JPH0556562B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thin film magnetic head, and more particularly to a thin film magnetic head in which a protective plate is bonded via an adhesive to a substrate on which an element made of a magnetic film is provided.

[Prior art]

In general, thin film magnetic heads are made of a magnetic film such as sendust or permalloy on a substrate such as ferrite.
Conductive films such as AU, CU, and AL are formed by thin film deposition methods such as sputtering and vapor deposition, and these thin films are photoetched to form magnetic circuits that make up the elements that perform recording and reproduction, as well as electrical circuits that guide recording and reproduction signals. forming a pattern.

In order to protect these circuit patterns and form a sliding surface for the magnetic recording medium, a protective plate made of ferrite, glass, or alumina is placed on the pattern using an adhesive such as low-melting glass, epoxy adhesive, or water glass. The magnetic recording medium sliding surface side is ground to obtain a completed thin film magnetic head.

During the process of manufacturing such thin-film magnetic heads, when attaching the protective plate to the pattern on the substrate, the protective plates are stacked with adhesive as described above, heated while applying sufficient pressure, and the adhesive is bonded. is undergoing curing.

By the way, if a structure is adopted in which the protective plates are bonded using an adhesive, the solvent in the adhesive may evaporate due to the heating that occurs when the adhesive hardens, or the outside air may be drawn into the adhesive when the protective plates are pasted together. Air bubbles may form in the adhesive due to factors such as water leakage.

In addition, when heating for curing is performed using a general furnace,
A temperature gradient occurs between the outside and inside of the adhesive layer, and curing starts from the outside of the adhesive layer, so that bubbles generated due to the above reasons are trapped in the adhesive layer.

The presence of air bubbles in the adhesive layer that joins the protective plates causes the following various problems.

(1) If air bubbles exist near the element part formed from the magnetic film of a thin-film magnetic head, especially near the sliding surface of the magnetic recording medium, it may cause problems when grinding the sliding surface of the magnetic recording medium to form a cylindrical surface. Grinding sag occurs in the adhesive layer, causing spacing loss, cracking and chipping of the adhesive layer, and significantly deteriorating the characteristics of the magnetic head.

(2) If air bubbles are generated at the interface between the substrate or protective plate of the thin film magnetic head and the adhesive layer, the adhesive area decreases, the adhesive strength decreases, and the protective plate peels off.

(3) The gas in the confined bubble expands or contracts due to temperature changes, reducing the reliability of the magnetic head.

(4) If air bubbles exist on the sliding surface side of the magnetic recording medium, magnetic powder on the magnetic recording medium side will accumulate in the traces of the air bubbles that have become recesses.

(5) Water enters behind the bubbles existing on the sliding surface side of the magnetic recording medium, making it easy for elements made of magnetic films to corrode.

〔the purpose〕

The present invention has been made to solve the above-mentioned problems, and it improves various characteristics and reliability by configuring the above-mentioned protective plate so that no air bubbles are present in the adhesive layer that bonds it to the substrate. The purpose of this invention is to provide a thin film magnetic head with improved performance.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Here, an example in which the present invention is applied to a magnetoresistive thin film magnetic head using a magnetoresistive element (hereinafter referred to as an MR element) as a recording/reproducing element will be described.

[First Embodiment] FIGS. 1 and 2 show the structure of a thin film magnetic head according to a first embodiment of the present invention. FIG. 1 shows the state before the protection plate is bonded, and FIG. 2 shows the state before the protection plate is bonded. It shows the later state.

In FIG. 1, the reference numeral 1 is a glass substrate formed into a rectangular flat plate. Three MR elements 2 made of elongated rectangular magnetic films are arranged in a straight line at predetermined intervals.

Further, on the substrate 1, six linear signal electrodes 3 for guiding signals from the MR elements 2 are provided in parallel to each other, and the tip of each electrode is connected to each end of the three MR elements 2. The rear end is guided to the lower side in the figure, that is, to the opposite side of the sliding surface. These signal electrodes are formed from aluminum thin films, for example.

Further, in this embodiment, a substantially U-shaped heat generating pattern indicated by reference numeral 4 is formed on the substrate 1. As shown in the figure, the heating pattern 4 is 3
Near the upper side (sliding surface side) of MR elements 2 and 6
They are provided near both sides of the signal electrode 3 of the book. This heating pattern 4 is formed from, for example, an aluminum thin film.

Then, as shown in FIG. 2, a rectangular protection plate 5 is placed on the glass substrate 1 with an adhesive, covering the entire three MR elements 1, the tops of the six signal electrodes 3, and the tops of the heat generating patterns 4. and are joined together. The protective plate 5 is made of, for example, ferrite, glass, alumina, etc., and the adhesive used is, for example, water glass.

In this embodiment, when bonding the protective plate 5 with an adhesive, the heating pattern 4 is made to generate heat in order to harden the adhesive, so that air bubbles generated in the adhesive layer are not trapped. harden the agent layer.

The manufacturing process of the thin film magnetic head, including the bonding process, will be explained in detail below with reference to FIG.

In the first step S1 in the manufacturing process shown in the figure, the glass substrate 1 mentioned above is cleaned.

In the next step S2, a magnetic film such as permalloy, which will later become the MR element 2 described above, and an aluminum film, which will become the signal electrode 3 and generation pattern 4, are deposited on the surface of the glass substrate 1 by a method such as vapor deposition or sputtering. It is deposited and formed by In this case, these magnetic films and aluminum films are formed in a continuous state.

Next, in step S3, the signal electrode 3 and the heat generating pattern 4 are formed by photolithographically etching the aluminum film.

Subsequently, in step S4, the magnetic film is etched by photolithography to form the MR element 2.

Furthermore, in step S5, silicon dioxide (SiO ₂ ) is sputtered onto the substrate 1 so as to cover the MR element 2 and the signal electrode 3.
A protective film is formed to protect the element 2 and the signal electrode 2 and improve the environmental resistance of the magnetic head.

Subsequently, in step S6, the above-mentioned protective film and the upper part of the heat generating pattern 4 are covered with the sliding surface side of the surface of the substrate 1, that is, the upper part shown in FIG.
Apply an appropriate amount of water glass adhesive.

Next, in step S7, the protective plate 5 is placed on the water glass coated portion of the glass substrate 1, that is, at the position shown in FIG. 2, and bonded together.

In the following step S8, the protective plate 5 bonded together in the previous step S7 is pressed in the direction of the substrate 1, and the heat generating pattern 4 is energized to generate heat.

This heat generation causes the water glass layer between the protection plate 5 and the substrate 1 to harden from the inside. Therefore, the solvent in the water glass may evaporate due to heat generation, and the protective plate 5 may
If outside air is drawn into the water glass layer during bonding and air bubbles are generated in the water glass layer, the generated air bubbles can escape from the water glass layer to the outside, and the water glass layer You won't be trapped inside.

Therefore, when the hardening of the water glass layer is completed by the heat generated by the heat generating pattern 4 in the subsequent step S9 and the bonding of the protective plate 5 is completed, no air bubbles will be present in the hardened water glass layer.

In particular, since a part of the heat generating pattern 4 is provided along the sliding surface side, the presence of air bubbles in this part is particularly prevented.

In the manner described above, a thin film magnetic head as shown in FIG. 2 is obtained. Further, a finished product is obtained by grinding and finishing the magnetic recording medium sliding surface side of this thin film magnetic head.

As described above, in this embodiment, the water glass of the adhesive is hardened from the inside during curing, so that no air bubbles are present in the water glass layer after curing is completed.
Furthermore, the presence of air bubbles in the adhesive layer near the particularly important sliding surface is effectively prevented.

Note that the shape and arrangement of the heat generating pattern are not limited to those in the above embodiments, and embodiments with different configurations in this respect will be described below.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention. As shown in the figure, in this embodiment, the heat generating pattern designated by reference numeral 6 is a pattern having the same shape and arrangement as the heat generating pattern 4 of the first embodiment, and 3
The pattern is formed by adding a pattern portion 6a formed in a straight line along the lower side of each MR element 2.

According to the above structure, the film formation and etching processes for the heat generating pattern 6 are increased compared to the first embodiment, but the immediate vicinity of the entire three MR elements 2 is surrounded by the heat generating pattern 6. Because of the arrangement, the heating pattern 6 in the manufacturing process described above
When the water glass layer is cured by heat generation, heating in the vicinity of the MR element 2 is performed more uniformly. Therefore, the temperature gradient generated around the MR element 2 during heating becomes lower, and bonding without foaming can be performed more efficiently in this particularly important area. In addition, adhesive strength is further improved because the adhesive is cured uniformly over a wider area.

[Third Embodiment] FIG. 5 shows the structure of a third embodiment of the present invention. As shown in the figure, in this embodiment, the heating pattern indicated by 7 has the first shape.
Although it is formed in a substantially U-shape as in the embodiment,
The upper linear pattern portion overlaps the three MR elements, and the linear pattern portions on both sides are arranged along the vicinity of both sides of the six signal electrodes 3.

In such a structure, the heating pattern 7 is used for heating for curing the adhesive, and
It is used as a bias electrode for the MR element 2 in the structure of the completed thin film magnetic head.

With this structure in which the heating pattern and the bias electrode are integrally formed, it is possible to prevent foaming to the maximum extent in the two most important parts of the MR element when the adhesive hardens, and compared to the first and second embodiments. Thus, the number of steps for forming bias electrodes can be reduced.

Note that the substrate 1 in the configuration described above, MR
It goes without saying that the present invention can also be applied to a thin film magnetic head in which the elements 2, signal electrodes 3, protective plate 5, adhesive and protective film are formed with different configurations, such as the material, number of shapes, arrangement, etc., from those of the above embodiments. The configuration of the heat generating pattern, such as the shape material, shape arrangement, number, etc., is not limited to the above embodiments.

It goes without saying that the present invention can also be applied to an inductive type thin-film magnetic head that does not use an MR element but has a conductor pattern of a magnetic film and a coil constituting a magnetic core.

〔effect〕

As is clear from the above description, the thin film magnetic head of the present invention employs a structure in which a heat generating pattern is formed on the substrate on which the magnetic film constituting the element is formed, to heat the adhesive when bonding the protective plate. Therefore, it is possible to prevent foaming in the adhesive layer between the substrate and the protective plate, and it is possible to solve the above-mentioned problems that occur when air bubbles are present in the adhesive layer. In other words, spacing loss due to grinding of the adhesive layer, deterioration of the characteristics of the magnetic head due to cracking or chipping of the adhesive layer, peeling of the protective plate due to a decrease in adhesive strength, and decrease in reliability of the magnetic head due to expansion and contraction of air bubbles. To provide a thin film magnetic head which solves various problems such as adhesion of dust such as magnetic powder to concave portions of air bubbles on the sliding surface, and corrosion of elements due to water intrusion, and which has excellent characteristics and improved reliability. I can do it.

[Brief explanation of the drawing]

Figures 1 to 3 explain the first embodiment of the present invention, where Figure 1 is a plan view showing the structure before the protection plate is bonded, and Figure 2 is a plan view showing the structure after the protection plate is bonded. , FIG. 3 is a flowchart showing the manufacturing process, FIG. 4 is a plan view showing the structure of a second embodiment of the invention, and FIG. 5 is a plan view showing the structure of the third embodiment of the invention. 1... Substrate, 2... MR element, 3... Signal electrode, 4, 6, 7... Heat generating pattern, 5... Protective plate.

Claims (1)

[Scope of Claims] 1. In a thin film magnetic head in which a protective plate is bonded via an adhesive to a substrate on which a magnetic film constituting an element is formed, a heating pattern is provided on the substrate to heat the adhesive during bonding. A thin film magnetic head characterized by the following: 2. The thin film magnetic head according to claim 1, wherein the heating pattern is arranged near the element. 3. The thin film magnetic head according to claim 1 or 2, wherein the heating pattern is formed so as to surround the vicinity of the element. 4. The thin film magnetic head according to any one of claims 1 to 3, wherein the element is a magnetoresistive element. 5. The thin film magnetic head according to claim 4, wherein the heating pattern is formed integrally with a bias electrode of the magnetoresistive element.