Abstract:
An image sensing device and a packaging method thereof is disclosed. The packaging method includes the steps of providing an adhesive layer; placing a substrate, having an opening, on the adhesive layer; disposing an image sensor within the opening on the adhesive layer; adding a filler between the image sensor and the substrate; connecting the image sensor and the substrate via a plurality of bonding wires; and removing the adhesive layer.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a semiconductor packaging method, and more particularly, to a packaging method of an image sensing device. 
       BACKGROUND OF THE INVENTION 
       [0002]    In recent years, solid-state image sensors such as charge coupled devices (CCDs) or complementary metal oxide semiconductor (CMOS) image sensors have been widely applied to electronic products for converting light into electrical signals. The applications of image sensor components include monitors, cell phones, scanners, digital cameras, and so on. Currently, these applications tend to have an overall size which is smaller and thinner so that it can be carried around easily. 
         [0003]    Conventionally, these sensors have been packaged for use by mounting them to a substrate and enclosing them within a housing assembly. For example, U.S. Pat. No. 6,268,231 discloses a CCD package  10  as shown in  FIG. 1 . The CCD package  10  includes a plastic base structure  12  for support beneath a flexible circuit board  18 . Electrical conductors are formed upon flexible circuit board  18 . Plastic ring frame  14  is placed on top of the flexible circuit board  18  creating a sandwich area defined by the base structure  12  and plastic ring frame  14  with flexible circuit  18  in between. The plastic ring frame  14  provides depth for an image sensor to be contained therein. The image sensor electrical connectors that make electrical contact with conductor pattern on the flexible circuit  18 . The ring frame  14  provides support for a glass cover  16  that provides isolation from ambient conditions for the enclosed CCD while allowing light to pass and become incident upon the CCD. The plastic base structure  12 , circuit board  18  and ring frame  14 , not to mention the glass cover  16 , overall forms a relatively thick package. 
         [0004]    Similarly, U.S. Pat. Nos. 6,034,429, 6,268,654 and 6,143,588 also disclose a CCD package including an IC die mounted on and wire bonded to a first side of a BT substrate, a bead or dam formed in varying manners around the IC die, a glass lid attached to the bead, and solder balls attached to a second side of the BT substrate. All of these packages are relatively thick and are limited by the thickness of the substrate. 
         [0005]    Therefore, a packaging method of an image sensing device having a reduced size and thickness is desperately desired so as to fit within those aforementioned smaller and thinner applications. 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, the prior arts are limited by the above problems. It is an object of the present invention to provide a packaging method of an image sensing device having a reduced size and thickness. 
         [0007]    In accordance with an aspect of the present invention, a packaging method for an image sensing device, includes the steps of providing an adhesive layer; placing a substrate, having an opening, on the adhesive layer; disposing an image sensor within the opening on the adhesive layer; adding a filler between the image sensor and the substrate; connecting the image sensor and the substrate via a plurality of bonding wires; and removing the adhesive layer. 
         [0008]    Preferably, the image sensor includes a light-receiving region exposed. 
         [0009]    Preferably, the packaging method further includes between the disposing step and the adding step a step of forming a barrier around the light-receiving region on the image sensor. 
         [0010]    Preferably, the packaging method further includes a step of laying a transparent lid on the barrier above the light-receiving region. 
         [0011]    Preferably, the barrier is formed by transfer molding, pot molding, injection molding, photolithographic process, exposure development process, laser cutting process, or stereolithographic process. 
         [0012]    Preferably, the barrier is defined by a photoresist mask. 
         [0013]    Preferably, the barrier is made of epoxy resin, solder mask, or photoresist. 
         [0014]    Preferably, the filler is added between the barrier and the substrate with the plurality of bonding wires being encapsulated. 
         [0015]    Preferably, the filler is added between the barrier and the substrate with the plurality of bonding wires being exposed. 
         [0016]    Preferably, the image sensor includes complementary metal oxide semiconductor (CMOS) image sensor or charge coupled device (CCD) image sensor. 
         [0017]    Preferably, the substrate includes aluminum nitride ceramic, fiberglass-reinforced epoxy resin, or bismaleimide-triazine resin. 
         [0018]    Preferably, the packaging method further includes a step of mounting a lens holder on the substrate above the image sensor. 
         [0019]    Preferably, the packaging method further includes a step of setting a lens on the lens holder. 
         [0020]    Preferably, the adhesive layer comprises boron, amorphous silicon, carbon, tantalum nitride, or titanium nitride. 
         [0021]    Preferably, the adhesive layer is removed by imposing heat on the adhesive layer to melt an adhesive adhered between the substrate and the image sensor. 
         [0022]    Preferably, the adhesive layer is removed by chemical etching to dissolve an adhesive adhered between the substrate and the image sensor. 
         [0023]    Preferably, the adhesive layer is a tape. 
         [0024]    In accordance with another aspect of the present invention, an image sensing device includes a substrate having an opening; an image sensor disposed within the opening of the substrate; a plurality of bonding wires for connecting the image sensor and the substrate; and a filler between the image sensor and the substrate. 
         [0025]    Preferably, the image sensor includes complementary metal oxide semiconductor (CMOS) image sensor or charge coupled device (CCD) image sensor. 
         [0026]    Preferably, the substrate includes aluminum nitride ceramic, fiberglass-reinforced epoxy resin, or bismaleimide-triazine resin. 
         [0027]    Preferably, the image sensing device further includes a lens holder mounted on the substrate above the image sensor. 
         [0028]    Preferably, the image sensing device further includes a lens disposed on the lens holder. 
         [0029]    Preferably, the image sensor includes a light-receiving region exposed. 
         [0030]    Preferably, the image sensing device further includes a barrier formed around the light-receiving region on the image sensor. 
         [0031]    Preferably, the image sensing device further includes a transparent lid laid on the barrier above the light-receiving region. 
         [0032]    Preferably, the barrier is formed by transfer molding, pot molding, injection molding, photolithographic process, exposure development process, laser cutting process, or stereolithographic process. 
         [0033]    Preferably, the barrier is defined by a photoresist mask. 
         [0034]    Preferably, the barrier is made of epoxy resin, solder mask, or photoresist. 
         [0035]    Preferably, the filler is between the barrier and the substrate with the plurality of bonding wires being encapsulated. 
         [0036]    Preferably, the filler is between the barrier and the substrate with the plurality of bonding wires being exposed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0037]    The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0038]      FIG. 1  illustrates an image sensing device according to the prior art; 
           [0039]      FIGS. 2A-2H  illustrate a packaging method of a first embodiment of an image sensing device according to the present invention; 
           [0040]      FIG. 3  illustrates a second embodiment of an image sensing device according to the present invention; and 
           [0041]      FIG. 4  illustrates a third embodiment of an image sensing device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed. 
         [0043]    Please refer to  FIGS. 2A-2H . They illustrate a packaging method of a first embodiment of an image sensing device according to the present invention. First, in  FIG. 2A , an adhesive layer  21  is provided as a base, and then a substrate  22  having an opening is placed on the adhesive layer  21 , as shown in  FIG. 2B . The substrate  22  could be made of plastic, fiberglass-reinforced epoxy resin, aluminum nitride ceramic, or bismaleimide-triazine resin. 
         [0044]    Later, an image sensor  23  having a light-receiving region  231  exposed is disposed on the adhesive layer  21  within the opening of the substrate  22 , as shown in  FIG. 2C . The image sensor  23  may be a complementary metal oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor. 
         [0045]    In the present invention, the adhesive layer  21  is used to provide a supporting surface for the image sensor  23  which is traditionally performed by a substrate. In this case, the adhesive layer  21  is made of dielectric material such as boron, amorphous silicon, carbon, tantalum nitride, or titanium nitride. Preferably, the adhesive layer can be a tape. 
         [0046]    After the image sensor  23  is positioned, a filler  24  is added into a gap formed between the image sensor  23  and the substrate  22  for physically connecting the image sensor  23  and the substrate  22  together, as shown in  FIG. 2D . In other words, the filler  24  is added into the opening of the substrate  22  leaving the image sensor  23  uncovered. Then, the image sensor  23  and the substrate  22  are electrically connected by several bonding wires  25 , as shown in  FIG. 2E . 
         [0047]    Once the image sensor  23  and the substrate  22  are physically and electrically connected, there will be no further need for the supporting of the adhesive layer  21 , and therefore, the adhesive layer  21  is then removed, thereby causing a significant reduce in a overall thickness of the image sensing device, as shown in  FIG. 2F . 
         [0048]    The removal of the adhesive layer  21  can be achieved in several different ways. For example, the adhesive layer  21  can be removed by imposing heat to the adhesive layer  21  to melt an adhesive adhered between the substrate  22  and the image sensor  23 . A temperature ranging from about 60° C. to 90° C. is preferable. The adhesive layer  21  can also be removed by chemical etching to dissolve an adhesive adhered between the substrate  22  and the image sensor  23 . The etchant used for chemical etching may be a sulfuric acid solution or an organic solvent. However, the etchant used should be non-reactive with the filler  24 , or else, the filler  24  will also be removed at the same time. Hence, the filler  24  should have a material different from that of the adhesive layer  21 . Furthermore, the adhesive layer  21  can also be ripped off as a tape manually or mechanically if the filler  24  is sensitive to heat or reactive to the etchant, and the aforementioned methods of removing the adhesive layer  21  can not be performed. 
         [0049]    After that, a lens holder  26  can be mounted directly on the substrate  22  above the image sensor  23 , as shown in  FIG. 2G , and then a lens  27  is finally disposed on the lens holder  26 , as shown in  FIG. 2H . 
         [0050]    In this first embodiment, the filler  24  is added into the gap formed between the image sensor  23  and the substrate  22 . However, it should be noted that the filler  24  is not limited thereto, it can also be added as shown in  FIGS. 3 and 4 . 
         [0051]    Please refer to  FIG. 3 .  FIG. 3  illustrates a second embodiment of an image sensing device according to the present invention. In the second embodiment, an image sensor  33  having a light-receiving region  331  is disposed within an opening of a substrate  32 . The image sensor  33  is electrically connected to the substrate  32  by several bonding wires  35 . Then, a barrier  38  is formed on the image sensor  33  around the light-receiving region  331 . After that, a filler  34  is added between the barrier  38  and the substrate  32 , leaving the bonding wires  35  being exposed. 
         [0052]    The barrier  38  is used to prevent the light-receiving region  331  from being accidentally covered by the filler  34 . The barrier  38  is usually made of epoxy resin, solder mask, or photoresist, and can be formed by transfer molding, pot molding, injection molding, photolithographic process, exposure development process, laser cutting process, or stereolithographic process. Due to the fact that the barrier  38  has a certain volume and height, the barrier  38  is usually defined by a photoresist mask. Later, a transparent lid  39  is laid on the barrier  38  above the light-receiving region  331  for protecting the light-receiving region  331  from being damaged or polluted. 
         [0053]    Now please refer to  FIG. 4 .  FIG. 4  illustrates a third embodiment of an image sensing device according to the present invention. Similar to the second embodiment, the third embodiment discloses an image sensor  43  having a light-receiving region  431  disposed within an opening of a substrate  42 . The image sensor  43  is electrically connected to the substrate  42  by several bonding wires  45 . A lens holder  46  is then mounted on the substrate  42 . Later, a barrier  48  is formed on the image sensor  43  around the light-receiving region  431 . After that, a filler  44  is added between the barrier  48  and the lens holder  46 , having the bonding wires  45  being encapsulated. By this way, the filler  44  can not only physically connect the image sensor  43  and the substrate  42  but also protect the bonding wires from being damaged. 
         [0054]    Same as the barrier  38  of the second embodiment, the barrier  48  is used to prevent the light-receiving region  431  from being accidentally covered by the filler  44 . The barrier  48  is usually made of epoxy resin, solder mask, or photoresist, and can be formed by transfer molding, pot molding, injection molding, photolithographic process, exposure development process, laser cutting process, or stereolithographic process. Due to the fact that the barrier  48  has a certain volume and height, the barrier  48  is usually defined by a photoresist mask. Later, a transparent lid  49  is laid on the barrier  48  above the light-receiving region  431  for protecting the light-receiving region  431  from being damaged or polluted. 
         [0055]    In conclusion, the present invention discloses a packaging method for producing an image sensing device having an overall reduced thickness by introducing an adhesive layer for providing a supporting surface for the image sensor which is traditionally performed by a substrate, and removing the adhesive layer afterwards so that the overall thickness of the image sensing device could be reduced. In other words, the overall thickness of the image sensing device of the present invention is thinner than that of a traditional image sensing device at least by the thickness of a substrate. 
         [0056]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.