JPS6226086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic head, and an object of the present invention is to prevent warpage of a core constituting a magnetic head and gap deviation caused by this.

In order to record high frequency signals such as video signals on high coercive force tapes such as metal tapes, conventional magnetic heads using ferrite materials cannot obtain the required saturation magnetic flux density. Therefore, the use of magnetic metal materials such as Sendust, which has a high saturation magnetic flux density, is being reconsidered. By the way, since this Sendust material is an alloy material, its specific resistance is extremely low at about 80 to 150 μΩ-cm. Therefore, eddy current loss becomes large in the video frequency region, and as a result, the magnetic permeability is on the order of tens to hundreds (compared to conventional ferrite). For wood, it decreases to over 500).
In order to keep this eddy current loss low, the core thickness needs to be very thin, for example around 20μ. It was confirmed that a magnetic permeability of 500 or more, which is the most important characteristic factor of a magnetic head, can be achieved with a thickness of this order. Therefore, in order to mass-produce the desired cores, as shown in Fig. 1, a pair of Sendust core block halves 1 and 2 are joined with a spacer 3 in the area corresponding to the front gear, and silver solder 4 and 5 in the area corresponding to the rear gear. If the core chip is then sliced as shown in the dashed line and further thickened to the desired core thickness, the completed core chip will become the second core chip.
As shown in the figure, the head was warped and the front gap was misaligned, making it impossible to obtain a magnetic head with a good yield. This can be avoided as shown in FIG. 4 even if reinforcement parts 7 and 8 are provided with silver solder at the tip of the front gear and the rear end of the winding hole 6, which will be removed in the future, as shown in FIG. Nakatsuta. According to experiments conducted by the present inventors, when the thickness after thickness processing is reduced to 60 microns or less, the core chip bonded to the jig for processing can be removed chemically using a release agent. When it was removed and looked at, it was found that the above-mentioned warping phenomenon was observed.

The present invention aims to provide a method for manufacturing a magnetic head that prevents this warping and gap deviation caused by it, and will be explained below based on examples.

A pair of Sendust core halves are butted against each other with a spacer corresponding to a predetermined gap length sandwiched between their front gap opposing parts, and both core halves are joined and integrated with silver solder therebetween. The technology for this integration is generally considered to be difficult, but by utilizing the invention related to the applicant's earlier application (see the attached specification of patent application (1) dated April 6, 1972). It is possible. Next, this integrated block is sliced as shown by the broken line in Figure 3 to approximately
A core chip 10 (FIG. 5A) with a thickness of 200 μm is obtained.
In order to primary polish one surface 10a of this core chip 10, it is bonded to a jig 11 formed of a quartz plate with an organic adhesive 12 (for example, Aron Alpha, trademark) (FIG. 5B). For this primary polishing, the core thickness is
This is done so that the thickness is 100μ. Thereafter, the adhesive 12 is chemically removed using a release agent, and the primary polished surface is attached to the jig 11 using an adhesive (Aron Alpha) 13.
(Figure 5 C). Thereafter, the other surface 10b of this core chip 10 is secondarily polished so that the core thickness becomes approximately 20 μm (see the broken line in FIG. 5C).

Next, while the core chips that have been primarily and secondarily polished in this way are still bonded to the jig 11 with the adhesive 13, they are pressed by a pressing plate 14 also made of quartz material (for example, 10 core chips of this type are placed in parallel). (Place about 20 grams of pressure plate on the items lined up)
Then, in this state, it is heated in a hydrogen atmosphere or in a vacuum in a furnace 16 having a heater 15 as shown in FIG. 6 at a temperature in the range of 500 DEG C. to 750 DEG C. for about 10 to 15 minutes. The temperature and heating time are selected mainly from the viewpoint of removing processing strain from the core and preventing diffusion of the silver solder used to join the core halves. Through this heating, processing distortion of the core chip is removed and the decomposition temperature is increased to 150~150℃.
The adhesive layer 13, which is at 200°C, is decomposed. Thereafter, the core chip sandwiched between the jig and the pressing plate is taken out of the furnace. The core chip has no processing distortion and is not warped.

In order to actually configure such a core chip as a magnetic head for a VTR, as shown in FIG.
Each surface of this core chip has a bridging piece 17 made of non-magnetic glass at the part facing the gap, and has a winding hole 18.
The ferrite cores 19, 19 are bonded together to improve mechanical properties and magnetic properties. The magnetic head is completed by winding the core shown in FIG. 7 and polishing its tape contact surface to obtain a predetermined gap depth.

As mentioned above, in conventional manufacturing methods, when sendust material is used as a magnetic head that handles high-frequency signals such as video signals, warping of the core and deviation of the gap caused by it are unavoidable in order to achieve a specified thickness. However, the present invention uses a new method of removing the adhesive layer between the jig and the core chip by thermal decomposition, which eliminates the core thickness limit (60 microns or more in the conventional example) that does not cause the core to warp. It has now become possible to manufacture a magnetic head made of sendust material suitable for the above-mentioned uses.
Further, this thermal decomposition step can also be used as an annealing step for removing processing strain.

[Brief explanation of the drawing]

Figures 1 and 3 are perspective views of core blocks, Figures 2 and 4 are perspective views of each core chip formed from each block by the conventional method, and Figures 5 A, B, and C are process diagrams of the present invention. , FIG. 6 is a block diagram of an electric furnace, and FIG. 7 is a perspective view of a magnetic head core according to the present invention. 10... core chip, 11... jig, 14...
Pressure plate.

Claims (1)

[Claims] 1. A step of primary polishing one surface of a core chip formed by joining a pair of sendust core halves, a step of bonding the primary polished surface of the core chip to a jig, and a step of bonding the core chip fixed to the jig. A step of secondary polishing the surface so that the total thickness of the core chip after processing becomes a predetermined thickness of 60 microns or less, and a step of decomposing the adhesive layer to the jig by heating the core chip under pressure. A method of manufacturing a magnetic head comprising: 2. The first polishing is completed when the total thickness of the core chip is 60 microns or more.
A method for manufacturing a magnetic head as described in Section 1. 3. The method for manufacturing a magnetic head according to claim 1 or 2, wherein the jig is a quartz plate. 4. The method for manufacturing a magnetic head according to claim 3, wherein the temperature condition is 500° C. or higher, which has an annealing effect on the sendust material.