layer. As described above, in the method for manufacturing a thin film magnetic head of the present invention, when forming a predetermined Q-shaped groove in a ferromagnetic ferrite substrate that forms the magnetic core of the thin film magnetic head, the specific resistance of the ferromagnetic ferrite substrate is 2
02Ω? -107Ω? This method is performed by electrolytic etching with a setting of Even if there is a slight change in the thickness of the groove, the difference in the amount of polishing will reduce the change in the width and pitch of the groove.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing one configuration of a conventional thin-film magnetic head, FIG. 2 is a cross-sectional view of a main part showing an embodiment of a thin magnetic head manufactured according to the present invention, and FIG. FIG. 4 is a cross-sectional view of a main part for explaining the present invention, FIG. 5 is a diagram showing the relationship between the resistivity of the substrate and the angle of the etched edge, and FIG. FIG. 7 is a sectional view of a main part showing another embodiment of a thin film magnetic head manufactured according to the invention. 1,101...Ferromagnetic substrate, 12,22...
...Resist, 13,108...Concave groove, 1
4,109...Nonmagnetic insulating material.

Claims (1)

[Scope of Claims] 1. Filling the grooves of a ferromagnetic ferrite substrate with a specific resistance of 20 to 10^7 Ωcm and having grooves whose surface has been electrolytically etched at least with a non-magnetic material, and then filling the grooves with a non-magnetic material on the upper surface thereof. A method for manufacturing a thin-film magnetic head, comprising: polishing a ferromagnetic ferrite substrate, and using the ferromagnetic ferrite substrate as part of a magnetic core. 2. The method of manufacturing a thin film magnetic head according to claim 1, wherein the nonmagnetic material filled in the groove provided in the ferromagnetic ferrite substrate is a nonmagnetic insulator.