JPH0845018A - Magnetic head and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a magnetic head that suppresses Barkhausen noise and obtains excellent recording and reproducing characteristics. A thermal expansion coefficient α at a glass transition temperature of primary fused glasses 13 and 14 used for forming magnetic gaps 8 and 11 of a magnetic head having a recording / reproducing magnetic core 1 and an erasing magnetic core 9 made of ferrite. The difference between the thermal expansion coefficient α _F of _G1 and the ferrite used in the recording / reproducing magnetic core 1 and the erasing magnetic core 9 at the glass transition temperature is −4.0.
The coefficient of thermal expansion α _{G2 at} the glass transition temperature of the secondary fused glass 15 to be molded in the notch groove after the track processing is set to a range of × 10 to ⁷ ≦ α _G1 −α _F ≦ 0, and the ferrite The difference in the coefficient of thermal expansion α _{F at} the glass transition temperature
By setting the range of 7.0 × 10 to ⁷ ≦ α _G2 −α _F ≦ 0, noise generation is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head, and more particularly to a magnetic head for a floppy disk device and a method for manufacturing the same.

[0002]

2. Description of the Related Art An example of a conventional magnetic head for a floppy disk device will be described with reference to FIGS. FIG.
In FIG. 1, reference numeral 1 is a recording / reproducing magnetic core, 2 is an erasing magnetic core, which are integrally joined to form a magnetic core chip 3, and the magnetic core chip 3 is sandwiched between ceramic sliders 4 and 5. 9 is an enlarged plan view of the magnetic core chip 3 of FIG. 8 in the vicinity of the track, and FIG.
3 is a side view of the magnetic core chip 3 of FIG. Here, the structure of the magnetic core chip 3 will be described in more detail. In FIGS. 9 and 10, 6 is a recording / reproducing core (hereinafter, referred to as R / W core),
7 is an R / W center core, 8 is an R / W gap provided on the R / W core 6, 9 is an erase core, 10 is an erase center core,
11 is an erase gap provided in the erase core 9, and 12 is R / W
It is a non-magnetic spacer that magnetically separates the core 6 and the erase core 9. The structure of the magnetic head is as described above. Next, a method of manufacturing the magnetic head will be described. First, the R / W core 6 and the R / W center core 7, and the erasing core 9 and the erasing center core 10 are fused with glass 13 and 14 as shown in FIG. 10 to perform gap joining (primary fusion). Then R / W
Track processing is applied to the core 6 and the erasing core 9, and the glass 15 is fused to the notch groove portion thereof and molded (secondary fusion).
I do. After that, the R / W core 6 and the erasing core 9 are bonded together with an adhesive via a non-magnetic spacer 12 to obtain a magnetic core chip 3, and the magnetic cores 1 and 2 have coils 16 respectively.
After mounting, the back core 17 is joined to complete the process. Here, it is a condition that the primary fusion glasses 13 and 14 do not melt in the secondary fusion, and therefore it is necessary that they have a glass transition point higher than the melting point temperature at the time of the secondary fusion. Become. Generally, as the glass 15 used for the secondary fusion, one having a fusion temperature of 500 ° C. or higher is used in order to ensure the minimum reliability (moisture resistance, hardness, etc.). Therefore, the primary fused glass is required to have a glass transition point of 500 ° C. or higher, but normally, a fused glass having a high melting point of 700 ° C. or higher is used. . Since this fused glass having a high melting point is chemically stable, it has the advantages that it can be washed with an organic solvent and that a strong bond can be obtained.

[0003]

However, when such a conventional magnetic head is used in, for example, a floppy disk device in which recording / reproducing is repeatedly performed for each sector, pulse characteristics are generated during repeated recording / reproducing. Barkhausen noise (hereinafter referred to as B-noise), which is noise, is generated. It is considered that this is due to leakage flux from the motor during reproduction and thermal expansion of the magnetic core and the fused glass. Further, in particular, in a small-sized floppy disk device, the distance from the motor to the magnetic head becomes short, so that the magnetic head is strongly affected by the B-noise, and thus the B-noise is reduced in such a magnetic head. Is strongly desired.

Therefore, conventionally, in order to suppress B-noise, a method of setting the difference between the coefficient of thermal expansion of the fused glass and the coefficient of thermal expansion of the magnetic core to 10 × 10 to ⁷ or less (for example, Japanese Unexamined Patent Application Publication No. Hei 5 (1999) -58)
-109014), the magnetic core chip is
A method of annealing at 00 ° C. or higher for 2 hours or longer (see, for example, Japanese Patent Laid-Open No. 5-109019) is used. However, B-noise cannot be sufficiently suppressed by such a method.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a magnetic head capable of suppressing B-noise and obtaining good recording and reproducing characteristics, and a method of manufacturing the same. .

[0006]

In order to achieve the above object, the present invention is a magnetic head comprising a recording / reproducing magnetic core made of ferrite and an erasing magnetic core, wherein primary fusion bonding is performed to form a magnetic gap. Glass is used, and the thermal expansion coefficient α _G of the first-order fused glass at the glass transition temperature is set to be equal to or less than the thermal expansion coefficient α _F of the magnetic core, and the difference in thermal expansion coefficient α _G −
α _F is set within the range of −4.0 × 10 ^{7 to} 0.

[0007]

The B-noise is molded into the primary fused glass used for forming the magnetic gap in the magnetic head and the notch groove formed by the track processing.
It has been found that there is a relationship with the thermal expansion coefficient of the next fused glass, and the present inventors have made the thermal expansion coefficient of the fused glass as close as possible to the thermal expansion coefficient of the ferrite that is the constituent material of the magnetic core. It was speculated that the residual stress exerted on the ferrite by the fused glass would be reduced by setting the value to. The result of the experiment also supports this, and therefore, it was possible to reduce the B-noise by bringing the thermal expansion coefficient of the fused glass close to the thermal expansion coefficient of ferrite which is a constituent material of the magnetic core.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic head and a method of manufacturing the same according to the present invention will be described below with reference to the drawings.

In the drawings, the same parts as those of the conventional device are designated by the same reference numerals. 1 is a perspective view showing a magnetic head for a floppy disk, which is an embodiment of the magnetic head of the present invention, FIG. 2 is an enlarged view of a track portion of FIG. 1, and FIG. 3 is an enlarged side view of a magnetic core chip. The structure of the magnetic head in this embodiment is shown in FIGS.
This is the same as the conventional one shown in FIG. 10, and as shown in FIG. 1, the magnetic core chip 3 in which the recording / reproducing magnetic core 1 and the erasing magnetic core 2 are integrally joined and the contact with the floppy disk are It is composed of a pair of ceramic sliders 4 and 5 for securing. The structure of the magnetic core chip 3 will be described in more detail. The main parts of the magnetic core chip 3 are the R / W core 6, the R / W center core 7, the R / W gap 8 and the erase core 9, as shown in FIGS. The erase center core 10, the erase gap 11 and the non-magnetic spacer 12 for magnetically separating the R / W core 6 and the erase core 9 are provided.

Next, a method of manufacturing this magnetic head will be described with reference to FIGS. First, for the recording / reproducing magnetic core 1, one side surface of a rectangular core block (not shown) made of Mn-Zn ferrite or the like is polished, and then the coil winding for the R / W core 6 is formed on the surface. Form a groove. Next, one surface of a core block (not shown) that was previously manufactured for the R / W center core 7 and
The main surfaces of the blocks of the R / W core 6 are butted against each other, and R
/ W gap 8 is formed. When the R / W core 6 and the R / W center core 7 are butted against each other, a gap film of SiO ₂ or the like, for example, 0.4 μm is provided on these butted surfaces.
After forming approximately, the primary fusion-bonding glass 13 is inserted into the winding groove, and joined and integrated (gap joining). The working temperature for this primary fusion is heat treatment at a temperature of 700 ° C to 800 ° C. If the working temperature at this time is 700 ° C. or less, the R / W gap 8 becomes loose during the heat treatment of the secondary fusion, and the reliability (moisture resistance,
It becomes difficult to use a secondary fusion-bonded glass that can secure hardness, etc.). Further, when the temperature exceeds 800 ° C., there arises a problem that cracks occur in ferrite, which is a constituent material of the magnetic core, or characteristics are deteriorated. On the other hand, as in the case of the recording / reproducing magnetic core 1, the erasing magnetic core 2 is first ground on one side surface of a rectangular core block made of Mn-Zn ferrite or the like, and then the erasing core 9 is formed on the surface. Forming a coil winding groove. Next, for the erase center core 10, an erase gap 11 is formed by abutting one surface of a previously manufactured core block and the main surface of the erase core block. When the erasing core 9 and the R / W center core 7 are butted, a gap film of SiO ₂ or the like is formed on their abutting surfaces, for example, about 2.5 μm, and the primary fused glass 14 is inserted in the winding groove. Then, the joining is integrated (gap joining). The working temperature at this time is the same as that of the recording / reproducing magnetic core 1,
Heat treatment at a temperature of 700 ℃ -800 ℃. Then, the gap-bonded R / W core 6 and erasing core 9 are subjected to track processing so as to have a predetermined track width, and the notch groove portion is filled with the secondary fusion-bonding glass 15 for molding. The working temperature at this time is heat treatment at a temperature of 600 ° C to 700 ° C. When a fused glass having a working temperature of 600 ° C. or lower is used as the secondary fused glass 15, it becomes difficult to secure reliability (moisture resistance, hardness, etc.). In particular, since the secondary fused glass 15 is exposed on the sliding surface of the medium, no step difference or discoloration should occur in the glass. If fused glass having a working temperature of 700 ° C. or higher is used, the R / W gap 8 and the erase gap 11 joined by the primary fused glasses 13 and 14 are loosened. Therefore, it is necessary to use fused glass having a working temperature of 600 ° C. or higher and 700 ° C. or lower. Then, the surfaces of the R / W center core 7 and the erasing center core 10 opposite to the surfaces facing the gap are flat-polished so that the gap distance between the R / W gap 8 and the erasing gap 11 becomes a predetermined dimension. For the purpose of magnetically separating the R / W core 6 and the erasing core 9, they are joined together via a non-magnetic spacer 12 with, for example, an epoxy resin adhesive. Then, the head block thus joined and integrated is cut in a direction substantially orthogonal to the direction in which the glass-molded cutout groove extends to manufacture individual magnetic core chips 3. Next, in order to secure the contact with the floppy disk, the magnetic core chip is fixedly adhered to a pair of sliders 4 and 5 made of ceramic such as calcium titanate, and finally a coil bobbin 16 around which a coil is wound is inserted. The back core 17 is joined to complete the magnetic head.

In this embodiment, the primary fused glasses 13 and 14 are used for the gap bonding, and the secondary fused glass 15 is used for the mold of the track notch groove, but the heat at the glass transition temperature of this fused glass is used. Expansion coefficients α _G1 , α _G2 (Hereinafter, the symbol α _G is used to generally describe the thermal expansion coefficient of fused glass)
, R / W core 6, erase core 9, R / W center core 7,
The thermal expansion coefficient of the ferrite material used for the erasing center core 10 is α _F (95 × 10 to ^{7 to} 115 × 10 to ⁷ / ° C) or less, and the difference from the thermal expansion coefficient of the primary fused glass α _G1 − α _F −4.0 × 10 ~ ⁷
It is above, and 0 or less is used, and the difference α _G2- α _F with the thermal expansion coefficient of the secondary fused glass is -7.0 × 10 to ⁷ or more and 0 or less is used. To do. Here, the thermal expansion coefficients α _G and α _F at the glass transition temperature will be described with reference to FIG. In FIG. 4, 18 is the thermal expansion curve of the glass, A
Is the thermal expansion coefficient α _G at the transition point. 19 is a thermal expansion curve of ferrite, and the point B is the thermal expansion coefficient α _F at the transition point.

Next, examples of the glass material having the coefficient of thermal expansion α _G in the above range include those having the glass physical properties shown in (Table 1).

[0013]

[Table 1]

Next, a magnetic head made of a combination of fused glass and ferrite shown in (Table 2) was prototyped and the B-noise was measured.

[0015]

[Table 2]

In measuring the B-noise, 10 times of the head output generated when the recording / reproducing operation was repeated 100 times was performed.
The level of B-noise was examined by measuring the number of times of occurrence of pulsed noise of% or more. FIG. 5 shows the results of measuring the B-noise of the magnetic head of the combination of fused glass and ferrite shown in (Table 2) as the primary fused glass. In FIG. 5, the horizontal axis represents the difference between the thermal expansion coefficient α _G1 of the fused glass and the thermal expansion coefficient α _F of the magnetic core made of ferrite, and the vertical axis represents the number of B-noise occurrences. As shown in FIG. 5, when the difference (α _G1 −α _F ) in the coefficient of thermal expansion between the primary fused glass and the magnetic core is set to −4.0 × 10 to ⁷ or more and 0 or less as in this example, B-noise is generated. It turns out that it becomes extremely small. Next, FIG. 6 shows the B-noise measurement results of the magnetic head of the combination of fusion glass and ferrite shown in (Table 2) as the secondary fusion glass. Similar to FIG. 5, in FIG. 6, the horizontal axis represents the difference between the thermal expansion coefficient α _G2 of the fused glass and the thermal expansion coefficient α _F of the magnetic core made of ferrite, and the vertical axis represents the number of B-noise occurrences. As shown in FIG. 6, the difference (α _G2 −α _F ) in the coefficient of thermal expansion between the secondary fused glass and the magnetic core is −7.0 × 10 ⁷ as in the present embodiment.
It can be seen that the B-noise becomes extremely small when the value is 0 or less.

The shapes in the vicinity of the tracks of the recording / reproducing head and the erasing head shown in the above embodiment are not limited to this. For example, the shapes shown in FIG.
Or even if there is no non-magnetic spacer between the R / W core and the erasing core as shown in (b) of the figure, or if the track processing is straight as shown in (c) of the figure. It has been confirmed that it has a similar effect.

[0018]

As is apparent from the above embodiments, the present invention is a fused glass for fusing magnetic cores made of ferrite, the coefficient of thermal expansion of which is less than that of the ferrite, and Since the value is selected to be close to this value, B-noise can be reduced even when it is used in a device having a large leakage magnetic field, such as a small floppy disk device in which a motor is closely arranged, and a good value. It is possible to provide a magnetic head having characteristics.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a magnetic head of the present invention.

FIG. 2 is an enlarged plan view in the vicinity of tracks of a magnetic core chip in the magnetic head of the present invention.

FIG. 3 is an enlarged side view of a magnetic core chip in the magnetic head of the present invention.

FIG. 4 is a diagram showing a thermal expansion coefficient curve with respect to temperatures of fused glass and ferrite.

FIG. 5 is a characteristic diagram showing a change in B-noise with respect to a difference between the thermal expansion coefficient α _G of the primary fused glass and the thermal expansion coefficient α _F of the magnetic core.

FIG. 6 is a characteristic diagram showing a change in B-noise with respect to a difference between a thermal expansion coefficient α _G of a secondary fused glass and a thermal expansion coefficient α _F of a magnetic core.

FIG. 7 is an enlarged plan view showing the vicinity of the track of another embodiment of the magnetic core chip in the magnetic head of the present invention.

FIG. 8 is a perspective view showing a conventional magnetic head.

FIG. 9 is an enlarged plan view in the vicinity of tracks of a magnetic core chip in a conventional magnetic head.

FIG. 10 is an enlarged side view of a magnetic core chip in a conventional magnetic head.

[Explanation of symbols]

1 ... Magnetic core for recording / reproducing, 2 ... Magnetic core for erasing, 3
... magnetic core chip, 4, 5 ... slider, 6 ... recording / reproducing core (R / W core), 7 ... R / W center core, 10 ... erase center core, 8 ... R / W gap, 9 ... erase core, 11 ... erase gap , 12 ... Spacer, 13, 14 ...
Primary fused glass, 15 ... Secondary fused glass, 16 ... Coil bobbin, 17 ... Back core, 18 ... Thermal expansion curve of fused glass, 19 ... Thermal expansion curve of ferrite.

Claims (3)

[Claims] 1. A magnetic head having a recording / reproducing magnetic core made of ferrite and an erasing magnetic core, wherein a thermal expansion coefficient at a glass transition temperature of a fused glass used for forming a magnetic gap is α _G1 . When the coefficient of thermal expansion of each of the magnetic cores at the glass transition temperature is α _F , the difference between the coefficients of thermal expansion α _G1 −α _F is within the range of −4.0 × 10 to ⁷ or more and 0 or less. Magnetic head. 2. A magnetic head comprising a recording / reproducing magnetic core made of ferrite and an erasing magnetic core, wherein a primary fused glass is used when forming a magnetic gap, and a secondary fused glass is used during track processing. When the coefficient of thermal expansion of the second fused glass at the glass transition temperature is α _G2 and the coefficient of thermal expansion of the magnetic cores at the glass transition temperature is α _F , the difference in thermal expansion coefficient α _G2 −α _F To −7.0 × 10 ~
A magnetic head characterized by being in the range of ⁷ or more and 0 or less. 3. When the coefficient of thermal expansion of the fused glass at the glass transition temperature is α _G1, and the coefficient of thermal expansion of the recording / reproducing magnetic core and the erasing magnetic core made of ferrite at the glass transition temperature is α _F , Difference in thermal expansion coefficient α _{G1 −} α _F
Of -4.0 × 10 to ⁷ or more and 0 or less is used, and this is fused to each magnetic core within a working temperature range of 700 ° C. to 800 ° C. to form a magnetic gap, then after performing a track processing in each of these magnetic cores, and the thermal expansion coefficient alpha _G2 in the glass transition temperature of the fused glass, the difference alpha _{G2-.alpha. F} of thermal expansion coefficient alpha _F of the magnetic core is -7.0 × 10 ~ ⁷ or more 0
Use the following fused glass as below,
A method of manufacturing a magnetic head, characterized in that the magnetic head is fused to a notch groove that regulates the track within a range of 600 ° C. or higher and 700 ° C. or lower.