KR20190029140A - High-strength and high-hardness capillary for wire bonding and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a capillary for wire bonding and a manufacturing method thereof, and more specifically, to a capillary for wire bonding and a manufacturing method thereof which can improve the strength and fracture toughness by optimizing the particle size and ratio of alumina and zirconia, respectively, and can improve wear resistance through DLC coating.

Description

TECHNICAL FIELD [0001] The present invention relates to a capillary for high-strength and high-hardness wire bonding, and a manufacturing method thereof. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to a capillary for wire bonding and a method of manufacturing the capillary, and more particularly, to a capillary for wire bonding which improves strength and fracture toughness by optimizing the particle size and ratio of alumina and zirconia, And a manufacturing method thereof.

As shown in FIG. 1 showing the concept of a wire bonding capillary and a metal for wire bonding bonded thereto, the capillary for wire bonding can transmit an electrical signal to a silicon chip and a semiconductor device with very fine wires It is a very precise ceramic tool to connect. Until now, the development direction of the capillary material has been improved due to the frequent defects due to abrasion, so as to focus on hardness as in Korean Patent No. 10-0932636. However, due to the ultra-high integration of the semiconductor process, a capillary with a very thin micro tip (<40 μm) was required, resulting in a breakage defect due to cutting resistance and impact rather than wear. In addition, abrasion phenomenon and foreign matter deposition phenomenon also occur during copper wire bonding. ,

As a result, the capillary manufacturer has introduced a diamond-like carbon (DLC) coating capillary as disclosed in Korean Patent No. 10-0955420 or Japanese Laid-Open Patent Application No. 2005-340400, but is currently being ignored in the market. DLC coating on the capillary material with low strength and fracture toughness still does not improve the problem of breakage, and there is also a problem of peeling during bonding.

Therefore, it is necessary to develop a ceramic composite material capillary that can prevent breakage in copper wire bonding and miniaturization of semiconductor process.

Korean Registered Patent No. 10-0932636 (Registered on December 10, 2009) Korean Registered Patent No. 10-0955420 (registered on April 22, 2010) Japanese Patent Application Laid-Open No. 2005-340400 (published on December 12, 2005)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a capillary for wire bonding, which is improved in strength and hardness to prevent breakage and is also excellent in abrasion resistance.

It is still another object of the present invention to provide a method of manufacturing the capillary for wire bonding.

The present invention may also be directed to accomplish these and other objects, which can be easily derived by those skilled in the art from the overall description of the present specification, in addition to the above-mentioned and obvious objects.

The capillary for wire bonding according to the present invention comprises 45 to 80 wt% of alumina, preferably 50 to 70 wt%, more preferably 55 to 65 wt% of alumina, and 20 to 20 wt% of zirconia, in order to achieve the above- Preferably 55 to 55% by weight, more preferably 30 to 50% by weight, and still more preferably 35 to 45% by weight.

The capillary for wire bonding may be diamond-like carbon coating (DLC coating).

The average particle diameter of the alumina may be 0.1 to 0.6 mu m, preferably 0.2 to 0.5 mu m, more preferably 0.2 to 0.4 mu m.

The average particle diameter of the zirconia may be 0.1 to 0.6 mu m, preferably 0.2 to 0.5 mu m, more preferably 0.2 to 0.4 mu m.

In addition, the zirconia may be partially stabilized.

The diamond-like carbon coating may be formed on the tip of the wire bonding capillary.

The diamond-like carbon coating layer may include a stress relieving layer on the capillary side for wire bonding and a hardness layer on the opposite side.

The hardness of the high hardness layer may be 2400 to 2800 HV, preferably 2400 to 2700 HV, and more preferably 2400 to 2600 HV.

The hardness of the stress relieving layer may be 2100 to 2350 HV, preferably 2150 to 2300 HV, and more preferably 2200 to 2300 HV.

The thickness of the high hardness layer may be 100 to 200 nm, preferably 110 to 180 nm, and more preferably 120 to 160 nm.

The thickness of the stress relieving layer may be 50 to 150 nm, preferably 60 to 140 nm, and more preferably 70 to 130 nm.

And, the diamond-like carbon coating may be a carbon ion coating.

And, the carbon ions can be formed by arc discharge under vacuum.

The diamond-like carbon coating may be coated with carbon ions that have passed through an X-band filter.

The high hardness layer may be formed by a capillary pulse voltage for wire bonding of 50 to 250 V, preferably 70 to 200 V, more preferably 80 to 150 V.

The stress relieving layer may be formed by a capillary pulse voltage for wire bonding of 300 to 800 V, preferably 320 to 600 V, more preferably 350 to 500 V.

Meanwhile, the manufacturing method of the capillary for wire bonding of the present invention

(A) 45 to 80% by weight, preferably 50 to 70% by weight, more preferably 55 to 65% by weight, and zirconia 20 to 55% by weight, preferably 30 to 50% by weight, 35 to 45% by weight;

(B) milling the mixture;

(C) a press-molding step of compressing and molding the milled mixture;

(D) a degreasing step of heating the press-molded workpiece at 600 to 800 DEG C for 1 to 3 hours;

(E) a first heat treatment step of heating the degreased molded product at 1400 to 1700 캜 for 1 to 5 hours;

(F) hot isostatic molding step of molding the hydrostatic pressure of the first heat-treating the molded product at 1300 to 1500 ℃ and 1000 to 1500 kg _f / cm ^2;

(G) a second heat treatment step of heating the hot isostatic molded product at 1100 to 1300 캜 for 5 to 10 hours;

(H) cooling the second heat-treated shaped article by air cooling; And

(I) a step of coating diamond-like carbon on the cooled molding.

The capillary for wire bonding according to the present invention is coated with diamond-like carbon at the tip end to improve the load-carrying property and the wear resistance, and the anti-seizure property is improved. Accordingly, the capillary for wire bonding according to the present invention can prevent the breaking due to the impact due to the cutting resistance and the wire bonding process, thereby prolonging the replacement cycle due to the capillary failure. This is because the wire bonding capillary according to the present invention optimizes the particle size and the ratio of alumina and zirconia to increase the strength and fracture toughness, thereby making it possible to manufacture a capillary having a smaller size. In order to prevent excessive shortening of the capillary replacement period due to abrasion, the lower hardness accompanied by the strength enhancement contributes to the precision machining. In order to prevent the capillary replacement cycle from being excessively shortened due to abrasion, the present invention increases the abrasion resistance by applying DLC coating to the tip of the capillary.

In particular, by adopting the DLC coating method carbon ions coating a non-carbon atoms or molecules state Among them, a high increased the sp ³ components hardness, consisting of a coating at a low speed at room temperature and reduced damage to the film, the micro-particles due to the filter . In addition, it has high adhesion energy due to high incident energy, low surface roughness due to ion coating, improved film uniformity and reproducibility. In particular, the present invention provides a stress relieving layer having a low hardness by first adjusting a voltage and a coating time, and forming a hardened layer thereon, thereby significantly improving the adhesion of the DLC coating film and thus extending the service life of the capillary .

1 is a conceptual view of a capillary for wire bonding and a wire bonding metal bonded thereto.
Fig. 2 is a photograph showing a state in which the capillary for wire bonding is broken.
3 is a photograph of a wear phenomenon of the capillary for wire bonding.
4 is a photograph of a state in which the DLC coating of the wire bonding capillary is peeled off.
5 is a view for explaining the HF standard used for determining the degree of adhesion force.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the following description, numerous specific details, such as specific elements, are set forth in order to provide a thorough understanding of the present invention, and it is to be understood that the present invention may be practiced without these specific details, It will be obvious to those who have knowledge of. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The capillary for wire bonding of the present invention comprises 45 to 80 wt%, preferably 50 to 70 wt%, more preferably 55 to 65 wt%, and 20 to 55 wt% of alumina, preferably 30 to 50 wt% By weight, more preferably 35 to 45% by weight. Conventionally, the capillary for wire bonding has been mainly focused on improvement of hardness in order to improve abrasion resistance. However, as miniaturization of electronic products has progressed rapidly, the size of the capillary for wire bonding has also been reduced. As a result, the thickness of the capillary body has become extremely thin and broken as shown in Fig. 2.

The main feature of the present invention is to improve the strength and fracture toughness by adjusting the blending ratio of alumina and zirconia in order to solve this problem. Due to the improved strength and fracture toughness, it is not broken by the force applied repeatedly during bonding, so that the replacement period of the capillary is extended. In addition, the capillary having the aforementioned mixing ratio has a low hardness, resulting in an increase in cutting workability, which also has the advantage of facilitating precision machining of a miniaturized capillary.

In order to sufficiently exhibit the above advantages, it is necessary to mix alumina and zirconia at the above-mentioned compounding ratio. If the content of zirconia is less than the above range, not only the strength of the capillary is lowered but also the workability of the product is lowered, There are disadvantages. On the other hand, when the content of zirconia is in excess of the above range, the abrasion resistance of the capillary is deteriorated and the service life is shortened.

In addition to the blending ratio of alumina and zirconia, the average particle size of each particle is also important for improving strength and fracture toughness. In the present invention, the alumina preferably has an average particle diameter of 0.1 to 0.6 mu m, preferably 0.2 to 0.5 mu m, more preferably 0.2 to 0.4 mu m. If the average particle diameter is less than the above range, It is required and cracked due to the springback phenomenon which is expected to return to the pre-deformation form during pressure forming. On the contrary, if the average particle diameter exceeds the above range, the molding density is lowered and the physical property value after the final sintering is lowered.

Likewise, it is preferable that the average particle diameter of zirconia is 0.1 to 0.6 mu m, preferably 0.2 to 0.5 mu m, more preferably 0.2 to 0.4 mu m. If the average particle diameter is less than the above range, On the other hand, if the average particle diameter exceeds the above range, there is a disadvantage that an excessively high temperature is required for complete densification in sintering. And, the zirconia may be partially stabilized.

As described above, the compounding ratio and the average particle diameter, which are optimized for the improvement of the strength and fracture toughness, inevitably lead to a decrease in hardness. Such a decrease in hardness necessarily leads to a shortening of replacement cycles due to wear . Another important characteristic of the present invention is that diamond-like carbon coating (DLC coating) is used for solving the problem of lowering hardness. Diamond-like carbon is one of solid-state carbon films having physical and chemical properties similar to those of diamond having high hardness. Diamond-like carbon coating is a coating method for improving surface hardness by forming a carbon film having a structure similar to diamond. This can increase wear resistance and prolong life.

The diamond-like carbon coating is particularly characterized in that a diamond-like carbon coating layer is formed on the tip of the capillary for wire bonding. The tip of the capillary indicates a substrate-side end where bonding of the wire is made. This area is subjected to intermittent force, which causes severe wear. In order to prevent this, a diamond-like carbon coating is formed in this area.

The diamond-like carbon coating may be coated with a carbon material such as a PVD (sputtering) method which is a physical coating method, a carbon coating method such as a CVD coating method such as a chemical coating method, and a carbon ion coating method such as an FCVA method . In the present invention, particularly, a method of coating carbon ions is more preferable because the incorporation of other ions such as hydrogen is effectively suppressed in the coating of carbon ions, and the probability of coating only the carbon ions on the capillary is increased. This lowers the ratio of sp ² and raises the ratio of sp ³ , resulting in a more diamond-like structure in more areas of the coating as a whole. The carbon ions can achieve a high hardness can be formed by arc discharge in a vacuum, in which case the charge is more than 70% sp ³ components, such as diamonds and structure, as for example FCVA (Filter Cathode Vacuum Arc) method.

Furthermore, it is further preferred that the carbon ions pass through an X-bend filter to minimize microparticles that degrade coating quality. In the FCVA method, coating is carried out at a low temperature at a room temperature, damage to the thin film is reduced, and the incident energy is high, so that the adhesion is excellent. In addition, ion coating has advantages of low surface roughness, high uniformity of film and high reproducibility

The diamond-like carbon coating layer formed by the FCVA method has an advantage that the synthesis temperature is low and the surface is smooth and the control of physical properties is easy. Furthermore, the coefficient of friction is very low, so that the sintering property and the chemical stability are excellent. It is also excellent in abrasion resistance and durability. Therefore, according to the manufacturing method of the present invention, the exchange cycle due to the capillary failure is prolonged in the wire bonding process in which a diamond-like carbon coating layer is formed on the surface.

In the present invention, the DLC coating layer may be a single layer, but it is more preferable to form the stress relieving layer having a low hardness first in the capillary, and then form a hardened layer thereon. When the double layer is formed in this manner, the adhesion force is increased and the peeling of the DLC coating layer is prevented. Particularly, as the hardness of the DLC coating layer is higher, there is a problem that the peeling can be easily performed as shown in FIG. 4. However, this problem is solved by introducing the double layer, and as a result, the capillary has high hardness and high wear resistance, .

Specifically, the hardness of the high hardness layer may be 2400 to 2800 HV, preferably 2400 to 2700 HV, and more preferably 2400 to 2600 HV. When the hardness is within the above range, hardness and abrasion resistance are exhibited while preventing peeling .

The hardness of the stress relieving layer may be 2100 to 2350 HV, preferably 2150 to 2300 HV, and more preferably 2200 to 2300 HV. When the hardness of the stress relieving layer is within the above range, the aforementioned adhesion force is exerted to prevent peeling It is effective.

The hardness layer may have a thickness of from 100 to 200 nm, preferably from 110 to 180 nm, and more preferably from 120 to 160 nm. When the hardness is within the above range, sufficient hardness and abrasion resistance Can be exercised.

The thickness of the stress relieving layer may be 50 to 150 nm, preferably 60 to 140 nm, and more preferably 70 to 130 nm. When the stress relaxation layer is within the above range, an appropriate residual stress value is exhibited, Can be sufficiently expressed.

The high hardness layer may also be formed by a capillary pulse voltage for wire bonding of 50 to 250 V, preferably 70 to 200 V, more preferably 80 to 150 V, The range of hardness can be implemented.

Similarly, the stress relieving layer may be formed by a capillary pulse voltage for wire bonding of 300 to 800 V, preferably 320 to 600 V, and more preferably 350 to 500 V, And an appropriate hardness value can be obtained.

The method for manufacturing a wire bonding capillary according to the present invention comprises firstly 45 to 80 wt% of alumina, preferably 50 to 70 wt%, more preferably 55 to 65 wt%, and zirconia 20 to 55 wt% By weight, preferably 30 to 50% by weight, more preferably 35 to 45% by weight. When blended in the above range, the best strength and fracture toughness values can be obtained as described above.

Followed by a milling step of milling the mixture. Through this process, the densification of the capillary molding for wire bonding is maximized, and the milling is performed, for example, by ball milling the mixture.

The milled mixture is subjected to a press-molding step in which compression molding is performed. Through this process, an appropriate molding density can be obtained. As a result, the desired mechanical properties are ensured, the occurrence of springback phenomenon is prevented, Can be prevented.

The press-molded workpiece is then subjected to a degreasing step at a temperature of 600 to 800 ° C for 1 to 3 hours. Through this process, a stable primary mechanical property is realized, so that optimum mechanical properties There is an advantage to be able to.

Thereafter, the degreased workpiece is subjected to a first heat treatment step of heating at 1400 to 1700 ° C for 1 to 5 hours. Through this process, an appropriate level of mechanical properties are secured, the occurrence of carbonization due to under- Which is preferable in terms of production efficiency and manufacturing cost.

The first go through a hot isostatic molding step of forming hydrostatic pressure to the heat-treated molded article in the 1300 to 1500 ℃ and 1000 to 1500 kg _f / cm ^2, to compact the texture of the molded article, and the porosity defects in the molded article is removed from the process .

The hot isostatic molded product is then subjected to a second heat treatment at 1100 to 1300 캜 for 5 to 10 hours, and then cooled through air cooling or the like.

By coating diamond-like carbon on the thus-cooled moldings, the hardness of the wire bonding capillary of the present invention can be increased. Although the DLC coating layer may be a single layer, it is preferable that the stress relieving layer is provided inside the hard- More preferable.

To this end, a capillary pulse voltage for wire bonding of 300 to 800 V, preferably 320 to 600 V, more preferably 350 to 500 V, is applied to the cooled molding to form a film having a thickness of 50 to 150 nm, A stress relieving layer of 60 to 140 nm, more preferably 70 to 130 nm, and a hardness of 2100 to 2350 HV, preferably 2150 to 2300 HV, and more preferably 2200 to 2300 HV are formed.

A capillary pulse voltage for wire bonding of 50 to 250 V, preferably 70 to 200 V, and more preferably 80 to 150 V is applied on the stress relieving layer to form a film having a thickness of 100 to 200 nm, nm, more preferably 120 to 160 nm, and a hardness layer having a hardness of 2400 to 2800 HV, preferably 2400 to 2700 HV, and more preferably 2400 to 2600 HV.

By forming the double DLC coating layer, it is possible to sufficiently realize the advantage of the present invention that the high hardness is exhibited but no peeling or breakage occurs.

Hereinafter, embodiments of the present invention will be described.

Example

Example 1: DLC coated capillary for wire bonding

60 g of alumina (SUMITIMO, Japan) having an average particle diameter of 0.4 탆 and 40 g of zirconia (TOSOH, Japan) having an average particle diameter of 0.3 탆 were mixed and milled. The milled mixture was pressure-molded into a capillary shape for 10 seconds at a pressure of 1 ton by using a pressure molding machine (Core Hole, Korea). Degreased and the molded shaped article is heated at 700 ℃ for 2 hours, and the mixture was molded in a hot-isostatic after the first heat treatment by heating at 1600 ℃ for 3 hours, 1400 ℃ and 1300 kg _f / cm ^2. The resultant was further heated at 1200 ° C for 8 hours to perform a second heat treatment and air cooling. Then, the capillary tip of the capillary was coated with an FCVA DLC coating system (NANOFILM, Singapore) at 100 V for 2000 seconds to obtain a wire bonding capillary Respectively. The bending strength of the capillary was 1020 MPa, the fracture toughness was 5.2 MPa · m ^1/2 , and the hardness was 2450 HV.

Example 2: Double Layer DLC Coating

The same procedure as in Example 1 was carried out and the FCVA DLC coating system was coated at 400 V for 1500 seconds and then at 100 V for 2000 seconds. In this case, the thickness of the stress relieving layer in contact with the capillary was 104 nm, and the thickness of the high hardness layer in contact with the stress relieving layer was 139 nm. The hardness of the capillary fabricated in this example was 2600 HV, the uniformity of the film was within 4%, the surface roughness was 9.7 nm or less, the coefficient of friction was 0.0165, and the adhesion strength was HF1 level. . The adhesion force was determined according to the HF standard shown in FIG.

Comparative Example 1: Alumina excess, zirconia superfine

The same procedure as in Example 1 was followed, except that 90 g of alumina and 10 g of zirconia were used. The bending strength of the capillary produced in this Comparative Example was 710 MPa, the fracture toughness was 3.6 MPa · m ^1/2 , and the hardness was 1900 HV.

Comparative Example 2: Alumina undersize, zirconia excess

The same procedure as in Example 1 was carried out, except that 20 g of alumina and 80 g of zirconia were used. The bending strength of the capillary fabricated in this comparative example was 1370 MPa, the fracture toughness was 4.3 MPa · m ^1/2 , and the hardness was 1000 HV.

Comparative Example 3: Excess alumina particle diameter

The same procedure as in Example 1 was followed, and alumina having an average particle diameter of 1.0 탆 was used. The bending strength of the capillary fabricated in this comparative example was 840 MPa, the fracture toughness was 4.5 MPa · m ^1/2 , and the hardness was 2400 HV.

Comparative Example 4: Alumina grain size lower

The same procedure as in Example 1 was followed, and alumina having an average particle diameter of 0.01 탆 was used. The bending strength of the capillary manufactured by this comparative example was 910 MPa, the fracture toughness was 5.3 MPa · m ^1/2 , and the hardness was 2450 HV.

Comparative Example 5: Excess zirconia particle size

The procedure of Example 1 was followed and zirconia having an average particle diameter of 1.0 탆 was used. The bending strength of the capillary produced in this Comparative Example was 950 MPa, the fracture toughness was 4.3 MPa · m ^1/2 , and the hardness was 1650 HV.

Comparative Example 6: Zirconia Particle Size

The same procedure as in Example 1 was followed, and zirconia having an average particle diameter of 0.01 탆 was used. The bipolar strength of the capillary produced in this comparative example was 1260 MPa, the fracture toughness was 6 MPa · m ^1/2 , and the hardness was 1600 HV.

Production Example 1: Excessive thickness of hardness layer

The same procedure as in Example 2 was carried out. The operating conditions of the FCVA DLC coating system were coated at 400 V for 1500 seconds and then at 100 V for 3000 seconds. The hardness of the capillary fabricated in the present example was 2350 HV, but the cohesion strength according to FIG. 5 was reduced to the HF4 level.

Production Example 2: Thickness of High Hardness Layer

The same procedure as in Example 2 was carried out. The operating conditions of the FCVA DLC coating system were coated at 400 V for 1500 seconds and then at 100 V for 500 seconds. The hardness of the capillary fabricated in the present example was as low as 2300 HV and the thickness of the high hardness layer was found to be excessively thin to perform the hardness layer function.

Production Example 3: Excessive Thickness of Stress Relaxation Layer

The same procedure as in Example 2 was followed. The operating conditions of the FCVA DLC coating system were coated at 400 V for 2500 seconds and then at 100 V for 2000 seconds. The hardness of the capillary produced in the present example was 2100 HV, and the adhesion force according to FIG. 5 was reduced to the HF3 level.

Production Example 4: Depth of Stress Relaxation Layer

The same procedure as in Example 2 was followed. The operating conditions of the FCVA DLC coating system were coated at 400 V for 500 seconds and then at 100 V for 2000 seconds. The hardness of the capillary fabricated in this example was as low as 2050 HV, and the thickness of the stress relieving layer was too thin to perform a function as a stress relieving layer.

Production Example 5: Voltage Excess of High Hardness Layer

The same procedure as in Example 2 was followed. The operating conditions of the FCVA DLC coating system were coated at 400 V for 1500 seconds and then at 350 V for 2000 seconds. The hardness of the capillary fabricated in the present example was as low as 2250 HV and the adhesion force according to FIG. 5 was reduced to the HF3 level after deviating from the optimum deposition condition of the hardness layer.

Production Example 6: Voltage of low hardness layer

The same procedure as in Example 2 was carried out. The operating conditions of the FCVA DLC coating system were coated at 400 V for 1500 seconds and then at 10 V for 2000 seconds. The hardness of the capillary fabricated in the present example was as low as 2200 HV and the adhesion force according to FIG. 5 was reduced to the HF3 level after deviating from the optimal deposition condition of the hardness layer.

Production Example 7: Voltage Excess of Stress Relaxation Layer

The same procedure as in Example 2 was carried out. The operating conditions of the FCVA DLC coating system were coated at 950 V for 1500 seconds and then at 100 V for 2000 seconds. The hardness of the capillary fabricated in the present example was as low as 2000 HV and the adhesion force according to FIG. 5 was reduced to the HF3 level after deviating from the optimal deposition condition of the stress relieving layer.

Production Example 8: Voltage of stress relieving layer undersubstance

The same procedure as in Example 2 was followed. The operating conditions of the FCVA DLC coating system were coated at 150 V for 1500 seconds and then at 100 V for 2000 seconds. The hardness of the capillary fabricated in the present example was as low as 1950 HV and the adhesion force according to FIG. 5 was reduced to the HF4 level after deviating from the optimum deposition condition of the stress relieving layer.

Claims (7)

45 to 80% by weight of alumina and
20 to 55% by weight of zirconia,
And a capillary for wire bonding. The method according to claim 1,
Wherein the capillary for wire bonding is a diamond-like carbon coating (DLC coating). The method according to claim 1,
Wherein the alumina has an average particle diameter of 0.1 to 0.6 占 퐉. The method according to claim 1,
Wherein the zirconia has an average particle diameter of 0.1 to 0.6 占 퐉. The method according to claim 1,
The capillary for wire bonding, wherein the zirconia is partially stabilized. The method of claim 2,
Wherein the diamond-like carbon coating has a diamond-like carbon coating layer on the tip of the wire bonding capillary. (A) 45 to 80% by weight of alumina and 20 to 55% by weight of zirconia;
(B) milling the mixture;
(C) a press-molding step of compressing and molding the milled mixture;
(D) a degreasing step of heating the press-molded workpiece at 600 to 800 DEG C for 1 to 3 hours;
(E) a first heat treatment step of heating the degreased molded product at 1400 to 1700 캜 for 1 to 5 hours;
(F) hot isostatic molding step of molding the hydrostatic pressure of the first heat-treating the molded product at 1300 to 1500 ℃ and 1000 to 1500 kg _f / cm ^2;
(G) a second heat treatment step of heating the hot isostatic molded product at 1100 to 1300 캜 for 5 to 10 hours;
(H) cooling the second heat-treated shaped article by air cooling; And
(I) a step of coating diamond-like carbon on the cooled moldings.

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