Abstract:
An image sensor packaging structure with a low transmittance encapsulant is provided. The image sensor packaging structure includes a substrate, a chip, a transparent lid, and the low transmittance encapsulant. The chip is combined with the substrate. The transparent lid is adhered to the chip and cover above a sensitization area of the chip to form an air cavity. The low transmittance encapsulant is formed on the substrate and encapsulates the chip and the transparent lid so as to accomplish the package of the image sensor packaging structure. Due to the feature of prohibiting from light passing through the low transmittance encapsulant, the arrangement of the low transmittance encapsulant can avoid the light from outside interfere the image sensing effect of the image sensor. Therefore, the quality of the image sensing can be ensured.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to image sensor packaging structures with low transmittance encapsulants, and more particularly, to an image sensor packaging structure for use in improving the image sensing quality. 
         [0003]    2. Description of the Prior Art 
         [0004]    The advent and prevalence of various digital video products are followed by ever-increasing demand for image sensors for use with digital video products, such as digital still cameras, cell phone cameras, and video phones. Image sensors work by converting received optical signals into electrical signals and then analyzing the electrical signals by an external device. Hence, image sensors can be integrated into electronic products to perform related imaging functions, such as taking pictures and shooting videos. 
         [0005]      FIG. 1A  is a disassembled schematic view of a conventional image sensor packaging structure  10 .  FIG. 1B  is an assembled schematic view of  FIG. 1A . 
         [0006]    Referring to  FIG. 1A , the conventional image sensor packaging structure  10  includes: an image sensor chip  12 ; and a lens assembly  13  provided above the image sensor chip  12 . The lens assembly  13  enables light rays to focus on the image sensor chip  12  and thereby enhances image sensing quality. 
         [0007]    Referring to  FIG. 1A  and  FIG. 1B , to prevent the light rays from entering the image sensor packaging structure  10  sideways to thereby cause multipath refraction, multipath reflection, and multipath scattering of the light rays inside the image sensor packaging structure  10  to the detriment of image sensing quality, the lens assembly  13  is enclosed by a housing  14  for blocking ambient light, which therefore maintains the image sensing performance of the image sensor packaging structure  10 . 
         [0008]    Although the housing  14  blocks ambient light and thereby improves image sensing quality, not only does alignment of the housing  14  pose a challenge, but the housing  14  incurs costs and increases the complexity of the fabrication process of the image sensor packaging structure  10 . 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention relates to an image sensor packaging structure with a low transmittance encapsulant for encapsulating the image sensor packaging structure, blocking ambient light, and ultimately preventing ambient light rays from entering the image sensor packaging structure sideways. 
         [0010]    The present invention relates to an image sensor packaging structure with a low transmittance encapsulant able to withstand light penetration to thereby prevent ambient light rays from entering the image sensor packaging structure sideways, preclude multipath refraction, multipath reflection, and multipath scattering of the light rays inside the image sensor packaging structure, and ultimately ensure image sensing quality. 
         [0011]    The present invention relates to an image sensor packaging structure with a low transmittance encapsulant which substitutes for a conventional housing so as to reduce parts and components of the image sensor packaging structure, simplify assembly of the image sensor packaging structure, and lower the material costs of the image sensor packaging structure. 
         [0012]    To achieve the above and other objectives, the present invention provides an image sensor packaging structure with a low transmittance encapsulant, comprising: a substrate having a carrying surface and a bottom surface, the carrying surface being disposed thereon with a plurality of first conductive contacts; a chip having a first surface and a second surface and provided with a plurality of second conductive contacts, the first surface being coupled to the carrying surface, the second surface being defined with a sensitization area, and the second conductive contacts being signal-connected to the first conductive contacts; a transparent lid having a third surface and a fourth surface and disposed above the sensitization area to thereby form an air cavity; and a low transmittance encapsulant formed on the substrate to encapsulate the chip and the transparent lid. 
         [0013]    Implementation of the present invention at least involves the following inventive steps: 
         [0014]    1. An image sensor packaging structure is encapsulated by a low transmittance encapsulant for preventing ambient light rays from entering the image sensor packaging structure sideways and ultimately maintaining the image sensing performance and the imaging performance. 
         [0015]    2. The low transmittance encapsulant is not penetrable by light and thus is effective in ensuring the quality of image sensing and imaging. 
         [0016]    3. The low transmittance encapsulant substitutes for a conventional housing so as to simplify the fabrication process of the image sensor packaging structure and cut material costs of the image sensor packaging structure. 
         [0017]    The features and advantages of present invention are described in detail hereunder to enable persons skilled in the art to understand and implement the disclosure of the present invention and readily apprehend objectives and advantages of the present invention with references made to the disclosure contained in the specification, the claims, and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1A  is a disassembled schematic view of a conventional image sensor packaging structure; 
           [0019]      FIG. 1B  is an assembled schematic view of  FIG. 1A ; 
           [0020]      FIG. 2A  is a partially disassembled cross-sectional view of an image sensor packaging structure with a low transmittance encapsulant according to the present invention; 
           [0021]      FIG. 2B  is a top view of  FIG. 2A ; 
           [0022]      FIG. 3A  is an exploded perspective view of an image sensor packaging structure in a semi-finished state according to the present invention; 
           [0023]      FIG. 3B  is an assembled cross-sectional view of the semi-finished image sensor packaging structure shown in  FIG. 3A  and provided with a dam; 
           [0024]      FIG. 3C  is a cross-sectional view of the semi-finished image sensor packaging structure shown in  FIG. 3B  and provided with a low transmittance encapsulant by molding; 
           [0025]      FIG. 4A  is a partially disassembled cross-sectional view of another image sensor packaging structure with a low transmittance encapsulant according to the present invention; 
           [0026]      FIG. 4B  is an assembled cross-sectional view of the image sensor packaging structure shown in  FIG. 4A ; 
           [0027]      FIG. 4C  is a cross-sectional view of another image sensor packaging structure with a low transmittance encapsulant according to the present invention; 
           [0028]      FIG. 5A  is a schematic view of a first embodiment of solder pads disposed on a bottom surface of a substrate according to the present invention; 
           [0029]      FIG. 5B  is a schematic view of a second embodiment of the solder pads disposed on the bottom surface of the substrate according to the present invention; and 
           [0030]      FIG. 6A  through  FIG. 6C  are cross-sectional views of an image sensor packaging structure provided with a low transmittance encapsulant formed by dispensing according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0031]    Referring to  FIG. 2A , in this embodiment, an image sensor packaging structure with a low transmittance encapsulant includes a substrate  20 , a chip  30 , a transparent lid  40 , and a low transmittance encapsulant  50 . 
         [0032]    Referring to  FIG. 2A , the substrate  20  is configured for general use with an image sensor packaging structure. For instance, the substrate  20  is a circuit board with a circuit structure. The substrate  20  has a carrying surface  21  and a bottom surface  22 . The carrying surface  21  is the upper surface of the substrate  20 . The bottom surface  22  is the lower surface of the substrate  20 . A plurality of first conductive contacts  211  is disposed on the carrying surface  21  of the substrate  20 . A plurality of solder balls  61  is implanted on the bottom surface  22  of the substrate  20 . 
         [0033]    The substrate  20  is provided with a circuit structure. The circuit structure allows the first conductive contacts  211  and the solder balls  61  to be signal-connected. Hence, the image sensor packaging structure can be further signal-connected to another external device via the solder balls  61 . 
         [0034]    The chip  30  is a complementary metal oxide semiconductor (CMOS) image sensing chip or a charge-coupled device (CCD) for receiving and sensing light. Referring to  FIG. 2A , the chip  30  has a first surface  31  and a second surface  32 . The first surface  31  is the lower surface of the chip  30 . The second surface  32  is the upper surface of the chip  30 . The first surface  31  of the chip  30  is coupled to the carrying surface  21  of the substrate  20 ; in other words, the chip  30  can be disposed on the carrying surface  21  of the substrate  20 . The chip  30  is adhered to the carrying surface  21  of the substrate  20  by an adhesive agent  71 . 
         [0035]    Referring to  FIG. 2A  and  FIG. 3A , the second surface  32  of the chip  30  is defined with a sensitization area  321  and provided with a plurality of second conductive contacts  322 . The sensitization area  321  includes a plurality of photosensitive elements. The second conductive contacts  322  are arranged to surround the sensitization area  321  and signal-connected to the photosensitive elements. The second conductive contacts  322  on the chip  30  are signal-connected to the first conductive contacts  211  on the substrate  20  by wire bonding, that is, via a plurality of metal wires  33 . As a result, the photosensitive elements are signal-connected to the solder balls  61 . 
         [0036]    Referring to  FIG. 2A , the transparent lid  40  is disposed above the sensitization area  321  of the chip  30  for protecting the chip  30  and preventing contaminants from contaminating the sensitization area  321  of the chip  30 . Light rays penetrate the transparent lid  40  to fall on the sensitization area  321  of the chip  30 . The transparent lid  40  has a third surface  41  and a fourth surface  42 . The transparent lid  40  is adhered, via the third surface  41  thereof, to the second surface  32  of the chip  30  by a first adhesive layer  72 . Referring to  FIG. 3B , the transparent lid  40  covers the sensitization area  321  from above, thereby allowing an air cavity  34  to be formed between the transparent lid  40  and the chip  30 . Referring to  FIG. 2A , the first adhesive layer  72  is made of an epoxy resin. The first adhesive layer  72  is disposed between the sensitization area  321  and the second conductive contacts  322 . The first adhesive layer  72  does not cover the sensitization area  321  and thereby does not jeopardize the light-sensing function of the chip  30 . 
         [0037]    Referring to  FIG. 2A  and  FIG. 2B , the low transmittance encapsulant  50  is formed on the substrate  20  to encapsulate the metal wires  33 , the chip  30 , and the transparent lid  40 . The low transmittance encapsulant  50  is formed on the substrate  20  by molding. The low transmittance encapsulant  50  is a black encapsulant and is not penetrable by light to thereby prevent ambient light rays from entering the image sensor packaging structure sideways, preclude multipath refraction, multipath reflection, and multipath scattering of the light rays inside the image sensor packaging structure, and ultimately ensure the quality of image sensing and imaging. 
         [0038]    Forming the image sensor packaging structure by molding can greatly reduce the cycle time of the fabrication process of the image sensor packaging structure, increase throughput, enable the image sensor packaging structure to be manufactured by batch-type production, and cut process costs. However, during the molding process of the image sensor packaging structure, it is necessary to prevent the image sensor packaging structure from being damaged by the pressure directly exerted on the transparent lid  40  by a mold. To this end, at least a dam  80  is disposed on the transparent lid  40 . The dam  80  functions as a baffle between the transparent lid  40  and the mold. 
         [0039]    Referring to  FIG. 2A  and  FIG. 2B , the dam  80  is disposed on the transparent lid  40  and, more specifically, disposed at the periphery of the fourth surface  42  of the transparent lid  40  (as shown in  FIG. 2B ), but does not cover the sensitization area  321  of the chip  30  (as shown in  FIG. 2A ). Hence, light penetrates the transparent lid  40  to fall evenly onto the sensitization area  321  of the chip  30 . The dam  80  is made of an epoxy resin or a film. Forming the dam  80  on the transparent lid  40  entails disposing the epoxy resin or the film at a predetermined position and then curing or semi-curing the epoxy resin or the film by UV radiation or baking. There is therefore an appropriate resilience required for close-fitting contact between an upper die and the dam  80  during a subsequent molding process. 
         [0040]    Afterward, the semi-finished image sensor packaging structure with the dam  80  is placed in a mold (not shown). The mold comprises an upper die and a lower die. The substrate  20  rests on the lower die when the bottom surface  22  of the substrate  20  comes into contact with the lower die. The sidewall of the upper die abuts against the carrying surface  21  of the substrate  20 . The substrate  20  is held in position by the upper die and the lower die from the carrying surface  21  and the bottom surface  22  of the substrate  20 , respectively. The upper surface inside the upper die is a flat even surface in contact with the top surface of the dam  80 , thereby allowing a cavity to be formed between the upper die and the lower die. 
         [0041]    The low transmittance encapsulant  50  is introduced into the cavity to encapsulate therein the metal wires  33 , the chip  30 , the transparent lid  40 , and the dam  80 . The dam  80 , the transparent lid  40 , and the upper die together form a baffle-like structure for blocking the low transmittance encapsulant  50  and stopping the low transmittance encapsulant  50  from spilling onto the fourth surface  42  of the transparent lid  40 . 
         [0042]    Referring to  FIG. 3A  through  FIG. 3C , there are shown diagrams of another embodiment of the image sensor packaging structure. As shown in  FIG. 3A  through  FIG. 3C , the image sensor packaging structure further comprises a support  90 . The support  90  is a frame. The support  90  has a fifth surface  91 , a sixth surface  92 , and an opening  93 . Referring to  FIG. 3B  and  FIG. 3C , the fifth surface  91  of the support  90  is adhered to the second surface  32  of the chip  30  by a second adhesive layer  73 . The second adhesive layer  73  is disposed between the sensitization area  321  of the chip  30  and the second conductive contacts  322 . 
         [0043]    Referring to  FIG. 3A , the third surface  41  of the transparent lid  40  is coupled to the sixth surface  92  of the support  90  to thereby cover the opening  93  of the support  90 . Since the opening  93  of the support  90  corresponds in position to the sensitization area  321  of the chip  30 , the sensitization area  321  is exposed from the opening  93  of the support  90  and thereby remains uncovered. 
         [0044]    Referring to  FIG. 3B  and  FIG. 3C , the dam  80  is peripherally disposed at the periphery of the fourth surface  42  of the transparent lid  40 , and the low transmittance encapsulant  50  is formed on the substrate  20  by molding to thereby encapsulate the metal wires  33 , the chip  30 , the transparent lid  40 , and the support  90 . The dam  80  blocks the low transmittance encapsulant  50  and stops the low transmittance encapsulant  50  from spilling onto the fourth surface  42  of the transparent lid  40 . 
         [0045]    Referring to  FIG. 4A  and  FIG. 4B , there are shown diagrams of yet another embodiment of the image sensor packaging structure, which is essentially the same as the embodiment shown in  FIG. 3A  through  FIG. 3C , except that the third surface  41  and the fourth surface  42  of the transparent lid  40  are coupled to a first lens  94  and a second lens  95 , respectively. The first lens  94  and the second lens  95  are spherical or non-spherical lenses. However, one of the first lens  94  and the second lens  95  must be a non-spherical lens, and the other one can be a spherical lens or a non-spherical lens. 
         [0046]    Referring to  FIG. 4A , an infrared filtering layer  96  for filtering out the infrared portion of visible light is disposed between the second lens  95  and the fourth surface  42  of the transparent lid  40 . Preferably, a light-blocking layer  97  is disposed on the infrared filtering layer  96 . A penetration window  971  corresponding in position to the second lens  95  is formed to penetrate the light-blocking layer  97 , such that a light path can penetrate the light-blocking layer  97  by passing through the penetration window  971 . 
         [0047]    Referring to  FIG. 4C , alternatively, the infrared filtering layer  96  is disposed between the first lens  94  and the third surface  41  of the transparent lid  40 , and the light-blocking layer  97  is disposed on the fourth surface  42  of the transparent lid  40 . Still, the penetration window  971  (not shown) corresponding in position to the second lens  95  is formed to penetrate the light-blocking layer  97 . 
         [0048]    Where the image sensor packaging structure is not provided with the infrared filtering layer  96  and the light-blocking layer  97 , the dam  80  is peripherally disposed at the periphery of the fourth surface  42  of the transparent lid  40  (not shown). Where the image sensor packaging structure is provided with the infrared filtering layer  96  and the light-blocking layer  97 , the dam  80  is peripherally disposed at the periphery of the light-blocking layer  97 , so as to block the low transmittance encapsulant  50  (as shown in  FIG. 4  A through  FIG. 4C ). 
         [0049]    Referring to  FIG. 5A  and  FIG. 5B , not only are the solder balls  61  implanted on the bottom surface  22  of the substrate  20 , but the bottom surface  22  of the substrate  20  is disposed thereon with a plurality of solder pads  62  signal-connected to the circuit structure of the substrate  20 . The solder pads  62  are signal-connected to the first conductive contacts  211  on the substrate  20  (not shown). The image sensor packaging structure is signal-connected to another external device via the solder pads  62 . Preferably, the solder pads  62  are peripherally disposed at the periphery of the bottom surface  22  of the substrate  20  (as shown in  FIG. 5A ) or disposed in array on the bottom surface  22  of the substrate  20  (as shown in  FIG. 5B ). 
         [0050]    Referring to  FIG. 6A  through  FIG. 6C , the low transmittance encapsulant  50  also can be formed on the substrate  20  by dispensing. Forming the low transmittance encapsulant  50  by dispensing removes the necessity of disposing the dam  80  on the image sensor packaging structure, and in consequence, the height and the volume of the finished image sensor packaging structure can be reduced. 
         [0051]    As disclosed in the above embodiments, the finalized image sensor packaging structure results in low transmittance, which enables the low transmittance encapsulant  50  to function as an encapsulant. The structure is also configured to prevent ambient light rays from entering the image sensor packaging structure sideways as well as preclude multipath refraction, multipath reflection, and multipath scattering of the light rays inside the image sensor packaging structure. These added advantages ultimately prevent the image sensing and imaging performance of the image sensor packaging structure from being affected by the ambient light rays. 
         [0052]    The foregoing embodiments are provided to illustrate and disclose the technical features of the present invention so as to enable persons skilled in the art to understand the disclosure of the present invention and implement the present invention accordingly, and are not intended to be restrictive of the scope of the present invention. Hence, all equivalent modifications and variations made to the foregoing embodiments without departing from the spirit and principles in the disclosure of the present invention should fall within the scope of the invention as set forth in the appended claims.