JPH0152809B2 - - Google Patents

Description

Detailed Description of the Invention Field of Application This invention relates to a method of manufacturing a magnetic head used in a narrow track width and high frequency range, such as an image head for a videotape recorder, and is concerned with the bonding strength of ferrite cores and gap length dimensional accuracy. The present invention relates to a method for manufacturing a magnetic head core, which improves the performance of magnetic head cores, and which uses two types of conventional high- and low-melting-point glasses and performs a single glass bonding process.

Prior Art Today's VTR picture heads have a track width of 20 mm.
It not only has a narrow track width of ~30 μm, but also has a gap length of 0.3 μm, making it even narrower and desirable for use in higher frequency ranges.

Therefore, manufacturing such a magnetic head requires precise machining, especially machining without surface distortion, and is manufactured through complicated processes.

To explain the general manufacturing method of this VTR image head, a pair of flat plates are cut out of a magnetic material such as Mn-Zn single-crystal ferrite, and a U-shaped groove is bored in one direction on a predetermined surface of the flat plate. Butt them together to form a part corresponding to the track width, cut out a suitable block from the flat plate, cut out winding grooves and welding horizontal grooves on one block to make a U-shaped block, and reinforce the U-shaped grooves of both blocks. After the gap forming surfaces to be butted are mirror-polished, a non-magnetic spacer is attached to form the specified gap, and both blocks are butted together by applying pressure through the spacer, and the above-mentioned reinforcement is applied. A magnetic head core was manufactured by placing bonded glass, which has a lower melting temperature than glass, into the winding groove and welding lateral groove and welding it by heating.

Problems with the conventional technology The problems with this conventional manufacturing method are:
There are two problems: as mentioned above, the glass bonding process is required twice, and it is difficult to process the gap forming surface without surface distortion.

In other words, the glass bonding process is required twice, which makes the process complicated.
It is necessary to use different low-melting point glasses, and the accompanying heat treatment process is prolonged, exposing the gap-forming surface to thermal erosion of the glass.

In addition, the above-mentioned gap forming surface for forming the head gap, which affects the performance of the magnetic head, is
Since it is ideal to have no surface distortion, in addition to regular mirror polishing, electrolytic polishing and chemical etching are used to reduce surface distortion and improve characteristics in the high frequency range.

On the other hand, the application of mechanochemical polishing has also been proposed; however, in a small piece of ferrite core such as an image head for a VTR, mechanochemical polishing is applied to the surface on which track forming grooves, winding grooves, and glass welding grooves have been processed. It is difficult.

In other words, from the relative dimension of the gap length, the edge portion of the machined groove is fractured due to the influence of strong mechanical processing, so pitting occurs during mechanochemical polishing and distortion-free processing cannot be achieved. is difficult.

Similarly, since it is a composite surface of ferrite and glass, it is possible to mechanochemically polish a composite surface made by filling the track width groove with reinforcing glass and solidifying it. Because it is a composite surface of ferrite and glass, both materials can be polished evenly and with no distortion using ultra-precise polishing. It would be extremely difficult to do so.

As described above, in the conventional manufacturing method, it is not easy to improve the high frequency characteristics of such a magnetic head, and moreover, the manufacturing process has to be complicated.

Therefore, the present invention has developed a magnetic head with a narrow track width, which can obtain the required high frequency characteristics, improve the bonding strength of the ferrite core and the gap length dimensional accuracy, and which is a simple method that requires only one glass welding process. The purpose is a manufacturing method.

Summary of the Invention This invention involves mechanically polishing the gap-forming (100) faces of a pair of single-crystal Mn-Zn ferrite cores constituting a magnetic circuit, and then applying a suspension of SiO ₂ fine powder with a particle size of 70 to 200 Å in pure water. Adjust to the acidic region, polish to a strain-free finish, coat each polished gap forming surface with a non-magnetic film that forms the gap, and then process vertical grooves that form the track width of the head. The tip of the vertical groove is configured to communicate with the transverse groove for winding provided on one side of the core, and a rear groove for glass welding is formed.These pair of cores are placed facing each other so that their track widths match, and are assembled for welding. The gist is to insert a glass rod that can be welded at approximately the same temperature as the gap forming film into the rear groove and the winding lateral groove with the rear groove facing upward, and to heat and press the pair of cores together.

In addition, in the Mn-Zn single crystal ferrite used for the ferrite core of the magnetic head, when various crystal planes are subjected to strain-free polishing,
No difference was found among the crystal planes in terms of surface roughness, which is important for shape accuracy.

(1) Regarding residual machining strain, the (100) crystal plane has the least amount of strain, and (2) the results of measuring residual strain by chemical etching show that the (100) plane has less after etching.
There was no deterioration in surface roughness such as scratches, and (3) significant differences were found in the polishing speed of the strain-free polish, with the (100) surface being the fastest.

As mentioned above, regarding (1) and (2) remaining residual strain, when forming a gap in the magnetic head, it causes the greatest deterioration of magnetic properties apart from shape accuracy, and regarding (3), it causes the greatest deterioration of magnetic properties. important in terms of

In this invention, a gap forming surface of a pair of single crystal Mn-Zn ferrite cores has a crystal plane (100).
The reason for using the surface is the above reason.

Effects of the Invention By the production method according to the present invention, single crystal Mn
- Magnetic head core chips made of Zn ferrite are manufactured by mechanochemically polishing the (100) plane of the gap forming surface under specific conditions without strain, and after applying a gap forming film, the vertical grooves and other grooves that make up the track width are formed. Because of the machining, chipping is less likely to occur in the track portion, and the characteristics of the magnetic head are improved due to the strain-free machining.

Moreover, not only is glass welding completed in one step, but the non-magnetic material used for the gap forming film, the glass for reinforcing the track width portion, and the glass for core welding have almost the same melting temperature, so the heat treatment process Thermal corrosion of the gap forming surface due to this phenomenon is reduced, and the characteristics of the magnetic head are improved.

Furthermore, since a strong welding force can be obtained in any part by one glass welding, a magnetic head with high strength can be manufactured.

Disclosure of the Invention Based on Drawings FIGS. 1 to 4 are explanatory diagrams of a ferrite core showing the steps of the manufacturing method according to the present invention. The present invention will be explained in detail below based on the drawings.

First, as shown in FIG. 1, a block of single-crystal Mn--Zn ferrite material is cut to a predetermined size to prepare a pair of cores 1 and 1a constituting a magnetic head.

The cores 1 and 1a are opposed to each other, and the gap forming surfaces (100) forming the gap are mechanically polished using diamond powder, and then polished using mechanochemical polishing under specific conditions to remove processing distortion.

Next, gap forming films 2, 2a made of a non-magnetic material having a thickness equivalent to 1/2 of a predetermined gap length are applied to each gap forming surface of the (100) plane of this polished single crystal Mn-Zn ferrite. is deposited by vapor deposition or sputtering.

Furthermore, as shown in FIG. 2, vertical grooves 3 for regulating the track width are formed at predetermined intervals on the surfaces of the cores 1, 1a on which the gap forming films 2, 2a are applied. A horizontal groove 4 having a U-shaped cross section, accommodating the winding wire, and also used for glass welding, is formed so that the tip of the vertical groove 3 communicates with one of the cores 1a.

A rear groove 5 is formed on the surface of the core 1a opposite to the longitudinal groove 3 to become a welding groove when the core 1 abuts against the core 1a.

As shown in FIG. 3A, each of the cores 1 and 1a which have been coated with the gap forming films 2 and 2a and subjected to groove processing is butted against each other, and the track width is further adjusted. The regulating vertical grooves 3 are combined so as to match each other, and pressure is applied from both sides.

Then, glass rods 6 and 7 for welding having almost the same melting temperature as the gap forming films 2 and 2a are used.
It is inserted into the rear groove 5 and the lateral groove 4 with the rear groove 5 side facing upward, and heated to a predetermined temperature and held while both cores 1 and 1a are pressurized toward the joining center.

At this time, the glass rod 7 inserted into the transverse groove 3 is melted and flows into the communicating pair groove 3, forming reinforcing glass for the track portion.

In this way, after welding is completed, it is cooled,
As shown in Figure 3b, the block is sliced along the dashed line, that is, at the center of the vertical groove 3, and both sides are lapped.

Then, as shown in FIG. 4, a ferrite core chip 8 for a magnetic head is obtained.

Through the above-mentioned one-time glass bonding, the reinforcing glass 7' on the track surface and the reinforcing glass 7' on the lateral groove are shared, and the welding glass 6' on the back side is also welded at the same time, thereby preventing performance deterioration due to thermal corrosion. A ferrite core chip 8 with a small quantity and excellent dimensional accuracy can be obtained.

Moreover, the gap-forming surface is mechanically polished and subjected to strain-free mechanochemical polishing in an acidic suspension containing SiO ₂ fine powder of a specific particle size, and then a gap-forming film is applied. In addition, since the grooves are processed after that, there is less chipping in the track part, and the distortion-free process described above is also applied.
The characteristics of the resulting magnetic head are greatly improved.

Examples Examples according to the present invention will be shown below to clarify its effects.

Two 10 x 5 x 1.6 mm blocks of Mn-Zn single crystal ferrite are used as the ferrite core, and the crystal plane (100) is used as the gap forming surface, mechanically polished with diamond 1/2 μm abrasive grains, and further grain diameter
Mechanochemical polishing was performed in an acidic region using 70-200 Å SiO ₂ powder to remove processing distortion caused by the previous mechanical polishing.

Thickness is applied to each gap forming surface obtained in this way.
A 0.15 μm glass layer was deposited by sputtering to form a gap-forming film.

After applying the gap forming film, the vertical grooves are made with a groove width.
A groove of 200 μm and a groove depth of 400 μm was left uncut, and a groove was processed to have a width of 20 μm, that is, a track width of 20 μm, and a horizontal groove and a rear groove were further processed.

Next, the ferrite core was assembled in a predetermined position with the gap forming films facing each other, and heat and pressure bonding was performed under heating conditions of 750° C. for 1.5 hours.

At this time, a lead glass rod with a diameter of 0.5 mm was used as the glass for welding.

Further, after welding was completed, it was cooled, sliced, and lapped to produce a 0.2 mmt ferrite core chip.

As a result, the ferrite core chip for VTR image heads produced by the method of the present invention has gap dimensional accuracy within a range of ±5% with respect to a predetermined 0.3 μm.
The track width is within the specified range, the gap forming surface is completely welded, and the welding strength due to the reinforced glass is also high.

In addition, in this invention, distortion-free mechanochemical polishing could be completely performed, so compared to the case where a mirror finish was achieved by conventional mechanical polishing alone and assembled into a magnetic head by the conventional method, the magnetic head according to this invention In the case of a head, the output difference is
The playback output increased significantly, with +3dB at 5MHz and 6dB at 8MHz.

[Brief explanation of drawings]

1 to 4 are explanatory diagrams of a ferrite core showing the steps of the manufacturing method according to the present invention. 1, 1a... Core, 2, 2a... Gap forming film, 3... Vertical groove, 4... Horizontal groove, 5... Rear groove,
6, 7...Glass rod for welding, 6'...Welding glass,
7'... Reinforced glass, 8... Core chip.

Claims (1)

[Claims] 1 After mechanically polishing the gap-forming (100) surface of a pair of single-crystal Mn-Zn ferrite cores that constitute a magnetic circuit, a suspension of SiO ₂ fine powder with a particle size of 70 to 200 Å in pure water was adjusted to an acidic region. After applying distortion-free polishing and coating each polished gap forming surface with a non-magnetic film forming the gap, vertical grooves forming the track width of the magnetic head are formed on one side of the core for winding. The tip of the vertical groove is configured to communicate with the horizontal groove, and a rear groove for glass welding is formed.
These pair of cores are assembled facing each other so that the track widths match, and a glass rod that can be welded at approximately the same temperature as the gap forming film is inserted into the rear groove and the winding lateral groove with the rear groove for welding facing upward. A method for manufacturing a magnetic head core, characterized by heat-pressing a pair of cores.