Abstract:
The present invention discloses a packaging structure of a light-sensing device with a spacer wall, wherein a spacer wall is used to protect the light-sensing region from external pollutants or two spacer walls are used to confine the glue to therebetween lest the overflow glue pollute the light-sensing region as in the conventional technology. Further, the present invention can reduce the packaging area and can promote the yield and quality obviously.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a packaging structure of a light-sensing device, particularly to a packaging structure of a light-sensing device with a spacer wall. 
   2. Description of the Related Art 
   With the wide popularity of audio/video multimedia, the digitization of images is a consequential trend, and the appearance of digital cameras, digital video cameras and image scanners signifies the arrival of the image-digitization age. CMOS (Complementary Metal Oxide Semiconductor) is a key technology for image digitization, and the quality, yield and cost thereof are critical factories in the campaign of image digitization. 
   Refer to  FIG. 1  a diagram schematically showing a conventional packaging structure of a CMOS image sensor. The conventional packaging structure comprises: a light transparent substrate  10 , which has multiple metallic traces  12  and multiple metallic balls  14  used to form the electric connection with the metallic traces  12 ; a light-sensing element  16 , having a light-sensing region  18  and multiple metallic pads  20 , wherein the light-sensing element  16  is installed to the substrate  10  via multiple metallic contacts  22  and those metallic contacts  22  are also used to electrically interconnect the light-sensing element  16  and the metallic traces  12  of the substrate  10 ; and a glue layer  17 , disposed between the substrate  10  and the light-sensing element  16 , used to seal the gap between the substrate  10  and the light-sensing element  16  and used to protect the light-sensing region from external pollutants. 
   However, when the glue is applied to the abovementioned packaging structure, owing to the fluidity of the glue, the glue will overflow into the neighboring regions and incurs some problems. For example, when the metallic pads  20  are disposed too much close to the light-sensing region  18 , the glue will overflow into the light-sensing region  18 , which will influence the function of the light-sensing element  16 ; when the metallic pads  20  are disposed too much close to the metallic balls  14 , the metallic balls  14  will be polluted by the overflow glue. When those metallic balls are processed with an SMT (Surface Mount Technology) infrared reflow, the yield loss will occur. As it is a current trend to fabricate slim and lightweight multimedia products, the spacing between the metallic pad  20  and the metallic ball  14  becomes more and more small; thus, the pollution problem becomes further serious, and the yield and quality is obviously influenced. 
   Accordingly, the present invention proposes a packaging structure of a light-sensing device with a spacer wall to overcome the abovementioned problems and promote the competitiveness. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide a packaging structure of a light-sensing device with a spacer wall, which can effectively protect the light-sensing region from external pollutants. 
   Another objective of the present invention is to provide a packaging structure of a light-sensing device with a spacer wall, which can effectively protect the light-sensing region and the metallic balls from the pollution of the overflow glue. 
   Further objective of the present invention is to provide a packaging structure of a light-sensing device with a spacer wall, which can effectively promote the yield of the fabrication process so that the fabrication cost can be reduced and the market competitiveness can be enhanced. 
   Further another objective of the present invention is to provide a packaging structure of a light-sensing device with a spacer wall, which can realize the area reduction of the packaging structure. 
   To achieve the abovementioned objectives, the present invention proposes a packaging structure of a light-sensing device with a spacer wall, which comprises: a light transparent substrate, which has metallic traces on its surface; a light-sensing element, which further comprises: a light-sensing region, multiple metallic pads, and multiple metallic contacts that are disposed on the metallic pads and used to form electric connection between the metallic pads and the metallic traces; and a first spacer wall, which is disposed between the light-sensing element and the metallic pads. 
   The present invention further proposes another packaging structure of a light-sensing device with a spacer wall, which comprises: a light transparent substrate, which has metallic traces on its surface; a light-sensing element, which further comprises: a light-sensing region, multiple metallic pads, and multiple metallic contacts that are disposed on the metallic pads and used to form electric connection between the metallic pads and the metallic traces; a first spacer wall, which is disposed between the light-sensing element and the metallic pads; and a glue layer, which is disposed between the light transparent substrate and the light-sensing element, and used to seal the gap between the light transparent substrate and the light-sensing element. 
   To enable the objectives, characteristics, and accomplishments of the present invention to be more easily understood, the embodiments of the present invention is to be described below in detail in cooperation with the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram schematically showing a conventional packaging structure of a CMOS image sensor. 
       FIG. 2  is a diagram schematically showing one embodiment of the present invention. 
       FIG. 3  is a diagram schematically showing another embodiment of the present invention. 
       FIG. 4  is a diagram schematically showing further embodiment of the present invention. 
       FIG. 5(   a ) to  FIG. 5(   c ) are diagrams schematically showing the embodiments of the spacer walls according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention discloses a packaging structure of a light-sensing device with a spacer wall, wherein a spacer is used to protect the light-sensing region from external pollutants and used to protect the regions where the electric contacts are to be formed from the overflow glue. 
   Refer to  FIG. 2  a diagram schematically showing one embodiment of the present invention. The packaging structure of a light-sensing device with a spacer wall according to one embodiment of the present invention comprises: a light transparent substrate  10 , which may filter out a light of a specific wavelength; metallic traces  12 , installed on the light transparent substrate  10 ; multiple metallic balls  14 , disposed on the metallic traces  12 ; a light-sensing element  16 , further comprising a light-sensing region  18  and multiple metallic pads  20 , wherein the metallic pads  20  have multiple metallic contacts  22  for the electric connection between the metallic pads  20  and the metallic traces  12 ; and a spacer wall  24 , disposed between the metallic pads  20  and the light-sensing region  18 , and used to protect the light-sensing region  18  from external pollutants, wherein the spacer wall  24  may be formed via a screen-printing method and can be made of an insulation polymer with slight elasticity, such as a polyimide. In this embodiment, the height of the spacer wall  24  is controlled to be slightly larger than the spacing between the light transparent substrate  10  and the light-sensing element  16  and used to protect the light-sensing region  18  from external pollutants. In this embodiment, the objective of retarding external pollutants can be achieved without any additional glue layer. Therefore, the problem of the overflow glue, which occurs in the conventional technology, can be avoided herein. 
   Refer to  FIG. 3  a diagram schematically showing another embodiment of the present invention. The packaging structure of a light-sensing device with a spacer wall according to another embodiment of the present invention comprises: a light transparent substrate  10 ; metallic traces  12 , installed on the light transparent substrate  10 ; multiple metallic balls  14 , disposed on the metallic traces  12 ; a light-sensing element  16 , further comprising a light-sensing region  18  and multiple metallic pads  20 , wherein the metallic pads  20  have multiple metallic contacts  22  for the electric connection between the metallic pads  20  and the metallic traces  12 ; two spacer walls  26 ,  28 , wherein the spacer wall  26  is formed on the light transparent substrate  10  and disposed corresponding to the position between the metallic pads  20  and the light-sensing region  18 ; the spacer wall  28  is formed on the light transparent substrate  10  and disposed between the metallic ball  14  and the metallic pad  20 ; and a glue layer  30 , used to seal the gap between the light-sensing element  16  and the light transparent substrate  10 . As shown in  FIG. 3 , the glue layer  30  is confined to between the spacer wall  26  and the spacer wall  28 . Even if the heights of the spacer walls  26 ,  28  do not exceed the spacing between the light-sensing element  16  and the light transparent substrate  10 , the glue overflow, which occurs in the conventional technology, will not occur in this embodiment because of the surface tension of the glue. Thus, the problem that the glue overflows onto the metallic balls  14  and the light-sensing region  18  can be effectively avoided herein. 
   Refer to  FIG. 4  a diagram schematically showing further embodiment of the present invention. In this embodiment, the spacer wall  26  in the abovementioned embodiment, which is originally formed on the light transparent substrate  10  and disposed corresponding to the position between the metallic pads  20  and the light-sensing region  18 , is otherwise formed on the lower surface of the light-element  16  and disposed between the metallic pads  20  and the light-sensing region  18 , as shown by the spacer wall  32  in  FIG. 4 . 
   As shown in the abovementioned embodiments, the spacer walls  26 ,  32  of the present invention are disposed between the metallic pads  20  and the light-sensing region  18 . Thus, it is reasonable to design the forms of the spacer walls  26 ,  32  according to the distribution contour of the metallic pads  20 , as those shown in from  FIG. 5(   a ) to  FIG. 5(   c ). In from  FIG. 5(   a ) to  FIG. 5(   c ), three common distribution contours of the metallic pads  20 —a loop, two parallel lines, and a U-shape—and the forms of the spacer walls  26 ,  32  corresponding to those three distribution contours, which are also are a loop, two parallel lines, and a U-shape, are exemplified with the spacer wall  32 , which is formed on the light-sensing element  16 . However, according to the objective of effectively retarding external pollutants, the spacer wall of a loop shape, which encloses the light-sensing region completely, can also be applied to the cases wherein the distribution contours of the metallic pads are of a U-shape or two parallel lines. 
   In summary, the present invention is a packaging structure of a light-sensing device with a spacer wall, which utilizes a spacer wall to protect the light-sensing region and the metallic balls from the pollution of the external pollutants or against the influence of the overflow glue in order to guarantee the yield and performance of the product. Confronting the trend of fabricating slim and lightweight electronic elements, the present invention can also overcome the problem of overflow-glue pollution, which the miniaturization of electronic elements must face but the conventional technology cannot solve. 
   Those described above are only the preferred embodiments of the present invention and not intended to limit the scope of the present invention. Any equivalent modification and variation according to the characteristics, the structures or the spirit of the present invention disclosed herein is to be included within the scope of the present invention.