Abstract:
A method for integrating and erecting CNT column, comprises following steps of: 1) providing a conductive layer; 2) applying a non-conductive layer over the conductive layer; 3) forming a via on the non-conductive substrate; 4) placing an electrode above the via; 5) deploying dispersive liquid containing CNT powder into the via; 6) applying a predetermined AC electric field between the conductive substrate and the electrode for integrating and erecting the CNT powder into CNT column under electric field force.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method for integrating carbon nanotube column, and more particularly to a method using vertical electricfield for integrating carbon nanotube column thus achieving erect nanotube column. 
         [0003]    2. Description of the Prior Art 
         [0004]    Since carbon nanotube (CNT) was discovered and reported by Japanese physical spiciest Sumio Iijima in 1991, the physical and electrical properties of the CNT is more and more appreciated by the industry as more and more genuine applications are introduced. 
         [0005]    However, the CNT must be integrated/assembled before it is used in a certain application. At present, a conventional method called dielectrophoresis (DEP) is used to integrate the CNT into an unitary structure. As shown in  FIG. 1 , the conventional method uses two electrodes disposed on a same side of a substrate and spaced to each other. Dispersive liquid with CNT powder will be dropped into a cavity disposed between the two electrodes. When an AC electric field is applied between the two electrodes, the CNT powder will be integrated into CNT column under electric field force. Such CNT column is suit for some applications, e.g., chemical sensor, but is not suit for application which needs the CNT having a three-dimensional structure. For example, contact of electrical connector for connecting Integrated Circuit (IC) package usually needs a three-dimensional structure. Therefore, the CNT art is hard to be used in electrical connector field. 
         [0006]    U.S. Pat. No. 6,626,684 issued to Stickler on Sep. 30, 2003 disclosed a nanotube socket system using three-dimensional nanotube column for transmitting electric signal. However, Stickler is silent on how to integrate the nanotube into CNT-column. 
         [0007]    Therefore, it is needed to find a new method to overcome the problems mentioned above. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, an object of the present invention is to provide a method for integrating nanotubes column, and more particularly to a method using vertical electric field for integrating and erecting nanotubes column thus achieving erect nanotubes column which can be used in electric socket field. 
         [0009]    In order to achieve the object set forth, a method for integrating and erecting CNT column, comprises following steps of: 1) providing a conductive layer; 2) applying a non-conductive layer over the conductive layer; 3) forming a via on the non-conductive substrate; 4) placing an electrode above the via; 5) deploying dispersive liquid containing CNT powder into the via; 6) applying a predetermined AC electric field between the conductive substrate and the electrode for integrating and erecting the CNT powder into CNT column under electric field force. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a sketch view of a conventional method for integrating CNT; 
           [0011]      FIG. 2  shows a schematic diagram of a method for integrating and erecting CNT column of the present invention; 
           [0012]      FIG. 3A  and  FIG. 3B  shows an integrate process for integrating CNT by using the method of the present invention in accordance with a first preferred embodiment; 
           [0013]      FIG. 4  is a photograph of a CNT-column made by the method of the present invention. 
           [0014]      FIG. 5A  and  FIG. 5B  shows an integrate process for integrating CNT by using the method of the present invention in accordance with a second preferred embodiment; 
           [0015]      FIG. 6  is an isometric view of an electrical socket of the present invention in accordance with the second preferred embodiment; and 
           [0016]      FIG. 7  is an exploded view of the electrical socket shown in  FIG. 6 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       [0017]    Reference will now be made to the drawings to describe the present invention in detail. 
         [0018]    Referring to  FIG. 2(   a )-( b ), schematic diagram of the present invention is shown. As we know, when an AC electric field is applied between two electrodes, the CNT powder will be moved under electric field force along direction of the electric field. Such phenomenon is called dielectrophoresis (DEP). 
         [0019]    Referring to  FIGS. 3A-3B , a method called vertical DEP in accordance with a first preferred embodiment of the present invention is shown, which uses vertical electric field to integrate and erect CNT powder into CNT columns with erect structure. According to the method, firstly, a base substrate  11  is provided with a number of vias  11   a  (only one is shown). The vias  11   a  are arranged in a manner of matrix or other layout. Then, a first electrode  10  and a second electrode  12  is disposed at two sides of the base substrate  11  respectively and corresponding to a via  11   a . According to a preferred embodiment of the present invention, the base substrate  11  is made from non-conductive matters. The first electrode  10  is a substrate made from gold and covering on a lower surface of the substrate  11 . Specially, the first electrode  10  and the base substrate  11  is disposed on a surface of a wafer  16 . The second electrode  12  is a conductor and of an acicular or columnar shape. According to the preferred embodiment of the invention, diameter of the second electrode  12  is smaller than that of the via  11   a , so as to control diameter of the CNT column, which will be erected. The second electrode  12  has a plate structure on a top end thereof for pulling up dispersive liquid  13  containing CNT powder  13   a  to form liquid column, thus increasing volume of the dispersive liquid  13  and the number of CNT powder  13   a  involved/used in the vertical DEP process. In the preferred embodiment of the present invention, only one second electrode  12  is shown. In fact, number of the second electrode  12  is equal to number of the vias  11   a.    
         [0020]    Thirdly, the dispersive liquid  13  having CNT powder  13   a  will be dropped into the via  11   a . Preparation of the dispersive liquid  13  will be described later. At last, an AC electric field is applied between the first electrode  10  and the second electrode  12 . Accordingly, the CNT powder  13   a  contained in the dispersive liquid  13  will be integrated and erected into a CNT column  14  (as shown in  FIG. 4 ) under electric field force. 
         [0021]    As shown in  FIG. 4 , the CNT column  14  formed from the vertical DEP solution is of an erect structure and can be used in more application, e.g. electrical connector field. Contrarily, CNT column from the conventional DEP art has a sheet structure and has a limited application. 
         [0022]    In the preferred embodiment, preparation of the dispersive liquid  13  comprises steps of mixing and dispersing the CNT powder  13   a  into a miscible liquid which is consisted of 50% distilled water in volume and 50% alcohol in volume, and a process of ultrasonic shock wash 1.5 hours. According to the preferred embodiment, ratio by volume of the water and alcohol may be between 1:1 and 1:3. Moreover, because volume and quality of the CNT powder  13   a  are very small, molecular force between the CNT powder  13   a  may becomes strong during process of the CNT powder  13   a  mixed and dispersed into the miscible liquid containing distilled water and alcohol, which will make the CNT powder  13   a  easily intertwined. Therefore, before the actual mixed and dispersed process of the application, the best to be addressed, the CNT powder  13   a  are experienced a process of acid treatment. The acid treatment is a known art and uses nitric acid and sulphuric acid for purifying the CNT powder  13   a . Use of the aforementioned dispersive way of CNT powder, can achieve a very good dispersive result. 
         [0023]    Referring to  FIGS. 5A-5B , a method called vertical DEP in accordance with a second preferred embodiment of the present invention is shown, which uses vertical electric field to integrate and erect CNT powder into CNT columns with erect structure. According to the method, firstly, a base substrate  11 ′ is provided with a number of vias  11   a ′ (only one is shown). The vias  11   a ′ are arranged in a manner of matrix or other layout. Then, a first electrode  10  and a second electrode  12 ′ is disposed at two sides of the base substrate  11 ′ respectively and corresponding to a via  11   a ′. According to a preferred embodiment of the present invention, the base substrate  11 ′ is made from non-conductive matters. The first electrode  10 ′ is a substrate made from gold and covering on a lower surface of the substrate  11 ′. The second electrode  12 ′ is a conductor and of an acicular or columnar shape. According to the preferred embodiment of the invention, diameter of the second electrode  12 ′ is smaller than that of the via  11   a ′, so as to control diameter of the CNT column, which will be erected. The second electrode  12 ′ has a plate structure on a top end thereof for pulling up dispersive liquid  13 ′ containing CNT powder  13   a ′ to form liquid column, thus increasing volume of the dispersive liquid  13 ′ and the number of CNT powder  13   a ′ involved/used in the vertical DEP process. In the preferred embodiment of the present invention, only one second electrode  12 ′ is shown. In fact, number of the second electrode  12 ′ is equal to number of the vias  11   a′.    
         [0024]    Thirdly, the dispersive liquid  13 ′ having CNT powder  13   a ′ will be dropped into the via  11   a ′. Preparation of the dispersive liquid  13 ′ will be described later. At last, an AC electric field is applied between the first electrode  10  and the second electrode  12 ′. Accordingly, the CNT powder  13   a ′ contained in the dispersive liquid  13 ′ will be integrated and erected into a CNT column  14  (as shown in  FIG. 4 ) under electric field force. 
         [0025]    As shown in  FIG. 4 , the CNT column  14  formed from the vertical DEP solution is of an erect structure and can be used in more application, e.g. electrical connector field. Contrarily, CNT column from the conventional DEP art has a sheet structure and has a limited application. 
         [0026]    In the preferred embodiment, preparation of the dispersive liquid  13 ′ comprises steps of mixing and dispersing the CNT powder  13   a ′ into a miscible liquid which is consisted of 50% distilled water in volume and 50% alcohol in volume, and a process of ultrasonic shock wash 1.5 hours. Moreover, because volume and quality of the CNT powder  13   a ′ are very small, molecular force between the CNT powder  13   a ′ may becomes strong during process of the CNT powder  13   a ′ mixed and dispersed into the miscible liquid containing distilled water and alcohol, which will make the CNT powder  13   a ′ easily intertwined. Therefore, before the actual mixed and dispersed process of the application, the best to be addressed, the CNT powder  13   a ′ are experienced a process of acid treatment. The acid treatment is a known art and uses nitric acid and sulphuric acid for purifying the CNT powder  13   a ′. Use of the aforementioned dispersive way of CNT powder, can achieve a very good dispersive result. 
         [0027]    Method for integrating and erecting CNT column can be used in electrical socket field for making an electrical socket. Referring to  FIGS. 6-7 , firstly, an insulative substrate  2  will be provided. The insulative substrate  2  has opposite upper surface  20 , lower surface  22  and a number of through holes  24  extending through both the surfaces. Then, the first electrode  10 ′ and the second electrode  12 ′ will be disposed at two sides of the insulative substrate  2  respectively and corresponding to a through hole  24 . Thirdly, the dispersive liquid  13 ′ having CNT powder  13   a  will be dropped into the through hole  24 . At last, an AC electric field is applied between the first electrode  10 ′ and the second electrode  12 ′. Accordingly, the CNT powder  13   a ′ contained in the dispersive liquid  13 ′ will be integrated and erected into a CNT column  14  along the through hole under electric field force. Accordingly, an electrical socket having CNT structure is provided. 
         [0028]    Although the present invention has been described with reference to particular embodiments, it is not to be construed as being limited thereto. Various alterations and modifications can be made to the embodiments without in any way departing from the scope or spirit of the present invention as defined in the appended claims.