Abstract:
An image sensing device package structure is formed by using a base and a light transparent layer to package an image sensing device. The image sensing device is electrically connected to metallization traces on the base by means of wire bonding. Through change of the positions of the metallization traces, contacts between bonding wires and the metallization traces are made slightly higher than the top of the image sensing device, thereby shortening the wire bonding pitch of the bonding wires and thus reducing the package area.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an image sensing device package structure and, more particularly, to an image sensing device package structure capable of reducing the package area.  
         [0003]     2. Description of Related Art  
         [0004]     As shown in  FIG. 1 , a conventional CMOS image sensing device package structure comprises a substrate  10 , a frame  20 , an image sensing device  30 , and a light transparent glass  40 . Several metallization traces  11  are provided on the surface of the substrate  10 . The frame  20  is adhered to the substrate  10  using a first glue layer  12 . The image sensing device  30  adheres to the substrate  10 . The image sensing device  30  has an image sensing area  31 . The image sensing device  30  is connected to the metallization traces  11  on the surface of the substrate  10  via bonding wires  32  by means of wire bonding to achieve electric connection between the image sensing device  30  and the substrate  10 . The light transparent glass  40  seals the substrate  10  using a second glue layer  13 . This package structure can be isolated from outside contaminants so that the CMOS image sensing device can truly sense the exterior environment.  
         [0005]     The above conventional package structure, however, has a primary drawback, Because the image sensing device  30  has a height different with respect to the substrate  10  during wire bonding, a corresponding wire bonding pitch S 1  is required. Moreover, when wire bonding is performed between the image sensing device  30  and the substrate  10 , a distance S 2  is kept between the frame  20  and the metallization traces  11  on the substrate  10  to prevent the capillary tip from touching the frame  20 . Therefore, there is much limit in the package area and volume of this package structure, hence being adverse to applications in portable products.  
       SUMMARY OF THE INVENTION  
       [0006]     An object of the present invention is to provide an image sensing device package structure, in which wire bonding positions of an image sensing device are changed to shorten the wire bonding pitch for reducing the package area, thereby accomplishing a miniaturized package of the image sensing device.  
         [0007]     To achieve the above object, an image sensing device package structure of the present invention comprises an image sensing device, a base, and a light transparent layer. The base has an upper surface and a lower surface. Several metallization traces are provided on the upper and lower surfaces. More than one bonding wire is used to connect the metallization traces on the upper surface with the image sensing device. The horizontal height of the top of the metallization traces on the upper surface is slightly larger than that of the top of the image sensing device to reduce the wire bonding pitch of bonding wire. The light transparent layer covers on the upper surface of the base.  
         [0008]     More specifically speaking, the difference between the horizontal heights of the top of the metallization traces on the upper surface of the base and the top of the image sensing device can be larger than 0.1 mm, and is preferred to be larger than 0.2 mm. The difference between the horizontal heights of the bottom of the light transparent layer and the top of the image sensing device can be smaller than 0.6 mm, and is preferred to be smaller than 0.4 mm. The difference between the horizontal heights of the light transparent layer and the top of the metallization traces on the upper surface of the base can be smaller than 0.5 mm or 0.3 mm, and is preferred to be smaller than 0.2 mm.  
         [0009]     In the embodiment of the present invention, in order to change positions of the metallization traces, a groove is formed on the upper surface of the base. A first upper surface is formed at the bottom of the groove. The image sensing device is installed on the first upper surface. The edge of the groove has a difference in height to form a second upper surface and a third upper surface. The horizontal height of the second upper surface is larger than that of the first upper surface. The horizontal height of the third upper surface is larger than that of the second upper surface. Several metallization traces are disposed on the second upper surface and the lower surface of the base. The image sensing device is connected to the metallization traces on the second upper surface via more than one bonding wire to achieve electric connection with the base. The light transparent layer covers on the third upper surface of the base so that the image sensing device can be covered in the light transparent layer and the base. In order to reduce the wire bonding pitch of bonding wire and also meet the requirement for the wire bonding height of bonding wire, the horizontal height of the second upper surface of the base is designed to be larger than that of the upper surface of the image sensing device so as to accomplish miniaturized package.  
         [0010]     Furthermore, in the above embodiment, the difference between the horizontal heights of the third upper surface and the second upper surface of the base can decrease to prevent the capillary tip from touching the edge of the base when performing bonding wire ball bonding. The required length of the second upper surface of the base can thus be reduced to shrink the area and volume of the package structure.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:  
         [0012]      FIG. 1  is a diagram of a conventional CMOS image sensing device package structure;  
         [0013]      FIG. 2  is a diagram of an image sensing device package structure according to an embodiment of the present invention;  
         [0014]      FIG. 3  is a diagram of an image sensing device package structure having a fastening portion according to another embodiment of the present invention;  
         [0015]      FIG. 4  is a diagram of an image sensing device package structure with a shaped metallization trace disposed at the inside and the outside of the base according to another embodiment of the present invention; and  
         [0016]      FIG. 5  is a diagram of an image sensing device package structure with a shaped metallization trace disposed at the inside of the base according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     As shown in  FIG. 2 , an image sensing device package structure of the present invention comprises a base  50 , an image sensing device  60 , and a light transparent layer  70 . The base  50  can be made of ceramic material. A groove  51  is formed on the upper surface of the base  50 . A first upper surface  511  is formed at the bottom of the groove  51 . The edge of the groove  51  has a difference in height to form a second upper surface  512  and a third upper surface  513  having different horizontal heights. The horizontal height of the second upper surface  512  is larger than that of the first upper surface  511 . The horizontal height of the third upper surface  513  is larger than that of the second upper surface  512 . Several metallization traces  52  are disposed on the second upper surface  512  and a lower surface  514  of the base  50 . The metallization traces  52  on the second upper surface  512  and a lower surface  514  are electrically connected together via a shaped metallization trace  53  at the outside of the base  50 .  
         [0018]     The image sensing device  60  is adhered to the first upper surface  511  at the bottom of the groove  51 . The upper surface  61  of the image sensing device  60  has an image sensing area  62 . The horizontal height of the upper surface  61  of the image sensing device  60  is smaller than that of the second upper surface  512  of the base  50 . The image sensing device  60  achieves electric connection with the base by means of wire bonding. That is, a first bonding wire ball is placed on the bonding pad of the upper surface  61  of the image sensing device  60 , a second bonding wire ball is placed on the second upper surface  512  of the base  50 , and a bonding wire  63  is then led from the second bonding wire ball to the first bonding wire ball to achieve electric connection.  
         [0019]     The light transparent layer  70  covers on the third upper surface  513  of the base  50  to seal the image sensing device  60 . This light transparent layer  70  can be a light transparent glass, or a lens used to filter out a light source with a specific wavelength range, e.g., an IR-cut filtering lens for filtering out far infrared light.  
         [0020]     In this embodiment, the groove  51  on the base  50  having a difference in height is used to shorten the wire bonding pitch S 1  ( FIG. 1 ) of the conventional bonding wire. Because it is necessary to take the height required for metal recrystallization into account when performing wire bonding to the bonding wire  63 , the horizontal height of the second upper surface  52  of the base  50  needs to be larger than that of the upper surface  61  of the image sensing device  60  to conform to the smallest height required for wire bonding. The wire bonding pitch S 1  ( FIG. 1 ) required for wire bonding can thus be reduced to decrease the area of the package structure.  
         [0021]     For instance, the difference between the horizontal heights Δh 1  of the second upper surface  512  of the base  50  and the upper surface  61  of the image sensing device  60  can be larger than 0.1 mm so that the bonding wire  63  can be conveniently led to and connected with the metallization trace on the second upper surface  512  of the base  50  after performing wire ball bonding to the bonding wire  63  on the bonding pad of the image sensing device  60 . This difference between the horizontal heights Δh 1  is preferred to be larger than 0.2 mm.  
         [0022]     Besides, when the bonding wire  63  is led to the second upper surface  512  of the base  50  for wire ball bonding, in order to prevent the capillary tip from touching the edge of the base  50 , the height of the third upper surface  513  is lowered to reduce the difference between the horizontal heights Δh 2  of the third upper surface  513  and the second upper surface  512  of the base  50 . For instance, the difference between the horizontal heights Δh 2  of the third upper surface  513  and the second upper surface  512  of the base  50  can be smaller than 0.5 mm or 0.3 mm, and is preferred to smaller than 0.2 mm so as to reduce the required length Δs 2  of the second upper surface  512  of the base  50  for shrinking the volume of the package structure.  
         [0023]     The difference between the horizontal heights Δh 3  of the third upper surface  513  of the base  50  and the upper surface  61  of the image sensing device  60  can be smaller than 0.6 mm, and is preferred to be smaller than 0.4 mm. The base  50  can further include an adhesion layer  54  to adhere the image sensing device  60  to the first upper surface  511  of the base  50 . The light transparent layer  70  and the third upper surface  513  of the base  50  can be adhered together using a glue layer  55 . This glue layer  55  can be a UV glue or a thermosetting glue. Moreover, in practical application, the base  50  can further has a fastening portion  56  to fix the position of the light transparent layer  70 , as shown in  FIG. 3 .  
         [0024]     In the above embodiments, the metallization traces  53  of the second upper surface  512  and the lower surface  514  of the base  50  are electrically connected together via a shaped metallization trace at the outside of the base  50 . In practice, the shaped metallization trace can be disposed at the inside or outside of the base. As shown in  FIG. 4 , a metallization trace  73  goes along the inside of the base  50  and extends to the outside of the base  50  after penetrating the base  50  to achieve electric connection of the metallization traces  53 ; As shown in  FIG. 5 , a shaped metallization  83  goes along the inside of the base  50  and is directly connected to the metallization traces  53  of the lower surface  514  of the base  50  after penetrating the base  50 .  
         [0025]     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.