Abstract:
A printed circuit board (PCB) adapted for mounting different kinds of light sensing modules thereon includes a lighting sensing area and a plurality of pads. The pads are disposed around the lighting sensing area, for configuring one light sensing module thereon. In the present invention, the PCB is suitable for different kinds of light sensing modules without redesign, which lowers the manufacturing cost of the PCB.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to printed circuit boards, and particularly to a printed circuit board and a light sensing device using the same. 
     2. Description of Related Art 
     Nowadays, liquid crystal display (LCD) panels are widely in devices, such as notebook computers or laptop computers. Generally, LCD panels use discharge lamps or other lamps of backlight modules as light sources, and employ a light sensor to sense ambient light to dynamically adjust the brightness of the LCD panel, consequently lowering power consumption of the backlight modules. 
     Normally, light sensors manufactured by various sensor suppliers are structurally different. Backlight module manufacturers have to design different PCB layouts to accommodate various light sensors, which complicates the PCB layouts. Especially, if one sensor supplier cannot provide light sensors to the backlight module manufacturer on time, the backlight module manufacturer should then redesign its PCB layout to fit another light sensor provided by some other supplier, which increases costs and leads to delays. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention provides a printed circuit board adapted for mounting different kinds of light sensing modules. The PCB comprises a light sensing area and a plurality of pads disposed around the light sensing area for electronically connecting one of the light sensing modules thereon. 
     Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustrated view of a printed circuit board according to an exemplary embodiment of the present invention; 
         FIG. 2  is an illustrated side view of a light sensing device mounted on the printed circuit board of  FIG. 1 ; 
         FIG. 3  is similar to  FIG. 1  but with the footprint of the light sensing device of  FIG. 2  indicated; 
         FIG. 4  is an illustrated side view of another light sensing module mounted on the printed circuit board of  FIG. 1  in accordance with another exemplary embodiment of the present invention; 
         FIG. 5  is similar to  FIG. 1  but with the footprint of the light sensing module of  FIG. 4  indicated; 
         FIG. 6  is an illustrated view of a printed circuit board according to a further exemplary embodiment of the present invention; 
         FIG. 7  is similar to  FIG. 6  but showing the footprint of the light module of  FIG. 2  with all of a plurality of pads on the printed circuit board used; and 
         FIG. 8  is similar to  FIG. 7  but showing a different footprint of the light module of  FIG. 2  with only some of the plurality of pads on the printed circuit board used. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an illustrated view of a printed circuit board (PCB)  1  or a circuit substrate of an exemplary embodiment of the present invention. The PCB  1  comprises a sensing area  12  and a plurality of pads  10  and  11  distributed around the sensing area  12 . The pads  10  and  11  are different kinds. In this embodiment, the pads  10  are disposed at two opposite sides of the light sensing area  12 , the pads  11  are disposed at another two opposite sides of the light sensing area  12 . The light sensing area  12  is a via in the PCB  1  for light going therethrough. In another embodiment, the light sensing area  12  may consist of a transparent object disposed over an opening in the PCB  1 , such as a light guide, transparent glass, etc. In other words, the light sensing area  12  is a transparent area of the PCB  1 . 
       FIG. 2  shows a light sensing device  201  comprising a light sensing module  20  mounted on the PCB  1 , and  FIG. 3  indicates the footprint of the light sensing module  20  when being used on the PCB  1 . In this exemplary embodiment, the light sensing module  20  is connected to the pads  10  on the PCB  1  to form the light sensing device  201 . 
     In this embodiment, the light sensing module  20  is disposed over the light sensing area  12  or the via, and is electrically connected to the PCB  1  by way of the pads  10 . Advantageously, the light sensing module  20  comprises a potting compound  21 , a chip  22 , a carrier board  23 , and at least a pair of pins  24 . In this embodiment, the number of the pins  24  is corresponding to that of the pads  10 , the pins  24  are electrically connected to the corresponding pads  10 . In other embodiment, parts of the pins  24  are used for electrically connecting to the corresponding pads  10 , and remainders are used for fixing the light sensing module  20  to the PCB  1 . The chip  22  is disposed on the carrier board  23 , and is electrically connected to the PCB  1  by way of the pins  24 . 
     The potting compound  21  comprises an upper potting compound  21 A and a lower potting compound  21 B, respectively symmetrically disposed on opposite faces of the carrier board  23 . In this embodiment, the lower potting compound  21 B encompasses the chip  22 , holding it directly over the via  12  defined in the PCB  1 . The potting compound  21  is transparent, thus the chip  22  can sense ambient light by way of the lower potting compound  21 B and the via  12 . 
       FIG. 4  shows another light sensing device  301  comprising a light sensing module  30  mounted on the PCB  1  in another embodiment of the present invention, and  FIG. 5  indicates the footprint of the light sensing module  30  when being used on the PCB  1 . In this exemplary embodiment, the pads  11  on the PCB  1  are applied to connect to the light sensing module  30  to form the light sensing device  301 . 
     In this embodiment, the light sensing module  30  is disposed on the PCB  1  over the via  12 , and is electrically connected to the PCB  1  by way of the pads  11 . Advantageously, the light sensing module  30  comprises a potting compound  31 , a chip  32 , a carrier board  33 , and at least one pair of pads  34 . In this embodiment, the pads  34  comprise at least one pair of lower pads  34 B mounted directly on the pads  11 , and at least one pair of upper pads  34 A mounted above the pads  34 B and sandwiching the carrier board  33  therebetween. The upper pads  34 A and the lower pads  34 B are electrically connected by way of a conductor  35 . The potting compound  31  packages the chip  32 , and is configured to correspond to the via  12 . In this embodiment, the potting compound  31  is transparent, and can be received in the via  12 . 
     As described above, although the light sensing modules  20  and  30  are structurally different, the PCB  1  of the present invention is adapted to selectively mount either one thereon without changing the design thereof. In the embodiments, the via  12  should be suitable for the sizes of the light sensing modules  20  and  30 , and meet light sensitivity requirements thereof. 
       FIG. 6  is an illustrated view of a PCB  4  according to a further exemplary embodiment of the present invention. The PCB  4  comprises a sensing area  42  and a plurality of pads  40  symmetrically disposed on two opposite sides of the light sensing area  42 . The light sensing area  42  is a via or an opening defined in the PCB  4  for light passing therethrough. In another embodiment, the light sensing area  42  may consist of a transparent object disposed in the opening in the PCB  4 , such as a light guide, transparent glass, etc. 
       FIG. 7  shows the footprint of the light sensing module  20  when used on the PCB  4  of  FIG. 6  and all the pads  40  are respectively connected to the pins  24 . 
       FIG. 8  shows the footprint of the light sensing module  20  applied to the PCB  4  when just some of the pins  24  are respectively connected to some of the pads  40  of the PCB  4 . 
     In general, the PCB  1  of  FIG. 1  and the PCB  4  of  FIG. 6  are respectively adapted for connecting various light sensing modules thereon, depending on different practical requirements. 
     While embodiments and methods of the present invention have been described above, it should be understood that they have been presented by way of example only and not by way of limitation. Thus the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.