JP2000103667A - Al2O3-TiC-BASED SINTERED PRODUCT AND SUBSTRATE FOR THIN FILM MAGNETIC HEAD USING THE SAME ii - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the surface grade after ion irradiation treatment and to prevent crystal grains from falling off by specifying the composition of a sintered compact including Al2O3 and TiC as main components and also a sintering additive component and by specifying its crystal grain size and its standard deviation. SOLUTION: When an Al2O3-TiC-based sintered compact includes (i) 100 pts.wt. main component consisting of 50-75 wt.% Al2O3 and 25-50 wt.% TiC and (ii) 0.03-0.5 pts.wt. sintering additive, an average crystal grain size corresponding to the circle is 0.4-1.2 μm and the standard deviation of crystal grain diameter corresponding to the circle is <=0.35. It is pref. that tenacity value K1c to cleavage fracture of the sintered compact is >=4.0 MPa.m0.5 and Young's modulus is 400 Mpa. This sintered compact is obtained by blending powder of Al2O3 and TiC both having ca. 0.3-1.5 μm with a sintering additive (e.g. MgO, Y2O3, CaO, Yb2O3, SiO2 or the like) in a predetermined content ratio and then calcining then mixture at ca. 1,500-1,750 deg.C by a hot press moulding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is a substrate or a jig for a thin film magnetic head BACKGROUND OF THE INVENTION relates to a measuring jig Al ₂ O ₃ -TiC based sintered body used for such, in particular as Slicing Al that can prevent particle dropping such as chipping of crystal grains when forming a magnetic head when forming a magnetic head. It is suitable for simple machining and surface processing by ion irradiation such as ion milling and reactive ion etching (Reactive Ion Etching).
_The present invention relates to a ₂ O ₃ -TiC-based sintered body.

[0002]

2. Description of the Related Art Conventionally, among magnetic heads, a thin film magnetic head has a magnetic head circuit formed on the surface of a predetermined substrate by a thin film technique such as sputtering, and the magnetic gap can be controlled to be small, so that high density recording is possible. is there.
Since the substrate used in this thin-film magnetic head has a surface facing the magnetic recording medium functioning as a slider floating surface, various processes such as grooves and step portions are formed on the substrate surface, and a desired head shape is obtained. Slicing is performed.

Conventionally, since these processing methods are performed, a substrate is required to have characteristics such as excellent wear resistance, mirror surface processing, chipping resistance, and machinability.

[0004] One may satisfy these requirements materials, Al ₂ O ₃ -TiC based sintered body containing TiC against Al ₂ O ₃ is often used. This Al ₂ O ₃ -TiC-based sintered body should be made completely dense by adding sintering aids such as MgO, Y ₂ O ₃ , and Yb ₂ O ₃ to satisfy the above characteristics. Thus, the mirror workability has been improved, and the chipping resistance during slicing and the machinability have been improved by growing the crystal grains of the sintered body to about 1.5 to 3 μm.

On the other hand, recently, as the magnetic recording density has increased, the flying height of the magnetic head from the magnetic recording surface has been further reduced, and accordingly, the flatness, surface roughness, crown , Camber, etc., required high dimensional accuracy.
(Transverse Pressurization Contour). In conventional machining, these requirements cannot be met with sufficient satisfaction, so the ion milling method, which performs machining while irradiating the machining mirror surface with ions such as Ar +, or
Processing is performed by the so-called RIE method in which processing is performed while irradiating ions to a processing mirror surface in a reactive gas such as CF ₄ , CCl ₄ , and BCl ₃ .

[0006]

A conventional Al ₂ O ₃ —TiC-based sintered body has a grain size of about 1.5 to 3 μm,
As shown in 35773, MgO, NiO, Cr ₂ O, or ZrO ₂
It is known that the addition of such a free-cutting property imparting agent in an amount of about 0.5 to 5 weight improves the chipping resistance in machining.

However, although the chipping resistance is improved by machining such as slicing,
In processes such as ion milling or RIE in which ABS rail processing that is the air bearing surface of the current head is applied, when the particle diameter is large, the step between Al ₂ O ₃ and TiC appears remarkably,
In addition, the free-cutting property imparting agent has a problem that projections and holes are generated due to a difference in the milling rate of Al ₂ O ₃ or TiC due to the processing, and it is difficult to obtain a satisfactory surface quality.

[0008] Therefore, in the present applicant Al ₂ O ₃ -TiC based sintered body, previously an average particle size of the Al ₂ O ₃ in JP-A 7-242463 is 5 to 50% than that of TiC increased, more The average grain size of the whole crystal is 1 μm or less, and the average grain size of TiC is
A sintered body having a grain boundary phase content of 1.0 μm or less and a grain size of 0.9 μm or less has been proposed, and according to this, the processed surface quality such as ion milling property and RIE property has been improved.

In addition, there has been a recent demand for a head material which is free from particles falling off due to the impact of contact between the head and the medium when the head material is mounted on an HDD device, and no strong knowledge has been obtained so far. There is a need to increase the force, ie, improve the sinterability. In order to improve the sinterability, there is a method of increasing the firing temperature or adding a sintering aid component. However, when the firing temperature is increased, crystal grains grow and it is difficult to obtain fine crystals. Adding a sintering aid component has not been a sufficient solution due to the problem that the surface quality after processing deteriorates due to the difference in processing rate during ion milling or RIE.

Therefore, an object of the present invention is to provide a head member which is excellent in surface quality after processing and in which crystal grains of a magnetic head do not fall off when processing by ion irradiation such as ion milling or RIE processing is required. It is an object of the present invention to provide a thin-film magnetic head substrate and an Al ₂ O ₃ —TiC-based sintered body used for the substrate.

[0011]

Means for Solving the Problems The inventors of the present invention have studied the above problems, and as a result, have controlled the crystal particle diameter in the sintered body of Al ₂ O ₃ and TiC to obtain a circle equivalent diameter of the crystal particles. By reducing the standard deviation of sintering, the internal stress interposed inside the sintered body due to sintering can be relaxed, the toughness against fracture can be improved, the chipping resistance during slicing,
The present inventors have found that the dropout of head particles can be significantly improved as compared with a conventional sintered body, and have reached the present invention.

Namely, Al ₂ O ₃ -TiC based sintered body of the present invention is Al ₂ O
An Al ₂ O ₃ -TiC-based sintered body containing 0.03 to 0.5% by weight of a sintering aid component containing ₃ and TiC as main components, wherein the average crystal grain size in the sintered body is 0.4 to 1.2 μm And the standard deviation of the equivalent circle diameter of each crystal grain is 0.35 or less.

Further, according to the present invention, the Al ₂ O ₃ —TiC-based sintered body has a toughness value K1c against cleavage fracture of 4.0 MPa · √m or more and a Young's modulus of 400 MPa or more. It is assumed that.

Hereinafter, the present invention will be described in detail. In the present invention
The Al ₂ O ₃ -TiC-based sintered body contains Al ₂ O ₃ and TiC as main components, and contains 50 to 75% by weight and 25 to 50% by weight, respectively. The reason why both components are limited to the above ranges is that when the amount of TiC is less than 25%, chipping resistance is reduced, and when the amount exceeds 50% by weight, the surface quality is improved but the number of contact points with the disk is increased, so that the magnetic head slider is increased. This is because the sliding characteristics as described above deteriorate.

The sintered body having the above composition is composed of Al ₂ O
_Although composed of _three crystal grains and a TiC crystal phase, if a sintering aid component is included, projections and holes may be formed in a stepped shape due to differences in the processing rate during ion milling and RIE processing, and the sliding characteristics may decrease. There is. Therefore, in the present invention, the content of the sintering aid component is reduced to 0.05 to 0.3 parts by weight.

If the amount of the sintering aid component is less than 0.05 parts by weight, the sinterability is poor. If the amount exceeds 0.3 parts by weight, the sinterability is improved. The characteristics deteriorate. The sintering aid _{MgO, Y 2 O 3, CaO} , Yb 2 O
₃ , SiO ₂ or the like is used.

The reason why the average value of the equivalent circle diameter of the crystal of the sintered body is limited is that when the average crystal particle diameter is smaller than 0.4 μm, the processing load is increased by slicing, and the addition of the sintering aid component is not required. Since the amount is extremely small, chipping resistance is reduced. Conversely, if it is larger than 1.2 μm, slicing workability is improved and chipping resistance is excellent, but as described above, surface quality is improved by surface milling such as ion milling and RIE. And greatly affects the flying characteristics of the magnetic head,
Further, the flying height of the magnetic head is not stable, and the head characteristics are not stable. If it is 0.4 to 1.2 μm, a suitable processed surface quality can be obtained and the characteristics of the head can be stabilized.

On the other hand, if the variation of the crystal equivalent diameter is large, that is, if the standard deviation exceeds 0.35, the slicing workability deteriorates, chipping increases, and the processed surface becomes rough. Therefore, when the head receives an impact, the particles are likely to fall off due to the roughened processing surface.

The Al ₂ O ₃ —TiC-based sintered body of the present invention is obtained by adding, for example, Al ₂ O ₃ powder and TiC powder, and further adding a predetermined sintering aid at a predetermined ratio as described above. After mixing and molding by an arbitrary method such as a ball mill, the molded body is 1500 to 1750 ° C., the weight ratio of Al ₂ O ₃ and TiC is approximately 7: 3, and the average crystal grain size of the primary particles is 1.0. In the case of about μm, firing is preferably performed by a hot press method in a temperature range of 1700 to 1730 ° C. Sintering can also be performed by a hot isostatic firing method (HIP method) or the like. As described above, Al ₂ O ₃ grains and T
In order to control the iC crystal grains, the starting materials are all small in particle size, preferably Al ₂ O ₃ having an average particle size of 0.3 to 1.0.
μm and TiC of 0.3 to 1.5 μm are used. It is also desirable to use a raw material having a small particle size variation and a uniform shape, and to set the firing temperature as low as possible in order to prevent grain growth.

[0020]

[Example] Spherical Al ₂ O ₃ raw material (purity 99.9% or more) and TiC raw material (purity 99.5% or more) with uniform particle diameters are used, and these become 70% by weight of Al ₂ O ₃ and 30% by weight of TiC. Weigh as
After adding about 15% by weight of TiO ₂ to TiC, Al ₂ O
Wet-mixed with ₃ balls. Then, it was formed into a desired shape and baked by hot pressing at 1700 ° C. and a pressure of 250 kg / cm ² for 1 hour. In the experiment, the average particle size of the Al ₂ O ₃ raw material powder was
0.3-1.5 μm, average particle size of 0.3-1.5 as TiC raw material powder
Several types of sintered bodies were produced using 2.0 μm.

After the surface of the obtained sintered body was mirror-finished, the average crystal grain size, the standard deviation of the circle equivalent diameter, and the K1c as a fracture toughness value were measured. In addition, for the measurement of the crystal grain size, a photograph was taken at a magnification of 2000 times with a metal microscope, and the measurement was performed from the photograph by employing a code method. The K1c was measured by an indentation fracture method (IF method) under a load of 10 kgf / cm ² . In addition, the standard deviation of the equivalent circle diameter of the crystal was measured by mirror-processing the sintered body, measuring the size of 200 particles arbitrarily selected from a 2000-fold metallographic photograph, and calculating the standard deviation.

Each of the above samples was tested for chipping resistance by 3
It is cut into a rectangular shape of × 4 × 30 mm, wrapped using a tin plate or the like until the surface becomes a mirror surface, and then a diamond foil (resin # 325, φ110 mm × 1 mmt) is rotated at 5500 rp.
m, the feed was set to 40 mm / min, and the rectangular body was cut using this, and chipping evaluation was obtained from the cut surface. As an evaluation standard, the length of a portion removed by chipping from the interface through which the diamond foil passed was measured. An arbitrary 500 μm of the interface through which the diamond foil has passed is selected, the maximum chipping width and the five points with the largest chipping widths below that are selected, and the average chipping width of the five points is used as an evaluation criterion. It was stated that the chipping resistance was degraded as the size became larger. Such evaluation criteria are as shown in Table 1.

Regarding the machinability, the disk-shaped sintered body was polished into a circular shape having a diameter of 76 mm and a thickness of 4 mm, and then a diamond foil (resin # 325, φ110 mm × 1 mmt) was rotated at 55 rpm.
00rpm, set to feed 100mm / min, cut the disk using this, when cutting, measured the load current of the rotary drive motor connected to the main shaft of the diamond foil,
The average current value during steady cutting was determined. It shows that when the average current value increases, the cutting resistance increases and the machinability decreases accordingly. The evaluation criterion is divided into three grades of ○, △, and ×. It indicates that machinability decreases.

According to Table 1, the average particle diameter increases and the standard deviation of the particle diameter appears remarkably.

Sample 1 has a large K1c and is excellent in chipping resistance, but has a small average crystal grain size, so that the processing load is increased and the machinability is deteriorated.

As can be seen from Samples 4 and 5, even if the average particle diameters are the same, the chipping property is deteriorated if the standard deviation is large, that is, if the particle diameter varies widely. This is presumably because particles having a large particle size exist locally, and a load is easily applied to the particles during processing, so that chipping, that is, particle detachment is likely to occur.

Samples 7, 8, and 9 are suitable for machining because the load due to machining is reduced because the average particle diameter is large, but the chipping resistance is deteriorated because the average particle diameter is large. Was done. In sample 8, the standard deviation of the particle diameter was small, but the chipping was larger due to the dropping of particles due to the large average particle diameter. Furthermore, K1c tends to decrease. The tendency is that if the average primary particle size is large, the sinterability deteriorates, so Al ₂ O ₃ and TiC
It is conceivable that the bonding strength becomes weak and the rigidity or toughness becomes low.

[0028]

[Table 1]

[0029]

As described in detail above, according to the present invention,
The average crystal grain size of the Al ₂ O ₃ -TiC-based sintered body is 0.4 to 1.
By setting the thickness to 2 μm and the standard deviation of individual crystal grain diameters to 0.35 or less, chipping resistance can be improved, and the effect of toughness on fracture is improved. This allows
The reliability of the magnetic head against dropping of crystal grains from the head member in a slider such as a thin film magnetic head can be improved.

In addition, the sintered body of the present invention is also excellent in machinability. For example, when this sintered body is used for a substrate for a thin film magnetic head, remarkable smoothness can be easily obtained when the ABS is mirror-finished. In this way, even when the mirror polishing conditions are strict so that the polishing amount per unit time is increased, the occurrence of grain drop is suppressed, and as a result, the mirror polishing time is shortened, and the production efficiency and the production cost are reduced. Be improved.

Further, the Al ₂ O ₃ —TiC-based sintered body of the present invention is excellent in precision workability, wear resistance, strength and slicing workability. It can also be used as a component.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G030 AA36 AA45 BA18 GA11 5D033 BA52 5D093 AA05 AC08 BD01 BD08 JB10 JC03 5D111 AA19 AA24 BB37 BB48 EE02 FF15 FF23 FF47 FF49 KK07

Claims (3)

[Claims] 1. A 50 to 75% by weight of Al ₂ O ₃ and 25 to 50 wt% of Ti
An Al ₂ O ₃ -TiC-based sintered body comprising C as a main component and containing at least 0.03 to 0.5 parts by weight of a sintering aid component with respect to 100 parts by weight of the main component, Al ₂ O ₃ -TiC based sintering characterized in that the circle-equivalent average crystal grain size in the sintered body is 0.4 to 1.2 μm or less and the standard deviation of the circle equivalent diameter of each crystal grain is 0.35 or less. body. 2. A toughness value K1c against cleavage fracture of 4.0 MPa · √
The Al ₂ O ₃ —TiC-based sintered body according to claim 1, wherein the Al ₂ O ₃ -TiC-based sintered body has a modulus of at least 400 m and a Young's modulus of 400 MPa or more. 3. A substrate for a thin-film magnetic head comprising the Al ₂ O ₃ —TiC-based sintered body according to claim 1.