Abstract:
A method for treating a surface of an element includes the steps of providing a photo-sensitive and flexible thin film, providing a planar photomask having a micro-structural pattern, transferring the micro-structural pattern to the thin film, attaching the thin film to the surface of the element and partially exposing a portion of the element, processing the exposed portion of the element, and removing the thin film to form a micro-structure on the surface of the element.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for treating the surface of an element, and more particularly, to a method using a photo-sensitive and flexible thin film to transfer a micro-structural pattern to an element having a non-planar surface. 
         [0003]    2. Description of the Prior Art 
         [0004]    The surface treatment of non-planar element is difficult due to its non-planar surface and the trend of miniaturization. Taking a fluid dynamic bearing as an example, the inner wall of the bearing has minute grooves with lubricant filled therein. When a shaft of a motor rotates, the lubricant filled in the grooves of the bearing will be drawn and spread all over the surface of the shaft, thereby generating a dynamic pressure. This dynamic pressure maintains the shaft in a central position of the bearing, and thus prevents friction between the shaft and the inner wall of the bearing, and restrains noises. 
         [0005]    However, the inner wall of the bearing is a curved surface so that to form the groove disposed thereon is difficult. The grooves to be formed have extremely minute width and depth, which makes it difficult to control the accuracy. Currently, several manufacturing techniques have been proposed, such as cutting technique, rolling technique, plastic injection technique, assembling technique and machining technique after thin film process. The methods, nevertheless, are costly because each of the methods requires particular machining tools, and have some disadvantages. For example, the turning section of the grooves formed by cutter technique is sometimes discontinuous, and the depth and width of the grooves are not identical. In addition, the problems such as the expensive cost of machining equipment, the fragility of cutter, the incapability of mass production, the low tolerance of vibration of the machining environment, and the requirement of professional worker, etc, are the difficulties that the conventional fluid dynamic bearing fabrication method have to overcome. 
       SUMMARY OF THE INVENTION 
       [0006]    It is therefore one of the objectives of the present invention to provide a method for treating a surface of an element to improve the high cost and inconsistent quality problems of the conventional surface treatment. 
         [0007]    According to the present invention, a method for treating a surface of an element includes steps of: providing a photo-sensitive and flexible thin film; providing a planar photomask having a micro-structural pattern; transferring the micro-structural pattern to the thin film; providing an element having a non-planar surface; attaching the thin film having the micro-structural pattern to the non-planar surface of the element. The thin film partially exposes the non-planar surface of the element, thereby forming at least an exposed region on the non-planar surface of the element. Subsequently, at least a material layer is disposed on the thin film and on the exposed region of the non-planar surface of the element by performing a coating process. Then, the thin film and the material layer formed on the thin film are removed to form a micro-structure on the non-planar surface of the element. 
         [0008]    According to the present invention, a method for treating a surface of an element includes steps of: providing a photo-sensitive and flexible thin film; providing a planar photomask having a micro-structural pattern; transferring the micro-structural pattern to the thin film; providing an element having non-planar surface; attaching the thin film having the micro-structural pattern to the non-planar surface of the element. The thin film partially exposes the surface of the element, thereby forming at least an exposed region on the surface of the element. Subsequently, the exposed region of the element is etched by performing an etching process, and the thin film is then removed to form a micro-structure on the non-planar surface of the element. 
         [0009]    According to the present invention, a method for treating a surface of an element includes steps of: providing a photo-sensitive and flexible thin film; providing a planar photomask having a micro-structural pattern; transferring the micro-structural pattern to the thin film; and attaching the thin film having the micro-structural pattern to a non-planar surface of the element. The thin film partially exposes the non-planar surface of the element, thereby forming at least an exposed region on the surface of the element. Subsequently, the exposed region of the non-planar surface of the element is treated by performing a surface treatment, and the thin film is removed to form a micro-structure on the non-planar surface of the element. 
         [0010]    The present invention uses a photo-sensitive, flexible and adhesive thin film to form a micro-structure on the non-planar surface of the element. The thin film is exposed in advance so that a micro-structural pattern is transferred from a planar photomask to the thin film, and the thin film is then attached to the non-planar surface of the element. The surface treatment such as an electroplating process or an etching process is implemented by virtue of the thin film with the micro-structural pattern. 
         [0011]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0013]      FIGS. 1-6  are schematic diagrams illustrating steps of a method for treating an element having a non-planar surface according to the first embodiment of the present invention. 
           [0014]      FIGS. 7 and 8  are schematic diagrams illustrating steps of a method for treating an element having a non-planar surface according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIGS. 1-6  are schematic diagrams illustrating steps of a method for treating an element having a non-planar surface according to the first embodiment of the present invention. As shown in  FIG. 1 , a thin film  10 , which is photo-sensitive, flexible and easy to attach, is provided, wherein the material of the thin film  10  may be various kinds of photoresist e.g. positive type, negative type, single-layered or multi-layered photoresist. Subsequently, a planar photomask  12  having a micro-structural pattern  12 A to be formed on an element having a non-planar surface is provided. 
         [0016]    As shown in  FIG. 2 , an exposure process is subsequently carried out to transfer the micro-structural pattern  12 A to the thin film  10  so that a micro-structural pattern  10 A corresponding to the micro-structural pattern  12 A is formed on the thin film  10 . Please note the micro-structural pattern  12 A of the planar photomask  12  must be consistent with the material of the thin film  10 . For instance, if the thin film  10  is positive type photoresist, the micro-structural pattern  12 A of the planar photomask  12  should be identical to the pattern of the thin film  10  after developed. On the other hand, if negative type photoresist is selected as the material of the thin film  10 , the micro-structural pattern  12 A of the planar photomask  12  and the pattern of the thin film  10  after developed should be complementary to each other. 
         [0017]    As shown in  FIG. 3 , an element  20  is provided. The material of the element  20  may be metal such as copper or non-metal such as glass. Then, the thin film  10  having the micro-structural pattern  10 A formed thereon is attached tightly to the curved surface of the element  20 . In the instant embodiment, a cylindrical tubal structured element is selected to illustrate the characteristic of the present invention, however, the method of the present invention is not limited and can be used to various types of non-planar surface treatment. 
         [0018]    As shown in  FIG. 4 , a development process is performed upon the thin film  10  to remove the unexposed portion of the thin film  10 . Accordingly, the thin film  10  partially exposes the curved surface of the element  20 , thereby forming at least one exposed region  22  on the surface. 
         [0019]    As shown in  FIG. 5 , a coating process is implemented to form at least a material layer  24  on the thin film  10  and on the exposed region  22  of the surface of the element  20  as well. The coating process may be various kinds of processes based on different material of the material layer  24  formed on the thin film  10 . For instance, the coating process can be a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, evaporation process, sputtering process, electroplating process, and non-electroplating process, etc. In addition, the material of the material layer  24  can be metal, nonmetal, oxide or a mixture of the aforementioned materials based on the micro-structure to be formed. The material layer  24  is not limited to single-layered, and may be multi-layered. It is appreciated that the material layer  24  shown in  FIG. 5  thoroughly covers the exposed region  22  of the element  20  and the surface of the thin film  10 . 
         [0020]    As shown in  FIG. 6 , a lift-off process is performed to remove the thin film  10  and the material layer  24  adhered to the thin film  20  to form a desired micro-structure on the curved surface of the element  20 . 
         [0021]    In the aforementioned embodiment, the micro-structure is formed on the non-planar curved surface of the element by thin film techniques, and the micro-structure is made of the material layer which protrudes out of the curved surface of the element. The method of the present invention is not limited by the above embodiment. Please refer to  FIGS. 7 and 8 .  FIGS. 7 and 8  are schematic diagrams illustrating a method for treating surface of an element having a non-planar surface according to the second embodiment of the present invention. Since the front-end process of this embodiment is similar to the first embodiment, please refer to  FIGS. 1-4  as well. It is appreciated that like components are designated by like numerals in these two embodiments, and repeated parts are not redundantly described. As shown in  FIG. 7 , the thin film  10  partially exposes the curved surface of the element  20  after developed, thereby forming the exposed region  22 . Subsequently, an etching process is performed using the thin film  10  as an etching mask to remove a portion of the element  20  in the exposed region  22 . The etching process may be a dry etching process or a wet etching process based on the material of the element  20  or the shape of the micro-structure to be formed. 
         [0022]    As shown in  FIG. 8 , the thin film  10 , which served as the etching mask, is removed to form the micro-structure on the curved surface of the element  20 . 
         [0023]    The method for treating a surface of an element of the present invention can be applied to form various types of elements having a non-planar surface such as a fluid dynamic bearing. In the aforementioned embodiments, an element having cylindrical tubal structure is used as an example and the micro-structure is formed on the outer surface (curved surface) of the cylindrical tubal element. However, the method of the present invention can also be applied to the inner surface of element and a three-dimensional element having various kinds of shapes e.g. a cylindrical structure or a cubic structure. 
         [0024]    The present invention uses a photo-sensitive, flexible and adhesive thin film to fabricate a micro-structure on a non-planar surface of element. The thin film is exposed in advance so that a micro-structural pattern is transferred from a planar photomask to the thin film, and the thin film is attached to the non-planar surface of the element. The surface treatment is implemented by virtue of the thin film with the micro-structural pattern. Compared with the conventional method, the method of the present invention is advantageous for its high efficiency, low cost and high applicability. 
         [0025]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.