JPH0827904B2 - Method for manufacturing core for magnetic head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of manufacturing a magnetic head core for recording / reproducing or erasing used in a VTR, a magnetic disk device, or the like, and in particular, a ferrite called a ferrite core. The present invention relates to a method of manufacturing a core for a magnetic head, which has a high bonding strength at a bonding portion of a ferrite member and is capable of forming a highly accurate magnetic gap width in a core made of a material.

(Prior Art) Conventionally, as a core for a magnetic head, a ferrite core configured by using ferrite as a core material has been known. This ferrite core, as is well known,
Generally, it has a ring shape composed of a pair of ferrite members, and the space at the center thereof is a hole for coil winding. More specifically, as shown in FIG. 1, a pair of generally C-shaped ferrite members 2 and 4, which are core halves, are butted against each other to form a large space 6 between them. It is said to be a hole for winding. An annular magnetic path (magnetic circuit) is formed by the two ferrite members 2 and 4, and a magnetic gap 10 having a predetermined gap: α is provided in a direction crossing the magnetic path. As is well known, predetermined recording and reproduction are performed on a magnetic recording medium such as a magnetic tape 12 or a magnetic disk that can be slid on the outer surfaces of the ferrite members 2 and 4 that sandwich it.

By the way, as described above, the magnetic gap 10 having the predetermined gap: α is provided between one ends of the two ferrite members 2 and 4 of such a ferrite core, but between the other ends. , Is bonded with glass to form an annular magnetic path as a whole and to fix its form.

However, in the conventional ferrite core that is bonded by such glass, the joint strength of the joint portion 14 of the two ferrite members 2 and 4 is low, and during handling such as coil winding performed in the subsequent process. In addition, there is a problem that the joint portion is damaged.

In addition, when heat treatment such as pouring of various kinds of glass is performed in another post-process, the heat treatment causes
The glass of 14 softens, which causes the magnetic gap width (α) to fluctuate, which lowers its accuracy, and uses two or more types of glass with different softening temperatures to prevent this problem. I had to do it.

Furthermore, in the case of joining the two ferrite members using glass, the two ferrite members 2 and 4 are temporarily fixed using a jig as shown in FIG. In the magnetic gap portion 18, the glass 16, 16
It will be poured and joined, but at that time,
If the pressing force applied to the ferrite member becomes non-uniform, there is a problem in that the accuracy of the width of the magnetic gap formed is reduced.

Then, in order to solve the above problems, the applicant of the present application has previously disclosed that, in producing a magnetic head core in JP-A-60-138710, etc., an annular magnetic path has a plurality of ferrites. It is made of members to form a ring,
We have clarified the magnetic head core and its manufacturing method in which the abutting parts of the ferrite members except the magnetic gap forming part are directly joined by a solid-state reaction to be integrated.

In short, such a manufacturing method, when assuming the magnetic gap width, of the two ferrite members forming the annular magnetic path, the gap forming surface of one ferrite member is chemically processed to have a thickness corresponding to the gap width (α). After removing only the amount, while the gap corresponding to the gap width (α) is maintained, the other ferrite member is joined and integrated by solid-phase reaction, and then glass is poured into the gap,
The glass-filled bonded body is subjected to a cutting operation for exposing the magnetic gap to the outside, thereby obtaining the desired ferrite core.

However, according to such a manufacturing method, in order to join and integrate two ferrite members by a solid-phase reaction,
It is said that the temperature rises to about 1100 ° C to 1250 ° C. However, when the temperature is raised to such a temperature, not only the ferrite outer surface but also the gap width (α) is caused by the oxygen partial pressure in the atmosphere around the ferrite member. Even on the surface of the ferrite forming the corresponding gap, volatilization of zinc, which is one component of ferrite, and redox reaction are caused, which causes a variation of the magnetic gap width (α) of ± 0.1 μm or more.

However, with the recent increase in density of magnetic recording media, the recording wavelength has become shorter, and the magnetic gap width of the core has been required to have a narrow gap and high accuracy. For example, 0.4 ± 0 for the magnetic head core for VTR images.
03μm, 0.8 ± 0.08 for cores for FDD and RDD magnetic heads
The magnetic gap width and accuracy of μm are required.

(Problem to be Solved) Here, the present invention has been made in view of such circumstances, and the problem to be solved is to provide a magnetic head in which a ring-shaped core is formed by a plurality of ferrite members. A method for manufacturing a magnetic core for a magnetic head, which has a high bonding strength of a ferrite member, a magnetic gap width with high accuracy, a good quality, and a stable magnetic head core. .

(Solution) According to the present invention, in order to solve such a problem, a ring shape is formed in the presence of a hole for coil winding, an annular magnetic path is formed, and the magnetic path is traversed. In a magnetic head core in which a magnetic gap having a predetermined gap is provided in a predetermined direction, the magnetic path is formed by a plurality of ferrite members to form a ring shape, and the magnetic gap forming portions of the ferrite members are excluded. When directly joining the contact parts by solid-phase reaction in the furnace to form one, the maximum holding temperature is 850 to 1080 ° C, and at a temperature of 850 ° C or higher, the furnace is closed and the atmosphere gas does not flow. While controlling the oxygen concentration in the atmosphere at a temperature of 850 ° C. or higher within the range of 30 to 2000 ppm, the method for manufacturing a core for a magnetic head is characterized in that It is an.

According to such a manufacturing method of the present invention, in the gap portion corresponding to the magnetic gap width, it is possible to effectively control the volatilization and redox reaction of zinc caused by the oxygen concentration around the ferrite, As a result, the accuracy of the magnetic gap width can be significantly improved, and the accuracy within ± 0.1 μm, which was difficult to achieve by the conventional method, can be achieved.

Further, in the present invention, since the same process as the conventional magnetic head core manufacturing method (manufacturing process) can be adopted, the manufacturing process is simple, and further, by such a method,
It has become possible to manufacture a magnetic head core in which there is no foreign phase such as glass at the abutting portions of a plurality of ferrite members to be joined and which has a high joining strength.

By the way, in the present invention, it is necessary to select the maximum holding temperature (maximum reaching temperature) in the range of 850 to 1080 ° C. when sintering the ferrite member by the solid phase reaction. That is, the lower the maximum holding temperature, the more difficult the ferrite surface is to cause the volatilization of zinc and the redox reaction at the gap forming site on the ferrite surface, which is advantageous in improving the accuracy of the magnetic gap width. At temperatures below 850 ° C, the diffusion of substances necessary for solid-state reaction does not take place actively. Also,
When the temperature exceeds 1080 ° C, the volatilization of zinc and the redox reaction become active, so highly accurate reproducibility is required to control the oxygen concentration in the surrounding atmosphere, and the product packing amount, dirt, and other subtlety It becomes necessary to control even the factors, and it becomes difficult to control the oxygen concentration. Furthermore, when a polycrystalline ferrite material is used for the ferrite member, the sintering temperature is low because thermal etching is caused by raising the temperature and irregularities are generated on the surface of the magnetic gap. It is desirable, therefore, that sintering temperatures that are too high should be avoided, generally below 1080 ° C.

Further, since the oxygen concentration in the atmosphere during the solid phase reaction has a great influence on the volatilization of zinc and the reaction rate of the redox reaction, in order to further improve the accuracy of the magnetic gap, the magnetic gap width (α) It is desirable that the redox reaction on the ferrite surface in the gap portion corresponding to is in an equilibrium state. Therefore, in general, the oxygen concentration is appropriately selected depending on the temperature, the composition of ferrite, and the crystal orientation in the case of using a single crystal, but particularly in the present invention, , The maximum holding temperature is 850-1
Magnetic gap accuracy is ±
When it is necessary to keep it within 0.08 μm, the oxygen concentration is 30
It is necessary to be controlled within the range of to 2000 ppm, preferably within the range of 100 to 1000 ppm.

Further, in the present invention, the magnetic gap accuracy is effectively increased, and particularly within ± 0.1 μm which has been conventionally desired,
In order to achieve an accuracy of ± 0.03 μm or less, the temperature at which the ferrite member is being sintered, in other words,
The temperature at which the transfer of substances on the surface of the ferrite member is actively performed, including volatilization of zinc and redox (850 to 1080
(° C), it is necessary to prevent the ambient atmosphere gas from flowing. That is, when the atmosphere gas is flowing in the longitudinal direction (lateral core direction) of the gap portion corresponding to the magnetic gap width, the oxygen concentration is distributed, and as a result, the magnetic gap width is distributed according to the temperature. Is caused. Therefore, at temperatures above 850 ° C, it is necessary to temporarily stop the introduction of atmospheric gas and seal the inside of the furnace.
At least while maintaining the maximum holding temperature in the furnace,
It is more desirable to keep the furnace sealed.

The ferrite member used in the present invention may be a single crystal ferrite material, a polycrystalline ferrite material, or a composite material thereof, but the surface of the single crystal has low activity for sintering. Since it is difficult to integrate single crystals by a solid-phase reaction, in order to integrate two ferrite members by a solid-phase reaction, the contact surface of at least one ferrite member should be polycrystalline. It is preferably composed of ferrite. Further, if a polycrystal is present on the magnetic gap constituting surface, the surface thereof is subjected to thermal etching as the temperature rises, and irregularities are generated on the magnetic gap constituting surface, which leads to a decrease in accuracy of the magnetic gap width. Therefore, it is most preferable that both sides of the magnetic gap constituting surface are made of single crystal. In view of the above points, it is desirable that at least one of the ferrite members to be joined is made of a composite material whose joining surface is polycrystalline and whose magnetic gap forming surface is single crystal.

In addition, such ferrite members to be solid-phase bonded,
It is more preferable that they have the same composition, and more preferably the same production lot. That is, when the ferrite members to be joined are composed of different compositions, the thermal expansion coefficient is different, so that strain is generated when the temperature is lowered after sintering, and the gap portion forming the magnetic gap width is formed. Is deformed, and the equilibrium oxygen concentration at each temperature is different depending on the composition, so that it is difficult to select an appropriate oxygen concentration necessary for improving the accuracy of the magnetic gap width. Further, even if the ferrite members have the same composition, if the ferrite members are fired in different manufacturing lots, the temperature conditions and atmospheric conditions are slightly different. It also affects the concentration, and the coefficient of thermal expansion and the equilibrium oxygen concentration are slightly different. Therefore, it is desirable that the ferrite members to be joined have the same composition and the same production lot.

By the way, when manufacturing a core for a magnetic head according to the present invention as described above, for example, the above-mentioned JP-A-60-1387 is used.
The process as disclosed in Japanese Patent No. 10 is suitably adopted. That is, as schematically shown in FIG. 3, (a) a groove 28 for forming a coil winding hole 34 in one ferrite member 22 of a pair of ferrite members, and Partition groove 26 that partitions the gap forming surface 30
And (b) before or after the groove forming step, the magnetic gap constituting surface 30 of the ferrite member 22 is ground or chemically treated with phosphoric acid or the like. Predetermined depth: Gap processing step of removing the surface by β, (c) Ferrite member 22 subjected to the groove processing step and the gap processing step, with the processed surface in between, Two ferrite members, butted against the ferrite member 24
A joining step of directly joining the abutting portions of 22, 24 by a solid-phase reaction to integrate them, and (d) glass on the magnetic gap 36 forming portion of the solid-phase joined ferrite joined body 32.
A method including a glass melting step of pouring 38 and (e) a slicing step of cutting out the ferrite bonded body 32 having undergone the glass melting step into a predetermined thickness so that the magnetic gap 36 is exposed to the outside is preferably adopted. Thus, the intended ferrite core 40 having the surface 42 on which a magnetic recording medium such as a magnetic tape is slidably contacted is manufactured.

(Examples) Hereinafter, some examples of the present invention will be shown to clarify the present invention more specifically. However, the present invention imposes some restrictions by the description of such examples. It goes without saying that you don't receive anything.

Further, in addition to the specific examples described above in addition to the following examples, the present invention includes various changes, modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that, etc. can be added.

Example 1 First, chemical composition Fe ₂ O _3: 53.8 mol%, ZnO: 16.7 mol%, MnO: consist 29.5 mol% Mn-Zn ferrite polycrystal and single crystal than configured monocrystalline, polycrystalline composite A ferrite member having a structure as shown in FIG. 4 was produced using the two.

That is, in one ferrite member 50 of the single crystal / polycrystal composite material having the above composition, the single crystal portion 50a
Is subjected to chemical etching in a phosphoric acid aqueous solution at 50 ° C. for 60 minutes to remove the ferrite member 50 over a depth of 0.4 μm, while the other ferrite member 52 has a surface facing the ferrite member 50. Groove 56 for coil winding
The groove 54 for pouring the gap glass and the gap glass was provided by machining with a diamond cutter. In FIG. 4, 50b is a polycrystalline portion of the ferrite member 50, and 52a and 52b are ferrite members 52, respectively.
Is a single crystal part and a polycrystal part.

And two ferrite members that have been subjected to these processing
50, 52, in the state where the processed surfaces are butted against each other, (water: 1 part by volume + concentrated nitric acid: 1
(0 parts by volume) After applying an aqueous solution and temporarily fixing it, it was set in an alumina sheath whose inner wall surface was surrounded by polycrystalline ferrite of the same composition, and according to the temperature and atmosphere schedule shown in FIG. Sintered and solid-phase reacted. The maximum holding temperature of the solid-state reaction magnet in the furnace is set at intervals of 50 ° C in the range of 900 ° C to 1250 ° C, and the oxygen concentration is 500 ppm (up to 850 ° C). A gas mixture of O ₂ + N ₂ ) was flowed for 30 minutes to replace the gas, and then the furnace was closed.

With respect to the ferrite bonded body thus obtained,
After pouring glass into the gap of the magnetic gap portion 58, polishing was performed until the magnetic gap portion 58 was exposed to form a ferrite core having a predetermined annular magnetic path.

The magnetic gap width of the ferrite core thus obtained was measured, and the result is shown in FIG.

As is clear from the results of FIG. 6, the lower the maximum holding temperature in the road, the smaller the variation of the magnetic gap width. For example, below 1050 ° C., the variation is within ± 0.04 μm. , ± 0.07μm above 1100 ℃
From the above variations, it was confirmed that the accuracy of the gap width was significantly improved in the magnetic head core obtained according to the present invention.

Example 2 When a ferrite core having the same composition and structure as in Example 1 was used and a ferrite core was manufactured according to the same method, the inside of the furnace was closed when the two ferrite members 50 and 52 were joined by a solid phase reaction. The accuracy of the width of the magnetic gap formed was measured in each of the cases of the above and the case of continuously flowing the atmospheric gas into the furnace.

The maximum holding temperature is 1000 ° C, and the oxygen concentration is
500ppm of at a temperature of 850 ° C. The (O ₂ + N ₂₎ gas mixture 30
It was adjusted by flowing for a minute and gas replacement. After that, while sealing the inside of one furnace, 1.0
The atmosphere gas was kept flowing at a flow rate of / min.

When the width of the magnetic gap portion 58 thus obtained was measured, the magnetic gap width was 0.35 when the inside of the furnace was sealed.
While it was ± 0.03 μm, it was 0.35 ± 0.06 μm when the gas was allowed to flow without sealing.

As is clear from these results, it was confirmed that the variation in the magnetic gap width was reduced to 1/2 when the inside of the furnace was closed, compared to when the gas was circulated.

Example 3 When a ferrite core having the same composition and structure as in Example 1 was used and a ferrite core was manufactured by the same method, the effect of the oxygen concentration during the solid phase reaction on the magnetic gap width was examined.

The maximum holding temperature is 1000 ° C, and the oxygen concentration is 85
A mixed gas of various concentrations was flowed at 0 ° C. for 30 minutes to replace each gas, thereby forming a gas atmosphere of various concentrations. Further, even after the gas replacement, the atmospheric gas of various concentrations was kept flowing at a flow rate of 0.5 / min. The results are shown in FIG.

As is clear from these results, the accuracy of the magnetic gap width is the best when the oxygen concentration is around 200 ppm, and the variation in the magnetic gap width may become large if the oxygen concentration is too high or too low. understood. Further, since the width of the formed magnetic gap is wider than the depth of the groove for defining the gap width, which is removed by etching as the oxygen concentration becomes lower, the zinc from the magnetic gap forming surface of ferrite is It was confirmed that oxidation occurred on the magnetic gap formation surface because the width of the formed magnetic gap became narrower as the oxygen concentration increased and the oxygen concentration increased. Therefore, it was found that it is desirable that the oxygen concentration near the magnetic gap forming surface be the equilibrium oxygen concentration during the solid phase reaction.

(Effects of the Invention) As is clear from the above description, according to the method of manufacturing the magnetic head core according to the present invention, the variation in the width of the magnetic gap can be set to within ± 0.03 μm. The accuracy is further improved, and since the ferrite members are directly joined and solidified by the solid-phase reaction, the strength of such joined parts is also improved, and the manufacturing process is simple. It has become possible to manufacture a magnetic head core with high cost at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of a normal magnetic head,
FIG. 2 is an explanatory view of one step in manufacturing a conventional magnetic head core, and FIG. 3 is an explanatory view for outlining the manufacturing example of the magnetic head core step by step. FIG. 4 is an explanatory view showing a combination form of ferrite materials adopted in Examples, FIG. 5 is a graph of temperature and atmosphere schedule in Example 1, and FIG. 6 is a graph in Example 1. FIG. 7 is a graph showing the effect of the maximum holding temperature on the accuracy of the magnetic gap width, and FIG. 7 is a graph showing the effect of oxygen concentration on the accuracy of the magnetic gap width. 2,4,22,24,50,52: Ferrite member 10,18,36,58: Magnetic gap 14: Joined part, 16,38: Glass 26: Partition groove, 32: Joined body 34: Hole, 40: Ferrite core

Claims (1)

[Claims] 1. A magnetic head, which has a ring shape in the presence of a hole for a coil winding, forms an annular magnetic path, and is provided with a magnetic gap having a predetermined gap in a direction traversing the magnetic path. In the core, such a magnetic path is composed of a plurality of ferrite members to form a ring shape, and the abutting portions of the ferrite members excluding the magnetic gap forming portion are directly joined in a furnace by a solid phase reaction. The maximum holding temperature is 850 to 1080 ° C, and when the temperature is 850 ° C or higher, the furnace is closed and the atmosphere gas does not flow while the oxygen concentration in the atmosphere is 850 ° C or higher. Is controlled within the range of 30 to 2000 ppm to be sintered, and a method of manufacturing a core for a magnetic head, comprising: