JPH07237964A - Nonmagnetic ceramics for record reproducing head and production thereof - Google Patents

Abstract

PURPOSE:To obtain the nonmagnetic ceramics with its deformation during processing suppressible, low in the load thereon during processing, large in the amount of processing per unit time, low in the unevenness after processed, and excellent in slidability with low adsorptive force or frictional force to disks. CONSTITUTION:This ceramics is composed mainly of 1-95vol.% of aluminum boride and 99-5vol.% of alumina and, pref. containing 0.1-5 pts.wt., based on 100 pts.wt. of the chief component, of zirconia. This ceramics can be obtained by hot press or hot hydrostatic pressure treatment of mixed powder comprising 1-95vol.% of aluminum boride <=2mum in feedstock average particle diameter and 99-5vol.% of alumina, a molded form or sintered compact thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to non-magnetic ceramics for recording / reproducing heads used for, for example, ceramic substrates for thin film magnetic heads, sliders for various magnetic heads, spacers for magnetic heads, tape guides for porcelain recording, etc. It relates to the manufacturing method, the material itself has a large hardness,
Since it has a Young's modulus, it can manufacture a head with high processing accuracy, can provide an information recording device with excellent reliability, and can also provide a frictional force and an attractive force with respect to a recording medium and a recording tape, which are high-density recording media. The present invention relates to a non-magnetic ceramic for a recording / reproducing head having a small value and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the densification of magnetic recording has made rapid progress. With this densification, high coercive force media such as a hard disk, an 8 mm VTR, an electronic still camera, a video floppy and a digital audio have been developed. As a magnetic head for recording / reproducing, a thin film head suitable for increasing the density of magnetic recording using a magnetic thin film has been attracting attention, in place of a conventional magnetic head using ferrite or the like.

A thin film head using a magnetic thin film is manufactured, for example, as follows. First, a sputtering film of alumina is formed as an insulating film on the surface of a substrate having a diameter of 6 inches to 3 inches, and then thousands of transducers are formed on the upper surface of the alumina film by using a lithography technique. An insulating alumina film is formed again on the substrate on which the transducer is formed. Then, it is obtained by cutting out individual magnetic heads from the substrate in consideration of the polishing allowance as the slider. After the bar material including the individual thin film heads is cut out, one surface of the bar material is polished as a sliding surface.

By the way, in recent years, as the recording density of the Winchester type magnetic head has been improved, the flying height of the magnetic head from the disk surface has been reduced to submicron or less. The flying height of the slider changes due to the difference. In order to reduce this change in the flying height, not only the conventional positive pressure portion is provided on the air bearing surface, but also a minute groove (recess) is formed in a part of the sliding surface to form a negative pressure portion. It has been proposed to make the flying height of the head constant at the inner and outer circumferences.

Therefore, for the above reasons, after polishing the sliding surface which is one surface of the bar material cut out from the substrate,
Grooves (recesses) are formed on this sliding surface. This groove is generally machined, but when forming a negative pressure slider having a groove of several μm, it is processed by ion beam milling, reactive ion milling, chemical etching or the like.

[0006]

In the conventional thin film head, the bar material for the slider is warped by a few microns per 50 mm in length during the above cutting process, and the magnetic gap depth (throat height) on the sliding surface is increased. Although the change in the value was about a few microns, the influence on the electric characteristics for reproduction and recording was small.

However, in a magnetic head for higher density recording, variations in the gap depth due to the warp cause deterioration of electrical characteristics. Therefore, the warp when the slider bar material is cut out needs to be submicron or less per 50 mm in length. Alumina / titanium carbide-based materials have been conventionally used as slider materials for magnetic heads for high-density recording, etc.
Although it is possible to reduce the warpage when the slider bar material is cut out to some extent, there is a problem that it is difficult to perform accurate cutting in a short time because the load when cutting with a diamond grindstone is large. It was

Further, when the groove is formed in the slider bar material, it is necessary to finely process the sliding surface by ion milling or the like, but from the viewpoint of mass production and accuracy, the processing time and the uniformity of the processed surface are required. Is an important property in manufacturing. But,
The conventional alumina / titanium carbide composite material has a problem that the processed surface after ion milling has large irregularities. That is, in recent years, there has been a demand for a material having small irregularities on the processed surface after ion milling.

Further, the conventional thin-film head slider material made of alumina / titanium carbide has a large attraction force and frictional force with the disk, which causes failure of the head crush or the like, and significantly reduces the reliability of the information recording apparatus. There was a problem. In order to improve the reliability of the magnetic head, there has been a demand for a material having a small sliding force and a small frictional force or an attractive force generated between the magnetic head and the disk.

In order to reduce the frictional force and the suction force between the recording disk and the recording / reproducing head, it has been proposed to reduce the suction force by forming a crown or the like on the air bearing surface of the head. , The size of this crown is a few nanometers.
It is necessary to improve the accuracy of the device, which makes it difficult to mass-produce inexpensive heads.

The present invention can suppress deformation during cutting of a bar material, polishing, and the like, fine processing is possible, a load during grinding is small, and unevenness after fine processing such as ion milling is small. An object of the present invention is to provide a non-magnetic ceramic having a small attraction force and a frictional force with a disk and excellent in sliding characteristics, and a manufacturing method thereof.

[0012]

As a result of studying the above-mentioned problems, the present inventor found that in the non-magnetic material for head,
It has been found that by increasing the Young's modulus of the material itself, it is possible to suppress deformation of the slider bar material during processing, and it is easy to perform fine processing. In addition, the non-magnetic ceramics for the recording / reproducing head is made of aluminum boride as
By being composed of 95% by volume and 99 to 5% by volume of alumina, the processing load is small, the unevenness of the processed surface after fine processing such as ion milling is small, the fine processing is easy, and the adsorption force with the disk The inventors have found that a material having a small frictional force and excellent sliding characteristics can be obtained, and have completed the present invention.

That is, the non-magnetic ceramic of the present invention contains aluminum boride in an amount of 1 to 95% by volume and alumina 99 to 99% by volume.
5% by volume of aluminum boride and
It is desirable to contain 0.1 to 5 parts by weight of zirconia based on 100 parts by weight of the main component composed of 95% by volume and 99 to 5% by volume of alumina. This non-magnetic ceramic is a mixed powder containing 1 to 95% by volume of aluminum boride and 99 to 5% by volume of alumina, the raw material of which has an average particle size of 2 μm or less, a compact of the mixed powder, or sintering of the mixed powder. It is made by hot pressing or hot isostatic pressing the body.

Here, aluminum boride and alumina are limited to the above-mentioned ratios because when aluminum boride is less than 1% by volume (alumina is more than 99% by volume), Young's modulus is lowered, It deforms during processing such as cutting out the bar material, making it difficult to process the air bearing surface of the slider into a flat surface with high accuracy, and reducing sinterability.
This is because pores with a size of μm or more will be present. If aluminum boride exceeds 95% by volume (alumina content is less than 5% by volume), the Young's modulus decreases and it becomes difficult to densify the sintered body. Especially, from the viewpoint of sinterability, aluminum boride is
It is desirable to contain 60% by volume and 90 to 40% by volume of alumina, and from the viewpoint of slidability, it is desirable to contain 10 to 50% by volume of aluminum boride and 90 to 50% by volume of alumina.

As aluminum boride, AlB ₂ , A
1B ₁₂ , AlB ₁₀ , or mixtures thereof are preferred.
This aluminum boride may contain a trace amount of unavoidable impurities.

The non-magnetic ceramic material of the present invention is
It is desirable that 0.1 to 5 parts by weight of zirconia is contained with respect to 100 parts by weight of the main component consisting of aluminum boride and alumina. This is because the addition of zirconia improves chipping characteristics during machining, This is because a flat sliding surface can be obtained. Here, 0.1 to 5 parts by weight of zirconia is contained with respect to the main component, because when the amount of zirconia is less than 0.1 parts by weight, the edge portion produced by diamond wheel processing or groove processing is This is because it is apt to chip, and when the amount is more than 5 parts by weight, the Young's modulus of the material tends to decrease, which is not preferable. The amount of zirconia with respect to 100 parts by weight of the main component composed of aluminum boride and alumina is 2 to 100 from the viewpoint of sinterability.
5 parts by weight, more preferably 0.1 to 3 parts by weight from the viewpoint of chipping resistance.

The Young's modulus of the non-magnetic ceramic material of the present invention is preferably 400 GPa or more. This is because when the Young's modulus is less than 400 GPa, for example, the deformation during processing such as cutting out the slider bar material tends to increase.

It is particularly desirable that the Young's modulus be 420 GPa or more from the viewpoint of suppressing deformation during cutting and other processing.

The non-magnetic ceramics of the present invention are mainly composed of alumina and aluminum boride, and are carbides or borides of elements of Group 4a of the periodic table, SiC, B.
₄ C may be contained in an amount of 30% by weight or less.

In the non-magnetic ceramics of the present invention, for example, the average particle diameter of the raw material is 2 μm or less (50% particle diameter by Microtrac, here, 50 by Microtrac).
% Particle size refers to a particle size at which the volume ratio in the cumulative particle size distribution is 50%), and a mixed powder containing aluminum boride and alumina is subjected to hot pressing or hot isostatic pressing (HI).
P), hot pressing or hot isostatic pressing of the mixed powder, or hot pressing or hot isostatic pressing of the sintered body obtained by molding and firing the mixed powder as described above. It is obtained by doing. Among these, it is particularly preferable to subject the pre-sintered body produced in a vacuum firing furnace, a reducing atmosphere firing furnace, or the like to hot isostatic pressing.

The average particle size of the aluminum boride raw material is set to 2 μm or less because the sintering temperature increases if the average particle size is more than 2 μm, and the particle size of the alumina crystal increases.
This is because pores remain in the sintered body and it becomes difficult to remove them. Further, even if the sintered body is densified, the surface roughness Ra of the processed surface finely processed by ion milling is 1
This is because it becomes as large as 00 nm or more and is not suitable as a slider material, for example. The raw material particle size of the aluminum boride is preferably 0.5 μm or less. The average particle size of the raw material of alumina is standard, but it is generally 0.2 to 1 μm. Moreover, the reason why hot pressing or hot isostatic treatment is adopted for firing is that pores of 1 μm or more in the sintered body can be removed. Hot press treatment is carbon type with pressure 100 ~ 500kg
f / cm < ² >, 1500-1900 [deg.] C. for 0.5-2 hours, and hot isostatic pressing is performed in an argon or nitrogen atmosphere at a pressure of 500-2000 kgf / cm < ² >, 1400-140.
Suitably, it is carried out at 1800 ° C. for 1 hour.

[0022]

When the air bearing surface of the slider is mirror-finished, it is necessary to strictly control the flatness of the air bearing surface facing the disk as the flying height decreases. FIG. 1 shows a schematic diagram in which the deformation amount of a work in a state where a load is applied to the work during mirror finishing is calculated by the finite element method. In such a state, when the work fixing jig is fixed with, for example, an adhesive, a force of f acts on the end portion due to the effect of the adhesive. still,
The work shape is 4 mm × 1.3 mm × 2.5 mm,
The load was 1.0 kgf. And Young's modulus is 130
00 kgf / mm ² , 25000 kgf / mm ² , 40
As a result of calculation for each material different from 000 kgf / mm ² , the work deformation amount Δx is 2.19 × 10 ⁻⁴ m
m, 1.14 × 10 ⁻⁴ mm, 7.13 × 10 ⁻⁵ mm, and it can be seen that the larger the Young's modulus, the smaller the deformation.
From this, it is understood that a material having a larger Young's modulus can be processed into a surface having less deformation and good flatness, which facilitates fine processing.

Therefore, the non-magnetic ceramic for a recording / reproducing head of the present invention is made of aluminum boride and alumina, which have a large Young's modulus, to improve the Young's modulus of the material itself, and to perform cutting or grooving with a diamond grindstone or the like. It is possible to suppress deformation during processing, mirror surface processing, etc., reduce the load during processing, reduce unevenness after ion milling, and reduce the frictional force and adsorption force with the disk. Becomes

Further, by adding zirconia to the main component composed of aluminum boride and alumina, it becomes possible to improve the chipping characteristics during machining and improve the surface roughness after machining.

[0025]

【Example】

Example 1 Aluminum boride raw material powder (A having an average particle diameter of 0.8 μm)
and lB _12), the alumina raw material powder having an average particle diameter of 0.2 [mu] m, the composition of the sintered body was weighed so as to Table 1, were pulverized and mixed alumina balls as a medium. The average particle size is 50% by Microtrac. The mixed raw material powder is dried, passed through a 40 mesh and sized, and then filled in a carbon mold, and a pressure of 350 kgf / cm ² is applied to the powder.
Hot pressing was performed at 750 ° C. for 1 hour. The characteristics of the sintered body are shown in Table 1.

[0026]

[Table 1]

Here, the density was measured using the Archimedes method, and the hardness was measured using a hardness meter of AVK (manufactured by Akashi Seisakusho). The measurement condition is a load of 20 kgf with a Vickers indenter.
Was added for 15 seconds, and then the size of the indentation by the indenter was measured. A test piece having a cross section of 3 mm x 4 mm was prepared, and the strength was measured by a 3-point bending test method with a span of 30 mm. The speed of the head at this time is 0.5 mm / mi
It was set to n. The Young's modulus was measured from the amount of deformation and the slope of the load value by making a sample having the same shape as that of the strength measurement, applying a load by three-point bending. For the presence or absence of pores, after polishing using diamond abrasive grains of 1 μm, the polished surface was observed with a scanning electron microscope to observe the presence or absence of pores of 1 μm or more.

Next, the sample was milled using an argon source of Kaufman type Miratron (manufactured by Commonwealth) to obtain the milling surface roughness. The acceleration voltage was 800 V, and the argon beam was irradiated from an angle of 45 degrees with the normal to the processed surface of the sample. For comparison, an alumina / titanium carbide composite material (TF700H) was simultaneously milled. For the surface roughness, a Nanoscope 2 atomic force microscope (AFM) manufactured by Digital Instruments was used.
For the AFM, a silicon nitride probe having a tip curvature R10 to 30 nm manufactured by Olympus Corporation was used. Also,
This measurement visual field was 10 μm square.

From Table 1, the non-magnetic ceramics of the present invention (Sample Nos. 2 to 10) have a Young's modulus of 390 GPa or more, which is almost equal to that of the conventional alumina / titanium carbide material, and the sintered body has a thickness of 1 μm. It can be seen that the above pores do not exist and the milling surface roughness Ra after milling is as small as 68 nm or less. In contrast, the conventional alumina-titanium carbide composite material (Sample No. 12) has a Young's modulus of 3
Although it is as high as 98 GPa, it is found that the load during processing is large and the milling surface roughness Ra is as large as 110 nm.

Next, the samples Nos. 2 to 10 and No. 1 in Table 1 were used.
Material No. 2 was made into a slider shape with two rails of size 1.6 x 2.2 x 0.9 mm, and the CSS tester manufactured by Haruna Tsushin Co., Ltd. was used. A test for evaluating damage was conducted. The test method is performed by sliding a slider on the disk, and the maximum rotation speed of the disk is 3600r.
pm, the time from the stop to 3600 rpm was set to 5 seconds, the speed was held at 3600 rpm for 3 seconds, and then stopped after 5 seconds, and this stopped state was held for 5 seconds. A series of these operations was performed once for the CSS. As a result, the No. 12 material causes damage to the disk or the head after 30,000 times, whereas the composite materials of Sample Nos. 2 to 10 of the present invention show no damage even after 30,000 times and exhibit excellent sliding characteristics. There was found.

Example 2 Aluminum boride (AlB ₁₂ ) having an average particle size of 2.0 μm
Then, alumina raw material powder having an average particle diameter of 0.2 μm was weighed so that the composition of the sintered body was as shown in Table 2, pulverized and mixed using alumina balls as a medium, and then fired in the same manner as in Example 1.
The characteristics of the sintered body, the presence or absence of pores, and the surface roughness were measured in the same manner as in Example 1, and the results are shown in Table 2.

[0032]

[Table 2]

From Table 2, it can be seen that the samples Nos. 14 to 22 have a large Young's modulus of 380 GPa or more, which is 1 μm in the sintered body.
It can be seen that there are no pores of m or more, and the milling surface roughness after milling also has good characteristics. In addition, Example 1
The sliding characteristics were examined in the same manner as in Example No. 14-
In No. 22, it was confirmed that even if the number of CSS times was 30,000, there was no damage to the disk or head and excellent sliding characteristics were exhibited.

Example 3 1 ton of raw materials having compositions No. 1 to 11 in Table 1 of Example 1 were used.
It was molded under a pressure of / cm ² and prebaked at 1000 ° C. for 2 hours. The pre-baked body was subjected to a pressure of 2000 atm at 1700 ° C. and was subjected to hot isostatic pressure treatment for 1 hour. The characteristics of the sintered body and the surface roughness after milling were measured in the same manner as in Example 1, and the results are shown in Table 3.

[0035]

[Table 3]

From Table 3, even when subjected to hot isostatic pressing, the Young's modulus is 400 GPa or more, there is no pore of 1 μm or more in the sintered body, and the milling surface roughness Ra after milling is 62 nm. It can be seen that it has the following favorable characteristics. Further, when the sliding characteristics were examined in the same manner as in Example 1, in Sample Nos. 25 to 33, the number of CSSs was 300.
No damage to the disk or head even after 00 times,
It was confirmed that it showed excellent sliding characteristics.

Comparative Example No. 1 in Table 1 3, a raw material having an average particle size of 8.68 μm as aluminum boride and 0.8 μm as alumina
The raw materials were pulverized and mixed using alumina balls as a medium, and fired in the same manner as in Example 1. The sintered body had pores of 1 μm or more, and the same sliding test as in Example 1 was carried out. As a result, the disk was damaged when CSS was performed 300 times.

[0038]

With the non-magnetic ceramics of the present invention, the Young's modulus of the material itself can be increased, the deformation during processing is small, and the flatness of the air bearing surface can be accurately controlled.
It is possible to obtain a material which is capable of microfabrication, has a high machining speed, has small irregularities on the microfabricated surface, has a small frictional force or an attractive force generated between the head and the disk, and has excellent sliding characteristics. As a result, for example, it is possible to obtain a non-magnetic ceramic for a read / write head, which is optimal for a ceramic substrate for a thin film magnetic head, a slider for various magnetic heads, a spacer for a magnetic head, a guide for a magnetic tape, and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram in which a deformation amount of a work in a state where a load is applied to the work during mirror finishing is calculated by a finite element method.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C04B 35/645 G11B 5/127 F 7303-5D 5/31 G 8935-5D C04B 35/64 302 Z

Claims (3)

[Claims] 1. Aluminum boride in an amount of 1 to 95% by volume,
A non-magnetic ceramic for a recording / reproducing head, which comprises 99 to 5% by volume of alumina. 2. Aluminum boride in an amount of 1 to 95% by volume,
A non-magnetic ceramic for a recording / reproducing head, characterized in that it contains 99 to 5% by volume of alumina and 0.1 to 5 parts by weight of zirconia per 100 parts by weight of this main component. 3. A raw material having an average particle diameter of 2 μm or less is 1 to 95% by volume of aluminum boride and 99 to 5% by volume of alumina.
A method for producing a non-magnetic ceramic for a recording / reproducing head, comprising hot-pressing or hot isostatically treating a mixed powder contained, a molded body of the mixed powder, or a sintered body of the mixed powder.