JPH0364926B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention relates to a composite substrate for a thin film magnetic head used in a magnetic disk device etc., particularly for magnetic recording,
The present invention relates to a composite substrate for a thin film magnetic head on which read and erase heads can be stacked.

BACKGROUND TECHNOLOGY In general, thin-film magnetic heads have excellent frequency characteristics and are manufactured using a manufacturing process based on semiconductor technology, making it possible to manufacture high-precision magnetic heads at low cost, and they will become the mainstream of magnetic heads in the future. considered to be a thing.

Thin film magnetic heads include inductive heads used as recording and reproducing heads, and magnetoresistive heads used as reproducing heads.

The inductive head is as shown in Figure 4.
Lower core 20 made of a substrate such as soft ferrite
, an upper core 21 made of permalloy, sendust, or amorphous disposed through a gap, a conductor 23 made of copper or the like disposed within an insulating layer 22 within the upper core 21, and a coating on the outside of the upper core. It consists of a protective film layer 24.

As shown in FIG. 5, the magnetoresistive element head includes a substrate 25 serving as a magnetic shielding material, a magnetoresistive element 26 made of permalloy disposed through a required gap, and yoke materials disposed on both sides of the element 26. 27 is built into the protective film layer 28.

In order to create a structure in which a recording head and a reproducing head are combined, such as tunnel type, straddle type, and bulk type magnetic heads for floppy disks, it is conceivable to form a thin film magnetic head into a two-layer structure. If the second layer thin film magnetic head is directly constructed after creating the first layer thin film magnetic head, the shape of the second layer substrate will be complicated due to the core shape of the first layer, and the magnetic properties will be affected. There are concerns about deterioration.

Furthermore, it is possible to provide a protective film layer between the first and second layer thin film magnetic heads, but the protective film layer is provided after the first layer magnetic head is fabricated, and then the protective film layer is polished, etc. There is a problem in that it is necessary to finish it into a desired shape, it is difficult to expect an improvement in dimensional accuracy, and it requires a large number of steps and costs to form a thick protective film layer.

Furthermore, in order to produce a thin film magnetic head with a laminated structure, there is a method of producing thin film magnetic heads individually and then bonding them together, but in this case, there are problems with alignment accuracy during bonding, and manufacturing is required in one piece. Since the work was done in units, there was a problem that required a large amount of man-hours and costs.

OBJECTS OF THE INVENTION In view of the current situation, the object of the present invention is to provide a substrate for a thin film magnetic head, which allows a thin film magnetic head having a laminated structure to be easily manufactured.

Structure and Effects of the Invention The present invention provides the following features:
The difference between the coefficient of thermal expansion of the above soft ferrite plate is 1
It is constructed by laminating non-magnetic oxide ceramic plates with a thermal expansion coefficient of ×10 ^-6 /deg or less with a glass adhesive layer in between, and the outer main surface of each soft ferrite has a surface roughness of 200 Å or less. 1. A composite substrate for a thin film magnetic head, characterized by having the following characteristics:

By the method of this invention, a composite substrate consisting of three main layers of soft ferrite, ceramics, and soft ferrite is obtained, and this composite substrate has a ceramic layer between the soft ferrite layers and a glass layer mainly for lamination adhesion. The two layers of soft ferrite are magnetically separated, and a magnetic circuit can be formed on each of the soft ferrite layers on both main surfaces of the substrate.

That is, as shown in FIG. 1, there is provided a floppy disk in which an erasing head 30 is formed on one surface of one soft ferrite layer of a composite substrate 10 according to the present invention, and a recording/reproducing head 31 is formed on two surfaces of the other soft ferrite layer. A thin film magnetic head with a bulk type structure for disks can be fabricated.

Further, as shown in FIG. 2, the composite substrate 10 according to the present invention has a structure in which a recording head 32 is formed on one surface of one soft ferrite layer, and a reproducing head 33 is formed on two surfaces of the other soft ferrite layer. A magnetoresistive element magnetic head can be fabricated.

DISCLOSURE OF THE INVENTION BASED ON DRAWINGS FIG. 3 is an explanatory assembly diagram showing a method for manufacturing a composite substrate according to the present invention.

In addition, in the manufacturing method shown in FIG. 3, one side of the non-magnetic oxide ceramic plate 3 is coated with a material having a softening point of 400°C to 850°C using a glazing method or a sputtering method.
Then, a glass layer 4 having a coefficient of thermal expansion whose difference between the coefficients of thermal expansion of the soft ferrite plates 1 and 2 is 1×10 ^-6 /deg or less is deposited, and the surface roughness of one of the soft ferrite plates 1 is 500 Å or less. facing the mirror-finished main surface side, and on the mirror-finished main surface of the other soft ferrite plate 2 with a surface roughness of 500 Å or less,
A glass layer 4 having similar properties is applied using a glazing method or a sputtering method, and this is placed opposite to the other main surface of the ceramic plate 3, which has been mirror-finished to a surface roughness of 500 Å or less. Layer 4 is laminated closely to the center side, heated to a temperature such that the glass viscosity of glass layer 4 is 10 ³ to 10 ^7.6 poise, and 0.1
Laminate molding by applying pressure of Kg/ ^cm2 to 100Kg/ ^cm2 ,
Thereafter, the outer main surfaces of each soft ferrite plate 1 and 2 are polished to a surface roughness of 200 Å or less by diamond polishing or mechanochemical polishing, and the soft ferrite plates 1, glass 4, ceramics 3,
This is a manufacturing method for manufacturing a composite substrate 10 according to the present invention, which is composed of multiple layers of glass 4 and soft ferrite 2.

In the manufacturing method shown in FIG.
The glass layer 4 is applied to both main surfaces of the glass layer 4 and laminated and crimped, or the glass layer 4 is applied to each ferrite plate 1 and 2 and laminated and crimped. The surface may be appropriately selected depending on workability, material of each layer, etc.

In addition, the glass layer 4 is first applied to the ceramic plate 3, and the glass layer 4 is crimped to one of the ferrite plates 1, and
A glass layer 4 is applied to the other ferrite plate 2,
These may be laminated and pressure-bonded together, and the mating material and main surface to which the glass layer is attached, and the lamination assembly order may be appropriately selected depending on workability, efficiency, the material of each layer, etc.

In addition, between two soft ferrite plates with their mirror-finished principal surfaces facing each other, the difference between the thermal expansion coefficient of the soft ferrite plate and the coefficient of thermal expansion is 1×10 ^-6 /deg or less, and both sides are mirror-finished. A non-magnetic oxide ceramic plate with a softening point of 400℃ to 850℃ is interposed between the soft ferrite plate and the non-magnetic oxide ceramic plate.
Then, these are laminated and adhered through a glass plate having a coefficient of thermal expansion with a difference of 1×10 ^-6 /deg or less from the coefficient of thermal expansion of the soft ferrite plate, so that the glass viscosity of the glass plate is 10 ³ to 10 ^7.6 Heat to a temperature of 0.1
Laminate molding is performed by applying a pressure of Kg/cm ² to 100/cm ² , and then the outer main surface of each soft ferrite is 200Å
A manufacturing method that involves polishing to the following surface roughness may also be used.

Preferred embodiment of the invention In this invention, the soft ferrite used is MnO21mol% as Mn-Zn ferrite.
~38mol%, ZnO6mol%~25mol%,
The composition of Fe ₂ O ₃ is preferably 51 mol% to 56 mol%, and as the Ni-Zn ferrite,
_NiO2 15mol%~25mol%, ZnO25mol%~35mol
%, a composition of 49 mol% to 59 mol% Fe ₂ O ₃ is preferred.

In addition, soft ferrite has a density that is lower than the theoretical density.
It is desirable that the ratio is 99.9% or more, and the size of the pores is preferably 0.5 μm or less.

The difference in thermal expansion coefficient of the intermediate layer oxide ceramic from that of the soft ferrite plate is 1×10 ^-6 /deg.
Non-magnetic ceramics with the following thermal expansion coefficients include Al ₂ O ₃ series, TiO ₂ -BaO series, TiO ₂ -CaO
ZrO ₂ -based, MgO-based, crystallized glass, etc. can be selected as appropriate. Further, the porosity of ceramics is preferably 0.01% or less.

Also, the difference between the coefficient of thermal expansion of ceramics and the coefficient of thermal expansion of soft ferrite plate is 1×10 ^-6 /deg.
Exceeding this is not preferable because cracks will occur in the ferrite or ceramics of the composite substrate and the magnetic properties of the ferrite will deteriorate.

Glass, which is mainly used for laminating adhesives, has a softening point of 400
℃~850℃, if the difference in thermal expansion coefficient from the soft ferrite plate is 1×10 ^-6 /deg or less, borosilicate-based, soda-lime-based, high lead-based glass, etc. Various glasses are available. Note that it is desirable that the glass has properties such as water resistance, abrasion resistance, and chemical stability.

Moreover, when the softening point of the glass is less than 400°C,
Because the required head dimensional accuracy could not be obtained during the heat treatment of the magnetic film in the post-process, it was not possible to commercialize the product, and
If the temperature exceeds 850℃, it is undesirable because the magnetic properties of soft ferrite will deteriorate due to heating when forming a layer of glass and ferrite, and the softening point will be 400℃.
~850℃.

Furthermore, if the difference between the coefficient of thermal expansion of the glass and the coefficient of thermal expansion of the soft ferrite plate exceeds 1×10 ^-6 /deg, cracks will occur in the ferrite or glass of the composite substrate, and the magnetic properties of the ferrite will deteriorate. This is not desirable because it causes

In this invention, when glass and ceramics or ferrite are bonded together, the glass viscosity is 10 ³ to 10 ^7.6.
Heating to a temperature of poise exceeds 10 ^7.6 poise. In other words, at temperatures below the softening point of glass, the adhesive strength with soft ferrite is weak, and at temperatures where the glass viscosity is less than 10 ³ poise, the fluidity of the glass becomes too large, causing the intermediate glass layer to flow and reduce shape accuracy. This is because the reaction between the ferrite and the glass is large, resulting in deterioration of the ferrite properties and the formation of air bubbles in the glass, which is undesirable.

Also, when pressing glass and ceramics or ferrite, apply a pressure of 0.1Kg/cm ² to 100Kg/cm ² .If it is less than 0.1Kg/cm ² , the adhesive force will be weak.
Areas that are not bonded easily are formed at the interface between ferrite and ceramics and glass, and
This is because if it exceeds Kg/cm ² , the deformation will be large and cracks will easily occur between the ferrite, ceramics, and glass.

In addition, in this invention, the reason why the surface roughness of the soft ferrite layer is limited to 200 Å or less is that a magnetic thin film is formed on this surface, and the surface roughness affects the properties of the thin film. A high degree of polishing is required, preferably 50 Å or less, and finishing by diamond polishing is also possible, but mechanochemical polishing is preferable to obtain higher properties.

The diamond polishing method uses abrasive grains: diamond, particle size of 1 μm or less, lapping pressure: 0.01 Kg/cm ² to 1 Kg/cm ² , rotation speed: 10 m/min to 100 m/min, lapping surface plate: Sn, Cu, cloth. For the mechanochemical polishing method, the following conditions are preferable: Abrasive grains: MgO, ZrO ₂ , Al ₂ O ₃ , SiO ₂ powder, particle size
The following conditions are preferable: 1 μm or less, lapping pressure: 0.01 Kg/cm ² to 1 Kg/cm ² , rotational speed: 10 m/min to 100 m/min, lapping surface plate: Sn, solder, cloth.

The thickness of the composite substrate obtained by this invention is
5 mm, considering the purpose of use, alignment during pattern formation, and ease of processing during mass production.
The following is desirable, and preferably 0.1 mm to 2 mm.

Further, the thickness ratio between the ceramic layer and the soft ferrite layer of the composite substrate is appropriately selected depending on the application, usage method, etc., but preferably ceramic thickness/soft ferrite thickness = 0.01 to 1.

In the manufacture of composite substrates, the glass layer thickness is 0.05
A glass plate can be used for a thickness of 0.05 mm or more, but since it is difficult to manufacture a glass plate of less than 0.05 mm, a glass layer is applied to the mirror-polished main surface of soft ferrite or ceramics using methods such as glazing or sputtering. Soft ferrite and ceramics can be easily bonded together by welding the glass layer and ferrite or ceramics, or by welding the glass layers together.
Please note that when a glass layer is applied using the glazing method, air bubbles may remain within the glass layer.
It can be eliminated by hot isostatic pressing in a post-process.

Examples Example 1 MnO26.7mol%, ZnO20.8mol%,
Fe ₂ O ₃ 52.5mol% composition, thermal expansion coefficient 106×10 ^-7 /
Mn-Zn ferrite material with dimensions of 50.8 mm x 80.8 mm was cut to a thickness of 0.4 mm, and the surface roughness was 0.5 μm.
Finished.

In addition, TiO ₂ with dimensions of 50.8 mm x 50.8 mm x thickness 0.2 mm
Both sides of the −CaO plate were mirror-polished to a surface roughness of less than 500 Å.

After that, the softening point is 560℃ and the coefficient of thermal expansion is 98×10 ^-7 /
screen-print a mesh size #350 paste of lead borosilicate glass with a #150 screen onto the mirror surface of the ceramic plate, hold it in the air at 400°C for 1 hour, and
Hold at 850℃ for 15 minutes, glaze, 20μ
A glass layer was formed on M, and then 5 μm of the glass surface was removed by mirror polishing to give a surface roughness of 500 Å or less.

The mirror-polished surfaces of ceramic glass were stacked on the mirror surfaces of two ferrite sheets, facing each other, and heated at 800°C (temperature equivalent to the above-mentioned glass particle size of 10 ⁴ poise) in an N ₂ atmosphere.
and pressure bonded with a pressure of 0.5 kg/cm ² .

The soft ferrite surface of the obtained multilayer composite substrate material was finished to a surface roughness of 50 Å by mechanochemical polishing under the following conditions. The thickness of the obtained composite substrate is
The thickness of each soft ferrite was 0.25 mm.

Mechanochemical polishing method conditions: Abrasive grains using suspension in pure water: MgO powder, average particle size 0.1 μm, lapping pressure: 0.1 Kg/cm ² , rotation speed: 50 m/min, lapping surface plate: Sn.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of a thin film magnetic head using a composite substrate according to the present invention. Figure 3a,
b is an assembly explanatory diagram showing a method for manufacturing a composite substrate according to the present invention. FIGS. 4 and 5 are explanatory diagrams of a thin film magnetic head using a conventional substrate. 1, 2...Soft ferrite plate, 3...Ceramics, 4...Glass layer, 10...Composite substrate, 3
0...Erasing head, 31...Recording/reproducing head, 3
2...recording head, 33...playback head.

Claims (1)

[Scope of Claims] 1. A non-magnetic oxide ceramic plate having a coefficient of thermal expansion that differs from the coefficient of thermal expansion of the soft ferrite plate by 1×10 ^-6 /deg or less between two soft ferrite plates, 1. A composite substrate for a thin-film magnetic head, comprising a laminated structure with a glass adhesive layer interposed therebetween, and characterized in that each soft ferrite has a surface roughness of 200 Å or less on the outer main surface.