KR20010073889A - Diamond-like carbon coated magnetic head and method of making same - Google Patents

Abstract

PURPOSE: A magnetic head and a producing method thereof are provided to improve life span of the magnetic head through coating a diamond like carbon film having excellent abrasion resistance and chemical stability. CONSTITUTION: A magnetic head is coated by a diamond like carbon film(6c) having a thickness of 0.5 micrometer. Herein, an error rate in reading a magnetic recording medium is less than 0.5%. Moreover, a head is formed by a material selected from a group formed by metal, ceramic, and polymer. Herein, the diamond like carbon film is combined on a surface of the head in a plasma chemical deposition method. Herein, an adhering force is improved by using an argon sputtering method by using high voltage bias, and by forming an adhering force improving layer inclining density of metal by forming a metal layer and a metal composition layer between the diamond like carbon film and the magnetic head surface.

Description

Magnetic head coated with diamond-like carbon film and its manufacturing method {DIAMOND-LIKE CARBON COATED MAGNETIC HEAD AND METHOD OF MAKING SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head for reading or writing a magnetic record of a magnetic recording medium such as a magnetic recording card, an aircraft, a subway ticket, and a check. In particular, a diamond-like carbon film having excellent abrasion resistance and excellent chemical stability on its surface (DIAMOND- LIKE CARBON FILM) and a method for manufacturing a magnetic head with improved lifespan.

The magnetic head surface is a portion which reads or writes a magnetic record of the recording medium in direct contact with the magnetic recording medium. As shown in FIG. 1, a magnetic core 1 made of a magnetic body and the magnetic core are fixedly accommodated in the head case 2. It consists of an epoxy 3 to be used, a gap 4 made of a nonmagnetic material as a site where magnetic fields for recording and reproduction are generated or induced, and a shielding material 5 for preventing leakage of magnetic flux.

As the use of magnetic cards in place of security or payment functions has exploded, the number of contacts between magnetic heads and magnetic recording media has increased, and the relative speeds between them in order to read or write the magnetic records of the media at high speeds have also increased. There is a trend. The magnetic core material of the magnetic head is generally composed of a magnetic material having a very low hardness, while the magnetic recording layer contains acicular iron oxide (γ-Fe ₂ O ₃ ) and chromium oxide (CrO ₂ ) in a base such as a polyester film. As a result, head wear at the site of contact with the magnetic recording medium is a serious problem. This wear causes the core tip to be worn out so that the gap disappears, or the stepped wear is caused by different materials constituting the core, case, and gap. As a result, the life of the magnetic head for recording and reproducing signals is greatly shortened.

In order to solve the problem of the above-mentioned head wear, there have been many efforts such as using a core material having excellent abrasion resistance such as sender with improved hardness instead of permalloy, or reinforcing wear resistance by embedding ceramic in the head case. . However, these efforts do not completely solve the problem of wear of the magnetic head at the contact point described above. Moreover, as the use of credit cards is becoming more common, the problem of corrosion in harsh environments is also an important issue. In particular, magnetic heads, which use more than 80% of iron and have a small amount of silicon, chromium, and cobalt as a core material as core materials, have very weak characteristics against corrosion in a salt water atmosphere. Therefore, countermeasures to improve corrosion resistance are needed.

Recently, a thin film coating technology has been developed to prevent wear and corrosion, for example, titanium nitride coating (TiN gradient coating) (Yanagi Michio, Kawakami Yoshio, JP-A-562119 (1993) ). This technique is a method of coating multi-layer titanium nitride thin films with different hardness on the magnetic head by changing the nitrogen flow rate by reactive sputtering method, which improves the wear resistance of the magnetic head to some extent, but the magnetic component of the magnetic recording medium is entangled. There is a problem of easily degrading the recording and reproduction characteristics of the magnetic head.

Diamond-Like Carbon Film is an amorphous solid phase and has similar hardness, electrical insulation, thermal conductivity, chemical stability, and optical properties as diamond, but can be synthesized at a much lower temperature than diamond. It is not greatly restricted, the physical and chemical properties of the film can be adjusted over a wide range, and can be adjusted to the characteristics required for specific applications by changing the synthesis conditions, and it is possible to synthesize a large and uniform thin film. (Kwang-Ryeol Lee, Kwang-Yong Lee, Korean Journal of Metals, 6, 345 (1993)). These diamond-like carbon films generally have very high density and hardness, excellent acid resistance, and very low coefficient of friction, making them well suited for wear, corrosion and lubrication coatings to enhance the life of magnetic heads.

Recently, attempts have been made to improve the wear resistance and corrosion resistance of heads by coating carbon or carbon-based hard films on the heads of audio or video heads and hard disks (Bharat Bhushan and BK Gupta et al, IEEE Transactions on magnetics). , 31, 6, (1995), G. Robert Gray, Arun Malhotra, US Pat. No. 5801909 (1998), Yuji Tsukamoto, Satoshi Yasuyoshi, Japanese Unexamined Patent Publication No. Hei 10-3631 (1998). However, in order to minimize the spacing loss, such heads should be kept at a thickness of less than 0.5 μm. In order to achieve sufficient mechanical properties under these conditions, there is a limitation that the hardness of the film and the hardness of the substrate used must be high. have. In addition, in the case of diamond-like carbon film, since hardness and residual stress have a proportional relationship (Lee Kwang-Ryul, for silver shine, Korean Society of Metals, 6, 345 (1993)), it is very difficult to improve the adhesion of such a film.

1 is a schematic diagram showing the surface configuration of a magnetic head.

2 is a schematic diagram of a thin film synthesis apparatus used to coat an adhesion promoting layer and a diamond-like carbon film.

3 is a cross-sectional view of the magnetic head coated with the adhesion promoting layer and the diamond-like carbon film according to the present invention.

Figure 4 is a photograph showing the surface state of each after the corrosion test of the magnetic head without a coating and the magnetic head coated with a diamond-like carbon film.

<Explanation of symbols for the main parts of the drawings>

1: magnetic core

2: head case

3: epoxy

4: gap

5: shielding material

6a: tungsten intermediate layer

6b: compound intermediate layer of tungsten and carbon

6c: diamond-like carbon film

In the present invention, a diamond-like carbon film is coated on the head for reading or writing magnetic records such as magnetic recording cards, subway and aircraft tickets, and checks of 0.5 μm or more, thereby improving wear resistance and corrosion resistance while maintaining the recording and reproducing performance of the head. The method is disclosed. As shown in Fig. 1, the portion of the head surface in contact with the magnetic recording medium is made of materials having a very low hardness, so that a film coating of at least 0.5 μm or more is required to secure sufficient wear resistance. In addition, the surface of the head is composed of a wide variety of materials belonging to metal, ceramic, or polymer series such as brass, permalloy or sendust, mica and epoxy. Thus, the development of techniques for enhancing the adhesion in these various materials is indispensable.

In the present invention, a diamond-like carbon film of 0.5 µm or more can be successfully synthesized on the head surface by using plasma chemical vapor deposition using hydrocarbon gas such as methane or benzene, and at this time, an argon sputtering method using a high voltage bias and diamond phase The adhesion could be improved by forming an adhesion enhancement layer composed of a metal layer and a compound layer of a metal between the carbon film and the magnetic head surface to incline the metal concentration. In addition, many other coating methods, such as ion beam deposition and vacuum arc coating, could be used to synthesize films with effects such as wear resistance and corrosion resistance on magnetic heads.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

2 is a schematic diagram of a thin film synthesis apparatus for coating argon sputtering and inclined layers and diamond-like carbon films. The magnetic head to be coated was first ultrasonically cleaned in an aqueous solution of acetone, methanol, and ethanol to remove impurities such as organic substances on the surface, and then mounted on the negative electrode plate in the synthesis apparatus. The argon sputtering method was used to remove impurities such as oxides to make the magnetic head surface more clean and to activate the magnetic head surface to improve adhesion. After argon gas is flowed into the synthesizer to bring the pressure to 3-4 mTorr, and a radio frequency voltage of 13.56 MHz is applied, a plasma is formed in the synthesizer, and a negative self-bias is generated around the cathode plate. Hit the magnetic head surface mounted on. At this time, argon ions, which are heavy and inert gases, sputter impurities on the surface. If the sputtering time is too long, the gap portion of the magnetic head surface is damaged, so that sputtering for 8 minutes when the negative self bias is 400V by adjusting radio frequency power, It was sputtered for 5 minutes at 700V.

Next, as a tungsten layer and a compound layer of tungsten and carbon, which can promote adhesion between the diamond-like carbon film and the magnetic head surface by forming carbides by combining carbon with affinity with all metals to enhance the adhesion of the film. To form an adhesion promoting layer. Gas as for coating a tungsten film was used as the WF ₆ of 6 sccm, with a gas mixture of WF ₆ and 1.5sccm C ₆ H ₆ of the 6sccm was coated a compound layer of tungsten and carbon. At this time, in order to enhance the adhesive force of the thin film, it is preferable to heat the temperature of the substrate to about 150 ℃. The synthesis conditions of the film were fixed at a synthesis pressure of 10 mTorr and a self bias of 400V, wherein the thicknesses of the tungsten layer and the compound layer of tungsten and carbon were 400 to 500 kPa and 200 to 300 kPa, respectively. Finally, the diamond-like carbon film was coated to a thickness of 0.5 to 3 μm at a synthesis pressure of 10 mTorr and a self bias of 400 V using 8 sccm of benzene gas. 3 is a cross-sectional view of the magnetic head coated with the diamond-like carbon film and the adhesion promoting layer synthesized in the present embodiment. This method was able to synthesize a film having excellent adhesion to the entire surface of the magnetic head. The hardness of the synthesized diamond-like carbon film was 18 GPa. In this embodiment, a tungsten layer and a compound layer of tungsten and carbon are used as the adhesion promoting layer of the diamond-like carbon film, but as the adhesion promoting layer, transitions such as Si, Al and Ti, Mo, Cr, Co, Ni, etc. Metal-based elements and compound layers of them and carbon may all be used. Therefore, the present invention is not limited to the case where only the compound layer of tungsten, tungsten and carbon is used as the adhesion promoting layer.

On the other hand, Figure 4 compares the surface state after the corrosion test of the magnetic head and the magnetic head coated with a diamond-like carbon film of 1㎛ thickness according to the embodiment with no coating. At this time, the magnetic core of the magnetic head was used as a high hardness but weak in the brine atmosphere, and the corrosion test was observed for one month by using the salt (0.9% NaCl) spray method. As shown in the figure, the uncoated magnetic head surface was highly corroded, whereas the magnetic head surface coated with the diamond-like carbon film having a thickness of 1 μm showed no corrosion at all.

Table 1 below shows the results of a read / write test using a real card reader device to measure wear resistance and reliability of the magnetic head coated by the above-described embodiment.

Coating thickness (㎛) Uncoated 0.5 1.0 1.5 2 2.5 3 Number of iterations 50,000 154,000 254,000 835,000 1,632,000 2,225,000 3,119,000 Error rate (%) 0 0 0 0.3 0.1 0.3 0.5

A magnetic head coated with a diamond-like carbon film having a thickness of 0.5 to 3 µm was passed through a magnetic recording card having a load of 200 gf at an average relative speed of 280 mm / sec to measure the number of repeated contact times until all the films at the contact portions were peeled off. It was. On the other hand, for comparison with uncoated heads, microscopic observation suggested the number of tests where damage to the uncoated head surface resulted in at least 50% of the total contact area. When reading / writing a test using an actual card reader device, the magnetic head may not represent the change of the magnetic field induced from the magnetic recording medium as an output due to various factors such as core loss and spacing loss. . The error rate of the magnetic head is calculated as a percentage of the cases where the magnetic head does not represent the output of the total number of repeated contacts with the magnetic recording medium. When the DLC film is coated on the magnetic head, if the thickness is too thick, the error rate of the magnetic head may increase due to spacing loss or the like. As shown in Table 1, as the thickness increases, the number of times the protective film of the contact portion withstands increases, and in all magnetic heads coated with a diamond-like carbon film having a thickness of 0.5 to 3 μm, the error rate is 0.5% or less, even if the thickness is thick. It can be seen that it has sufficient reliability. In addition, it can be seen that the life of the diamond-coated carbon film coated head is at least three times higher than the uncoated head.

As described above, according to the embodiment of the present invention, a diamond-like carbon film having excellent abrasion resistance and chemical stability on the surface of the magnetic head is coated with a thickness of 0.5 μm or more, which significantly reduces the wear of the magnetic head and improves the life of the magnetic head. It can be improved.

On the other hand, in the above embodiment, although the plasma chemical vapor deposition method is only presented as a method of synthesizing the film, this is for illustrative purposes only, since all the various methods for synthesizing the diamond-like carbon film can be applied, the scope of the present invention is It is not limited to only the above embodiment.

Claims (10)

A magnetic head coated with a diamond-like carbon film (DIAMOND-LIKE CARBON FILM) with a thickness of 0.5 µm or more. The magnetic head according to claim 1, wherein an error rate when the magnetic head reads the magnetic recording medium is 0.5% or less. The magnetic head of claim 1, wherein the surface of the head is made of at least one material selected from the group consisting of metal, ceramic, and polymer. A magnetic head comprising coating a diamond-like carbon film (DIAMOND-LIKE CARBON FILM) having a thickness of 0.5 μm or more on a magnetic head surface by any one of plasma chemical vapor deposition, ion beam deposition, or vacuum arc coating. Manufacturing method. 5. The method of claim 4, wherein a hydrocarbon gas is used for the plasma chemical vapor deposition method. The method of claim 4, wherein argon sputtering is performed using a high voltage bias. Magnetic head manufacturing method characterized in that it further comprises. The method of claim 4, further comprising: forming an adhesion promoting layer between the magnetic head surface and the diamond-like carbon film. Magnetic head manufacturing method characterized in that it further comprises. The method of claim 7, wherein the adhesion promoting layer comprises a first layer comprising tungsten, A method of manufacturing a magnetic head comprising a second layer comprising a compound of tungsten and carbon. The method of claim 7, wherein the adhesion promoting layer comprises: a first layer including at least one of Si, Al, or a transition metal-based element selected from Ti, Mo, Cr, Co, and Ni; A second layer comprising the compound of at least one element and carbon Magnetic head manufacturing method characterized in that consisting of. The method of manufacturing a magnetic head according to claim 8 or 9, wherein the thickness of the first layer is 400 to 500 kPa and the thickness of the second layer is 200 to 300 kPa.