JPH0827900B2 - Magnetic head core manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a magnetic head core by bonding a single crystal ferrite and a polycrystalline ferrite or a polycrystalline ferrite and a polycrystalline ferrite.

(Prior Art) Conventionally, a magnetic head core in which a single crystalline ferrite and a polycrystalline ferrite or a polycrystalline ferrite and a polycrystalline ferrite are bonded to each other to form a magnetic gap has first formed a recess corresponding to the magnetic gap by preliminary etching. After that, the glass was sealed in the magnetic gap and the rear bonding interface was bonded to manufacture.

In the above-mentioned direct bonding of single crystal and polycrystal or polycrystal and polycrystal, even if an organic acid or an inorganic acid is present at the bonding interface, the solid state reaction becomes insufficient and the bonding state deteriorates at low temperature heat treatment. Therefore, for example, when joining ferrites, it is common to heat at 1000 ° C. or higher to integrate them.

(Problems to be Solved by the Invention) However, in the solid-phase reaction at 1000 ° C. or higher, the mass transfer of polycrystalline ferrite is induced, and FIG.
As shown in (b), for example, 0.1
There was a problem that a recess 11 of .about.0.15 .mu.m was generated, the accuracy and linearity of the magnetic gap 12 were deteriorated, and the head characteristics were deteriorated. For example, an accuracy of 1.6 μm ± 0.4 μm is required for a 1 MB floppy disk, and 1.2 μm ± 0.1 μm is required for a 1.6 MB floppy disk. Although required, it was difficult to achieve this requirement with the magnetic head obtained by the above-described conventional manufacturing method.

In addition, at the junction between the single crystal ferrite and the polycrystalline ferrite at the rear of the magnetic head, a part of the polycrystalline ferrite directly joined to the single crystal ferrite has the same crystal plane as the joined single crystal, and the boundary portion is a wavy straight line. Not
As a result, there is also a problem that the variation in the characteristics of the magnetic head becomes large.

An object of the present invention is to solve the above-mentioned problems and to provide a method of manufacturing a magnetic head in which the linearity of the magnetic gap is good and the linearity at the boundary portion of the bonding surface is good.

(Means for Solving the Problems) A method of manufacturing a magnetic head core of the present invention is a method of manufacturing a magnetic head core, in which a single crystal ferrite and a polycrystalline ferrite or a polycrystalline ferrite and a polycrystalline ferrite are joined to form a magnetic gap, By interposing a joining aid consisting of nitric acid containing 5 wt% or less of sodium silicate on the joining boundary surface and performing heat treatment at a temperature of 700 ° C or more and less than 1000 ° C that is less than the temperature at which polycrystalline ferrite mass-transfers, It is characterized in that the joint boundary surfaces are integrally joined in a state where no intermediate layer is present on the surfaces.

(Operation) In the above-mentioned configuration, by performing direct bonding at a temperature equal to or lower than the temperature at which polycrystalline ferrite mass-transfers,
Since the polycrystalline ferrite does not move due to the heating at the time of bonding and neither the depression of the magnetic gap surface nor the movement to the single crystal surface of the bonding surface occurs, the linearity of the magnetic gap and the linearity of the bonding surface can be enhanced. The above-mentioned temperature is generally a temperature at which the solid-phase reaction does not sufficiently occur, but a bonding aid, preferably a solution of sodium silicate or glass powder dissolved in an acid or alkali, or a solution containing metal ions is interposed at the bonding interface. By activating the joint surface,
Bonding with sufficient strength can be achieved even at this temperature.

Further, since the above temperature is relatively low, it is possible to achieve glass encapsulation in the magnetic gap at the same time as heating during bonding.

The temperature at which the polycrystalline ferrite mass-transfers is the temperature at which the polycrystalline ferrite shows crystal growth, and in the case of ferrite, it is about 1000 ° C or more and 1600 ° C or less.

(Example) Hereinafter, an actual example will be described.

Example 1 Mn-Zn ferrite (composition of main component: MnO = 31 mol%, Zn
O = 16.5 mol%, Fe ₂ O ₃ = 52.5 mol%) polycrystals and single crystals were cut, polished, grooved and etched, as shown in FIG. 1 (a). Two joining faces 1
And a polycrystal boat 4 having a flat surface 2 for regulating the gap length and a groove portion 3 for inserting a glass rod, and two joining surfaces 5 and a gap length as shown in FIG. 1 (b). A single crystal etching product 7 having a concave portion 6 for controlling the above was prepared. However, the joint surface was mirror-polished at 0.03 S or less.

Next, with respect to Na ₂ SiO ₃ 1 g as a bonding aid on the bonding surface,
A solution prepared by adding 50 ml of HNO ₃ (1 + 1), which was a mixture of concentrated nitric acid and water in the same volume, was added dropwise, and after rubbing and drying, close contact and temporary joining were performed. After temporary bonding, insert a glass rod into the center groove, and heat for 30 minutes at 920 ℃ below the temperature at which polycrystalline ferrite mass-transfers in an inert gas atmosphere while applying pressure,
The encapsulation of Gap glass and the direct joining of the joints were performed at the same time.

Next, the obtained bar material is divided into two, and the relationship between the gap length obtained after grooving so that the bonded portion remains, chip slicing, and mirror-polishing, and the etching depth previously provided before bonding is shown. Along with the examination, microscopic observation of the gap portion was performed. The results of the gap length are shown in Table 1, and FIGS. 2 (a) and 2 (b) show micrographs of the gap portion of the present invention and the conventional example for comparison, respectively. In Table 1, for the etching depth, a surface roughness meter (× 20
000) was used and the gap length was measured by an auto-telecomparator.

From the results in Table 1, it was found that the etching depth and the gap length are in good agreement. FIG. 2 (a),
From the micrograph of the gap portion shown in (b), in the conventional gap portion shown in FIG. 2 (b), a plurality of dents are recognized on the gap surface of the polycrystalline ferrite, and the linearity is poor. It can be seen that in the gap portion of the present invention shown in (a), no indentation is observed on the gap surface of the polycrystalline ferrite and the linearity is good.

In addition, when observing the obtained rear junction with a metallurgical microscope, no intermediate layer was observed optically.

Further, from the micrograph showing the boundary between the polycrystalline ferrite and the single crystal ferrite in the joint portion of the present invention shown in FIG. 3, a part of the polycrystalline ferrite does not have the same crystal plane as the joined single crystal, It was found that the surface behaved similarly to the polycrystalline grain boundary and was strongly bonded.

Example 2 In order to investigate the influence of the bonding aid, a solution of glass powder dissolved in nitric acid, a solution of glass powder dissolved in ammonia solution, a solution containing metal ions such as sodium and potassium were used as the bonding aid. In the same manner as in Example 1 except that the heat treatment was carried out at 800 ° C. for 30 minutes, glass encapsulation of the gap portion and direct joining of the joining surfaces were simultaneously performed to obtain a joined body.

When the bonded body was cut and polished, and the gap portion and the bonded portion were observed with a metallographic microscope as in Example 1, the linearity of the gap portion was maintained and no intermediate layer was observed in the bonded portion. It was found that the faces were strongly bonded and integrated with the behavior similar to that of polycrystalline grain boundaries.

When the relationship between the gap etching depth and the gap length was measured, the etching depth and the gap length were in good agreement as shown in Table 2.

Example 3 To examine the effect of sodium silicate concentration on nitric acid solution, the concentration of sodium silicate on nitric acid solution was measured.
Same as Example 1 except that after 0.1%, 0.2%, 2%, 5%, 10%, 20% of joining aids were rubbed together and tentatively joined, heat treatment was performed at 800 ° C for 30 minutes while applying pressure. Depending on the method, glass encapsulation of the gap part and direct bonding of the bonding surface were simultaneously performed. Then, the etching depth and the gap length were measured for each of the 20 bonded bodies in the same manner as in Example 1, and the average and the fluctuation range were obtained. The results are shown in Table 3.

From the results shown in Table 3, it was found that when the concentration of sodium silicate was 10% or more, the solid content was generated due to hydrolysis, the adhesion at the time of temporary joining was deteriorated, and the gap accuracy was not stable. It can be seen that when the concentration of sodium silicate is in the range of 0.1% to 5%, the generation of solids due to hydrolysis is delayed and temporary bonding can be performed in a solution state, so that the adhesiveness is excellent and the gap length accuracy is stable. The concentration of sodium silicate is
The range of 0.2% to 2% is preferable.

Example 4 In order to investigate the influence of the bonding temperature, a solution having a sodium silicate concentration of 2% with respect to a nitric acid solution was used as a bonding auxiliary agent, and after the temporary bonding, the temperature was lower than the temperature at which the polycrystalline ferrite mass-transferred while being pressed. 400 ℃, 500 ℃, 600 ℃,
Joining was integrated by the same method as in Example 1 except that heat treatment was performed at 700 ° C. and 900 ° C. for 30 minutes each. afterwards,
When a magnetic core was produced by cutting the bonded body, the one heat-treated at 400 ° C. was peeled off the bonded surface during the cutting process and could not be used practically. Other bonded bodies did not peel off in the processing step, and there was no problem in manufacturing the magnetic head. Also, when the mechanical strength of the joint surface was measured, it was 4
The results in the table are obtained, and the bending strength of the polycrystalline ferrite alone is 1
The heat treatment at 600 ° C for 30 minutes was insufficient for 2.3 ± 1.3 kg / mm ² . However, the heat treatment at 700 ℃ or higher gave the same result as the bending strength of ferrite alone.

From the above results, the mechanical strength of the ferrite alone was not improved at 600 ° C. or lower, but there was no problem in head manufacturing. However, the mechanical strength is preferably sufficient by heat-bonding at 700 ° C. or higher, and they are completely integrated.

(Effects of the Invention) As is apparent from the above description, according to the method of manufacturing a magnetic head core of the present invention, direct bonding is performed at a temperature equal to or lower than the temperature at which polycrystalline ferrite mass-transfers by using a bonding material As a result, it is possible to improve the linearity of the magnetic gap and the linearity of the joint surface, and as a result, it is possible to obtain a magnetic head with less variation in magnetic characteristics.

[Brief description of drawings]

1 (a) and 1 (b) are perspective views showing a polycrystalline boat-shaped product and a single-crystal etched product used in the embodiments of the present invention, and FIGS. 2 (a) and 2 (b) are the present invention and a conventional product, respectively. A photograph showing the crystal structure of the gap portion of the magnetic head core of the example, FIG. 3 is a photograph showing the crystal structure of the junction portion of the magnetic head core of the present invention, and FIGS. 4 (a) and 4 (b) are magnetic gaps of the conventional example, respectively. It is a figure which shows a part typically.

Claims (3)

[Claims] 1. A nitric acid containing 5 wt% or less of sodium silicate at a joint boundary surface in a method of manufacturing a magnetic head core in which a monocrystalline ferrite and a polycrystalline ferrite or a polycrystalline ferrite and a polycrystalline ferrite are bonded to each other to form a magnetic gap. By interposing a joining aid consisting of, and performing heat treatment at a temperature of 700 ° C or more and less than 1000 ° C that is less than or equal to the temperature at which the polycrystalline ferrite mass-transfers, the joining boundary surface is integrated without the intermediate layer. A method of manufacturing a magnetic head core, which comprises bonding. 2. The method of manufacturing a magnetic head core according to claim 1, wherein the joining of the joining surfaces and the encapsulation of glass in the magnetic gap are performed simultaneously. 3. The method of manufacturing a magnetic head core according to claim 1, wherein the integral joining is performed under pressure.