Abstract:
Disclosed herein is a highly-durable electrode tool for electrochemical machining, which can prevent the corrosion and abrasion of a conductive pattern at the time of electrochemical machining for forming dynamic pressure-generating grooves of a fluid dynamic bearing, and a method of manufacturing the same. The electrode tool for electrochemical machining includes: an electrode substrate on which a conductive pattern is formed to have protrusions corresponding to the fine grooves and to which negative current is applied; a nonconductive insulating layer, covering an entire top surface of the electrode substrate excluding the conductive pattern; and a conductive layer, which is formed on the conductive pattern to protect the conductive pattern, and a top surface of which is the same height as a top surface of the nonconductive insulating layer.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2008-0059065, filed Jun. 23, 2008, entitled “Electrode Tool for the Electro chemical Machining and Method for Manufacturing the Electrode Tool”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrode tool for electrochemical machining and a method of manufacturing the same, and, more particularly, to a highly-durable electrode tool for electrochemical machining, which can prevent the corrosion and abrasion of a conductive pattern at the time of electrochemical machining for forming dynamic pressure-generating grooves of a fluid dynamic bearing, and a method of manufacturing the same. 
     2. Description of the Related Art 
     Electrochemical machining (ECM) is a method of etching fine grooves in a metallic material, which is a workpiece, by removing a metal oxide layer, which forms when the metallic material is electrochemically dissolved, and is used to form fine dynamic pressure-generating grooves in a fluid dynamic bearing. 
     In such a method of forming dynamic pressure generation grooves in a fluid dynamic bearing, positive current is applied to a bearing member in which dynamic pressure-generating grooves are to be formed, negative current is applied to an electrode tool in which a conductive pattern corresponding to the dynamic pressure-generating grooves is formed, and a high-pressure electrolyte flows between the bearing member and the electrode tool, thereby the dynamic pressure-generating grooves are electrochemically etched in the bearing member in the form of the conductive pattern. 
     Therefore, in order to conduct the electrochemical machining, a conductive pattern must be formed in an electrode tool in the form of dynamic pressure-generating grooves, and the electrode tool must not be abraded by a high-pressure electrolyte, and must be electrochemically durable. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and the present invention provides an electrode tool, which is not abraded by a high-pressure electrolyte and is electrochemically durable because its conductive pattern, corresponding to dynamic pressure-generating grooves, is formed to have a lower height than a nonconductive insulating layer and a conductive layer is formed on the conductive pattern, and a method of manufacturing the electrode tool. 
     In an aspect, the present invention provides an electrode tool for electrochemical machining, which is used to form fine grooves in the surface of a workpiece to which positive current is applied, including: an electrode substrate on which a conductive pattern is formed to have protrusions corresponding to the fine grooves and to which negative current is applied; a nonconductive insulating layer covering the entire top surface of the electrode substrate, excluding the conductive pattern; and a conductive layer, which is formed on the conductive pattern to protect the conductive pattern, and the top surface of which is the same height as the top surface of the nonconductive insulating layer. 
     Here, the conductive pattern of the electrode substrate may be formed to have a lower height than the nonconductive insulating layer. 
     Further, the conductive layer may be formed only on the top surface of the conductive pattern. 
     Alternatively, the conductive layer may be integrally formed on the top surface and lateral side of the conductive pattern. 
     Here, the conductive layer may be an insoluble metal plated layer made of gold, platinum or iridium having high electroconductivity. 
     In another aspect, the present invention provides a method of manufacturing an electrode tool for electrochemical machining, including: forming a conductive pattern on an electrode substrate such that the conductive pattern corresponds to fine grooves which are to be formed in the surface of a workpiece; forming a nonconductive insulating layer on the electrode substrate such that the nonconductive insulating layer covers the entire top surface of the electrode substrate to prevent the top surface of the conductive pattern from being exposed; polishing the nonconductive insulating layer to expose the top surface of the conductive pattern; etching the conductive pattern such that the top surface of the conductive pattern is stepped to be lower than the top surface of the nonconductive insulating layer; and forming a conductive layer on the top surface of the etched conductive pattern. 
     Here, in the etching of the conductive pattern, the conductive pattern may be etched through chemical etching. 
     Further, in the etching of the conductive pattern, the conductive pattern may be etched by applying positive current to the electrode substrate and then electrochemically machining the conductive pattern. 
     Further, in the forming of the conductive layer, the conductive layer may be formed such that the top surface of the conductive layer is the same height as the top surface of the nonconductive insulating layer. 
     Further, the conductive layer may be an insoluble metal plated layer made of gold, platinum or iridium, having high electroconductivity. 
     In a further aspect, the present invention provides a method of manufacturing an electrode tool for electrochemical machining, including: forming a conductive pattern on an electrode substrate such that the conductive pattern corresponds to fine grooves which are to be formed in the surface of a workpiece; forming a conductive layer on the electrode substrate such that the conductive layer covers the entire upper portion of the electrode substrate, including the top surface and lateral side of the conductive pattern; forming a nonconductive insulating layer on the conductive layer such that the nonconductive insulating layer covers the entire top surface of the conductive layer to prevent the conductive layer formed on the conductive pattern from being exposed; and polishing the nonconductive insulating layer to expose the conductive layer formed on the conductive pattern. 
     Here, in the polishing of the nonconductive insulating layer, the nonconductive insulating layer may be polished such that the top surface of the conductive layer is the same height as the top surface of the nonconductive insulating layer. 
     Further, the conductive layer may be an insoluble metal plated layer made of gold, platinum or iridium having high electroconductivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic sectional view showing an electrode tool for electrochemical machining according to a first embodiment of the present invention; 
         FIG. 2  is a schematic sectional view showing an electrode tool for electrochemical machining according to a second embodiment of the present invention; 
         FIG. 3  is a schematic flow chart showing a method of manufacturing the electrode tool of  FIG. 1 ; 
         FIGS. 4 to 8  are sectional views sequentially showing the method of manufacturing the electrode tool based on the flow chart of  FIG. 3 ; 
         FIG. 9  is a schematic flow chart showing a method of manufacturing the electrode tool of  FIG. 2 ; and 
         FIGS. 10 to 13  are sectional views sequentially showing the method of manufacturing the electrode tool based on the flow chart of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
     Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. 
     As shown in  FIGS. 1 and 2 , an electrode tool  100  includes an electrode substrate  110 , a nonconductive insulating layer  120  and a conductive layer  130 , and an electrode tool  200  includes an electrode substrate  210 , a nonconductive insulating layer  220  and a conductive layer  230 . 
     The electrode substrate  110  has the nonconductive insulating layer  120  and the conductive layer  130  placed thereon, and the electrode substrate  210  has the nonconductive insulating layer  220  and the conductive layer  230  placed thereon. Each of the electrode substrates  110  and  210  may be made of aluminum or aluminum alloy or may be made of iron or iron alloy, but the present invention is not limited thereto. 
     The electrode substrate  110  is formed thereon with a conductive pattern  111  corresponding to dynamic pressure-generating grooves in a fluid dynamic bearing, and the electrode substrate  210  is formed thereon with a conductive pattern  211  corresponding to the dynamic pressure-generating grooves in the fluid dynamic bearing. The process of forming each of the conductive patterns  111  and  211  will be described in detail below. 
     When cathode current is applied to each of the conductive patterns  111  and  211  at the time of electrochemical machining, dynamic pressure-generating grooves are formed in a bearing member facing each of the conductive patterns  111  and  211 . In this case, the conductive patterns  111  and  211  may be formed to have lower heights than the respective nonconductive insulating layers  120  and  220 . More specifically, the conductive pattern  111  and  211  are formed thereon with additional conductive layers  130  and  230 , respectively, in order to prevent the abrasion of the conductive patterns  111  and  211  and thus increase the durability thereof. In this case, the conductive pattern  111  and  211  may be stepped to be lower than the nonconductive insulating layers  120  and  220 , respectively, such that the top surfaces of the conductive layers  130  and  230  are the same height as those of the nonconductive insulating layers  120  and  220 , respectively. 
     The nonconductive insulating layers  120  and  220  serve to prevent an electrochemical reaction from occurring in the portions excluding the conductive pattern  111  and  211 , and are formed on the respective electrode substrates  110  and  210  such that only the conductive patterns  111  and  211  are exposed. 
     The conductive layers  130  and  230  are formed on the respective conductive patterns  111  and  211 , and thus serve to prevent the abrasion or corrosion of the conductive patterns  111  and  211  and thus increase the durability thereof. Further, the conductive layers  130  and  230  are formed to cover the top surfaces of the respective conductive patterns  111  and  211 , stepped to be lower than the respective nonconductive insulating layers  120  and  220 . In this case, the top surfaces of the conductive layers  130  and  230  may be the same height as those of the nonconductive insulating layers  120  and  220 , respectively. Here, each of the conductive layers  130  and  230  may be an insoluble metal plated layer made of gold, platinum, iridium or the like, and, in the embodiments of the present invention, each of the conductive layers  130  and  230  is a gold plated layer having excellent electrochemical machinability. 
     Hereinafter, the above electrode tools  100  and  200  according to preferred embodiments of the present invention will be described in detail with reference to  FIGS. 1 and 2 . 
     As shown in  FIG. 1 , the electrode tool  100  for electrochemical machining according to a first embodiment of the present invention includes an electrode substrate  110 , a conductive pattern  111  formed on the electrode substrate  110  through etching, electrochemical machining or physical machining, and a nonconductive insulating layer  120  covering the conductive pattern  111  such that only the top surface of the conductive pattern  111  is exposed. 
     In this case, the top surface of the conductive pattern  11  is stepped to be lower than the top surface of the nonconductive insulating layer  120 , and a gold plated layer  130  is formed on the top surface of the conductive pattern  111 . 
     According to the first embodiment of the present invention, since the top surface of the gold plated layer  130  is the same height as that of the nonconductive insulating layer  120 , it is possible to prevent the gold plated layer  130  from peeling even when a high-pressure electrolyte flows onto the top surface of the gold plated layer  130 . 
     The method of manufacturing the electrode tool  100  according to the first embodiment of the present invention will be described in more detail with reference to  FIGS. 3 to 8  below. 
     As shown in  FIG. 2 , the electrode tool  200  for electrochemical machining according to a second embodiment of the present invention includes an electrode substrate  210 , a conductive pattern  211  formed on the electrode substrate  110  through etching, electrochemical machining or physical machining, and a gold plated layer  230  completely covering the top surface of the electrode substrate  210 . 
     That is, in the second embodiment of the present invention, unlike the first embodiment of the present invention, the gold plated layer  230  is formed on the lateral side of the conductive pattern  211  as well as on the top surface of the conductive pattern  211  and part of the electrode substrate  210 , on which a nonconductive insulating layer  220  is to be formed. 
     The nonconductive insulating layer  220  is formed on the electrode substrate  210  such that the conductive pattern  211 , on which the gold plated layer is formed, is exposed. In this case, the top surface of the gold plated layer  230  formed on the conductive pattern  211  may be the same height as the top surface of the nonconductive insulating layer  220 . 
     According to the second embodiment of the present invention, since the top surface of the gold plated layer  230  is the same height as that of the nonconductive insulating layer  220  and the gold plated layer  230  is integrally formed on the top surface and later side of the conductive pattern  211 , it is possible to prevent the gold plated layer  230  from peeling even when a high-pressure electrolyte flows onto the top surface of the gold plated layer  230 . 
     A method of manufacturing the electrode tool  200  according to the second embodiment of the present invention will be described in more detail with reference to  FIGS. 9 to 13  below. 
       FIG. 3  is a flow chart showing a method of manufacturing the electrode tool  100  according to a first embodiment of the present invention, and  FIGS. 4 to 8  are sectional views showing the method of sequentially manufacturing the electrode tool based on the flow chart of  FIG. 3 . 
     First, as shown in  FIG. 4 , a conductive pattern  111  is formed on an electrode substrate  110 . In this case, the conductive pattern  111  may be formed by etching a part of the electrode substrate  110 , excluding the conductive pattern  111 , through a chemical method. In addition, the conductive pattern  111  may also be formed by physically treating the electrode substrate  110 . Here, the conductive pattern  111  is formed such that it corresponds to dynamic pressure-generating grooves in a fluid dynamic bearing (S 110 ). 
     Subsequently, as shown in  FIG. 5 , the entire top surface of the electrode substrate  110  is covered with a nonconductive insulating layer  120 . That is, the nonconductive insulating layer  120  is formed such that it also completely covers the conductive pattern  111  formed on the electrode substrate  110  (S 120 ). 
     Subsequently, as shown in  FIG. 6 , the nonconductive insulating layer  120  formed on the top surface of the electrode substrate  110  is polished to expose the top surface of the conductive pattern  111 . In this case, the polishing of the nonconductive insulating layer  120  may be conducted through physical polishing, that is, lapping (S 130 ). 
     Subsequently, as shown in  FIG. 7 , the conductive pattern  111  is etched such that the top surface of the conductive pattern  111  is stepped to be lower than the top surface of the nonconductive insulating layer  120 . In this case, the etching of the conductive pattern  111  may be conducted through chemical etching or electrochemical machining (ECM). More specifically, the conductive pattern  111  may be chemically etched by applying an etchant on the nonconductive insulating layer  120  or by forming an additional mask over the nonconductive insulating layer  120  and then applying an etchant on the nonconductive insulating layer  120 . In addition, the conductive pattern  111  may be etched by applying positive current to the electrode substrate  110  (S 140 ). 
     Finally, as shown in  FIG. 7 , a gold plated layer  130  is formed on the conductive pattern  111 , which is stepped to be lower than the nonconductive insulating layer  120 . In this case, the top surface of the gold plated layer  130  is the same height as the top surface of the nonconductive insulating layer  120  to prevent the gold plated layer  130  from peeling (S 150 ). 
       FIG. 9  is a flow chart showing a method of manufacturing the electrode tool  200  according to a second embodiment of the present invention, and  FIGS. 10 to 13  are sectional views showing the method of sequentially manufacturing the electrode tool based on the flow chart of  FIG. 9 . 
     First, as shown in  FIG. 10 , a conductive pattern  211  is formed on an electrode substrate  210 . In this case, the conductive pattern  211  may be formed by etching a part of the electrode substrate  210 , excluding the conductive pattern  211 , through a chemical method. In addition, the conductive pattern  211  may also be formed by physically treating the electrode substrate  210  (S 210 ). 
     Subsequently, as shown in  FIG. 11 , the entire top surface of the electrode substrate  210  is covered with a gold plated layer  230 . That is, the gold plated layer  230  is formed such that it completely covers the conductive pattern  211  formed on the electrode substrate  210  (S 220 ). 
     Subsequently, as shown in  FIG. 12 , the entire top surface of the electrode substrate  210  covered with the gold plated layer  230  is covered with a nonconductive insulating layer  220 . That is, the nonconductive insulating layer  220  is formed such that it completely covers the gold plated layer  230  formed on the conductive pattern  211  (S 230 ). 
     Subsequently, as shown in  FIG. 13 , the nonconductive insulating layer  220  formed on the conductive pattern  211  is polished to expose the top surface of the conductive pattern  111 , that is, the top surface of the gold plated layer  230  formed on the conductive pattern  211 . In this case, since the top surface of the gold plated layer  230  is the same height as that of the nonconductive insulating layer  220  and the gold plated layer  230  is integrally formed on the top surface and lateral side of the conductive pattern  211 , it is possible to prevent the gold plated layer  230  from peeling (S 240 ). 
     As described above, although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.