JP2589870B2 - Manufacturing method of magnetic head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a magnetic head necessary for performing high-density magnetic recording and reproduction in a video tape recorder (hereinafter, referred to as a VTR) or the like.

[Conventional technology]

Conventionally, as shown in FIG. 30, for example, a magnetic head for a VTR has a high magnetic permeability such as sendust between a pair of substrates 31 made of an oxide magnetic material having a high magnetic permeability such as ferrite. A magnetic head chip 30 on which an alloy magnetic thin film 38 having a high saturation magnetic flux density is formed is used.

The manufacturing process of the magnetic head will be described in this order. First, a pair of substrates 31 and shown in FIGS. 21 and 22 will be described.
31 has an external winding groove 32 and a glass filling groove 33, respectively.
On one substrate 31 shown in FIG. 22, an internal winding groove 34 is further formed sequentially. Then, the gap opposing surface of each substrate 31
35 and the tape sliding surface 36 are mirror-polished, and then
As shown in FIGS. 23 and 24, each gap facing surface 35
A plurality of grooves (hereinafter, referred to as track grooves) 37 are provided at predetermined intervals. After that, the work-affected layers on the surfaces of the gap opposing surfaces 35 and the track grooves 37... Are removed by etching.

Subsequently, as shown in FIGS. 25 to 27, an alloy magnetic thin film 38 is formed on the gap facing surfaces 35, 35 and on the wall surfaces of the track grooves 37 by a sputtering method or the like. A non-magnetic material (not shown) such as SiO ₂ as a gap material is about 0.3 μm on the magnetic thin films 38.
m is formed. Next, as shown in FIG. 28, the formation surface side of each alloy magnetic thin film 38 is brought into contact with each other, and the glass filling groove is formed.
Bar-shaped joining glasses 39, 39 are inserted into the 33, 33 and the internal winding groove 34, respectively. By this bonding glass 39 ・ 39,
The two substrates 31 and 31 are mutually heated and welded to produce a substrate block 40 shown in FIG.

Subsequently, by cutting along the broken line H between the gap portions 41 on the tape sliding surface 36 of the substrate block 40, the magnetic head chip 30 shown in FIG. 30 is formed. Thereafter, a coil winding is applied to the magnetic head chip 30, and the magnetic head chip 30 is adhered to a base for the magnetic head chip, thereby producing a magnetic head.

Thus, the welding of the substrates 31 is performed using the bonding glass 39.In this case, in the process of cooling to room temperature after being heated to the bonding work point temperature of the bonding glass 39,
If the degree of thermal contraction between the substrate 31 and the bonding glass 39 is significantly different, the bonding glass 39 is cracked or distorted. As a result, a change in the gap length or the like occurs, and the magnetic characteristics are degraded. Therefore, it is necessary to select a glass having a thermal expansion coefficient as close as possible to the substrate 31 as the bonding glass 39 described above.

By the way, the thermal deformation of the glass usually causes an elongation proportional to the temperature rise from room temperature to a temperature A called a glass transition point, as shown by a solid line G in FIG. Having a constant coefficient of thermal expansion α ₁ , but beyond the glass transition point, the glass extends along a steeply sloping straight line up to a temperature B called the yield point, at which point the expansion stops. .

And, conventionally, the bonding glass is based on the idea of joining the substrate at the glass transition point, thermal expansion coefficient alpha ₁ to the glass transition point of room temperature glass bonding substantially matches the thermal expansion coefficient of the substrate 31 39 have been selected.

[Problems to be solved by the invention]

However, the magnetic head manufactured using the bonding glass 39 selected as described above has a problem that sufficient magnetic properties cannot always be obtained.

Therefore, an object of the present invention is to provide a method of manufacturing a magnetic head that can improve magnetic characteristics.

[Means for solving the problem]

The inventor of the present application has conducted intensive studies on the heat shrinkage deformation in the bonding process of the substrate due to the welding of the bonding glass,
The present inventors have found that the bonding glass becomes bonded to the substrate at a temperature higher than the glass transition point, and have completed the present invention.

That is, the manufacturing method of the magnetic head according to the present invention, as a bonding glass for bonding a pair of substrates to each other,
The glass is characterized in that an average coefficient of thermal expansion from room temperature to an intermediate temperature between the glass transition point and the yield point matches the coefficient of thermal expansion of the substrate.

(Operation)

In the process of welding with the joining glass as described above, when the joining glass that has been heated and melted to the joining operation temperature starts to cool, the joining glass is in a liquid state at a temperature up to the yield point, and from the yield point. A sharp increase in the viscosity occurs up to the glass transition point, and when the viscosity reaches the glass transition point, the solid state is formed without fluidity.

However, it is considered that the glass for bonding reaches a bonding state with the substrate at a very high viscosity stage before reaching the glass transition point, and is in a state where almost no deformation due to fluidity can occur. For this reason, if there is a difference in the total amount of thermal shrinkage in the temperature change range from this temperature to room temperature, residual strain is generated, and as a result, the magnetic properties are reduced.

Therefore, as described above, by using a bonding glass in which the average thermal expansion coefficient up to the intermediate temperature between the glass transition point and the yield point and the thermal expansion coefficient of the substrate are used, the bonding temperature when cooled to room temperature is reduced. The difference in the total amount of heat shrinkage between the glass and the substrate can be made smaller than before. As a result, it is possible to manufacture a magnetic head with a reduced residual strain.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 20.

 First, the manufacturing process of the magnetic head will be described.

As shown in FIG. 2 and FIG.
1 are each formed in a substantially rectangular parallelepiped shape from an oxide magnetic material having a high magnetic permeability such as, for example, a single crystal of MnZn ferrite, and these substrates 1.1 each have an external winding groove 2 and a glass filling groove 3. It is formed. Further, an internal winding groove 4 is further formed on one substrate 1 shown in FIG.

Thereafter, as shown in FIG. 4 and FIG.
The gap opposing surface 5 and the tape sliding surface 6 in 1 are mirror-polished, and a plurality of grooves (hereinafter, referred to as track grooves) 7... And in a direction extending substantially perpendicular to the tape sliding surface 6. Thereafter, etching is performed to remove the affected layer on the surfaces of the gap opposing surfaces 5 and the track grooves 7.

Then, as shown in FIG. 6 to FIG. 8, an alloy magnetic thin film having a high magnetic permeability and a high saturation magnetic flux density of sendust or the like is formed on each of the gap opposing surfaces 5.5 and on the wall surfaces of the track grooves 7. 8 is formed by a sputtering method or the like. Thereafter, a non-magnetic material such as SiO ₂ as a gap material, not shown, is formed on each of the alloy magnetic thin films 8.
For example, it is formed with a thickness of about 0.3 μm.

Next, as shown in FIG. 9, assembly is performed in which the two substrates 1.1 are brought into close contact with each other by abutting the gap opposing surfaces 5.5 on which the alloy magnetic thin films 8 are formed. The rod-shaped joining glasses 9.9 are arranged in the glass filling grooves 3 and the internal winding grooves 4, respectively, and heating is performed to a joining operation temperature at which the joining glasses 9.9 melt. As a result, the two substrates 1 are welded to each other to produce a substrate block 10 as shown in FIG. The substrate block 10 has a tape sliding surface 6.
The gaps 11... At which the alloy magnetic thin films 8 and 8 face each other with a gap material interposed therebetween substantially at the center line of the track grooves 7.
It is formed between them.

Subsequently, a curved surface finishing process for giving a predetermined curvature to the tape sliding surface 6 of the substrate block 10 is performed. Thereafter, the tape sliding surface 6 is cut along broken lines H in FIG. The head chip 12 is manufactured. Thereafter, a coil winding is applied to the magnetic head chip 12, and the magnetic head chip 12 is adhered to a base for the magnetic head chip to constitute a magnetic head.

As shown in FIG. 1, the bonding glass used in the above-described manufacturing process has an average coefficient of thermal expansion in a temperature range from room temperature to an intermediate temperature C between a glass transition point A and a deformation point B. A coefficient equivalent to the thermal expansion coefficient of

Experiments have shown that a magnetic head with good magnetic properties can be produced by such selection.
Hereinafter, the experimental method and the result will be described.

First, a method for evaluating strain during glass welding will be described.

This involves forming a test core material 1 by molding a single crystal of Mn-Zn ferrite used as a substrate of a magnetic head into a substantially rectangular plate shape, as shown in FIG. Measure. Thereafter, as shown in FIG. 13, the bonding glass 9 is welded and molded to the surface of the test core material 1 opposite to the surface D, and then, as shown in FIG. The surface of the glass 9 is ground in a plane with a predetermined thickness in parallel with the test core material 1. Subsequently, the processing stress applied by the grinding processing is removed by a heat treatment.
Then, the warpage of the D surface in the test core material 1 is measured and compared with the warpage of the bonding glass 9 before molding.

According to the above evaluation method, as shown in FIG. 15, when the bonding glass 9 side is concave, the effective thermal expansion coefficient of the bonding glass is larger than that of the test core material 1, As shown in FIG. 16, when the bonding glass 9 side is convex, the effective thermal expansion coefficient of the bonding glass 9 is smaller than that of the test core material 1. The magnitude of the warpage is proportional to the difference between the effective thermal expansion coefficient of the bonding glass 9 and the thermal expansion coefficient of the substrate 1.

Next, according to the above-described method, the warpage of each of the various combinations of the bonding glass 9 and the substrate 1 was measured, and the correlation between the warpage and the thermal expansion coefficient of the bonding glass 9 was determined.
This is shown in FIGS. 17 to 19. The amount of warpage is plotted on the positive side when the bonding glass 9 is deformed in a convex shape, and on the negative side when the glass is concave.

17 is a graph representation by the thermal expansion coefficient alpha ₁ in the temperature range from room temperature to the glass transition point of the bonding glass on the horizontal axis. Further, FIG. 18 is a graph representation by a Kakenetsu expansion coefficient alpha ₂ viewed averaged in the temperature range from room temperature to the yield point of the bonding glass on the horizontal axis. FIG. 19 shows an averaged apparent thermal expansion coefficient α ₃ (hereinafter, referred to as a third thermal expansion coefficient α _{3) in} a temperature range from room temperature to an intermediate temperature from the glass transition point to the yield point. ) Is a graph with the abscissa axis. The substrate 1
The thermal expansion coefficient of the Mn-Zn ferrite single crystal used as is indicated by a broken line a in each figure.

As shown in FIG. 19, when the amount of warpage is plotted with the _third coefficient of thermal expansion α3 as the horizontal axis, a substantially linear interpolation line is obtained, and this line is used as the thermal expansion coefficient of the substrate. At the point where the coefficient intersects with the coefficient, that is, when the third coefficient of thermal expansion α ₃ in the bonding glass 9 matches the coefficient of thermal expansion of the substrate 1,
It was found that the warpage was almost zero.

Further, results of producing magnetic heads using various bonding glasses and measuring the reproduction output of each magnetic head are shown in FIG. The figure, has the third thermal expansion coefficient alpha ₃ in the horizontal axis, as shown, is equal to the third thermal expansion coefficient alpha ₃ thermal expansion coefficient of the substrate in the bonding glass (in the figure, the dashed line b) At the time, that is, when the residual strain after welding does not occur, the highest reproduction output is obtained. The measurement conditions of the reproduction output were as follows: magnetic head / magnetic tape relative speed; 5.8 m / s, magnetic tape;
An oxide tape was used at a measurement frequency of 5 MHz.

As described above, conventionally, the substrate was welded using a bonding glass having a coefficient of thermal expansion from room temperature to a glass transition point that matches the coefficient of thermal expansion of the substrate. The substrate is welded using a bonding glass having an average coefficient of thermal expansion up to an intermediate temperature between the glass transition point and the deformation point and the coefficient of thermal expansion of the substrate. Thereby, the residual strain at the time of cooling to room temperature after welding becomes smaller than in the conventional case. In other words, the joining glass heated and melted to the joining operation temperature, with the temperature drop, between the sagging point and the glass transition point, accompanied by a sharp increase in viscosity, and has no fluidity when reaching the glass transition point. It is considered that the solid state is reached, but the viscosity becomes extremely high before reaching the glass transition point during the course of the process, so that the state reaches the bonding state with the substrate and almost no deformation due to fluidity can occur.
For this reason, if there is a difference in the total amount of thermal shrinkage at the stage when the temperature is lowered from this temperature to room temperature, residual strain is generated, and as a result, the magnetic properties are reduced. Therefore, as described above, the average coefficient of thermal expansion up to the temperature at which the substrate and the bonding glass are in a bonded state in a temperature range exceeding the glass transition point,
By using the bonding glass having the same coefficient of thermal expansion as that of the substrate, the total amount of thermal shrinkage when cooled to room temperature is substantially the same between the bonding glass and the substrate, and no residual distortion occurs. As a result, for example, it is possible to stably produce a magnetic head having a small gap length or the like and a high joining accuracy, and to produce a magnetic head with improved magnetic characteristics with a high yield.

In the above embodiment, an oxide magnetic material having a high magnetic permeability such as a single crystal of Mn-Zn ferrite is used as a core main body (substrate), and an alloy magnetic thin film having a high saturation magnetic flux density and a high magnetic permeability is provided near a gap. The manufacturing method of the magnetic head for forming the magnetic head is described as an example, but other examples include a magnetic head using an alloy magnetic material having a high magnetic permeability and a high saturation magnetic flux density as a core material (substrate), and a method for manufacturing a magnetic head having a high magnetic permeability. The present invention can be applied to the manufacture of a magnetic head using an oxide magnetic material as a core material, and a magnetic head including a soft magnetic thin film forming a magnetic circuit and a substrate supporting the soft magnetic thin film. It is.

〔The invention's effect〕

As described above, the method for manufacturing a magnetic head according to the present invention provides, as a bonding glass for bonding a pair of substrates to each other, an average coefficient of thermal expansion from room temperature to an intermediate temperature between a glass transition point and a yield point. Uses glass that matches the coefficient of thermal expansion of the substrate.

As a result, the amount of residual strain at the stage when the temperature is lowered to room temperature after welding with the bonding glass becomes smaller than before,
This produces an effect that a magnetic head with improved magnetic characteristics can be manufactured.

[Brief description of the drawings]

1 to 20 show an embodiment of the present invention. FIG. 1 is a graph showing the thermal expansion of the bonding glass and the substrate with respect to a temperature change. FIG. 2 is a perspective view of one substrate on which an external winding groove and a glass filling groove are formed. FIG. 3 is a perspective view of the other substrate on which an internal winding groove is further formed. 4 and 5 are perspective views of the substrate on which track grooves are formed. FIG. 6 and FIG. 7 are perspective views of the substrate on which the alloy magnetic thin film is formed, respectively. FIG. 8 is a partially enlarged sectional view of the substrate on which the alloy magnetic thin film is formed. FIG. 9 is a perspective view of a pair of substrates on which the bonding glass is arranged in a mutually abutting state. FIG. 10 is a perspective view of a substrate block. FIG. 11 is a perspective view of a magnetic head chip. FIG. 12 is a perspective view of a test core material for measuring warpage. FIG. 13 is a perspective view of a test core material obtained by molding a bonding glass. FIG. 14 is a perspective view of a test core material obtained by polishing a bonding glass. FIG. 15 and FIG. 16 are schematic front views of the test core material showing a warped state, respectively. FIG. 17 is a graph showing the relationship between the coefficient of thermal expansion from room temperature to the glass transition point and the warpage of the bonding glass. FIG. 18 is a graph showing the relationship between the average thermal expansion coefficient from room temperature to the yield point and the warpage of the glass for bonding. FIG. 19 is a graph showing the relationship between the average thermal expansion coefficient and the warpage of the bonding glass from room temperature to an intermediate temperature between the glass transition point and the yield point. FIG. 20 is a graph showing the relationship between the average thermal expansion coefficient from room temperature to an intermediate temperature between the glass transition point and the sagging point of the bonding glass and the reproduction output of the magnetic head. FIGS. 21 to 32 show a conventional example. FIG. 21 is a perspective view of one substrate on which an external winding groove and a glass filling groove are formed. FIG. 22 is a perspective view of the other substrate on which an internal winding groove is further formed. FIG. 23 and FIG. 24 are perspective views of the substrate on which track grooves are formed. FIG. 25 and FIG. 26 are perspective views of the substrate on which the alloy magnetic thin film is formed, respectively. FIG. 27 is a partially enlarged sectional view of the substrate on which the alloy magnetic thin film is formed. FIG. 28 is a perspective view of a pair of substrates on which bonding glass is arranged. FIG. 29 is a perspective view of a substrate block. FIG. 30 is a perspective view of a magnetic head chip. FIG. 31 is a graph showing the thermal expansion of glass with respect to temperature change. FIG. 32 is a graph showing the thermal expansion of the glass and the substrate with respect to the temperature change. 1 is a substrate, 9 is a glass for joining.

Claims (1)

(57) [Claims] 1. A bonding glass for bonding a pair of substrates to each other, wherein an average coefficient of thermal expansion from room temperature to an intermediate temperature between a glass transition point and a deformation point matches the coefficient of thermal expansion of the substrate. A method for manufacturing a magnetic head, comprising using glass.