JPS6346482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic head using a ferromagnetic oxide as a magnetic core, and in particular, it relates to a method for manufacturing a magnetic head with a magnetic core made of ferromagnetic oxide. The object of the present invention is to provide a method for manufacturing a high performance narrow track magnetic head.

Conventionally, in the manufacturing method of a magnetic head using a ferromagnetic oxide as a magnetic core, a material is cut and ground to form a rectangular parallelepiped block, and then a track of a predetermined width is formed in a direction perpendicular to the longitudinal direction of the rectangular parallelepiped block. After that, the notched grooves are filled with a non-magnetic filler such as glass, and the gap-forming surfaces are ground and ground, and then the notched grooves are faced with a spacer made of a non-magnetic material of a predetermined thickness interposed therebetween. A common method is to form a gapped bar by butting it against a core block and fixing it with glass or the like. In the above series of steps, the grooves forming the track portions are generally processed by grinding. However, recent improvements in recording density have been remarkable, and the track width required for magnetic heads has become smaller year by year.Currently, track widths of about 30 μm are in practical use, and in the future, track widths of about 30 μm are in practical use. is required.
In general, hard and brittle materials such as ferrite have mechanical brittle properties, and when subjected to processing such as grinding and cutting, they form a fairly deep crack layer and a process-altered layer on their surface layer, which impairs their magnetic properties. Significantly deteriorates. Figure 1 shows the frequency characteristics of magnetic permeability when Mn-Zn ferrite is cut into a ring shape.
Compared to the case of cutting at m, there is a large deterioration in almost the entire range below 10 MHz. It is easy to see that when the thickness of the ring becomes 50 μm or less, the magnetic permeability deteriorates further. As the thickness becomes thinner, the stress applied to the ferrite increases, the cracks increase, and the effect of the processed layer on the surface increases. Furthermore, in order to generally improve wear resistance, the above-mentioned notch grooves are usually filled with glass, etc., but the presence of cracks and the presence of a damaged layer as described above promotes penetration and erosion by molten glass. Furthermore, it deteriorates the magnetic properties of the ferrite core. Further, when the thickness is large, strain removal effects such as etching after groove processing are effective for restoring magnetic properties, but when the thickness becomes thin, erosion due to cracks cannot be ignored and is no longer an effective means. When attempting to manufacture a magnetic head with such a very narrow track, it is difficult to manufacture a magnetic head with good performance using the current combination of ferrite and grindstone.

The present invention is intended to eliminate the above-mentioned drawbacks, and is characterized by recrystallizing the track component to eliminate microcracks and process-affected layers in the track component.

As mentioned above, in FIG. 1, the magnetic permeability of Mn--Zn ferrite deteriorates as the thickness of the core becomes thinner, for example, during cutting, and the range of deterioration further expands to the high frequency range. According to the inventor's experiments,
The magnetic permeability of a 50 μm thick cutting ring is about 1/4 of that of a 200 μm thick cutting ring in the low range, and is considerably degraded even in the video frequency band. However, when both are subjected to heat treatment at 1100° C. in 1% oxygen for 1 hour, as shown in the figure, both recover to almost the bulk magnetic permeability state. For reference, when a similar ring is subjected to chemical etching or thermal annealing at about 700°C, some recovery can be seen, but neither of these recovers the magnetic permeability to the bulk state, and the thinner the ring, the less the degree of recovery. As described above, recrystallization heat treatment is an extremely effective method for eliminating microcracks and process-altered layers generated in ferrite due to processing and returning the ferrite to an almost perfect bulk state.

An embodiment of the present invention will be described below with reference to the drawings. First, a ferromagnetic oxide material is cut and ground to form a rectangular parallelepiped block 1 (Fig. 2a), and then a track portion of a predetermined width is formed in a direction perpendicular to the longitudinal direction of the rectangular parallelepiped block. Notch grooves 2 at intervals are formed by a means such as a dicing saw or a wire saw (FIG. 2b). After that, heat treatment is performed in the range of 900 to 1300°C in an inert atmosphere or an oxidizing atmosphere in which the oxygen partial pressure concentration of the ferromagnetic oxide core and the furnace atmosphere are approximately in equilibrium (second stage).
Figure c). In addition, in Fig. 2c, 3 is a furnace;
4 is a furnace tube, and 5 is a processing boat. The recrystallization rate depends on the processing temperature, and the higher the temperature, the more sufficient recrystallization can be achieved in a shorter time, but the same effect can be obtained even at a lower temperature of about 900°C by extending the processing time. However, if the temperature is below 900℃, the core shape will change to a large convex shape as the processing time increases, and if the temperature exceeds 1300℃, it will change to a large concave shape, causing problems in subsequent processing steps. Also, accuracy is lost when aiming at narrow tracks. Therefore, the core shape is stable at the heat treatment temperature.
A temperature range of 900°C to 1300°C is desirable. The oxygen partial pressure concentration is also important; if the oxygen partial pressure concentration in the furnace atmosphere deviates significantly from the equilibrium state with the oxygen concentration in the core block, the core block will be oxidized or reduced, and the magnetic properties will deteriorate. It becomes like this. For example, if the track portion is held at 1100° C. for 1 hour at an oxygen partial pressure of 1%, the track portion is almost completely recrystallized into a bulk state. In addition, in the case of 1300℃, the oxygen partial pressure is 1~
When the temperature is 20% and 900°C, an atmosphere suitable for recrystallization is in the range of 0.001 to 0.1%, but when the temperature is about 900°C, almost the same effect can be obtained even in an inert atmosphere. In this way, the optimal oxygen partial pressure concentration changes depending on the temperature. That is, the heat treatment is performed in a state where the oxygen partial pressure concentration in the core block and the oxygen partial pressure concentration in the atmosphere in the furnace are approximately equal. Thereafter, the notch groove 2 is filled with a non-magnetic filler 6 such as glass, and the gap forming surface 7 is ground and polished (FIG. 2d) to form a winding groove, and then a non-magnetic gear spacer 8 of a predetermined thickness is formed. The gapped bar is formed by contacting the opposed block 1' through the gap and heating and bonding it (FIG. 2e). After that, it is cut at a predetermined track position and core thickness, and a wire is wound to complete one head.

As described above, according to the present invention, the magnetic properties of the narrow track portion where the magnetic properties have deteriorated due to the influence of processing can be restored to almost the properties of the bulk state, and microcracks and processing-altered parts can also be eliminated from the crystallographic perspective. For example, penetration into the core by glass filling,
A narrow track head with low erosion, high performance and high accuracy is obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the frequency characteristics of magnetic permeability of Mn--Zn ferrite, and FIG. 2 is a diagram showing the manufacturing process of a magnetic head according to an embodiment of the present invention. 1... Rectangular parallelepiped block, 2... Notch groove, 7...
...Gap forming surface, 8...Spacer.

Claims (1)

[Claims] 1. After forming notch grooves at regular intervals to form tracks in a direction perpendicular to the longitudinal direction of the rectangular parallelepiped block made of ferromagnetic oxide, the notch grooves are placed in an inert atmosphere or with a ferromagnetic oxide core. Heat treatment is performed at 900 to 1300°C in an oxidizing atmosphere in which the oxygen partial pressure concentration in the furnace atmosphere is in a substantially equilibrium state to recrystallize the track portion formed by the notch groove, and then the block is re-crystallized. 1. A method of manufacturing a magnetic head, which comprises polishing a gap forming surface and joining the head to an opposing block through a non-magnetic gear spacer of a predetermined thickness.