Patent Publication Number: US-2013229365-A1

Title: Touchpad structure and manufacturing method thereof

Description:
FIELD OF THE INVENTION 
     The present invention is related generally to a touchpad structure and manufacturing method thereof and, more particularly, to a thinner touchpad structure with a sensing layer formed on the shielding layer by a circuit forming process for reducing manufacturing processes and a manufacturing method thereof. 
     BACKGROUND OF THE INVENTION 
     Touchpads have been commonly used as an input interface for electronic devices. For example, touchpads embedded in laptops or touchpads connected to desktop PCs in a wired or wireless manner. Users can implement commands such as selecting, dragging and executing by the touchpads. 
     As shown in  FIG. 1 , a conventional touchpad structure  7  comprises a circuit board  71 , a hard coat  72 , an adhesive layer  73  and plural driving elements  74 . The circuit board  71  is a printed circuit board (PCB), on which plural sensors and plural conducting wires connected to the sensors are laid. The hard coat  72  is a Mylar and adhered to one side of the circuit board  71  through the adhesive layer  73 . The driving elements  74  are disposed at an opposite side of the circuit board  71  using surface mounting technology (SMT). 
     Since the conventional circuit board  71  is rigid, the adhesive layer  73  is necessary for affixing the hard coat  72  to the circuit board  71 . During the adhering process, the layers have to be accurately aligned and appropriately stuck, so the operation of the adhering process is relatively difficult and the yield is relatively poor. In addition, for allowing the sensors that is directly formed on the circuit board  71  to detect touch gestures made on the hard coat  72 , so the circuit board  71  has to be assembled to the side of the hard coat  72  in position, making the overall thickness of the conventional touchpad structure  7  be the sum of the respective thicknesses of the circuit board  71 , the hard coat  72 , the adhesive layer  73  and the driving elements  74 . Moreover, the thicknesses of the circuit board  71  and the driving elements  74  can not significantly be reduced due to inherent layout requirements of the circuit board  71  and the driving elements  74 , so the task of reducing the overall thickness of the conventional touchpad structure is difficult. Consequently, the target that is to lighten and to thin the touchpad can&#39;t be achieved. 
     Additionally, the Mylar that is used by the hard coat  72  does not provide good feel and in practice tends to hinder fingers from smoothly moving on the hard coat  72 . It is adverse to smoothness and quality of the operation. 
     As shown in  FIG. 2 , another conventional touchpad structure  8  comprises a substrate  81 , a sensing layer  82 , an adhesive layer  83 , a circuit board  84  and plural driving elements  85 . The substrate  81  is a glass substrate and the sensing layer  82  has a sensing circuit structure which is directly forming on a thin film by printing manner. The sensing layer  82  is affixed to one side of the substrate  81  through an adhesive layer  83 , and one end of the circuit board  84  is electrically connected to the sensing layer  82 , while the driving elements  85  are mounted on one side of the circuit board  84 . 
     Although the conventional touchpad structure  8  uses glass to replace the Mylar of the conventional touchpad structure  7  and thereby improves feel, its substrate  81  is also rigid so the sensing layer  82  also has to be affixed to the side of the substrate  81  using the adhesive layer  83 . Thus, the problems about difficult operation of adhering process and poor yield caused by using the adhesive layer  73  or  83  remain unsolved. 
     The conventional one glass solutions (OGS) are mainly used in electronic touch devices, such as smart mobile phones and iPads. As shown in  FIG. 3 , a conventional OGS  9  comprises a substrate  91 , an ink layer  92 , a covering layer  93 , a sensing layer  94  and a circuit board  95 . The substrate  91  is a glass substrate and the ink layer  92  is arranged along a periphery of one surface of the substrate  91 , so that the central area of the substrate  91  is left as an area that can be seen through. The covering layer  93  is transparent and laid on the surface of the substrate  91  on which the ink layer  92  is arranged so as to fully cover the substrate  91  and the ink layer  92 . The sensing layer  94  is formed on a surface of the covering layer  93  by a thin film forming process, and one end of the circuit board  95  is electrically connected to the sensing layer  94 . 
     Comparing the conventional touchpad structures  7  and  8 , although OGS  9  eliminates the problems coming from the adhesive layer  73  or  83 , its application field is different from that of the conventional touchpad structures  7  and  8  in nature. Furthermore, due to the seeing-through area formed in the central area of conventional OGS  9 , the ink layer  92  on the surface of the substrate  91  forms a thickness drop. The surface of the substrate  91  having the ink layer  92  is not even, so the covering layer  93  has to be added to cover the surfaces of the substrate  91  and the ink layer  92  in order to provide an even plane that allows the sensing layer  94  to be laid evenly and uniformly on the side of the substrate  91 . Consequently, the manufacturing process of the conventional OGS  9  is very complicated. In addition, for allowing users to see images through the seeing-through area, the sensing layer  94  in the OGS  9  can only be made of transparent metallic material. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a touchpad structure, wherein a sensing layer is formed on a shielding layer using a circuit forming process, so that the overall thickness of the touchpad structure can be reduced. 
     Another objective of the present invention is to provide a manufacturing method of a touchpad structure, wherein a sensing layer is formed on a shielding layer using a circuit forming process, so that the manufacturing process can be simplified and the yield can be improved. 
     According to the present invention, a touchpad structure comprises a substrate, a shielding layer and a sensing layer, wherein the substrate has a first surface fully covered by the shielding layer, and the sensing layer is formed on one side of the shielding layer, so that the shielding layer is sandwiched between the substrate and the sensing layer. 
     According to the present invention, a touchpad structure comprises a substrate, a shielding layer and a sensing layer, wherein the substrate has a first surface and the shielding layer covers the first surface of the substrate. The sensing layer is formed on one side of the shielding layer by a circuit forming process, so that the shielding layer is sandwiched between the substrate and the sensing layer. 
     According to the present invention, a manufacturing method of a touchpad structure comprises providing a substrate, forming a shielding layer on a first surface of the substrate, and forming a sensing layer on the shielding layer by a circuit forming process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objectives, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments according to the present invention taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view of a conventional touchpad structure; 
         FIG. 2  is a cross-sectional view of another conventional touchpad structure; 
         FIG. 3  is a cross-sectional view of a conventional OGS; 
         FIG. 4  is a cross-sectional view of a touchpad structure according to one preferred embodiment of the present invention; 
         FIG. 5  is a bottom view of a sensing layer according to the preferred embodiment of the present invention; 
         FIG. 6  is a bottom view of another embodiment of the sensing layer according to the preferred embodiment of the present invention; 
         FIG. 7  is a flow chart of a manufacturing method according to the preferred embodiment of the present invention; 
         FIG. 8  is a cross-sectional view of a part of the sensing layer circled by a dotted circle in  FIG. 5 ; 
         FIG. 9  is a cross-sectional view of another embodiment of the sensing layer circled by a dotted circle in  FIG. 5 ; and 
         FIG. 10  shows a circuit component according to the preferred embodiment of the present invention connected to the sensing layer through a flexible flat cable. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 4  and  FIG. 5 , in a preferred embodiment according to the present invention, a touchpad structure comprises a substrate  1 , a shielding layer  2 , a sensing layer  3  and a circuit component  4 . The substrate  1  is preferably a glass substrate. Two opposite surfaces of the substrate  1  are defined as a first surface  12  and a second surface  14 , respectively. The shielding layer  2  is formed on and fully covers the first surface  12 . The second surface  14  acts as an operative surface on which a user can operate by an object, e.g. a finger or a touch pen, to control a cursor or input commands. 
       FIG. 5  is a bottom view of the sensing layer  3  of the touchpad structure according to the present invention. The sensing layer  3  has a sensing circuit structure directly formed on the shielding layer  2  for detecting touch gestures performed on the substrate  1  and generating sensing signals accordingly. The sensing circuit structure comprises plural first direction traces  32  and plural second direction traces  34 . The first direction trace  32  has plural first direction sensors  322  and plural conducting wires  324 , wherein the conducting wires  324  are electrically connected to the first direction sensors  322 . The second direction trace  34  has plural second direction sensors  342  and plural conductive bridges  344 . The conductive bridge  344  cross the conducting wire  324  of the first direction traces  32  and are electrically connected to the second direction sensors  342 . In this embodiment, the first and second direction traces  32 ,  34  are orthographically arranged but may be arranged otherwise in other embodiments. In practical use, as shown in  FIG. 6 , the first and second direction traces  32 ,  34  may be arranged in interlaced and parallel or any other feasible circuit layouts. 
     The circuit component  4  may be a PCB or a flexible printed circuit board (FPC) according to practical needs. The circuit component  4  is electrically connected to the sensing layer  3  and has a driving element  42 . The circuit component  4  receives the sensing signals from the sensing layer  3  and uses the driving element  42  to drive the electronic device to perform corresponding commands. 
       FIG. 7  illustrates a manufacturing method of the foregoing touchpad structure. In a step S 20 , a substrate  1  is provided. Further, in the step S 20 , the substrate  1  may be selectively proceeded at least one pre-treatment process, such as surface roughening (fogging) treatment, strengthening treatment or grinding and polishing treatment. For example, in this embodiment, the second surface  14  of the substrate  1  is fogged by etching or sandblasting in advance, so as to allow users&#39; fingers to operate on the second surface  14  with better feel and smoothness. Afterward, the substrate  1  proceeds strengthening treatment so as to improved structural strength oneself. In a step S 22 , a shielding layer  2  is formed on the first surface  12  of the substrate  1 . In this embodiment, the method for forming the shielding layer  2  is transferring ink to the first surface  12  by a printing manner. Alternatively, the shielding layer  2  may be formed as a metal layer on the first surface  12  by a vapor deposition process, such as sputtering or evaporation, depending on the material requirement. Preferably, the shielding layer  2  is an opaque or semi-opaque layer fully covering the first surface  12 . The shielding layer  2  may have a primary color that matches the hues of the electronic product so as to improve the elegance and visual effects of the product. 
       FIG. 8  is a partial cross-sectional view of the part circled by a dotted circle of sensing layer  3  in  FIG. 5 . For the convenience of illustrating the formation of the sensing layer  3 , the substrate  1  is placed at the bottommost level in  FIG. 8 . In a step S 24 , the sensing layer  3  is formed on the shielding layer  2  by a circuit forming process. According to requirement, the circuit forming process may be the thin film process, including a process combination of the vapor deposition and the lithography or a process combination of the vapor deposition and the laser, or the printing circuit process. In this embodiment, the sensing layer  3  is formed by a thin film process. First, the first direction sensors  322 , conducting wires  324  and the second direction sensors  342  are formed on the shielding layer  2  using vapor deposition and lithography processes, and then an isolation layer  36  is formed to cover the first direction sensors  322 , the conducting wires  324  and the second direction sensor  342 . The isolation layer  36  is etched to partially expose the second direction sensors  342 . Conductive poles  3442  are formed on the exposed parts of the second direction sensors  342 , and conductive plates  3444  are formed on the isolation layer  36 . The conductive poles  3442  and the conductive plates  3444  are mutually connected and form conductive bridges  344  that span the conducting wires  324  to make the adjacent second direction sensors  342  electrically connected with each other, thereby forming the second direction traces  34 . At last, the hard coat  38  is formed to cover the conductive bridges  344  and the isolation layers  36 . Preferably, the hard coat  38  is made of isolation material. 
       FIG. 8  shows one sensing circuit structure of the sensing layer  3  formed on the shielding layer  2  by the thin film forming process, and  FIG. 9  discloses an alternative sensing circuit structure of the sensing layer  3 . In another embodiment, the conductive plates  3444  are first formed on the shielding layer  2  directly, and then the isolation layer  36  is formed to cover the conductive plates  3444 . Afterward, the isolation layer  36  is etched to partially expose the conductive plates  3444 , and then the conductive poles  3442  are formed at where the conductive plates  3444  are exposed such that the conductive poles  3442  and the conductive plates  3444  are connected mutually to form the conductive bridges  344 . Subsequently, by vapor deposition and etching processes, the first direction sensors  322 , the conducting wires  324  and the second direction sensor  342  are formed on the conductive poles  3442  and the isolation layer  36 . The adjacent second direction sensors  342  are electrically connected to each other through the conductive bridges  344 . At last, the hard coat  38  is formed to cover the first direction sensors  322 , the conducting wires  324 , the second direction sensors  342  and the isolation layer  36 . 
     Referring to  FIG. 4  and  FIG. 10 , in a step S 26 , the circuit component  4  is electrically connected to the sensing layer  3 . If the circuit component  4  is a printed circuit board, the circuit component  4  is connected to the sensing layer  3  through a flexible flat cable (FFC) a. If the circuit component  4  is a flexible printed circuit board, one end of the circuit component  4  may be directly electrically connected to the sensing layer  3 . 
     By forming the sensing layer  3  directly on a relatively thin shielding layer  2 , the present invention eliminates the use of an adhesive layer used in the conventional touchpad structures and eliminates the use of a covering layer used in the conventional OGS, thus significantly reducing the overall thickness of the touchpad structure. In addition, since there is no use of any adhesive or covering layers, the present invention can effectively improve yield because the difficult adhering process between layers and the additional procedures for evening are both eliminated from the practical manufacturing process. 
     Also, since the shielding layer  2  of the present invention is opaque or semi-opaque and fully covers the first surface  12  of the substrate  1  so as to completely or partially block users&#39; line of sight, users can not see the sensing layer  3  clearly through the substrate  1 , so the material color of the sensing layer  3  are non-limitation. The sensing layer  3  can be transparent or non-transparent. The first and second direction traces  32 ,  34  may be made of transparent electric conductivity material, such as ITO, or may be made of low-impedance non-transparent electric conductivity material, such as gold, silver, copper, nano silver, grapheme and carbon nanotubes. 
     Moreover, since the shielding layer  2  of the present invention fully covers the first surface  12  of the substrate  1 , there is no need to perform additional surface evening treatment for the first surface  12 , and the sensing layer  3  can be directly formed on the shielding layer  2 . Thereby, the present invention is contributive to simplifying the manufacturing process. 
     While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.