Abstract:
The invention provides a method for manufacturing bearing assembly. The method comprises: coating a photoresist on an inner wall of a through hole of a bearing; inserting an ultraviolet lamp having a transparent groove pattern thereon into through hole and performing exposure process so as to photosensitize the photoresist corresponding to the groove pattern; removing the ultraviolet lamp and cleaning the photosensitized portion of the photoresist by developer; etching the inner wall not covered with the photoresist by an etchant or forming a deposited layer on the inner wall not covered with the photoresist; removing the photoresist reminding on the inner wall by a stripping agent so as to complete the method for manufacturing a dynamic bearing. The method is also proved to a surface of a shaft to manufacture the dynamic bearing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Continuation-In-Part of pending U.S. patent application Ser. No. 11/405,631, filed Apr. 18, 2006 and entitled “DYNAMIC BEARING MANUFACTURING METHOD”, and claims priority under 35 U.S.C. §119(a) on Patent Application No. 095130272 filed in Taiwan, Republic of China on Aug. 17, 2006, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to a method for manufacturing bearing assembly, and more particularly, to a method for manufacturing bearing assembly with pressure-generating grooves in photolithography process.  
         [0004]     2. Description of the Related Art  
         [0005]     A dynamic bearing comprises fine pressure-generating grooves on the inner walls thereof. As the axle of a motor spins, lubricant in the pressure-generating grooves is drawn to distribute between axle and the bearing and generate dynamical pressure therebetween, which reduces the friction between the axle and the bearing and eliminates the noise due to the friction. The pressure-generating grooves on the inner wall of the bearing, however, are difficult to be fabricated because of the minute scale of width and depth thereof. The costs of conventional manufacturing methods such as cutting, rolling, injection, or combination etc. are very high because these methods need special processing tools and skills. In addition, pressure-generating grooves processed by cutting processing often cause breach at the turning point and have inconsistent depth and width. Furthermore, the expensive processing machine and fragile cutting tools cannot be effectively and efficiently applied to mass production.  
       BRIEF SUMMARY OF INVENTION  
       [0006]     Ameliorating the aforementioned problems, the invention provides a method for manufacturing bearing assembly in photolithography process.  
         [0007]     According to the invention, a method of manufacturing a bearing assembly is provided. An exemplary embodiment of the method comprises the steps of: providing a bearing having a through hole; applying a photoresist on an inner wall of the through hole of the bearing; providing an ultraviolet lamp capable of entering into the through hole; attaching a mask having patterns of pressure-generating grooves to the surface of the ultraviolet lamp; inserting the ultraviolet lamp into the through hole to expose the photoresist through the mask; removing the exposed portions of photoresist to make its underneath portions of the inner wall appear; etching the appeared portions of the inner wall to form grooves; and stripping the remaining photoresist from the inner wall of the bearing.  
         [0008]     According to the exemplary embodiment, the bearing is preferably made of copper.  
         [0009]     According to the exemplary embodiment, the photoresist is preferably coated by spray coating, dipping, spin coating or centrifugal coating.  
         [0010]     According to the exemplary embodiment, after the photoresist has been coated, a baking step is preferably executed to cure the photoresist.  
         [0011]     According to the exemplary embodiment, the ultraviolet lamp preferably comprises cold cathode fluorescent lamp (CCFL) or light optical fiber.  
         [0012]     According to the exemplary embodiment, a portion of the mask, the patterns of pressure-generating grooves located, is transparent and the other portion is opaque.  
         [0013]     According to the exemplary embodiment, the mask does not only have the groove patterns, but also have a oil reservoir pattern to simultaneously form grooves and the oil reservoir on the inner wall of the through hole in the bearing.  
         [0014]     According to the exemplary embodiment, the mask preferably comprises a slice attached to the ultraviolet lamp, or a metal pattern directly formed on the wall of ultraviolet lamp.  
         [0015]     According to the exemplary embodiment, a portion of the mask, the groove patterns located, is opaque and the other portion thereof is transparent. An exposed portion of photoresist, such as positive photoresist, is removed by a developer, a deposited layer is then formed on a portion of the inner wall where the photoresist has been removed. The residual positive photoresist on the inner wall is removed by stripping agent to form the grooves between the two adjacent deposited layers. Washing the bearing by water is to complete dynamic bearing.  
         [0016]     According to the exemplary embodiment, the deposited layer is preferably made of a wear resistant material which is different from the bearing.  
         [0017]     According to the exemplary embodiment, the deposited layer on the portion of the inner wall which is not covered with photoresist is preferably formed by electroplating, sputtering, chemical reaction, or any other suitable manner for forming deposited layers.  
         [0018]     According to the exemplary embodiment, a negative photoresist can also be applied to coat on the inner wall to manufacture the bearing. Differences of the steps between examples of using negative and positive photoresists are the following: while the mask with the pattern of grooves is opaque, a portion of the inner wall without covering the photoresist is etched by etchant to a desirable depth to form the bearing with grooves; and while the mask with the pattern of grooves is transparent, a deposited layer is formed on the portion of the inner wall, where the photoresist not covered, by electroplating, sputtering, a chemical reaction, or any other suitable manner for forming deposited layer, to form a dynamic bearing having grooves formed between the two adjacent deposited layers.  
         [0019]     The method for manufacturing the bearing assembly according to the invention, a surface of a shaft can be processed by photolithography process to eliminate difficulty in manufacturing fine grooves of small bearing assembly.  
         [0020]     According to the method of manufacturing bearing assembly, an exemplary embodiment of the method comprises the steps of: providing a shaft; applying a positive photoresist on a surface of the shaft; providing an ultraviolet lamp with circular shape, and the inner surface thereof attached a mask having patterns of grooves; inserting the shaft into the ultraviolet lamp to expose and produce a photosensitized portion of the positive photoresist corresponding to a transparent portion of the mask; taking the shaft out the lamp and removing the exposed portion of the positive photoresist on the surface of the shaft by a developer; etching the surface of the shaft without covered with the positive photoresist to form a desirable depth; stripping the remaining positive photoresist from the surface of the shaft; and washing the shaft by water to complete manufacture of a dynamic bearing having grooves.  
         [0021]     According to the exemplary embodiment, the shaft is preferably made of copper or alloys thereof.  
         [0022]     According to the exemplary embodiment, the positive photoresist is preferably coated on the surface of the shaft by spray coating, dipping, spin coating or centrifugal coating. Preferably, a baking step is executed to cure the positive photoresist after the coating step.  
         [0023]     According to the exemplary embodiment, the groove pattern of the mask is transparent and the other pattern thereof is opaque.  
         [0024]     According to the exemplary embodiment, the mask does not only have the groove patterns, but also have a oil reservoir patterns to simultaneously form grooves and the oil reservoir on the surface of the shaft.  
         [0025]     According to the exemplary embodiment, a portion of the mask with the patterns of grooves is opaque and the other portion thereof is transparent. An exposed portion of positive photoresist is removed by a developer to form an appeared surface of the shaft and a deposited layer is then formed on the appeared surface of the shaft. The positive photoresist reminding on the surface of the shaft is removed by a stripping agent to form the grooves between the two adjacent deposited layers. Washing the bearing by water is to complete a dynamic bearing.  
         [0026]     According to the exemplary embodiment, the deposited layer is preferably made of a wear resistant material and can be a material which is different from or the same as the bearing.  
         [0027]     According to the exemplary embodiment, the deposited layer on the appeared surface of the shaft is preferably formed by electroplating, sputtering, chemical reaction, or any other suitable manner.  
         [0028]     According to the exemplary embodiment, a negative photoresist can be in place of the positive photoresist to manufacture the bearing assembly.  
         [0029]     In the embodiment, differences of the steps between examples of using negative and positive photoresists are the following: while the mask with the pattern of grooves is opaque, a portion of the surface of the shaft without covering the photoresist is etched by an etchant to a desirable depth to form the bearing having grooves; and while the mask with the pattern of grooves is transparent, a deposited layer is formed on the portion of the surface of the shaft where the photoresist does not cover thereon by electroplating, sputtering, chemical reaction, or any other suitable manner for forming deposited layer so that the bearing having grooves formed between the two adjacent deposited layer.  
         [0030]     The method for manufacturing the bearing of the invention, reduces equipment cost, and enables high the throughput. The method is introduced into automation or semi-automation. The dimensions of the formed groove are equal. Any groove shape is formed easily. A typical operator can easily perform the method. Because the manufacturing cost is lower, a medium-small ball bearing and solid lubricating bearing is replaced by a bearing manufactured according to the method of the invention.  
         [0031]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0032]     The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0033]      FIG. 1  is a cross section of a bearing according to a first embodiment of the invention;  
         [0034]      FIG. 2  is a cross section of a bearing coated with photoresist on the inner wall thereof according to the first embodiment of the invention;  
         [0035]      FIG. 3  shows a lamp used in an exposure process according to the first embodiment of the invention;  
         [0036]      FIG. 4  is a diagrammatic view of an exposure process according to the first embodiment of the invention;  
         [0037]      FIG. 5  is a diagrammatic view of a bearing after developing process according to the first embodiment of the invention;  
         [0038]      FIG. 6  is a diagrammatic view of a bearing after etching and stripping process according to the first embodiment of the invention.  
         [0039]      FIG. 7  is a diagrammatic view of the exposure lamp according to a second embodiment of the invention;  
         [0040]      FIG. 8  is a diagrammatic view of a photolithography step according to the second embodiment of the invention;  
         [0041]      FIG. 9  is a diagrammatic view of the bearing after development according to the second embodiment of the invention;  
         [0042]      FIG. 10A  is a diagrammatic view of the bearing after electroplating according to the second embodiment of the invention;  
         [0043]      FIG. 10B  is a fragmentary sectional view of the bearing in  FIG. 10A ;  
         [0044]      FIGS. 11A and 11B  are diagrammatic views of the bearing in  FIGS. 10A and 10B  after stripping, respectively;  
         [0045]      FIGS. 12 and 13  are fragmentary sectional views of the deposited layer according to the second embodiment of the invention and formed by adjusting different electroplating parameter, respectively;  
         [0046]      FIG. 14A  is a diagrammatic view of the bearing after sputtering according to a third embodiment of the invention;  
         [0047]      FIG. 14B  is a fragmentary sectional view of the bearing in  FIG. 14A ;  
         [0048]      FIGS. 15A and 15B  are diagrammatic views of the bearing in  FIGS. 14A and 14B  after stripping, respectively;  
         [0049]      FIG. 16A  is a diagrammatic view of bearing after chemical reaction according to a fourth embodiment of the invention:  
         [0050]      FIG. 16B  is a fragmentary sectional view of the bearing in  FIG. 16A ;  
         [0051]      FIGS. 17A and 17B  are diagrammatic views of the bearing in  FIGS. 16A and 16B , respectively, after stripping;  
         [0052]      FIG. 18  is a diagrammatic view illustrating steps for manufacturing a shaft according to a fifth embodiment of the invention;  
         [0053]      FIG. 19  is a diagrammatic view illustrating steps for manufacturing the shaft according to a sixth embodiment of the invention;  
         [0054]      FIG. 20  is a diagrammatic view illustrating steps for manufacturing the shaft according to a seventh embodiment of the invention;  
         [0055]      FIG. 21  is a diagrammatic view illustrating steps for manufacturing the shaft according to a eighth embodiment of the invention;  
         [0056]      FIG. 22  is a diagrammatic view illustrating steps for manufacturing the shaft according to a ninth embodiment of the invention; and  
         [0057]      FIG. 23  is a diagrammatic view illustrating steps for manufacturing the shaft according to a tenth embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0058]     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.  
       First Embodiment  
       [0059]     According to the invention, a method of manufacturing bearing at first is to form a desired shape of a bearing having a through hole by cutting or turning or by powder sintering way. The bearing, as shown in  FIG. 1 , is preferably made of copper.  
         [0060]     An inner wall  10  defining the through hole is coated with a photoresist  20  uniformly, as shown in  FIG. 2 , by spray coating, dipping, spin coating or centrifugal coating. The photoresist  20  coated on the inner wall  10  comprises polyimide, diazonium salt, or sulfonamide chlorine. In this embodiment of the invention, the photoresist  20  coated on the inner wall  10  is a kind of positive photoresist, for example “Electrolube PRP-200.” 
         [0061]     Then, the photoresist  20  coated on the inner wall  10  is dried by baking process for securing the adhesion between the inner wall  10  and the photoresist  20 . As shown in  FIG. 3 , an ultraviolet lamp  30  with a mask  40  attached on the surface thereof is provided. The mask  40  comprises patterns of pressure-generating grooves  401  and an oil reservoir  402  thereon. The ultraviolet lamp  30  is preferably a cold cathode fluorescent lamp or an optical fiber illuminant, which can emit ultraviolet light having wavelength ranging from 350 nm to 450 nm. With positive photoresist in this embodiment, the patterns of pressure-generating grooves  401  and oil reservoir  402  are transparent on the mask and the other portion thereof is opaque. In this embodiment, the groove on the mask is V-shaped. As shown in  FIG. 4 , after baking process, the ultraviolet lamp  30  with the mask  40  attached thereon is inserted into the through hole of the bearing, and activated to emit ultraviolet light to execute an exposure process. During the exposure process, a part of the photoresist  20  is sensitized by the ultraviolet light emitted from the ultraviolet lamp  30  through the patterns on the mask  40 .  
         [0062]     After the exposure process, as shown in  FIG. 5 , the ultraviolet lamp  30  is removed, and the exposed photoresist is removed by a developer to make the underneath portions of the inner wall  10  appear. The concentration of the developer is determined by the type of photoresist. In this embodiment, NaOH solution is used to serve as a developer.  
         [0063]     After the developing process, the bearing is cleaned by water. The appeared inner wall  10 , the portion of the inner wall  10  uncovering the photoresist  20 , is then etched by an etchant to form grooves  12  and an oil reservoir  13  with desirable dimensions. The etchant can comprise ferric chloride, cupric chloride or ammonium sulfide solution.  
         [0064]     After the etching process, the bearing is cleaned by water, and the photoresist  20  remaining on the inner wall  10  is stripped by a stripping solution such as alcohol. Then, the bearing is cleaned by water to remove the solutions and expose the grooves  12  and the oil reservoir  13 . The finished bearing of the invention is shown in  FIG. 6 .  
         [0065]     The feature of the invention is to form the pressure-generating grooves on the inner wall of a bearing by photolithography, so the solutions used in this invention are not limited. In addition, the grooves on the inner wall are also not limited in any shape, and it can be in fish bone shape, substantially-modified-X-shape, twill or straight stripe shape.  
       Second Embodiment  
       [0066]     According to a second embodiment of the invention, a method for manufacturing the bearing at first is to form a desired shape of a bearing having a through hole and then coat a photoresist on an inner wall of the through hole in the bearing by the similar steps to the first embodiment, as shown in  FIGS. 1 and 2 . Preferably, the bearing  1  is made of copper or alloys thereof. The photoresist  20  is preferably a positive photoresist such as, but not limited to, photosensitive polyimide (PSPI) photoresist, diazo photoresist, chlorine sulfonamide, naphthoquinone diazide derivative or novolakresin derivative, and can be coated by spray coating, dipping, spin coating or centrifugal coating. In the second embodiment, the photoresist  20  is AZP-4620 comprising of naphthoquinone diazide derivative and novolakresin derivative produced by Clariant Incorporation.  
         [0067]     The photoresist  20  coated on the inner wall  10  can be cured by baking. Alternatively, the photoresist  20  can be cured by natural drying at room temperature.  
         [0068]     Furthermore, as shown in  FIG. 7 , a lamp  30   a , also referred to as a ultraviolet lamp, capable of passing through the through hole and emitting light in ultraviolet spectrum, wherein the lamp  30   a  having a mask  40   a  with a pressure-generating groove pattern  401   a  thereon, is provided. Specifically, the mask  40   a  can be a slice having the pressure-generating groove pattern  401   a  thereon, attached to the lamp  30   a , or have metal pattern with the pressure-generating groove pattern  401   a  thereon, for example chromium (Cr), formed on the lamp  30   a . The lamp  30   a  is capable of emitting a light for photosensitizing the photoresist  20 . In this embodiment, the light is preferably ultraviolet having a wavelength of between about 350 nm and 450 nm. In this embodiment, a portion of the mask  40   a , where the pressure-generating groove pattern  401   a  located, is opaque. The pressure-generating groove pattern  401   a , as shown in  FIG. 7 , is only an exemplary embodiment, its shape can be varied with design and is thus not limited thereto.  
         [0069]     As shown in  FIG. 8 , the lamp  30   a  is placed inside the through hole of the bearing body  1  after curing and baking, the power thereof is then turned on to emit ultraviolet light so that the photoresist  20  can be exposed. Thus, a portion of the photoresist  20  corresponding to a transparent portion of the mask  40   a  is photosensitized.  
         [0070]     After exposing, the lamp  30   a  is then removed. The photosensitized portion of the positive photoresist  20  is removed by a developer to appear a portion of the inner wall  10 , as shown in  FIG. 9 . In this embodiment, the developer can be, for example AZ-300 made of tetramethyl ammonium hydroxide, produced by Clariant incorporation. Note that the composition and concentration of the developer depends on the material of the photoresist, thus is not limited to the described example.  
         [0071]     Referring to  FIG. 10A , the appeared portion of the inner wall  10 , without covered with the photoresist  20 , is coated with a wear-resistant material, for example nickel-cobalt (NiCo) alloy, nickel-phosphor (NiP) alloy or nickel-cobalt-phosphor (NiCoP) alloy, by electroplating to form a deposited layer  50 .  FIG. 10B  is a fragmentary sectional view of the bearing in  FIG. 10A .  
         [0072]     In  FIG. 11A , the photoresist  20  remaining on the inner wall  10  is stripped by a stripping solution to form a desirable, pressure-generating groove  12   a  between the two adjacent deposited layer  50 . In this embodiment, the stripping agent can be acetone. Thereafter, the solutions, using foregoing steps, are cleaned with water to perform a dynamic bearing according to the embodiment of the invention.  FIG. 11B  is a fragmentary sectional view of the bearing in  FIG. 11A .  
         [0073]     In this embodiment, the deposited layer formed by electroplating is not limited by the depth and width of the pressure-generating groove. Furthermore, the formation of the deposited layer can be modified by adjusting electroplating parameters, for example the electroplating duration, rate of electroplating, electroplating plus current and electroplating liquor additive. As a fragmentary sectional view of the bearing  1  shown in  FIG. 12 , a thickness of the deposited layer  50  is greater than that of the photoresist  20 . An arched top is formed, decreasing the area of a surface contacting a shaft for reducing friction between the deposited layer and the shaft. Additionally, by supplying different current to the exposed surface of the inner wall  10 , the thickness of the deposited layer  50  can be changed as desired, as a fragmentary sectional view of another bearing  1  shown in  FIG. 13 .  
       Third Embodiment  
       [0074]     According to a third embodiment of the invention, a method for manufacturing the bearing is substantially similar to the second embodiment. The formation of the deposited layer, according to the third embodiment of the invention, differs only slightly from the second embodiment. The similar steps, for example modeling, exposing and developing, already described in the second embodiment are not described again here. Note that the bearing  1  in the third embodiment can be metal such as brass, or nonmetal such as aluminum oxide ceramic.  
         [0075]      FIGS. 14A and 14B , a diagrammatic view and a fragmentary sectional view of the bearing  1  after developing, respectively. In this embodiment, subsequent to the developing step, a wear resistant material, for example nickel-cobalt (Ni—Co) alloy, silicon carbon (SiC), tungsten carbide (WC), is deposited on the photoresist  20  and the surface of the inner wall  10 , which is not covered by the photoresist  20  (also referred to as the surface of the appeared portion of the inner wall  10 ), by sputtering to form the deposited layer  60 . In  FIGS. 15A and 15B , the photoresist  20  and the wear resistant material deposited thereon are stripped by lift-off, to form the pressure-generating groove  12  between the two adjacent deposited layers  60 , so as to perform a dynamic bearing according to the third embodiment of the invention.  
       Fourth Embodiment  
       [0076]     The process of forming the deposited layer of the fourth embodiment of the invention differs only slightly from the second embodiment. The similar steps to the second embodiment, for example modeling, exposing and developing, may refer to  FIGS. 7-9  and its corresponding descriptions, and are not provided again here. Note that the bearing in this embodiment can be metal such as aluminum or alloys thereof.  
         [0077]     Subsequent to the developing step, a chemical reaction occurs between the surface of the inner wall  10 , which is not covered by the photoresist  20 , with ambient reactant to form a compound. In this embodiment, the bearing  10  comprising, for example, aluminum or aluminum alloy, is dipped into oxalic acid solvent. In  FIGS. 16A and 16B , an anode oxidation treatment is executed, the wear resistant material is then generated on the surface of the inner wall  10 , which is not covered by photoresist  20 , to form the deposited layer  70  comprising aluminum oxide. The photoresist  20 , reminding on the surface of the inner wall  10 , is removed by a stripping agent, such as acetone, following by washing with water and drying, to form the pressure-generating groove between the two adjacent deposited layers  70 . The dynamic bearing, as shown in  FIGS. 17A and 17B , according to the fourth embodiment of the invention, is complete. Noted that, in this embodiment the ambient reactant is liquid phase, but the ambient reactant can be liquid or gas phase, have a capable of reaction with the surface of the inner wall of the bearing.  
       Fifth Embodiment  
       [0078]      FIG. 18  is a diagrammatic view illustrating steps for manufacturing the bearing according to a fifth embodiment of the invention, in which the baring is shown in cross sectional view. In this embodiment, the bearing is preferably made of copper or alloys thereof.  
         [0079]     As shown in (a) of  FIG. 18 , the surface of inner wall of the bearing  1  is coated by photoresist  20   a  by the same steps as the first embodiment. Thus, the repeated descriptions are not provided. In this embodiment, the photoresist  20   a  is a negative photoresist, for example, comprising acrylic resin and propylene glycol monomethyl ether acetate, or a negative photoresist comprising epoxy resin and gamma butyrolactone.  
         [0080]     As shown in (b) of  FIG. 18 , the lamp  30   a  capable of emitting a wavelength in ultraviolet is placed inside the bearing  1  to expose the photoresist  20   a . In this embodiment, the lamp  30   a  has a mask with a pressure-generating groove pattern thereon and has an opaque area where the groove pattern located. In this embodiment, the lamp  30   a  can be similar to the one shown in  FIG. 7 .  
         [0081]     After exposing, the lamp  30   a  is removed. A portion of the photoresist  20   a  without photosensitizing is cleaned by developer and the portion of the inner wall made of copper is appeared, as shown in (c) of  FIG. 18 .  
         [0082]     Subsequently, as shown in (d) of  FIG. 18 , the portion of the inner wall without covering the photoresist  20   a , also referred to as an appeared portion of the inner wall, is etched by an etchant to form a desirable groove  12 . Next, the photoresist  20   a  reminding on the inner wall is stripped by a stripping agent to form a desirable groove pattern  12 .  
         [0083]     The steps for manufacturing the bearing are substantially the same as the first embodiment, unless the negative photoresist is utilized in this embodiment. Thus, groove pattern of the mask on the lamp in this embodiment is corresponding complement to that in the first embodiment.  
       Sixth Embodiment  
       [0084]      FIG. 19  is a diagrammatic view illustrating steps for manufacturing the bearing according to a sixth embodiment of the invention, in which the bearing is shown in cross sectional view. In this embodiment, the bearing is preferably made of copper or alloys thereof.  
         [0085]     As shown in (a) of  FIG. 19 , the surface of inner wall of the bearing  1  is coated by photoresist  20   a  by the similar steps to the first embodiment. Thus, the repeated descriptions are not provided. In this embodiment, the photoresist  20   a  is a negative photoresist.  
         [0086]     As shown in (b) of  FIG. 19 , the lamp  30  capable of emitting a ultraviolet wavelength is placed inside the bearing  1  to expose the photoresist  20   a . In this embodiment, the lamp  30  has a mask with a pressure-generating groove pattern thereon. The groove pattern located on the lamp  30  is transparent. In this embodiment, the lamp  30  can be the same as the one shown in  FIG. 3 .  
         [0087]     After exposing, the lamp  30  is removed. A portion of the photoresist  20   a  without photosensitizing is cleaned by a developer and the portion of the inner wall made of copper is appeared, as shown in (c) of  FIG. 19 .  
         [0088]     As shown in (d) of  FIG. 19 , a deposited layer  80  is deposited on the portion of the inner wall, which is not covered with the photoresist  20   a , also referred to as an appeared portion of the inner wall. Next, the photoresist  20   a  is stripped by a stripping agent and a desirable groove pattern  12   a  is formed between the two adjacent deposited layers  80 .  
         [0089]     This embodiment is the same as the fifth embodiment, unless the groove pattern of the mask on the lamp is transparent. The desirable groove pattern is formed by deposited layers.  
         [0090]     In the sixth embodiment, the deposited layer  80  is preferably made of a wear resistant material and is formed by the similar step to the second, third and fourth embodiments.  
       Seventh Embodiment  
       [0091]      FIG. 20  is diagrammatic view illustrating steps for manufacturing a shaft according to a seventh embodiment of the invention, in which the shaft is shown in cross sectional view. In this embodiment, the shaft is formed by cutting, turning or powder sintering and is made of copper or alloys thereof.  
         [0092]     As shown in (a) of  FIG. 20 , photoresist  20  is coated on the surface of the shaft  2  by spray coating, dipping, spin coating or centrifugal coating. Preferably, the photoresist  20  is made of a positive photoresist.  
         [0093]     As shown in (b) of  FIG. 20 , the shaft  2  is placed into a circular lamp  90  capable of emitting ultraviolet wavelength to expose the photoresist  20 . A slice with a pressure-generating groove pattern is attached to an inner surface of the circular lamp  90 . Then, the exposing is executed to photosensitize the positive photoresist corresponding to the transparent portion of the slice.  
         [0094]     In this embodiment, the slice is made of a mask  40  with the pressure-generating groove pattern and an area thereof with the pressure-generating groove pattern  401  located is transparent.  
         [0095]     After exposing, the shaft is removed from the circular lamp  90 . A portion of the photoresist  20  without photosensitizing is cleaned by a developer and the surface of the shaft made of copper is partly appeared, as shown in (c) of  FIG. 20 .  
         [0096]     As shown in (d) of  FIG. 20 , the surface of the shaft without covering the photoresist  20 , also referred to as an appeared surface of the shaft, is etched by an etchant. The photoresist  20  is then stripped by a stripping agent to form a desirable groove pattern  12 .  
         [0097]     This embodiment is substantially the same as the first embodiment, unless the groove is formed on the surface of the shaft by photolithography and the circular lamp is utilized to expose the surface of the shaft.  
       Eighth Embodiment  
       [0098]      FIG. 21  is diagrammatic view illustrating steps for manufacturing a shaft according to an eighth embodiment of the invention, in which the shaft is shown in cross sectional view. In this embodiment, the shaft is formed by cutting, turning or powder sintering, and is made of copper or alloys thereof.  
         [0099]     As shown in (a) of  FIG. 21 , the surface of the shaft  2  is coated by photoresist  20  by the similar steps to the seventh embodiment. Thus, the repeated descriptions are not provided here. In this embodiment, the photoresist  20  is a positive photoresist.  
         [0100]     As shown in (b) of  FIG. 21 , the shaft  2  is placed into a circular lamp (not shown) capable of emitting ultraviolet wavelength to expose the photoresist  20 . The exposing step in this embodiment is the same as that in the seventh embodiment unless the mask  40   a  with pressure-generating groove located is opaque.  
         [0101]     After exposing, the shaft is removed from the circular lamp. A portion of the photoresist  20  not photosensitized is cleaned by a developer to appear the surface of the shaft made of copper and form a groove pattern  401   a  corresponding to the groove pattern of the mask  40   a , as shown in (c) of  FIG. 21 .  
         [0102]     As shown in (d) of  FIG. 21 , the deposited layer  80  is formed on the surface of the shaft without covering the photoresist  20 , also referred to as an appeared surface of the shaft. The photoresist  20  is then stripped by a stripping agent to form a desirable groove pattern  12   a  between the two adjacent deposited layers.  
         [0103]     This embodiment is substantially the same as the seventh embodiment unless the groove pattern of the mask on the lamp is opaque. Thus, the desirable groove pattern is formed by the deposited layer.  
         [0104]     In this embodiment, the deposited layer  80  is preferably made of wear resistant material and formed by the similar steps to the second, the third and the fourth embodiments.  
       Ninth Embodiment  
       [0105]      FIG. 22  is diagrammatic view illustrating steps for manufacturing a shaft according to a ninth embodiment of the invention, in which the shaft is shown in cross sectional view and is preferably made of cooper or alloys thereof.  
         [0106]     As shown in (a) of  FIG. 22 , the surface of the shaft  2  is coated by photoresist  20   a  by spray coating, dipping, spin coating or centrifugal coating. Preferably, the photoresist  20   a  is a negative photoresist.  
         [0107]     As shown in (b) of  FIG. 22 , the shaft  2  is placed into a circular lamp (not shown) capable of emitting ultraviolet wavelength to expose the photoresist  20   a . The exposing step in this embodiment is the same as that in the eighth embodiment and the repeated descriptions are not provided here.  
         [0108]     After exposing, the shaft is removed from the circular lamp. A portion of the photoresist  20   a  not photosensitized is cleaned by a developer to appear the surface of the shaft made of copper and form a groove pattern  401   a  corresponding to the groove pattern of the mask  40   a , as shown in (c) of  FIG. 22 .  
         [0109]     As shown in (d)  FIG. 22 , the surface of the shaft without covering the photoresist  20   a , also referred to as an appeared surface of the shaft, is etched by an etchant. The photoresist  20   a  is then stripped by a stripping agent to form a desirable groove pattern  12 .  
         [0110]     This embodiment is substantially the same as the eighth embodiment unless the photoresist is the negative photoresist. Thus, the groove is formed on exterior surface of the shaft by etching.  
       Tenth Embodiment  
       [0111]      FIG. 23  is a diagrammatic view illustrating steps for manufacturing a shaft according to a tenth embodiment of the invention, in which the shaft is shown in cross sectional view and is preferably made of cooper or alloys thereof.  
         [0112]     As shown in (a) of  FIG. 23 , the surface of the shaft  2  is coated by photoresist  20   a . In this embodiment the photoresist  20   a  is a negative photoresist.  
         [0113]     As shown in (b) of  FIG. 23 , the shaft  2  is placed into a circular lamp  90  capable of emitting ultraviolet wavelength to expose the photoresist  20   a . A slice with a pressure-generating groove pattern is attached to an inner surface of the circular lamp  90 . Then, the exposing is executed to photosensitive the negative photoresist corresponding to the transparent portion of the slice. In this embodiment, the slice is a mask  40  with pressure-generating pattern and an area where the pressure-generating groove  401  located is transparent.  
         [0114]     After exposing, the shaft is removed from the circular lamp  90 . A portion of the photoresist  20   a  not photosensitized is cleaned by a developer to appear the surface of the copper shaft and form a groove pattern  401  corresponding to the groove pattern of the mask  40 , as shown in (c) of  FIG. 23 .  
         [0115]     As shown in (d) of  FIG. 23 , a deposited layer  80  is formed on the surface of the shaft without covering the photoresist  20   a , also referred to as an appeared surface of the shaft. The photoresist  20   a  is then stripped by a stripping agent to form a desirable groove pattern  12   a  between the two adjacent deposited layers  80 .  
         [0116]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.