Abstract:
A digital camera module ( 200 ) includes a lens holder ( 20 ), a lens module ( 30 ) received in the lens holder, and an image sensor chip package ( 40 ) mounted to the lens holder. The lens module includes a lens barrel ( 301 ) movably engaged in the lens holder and at least one lens ( 302 ) received in the lens barrel. The image sensor chip package includes a base ( 401 ), an image sensor chip ( 402 ) mounted on the base, a transparent cover ( 405 ), and an adhesive ( 50 ) positioning the transparent cover with respect to the image sensor chip. The adhesive and the transparent cover cooperatively seal the image sensor chip therein.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to digital camera modules, and more particularly to a digital camera module with a small sized image sensor chip package which is used in portable electronic devices such as mobile phones, palm-top computers, personal digital assistants (PDAs) and so on. 
     2. Discussion of the Related Art 
     Generally, digital cameras are image recording media capable of photographing a plurality of still images without using film. Such a digital camera typically uses an image pickup device, which is a kind of semiconductor device, such as a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS). In the digital camera, an object image formed on the image pickup device through a lens is converted into an electrical signal by the image pickup device, and the electrical signal is stored as a digital signal in a mobile phone or PDA in which the digital camera is mounted. 
     A typical digital camera module  100  is illustrated in  FIG. 1 . The digital camera module  100  is constructed to include a holder  11 , a lens module  12  and an image sensor chip package  13 . The lens module  12  includes a barrel  121 , a lens  122 , an IR (infra-red) cut filter  123  and a cover  124 . The barrel  121  is placed in and threadingly engaged with the holder  11 . The lens  122  is received in the barrel  121 . The cover  124  is fixed to the barrel  121 , on a front end of the barrel  121  which is exposed to outside. The cover  124  has a transparent area  125  which transmits light from outside to the lens  122 . The IR-cut filter  123  is fixed to the barrel  121 , opposite to the cover  124 . The image sensor chip package  13  includes a bottom layer  131 , a frame layer  132 , an image sensor chip  133 , a plurality of wires  134  and a transparent board  135 . The bottom layer  131 , which is made of printed circuit board (PCB), includes a plurality of top pads  1311  on a top surface thereof and a plurality of bottom pads  1312  on a bottom surface thereof. Each top pad  1311  corresponds and connects to a respective bottom pad  1312 . The frame layer  132  is mounted on the top surface of the bottom layer  131 , containing the top pads  1311  therein. The image sensor chip  133  is located on the top surface of the bottom layer  131 , surrounded by the top pads  1311 . The image sensor chip  133  includes a plurality of chip pads  1331  provided on a top surface thereof. Each chip pad  1331  is electrically connected with a corresponding top pad  1311  via a respective wire  134 . The transparent board  135  is secured to the top of the frame layer  132 . The image sensor chip package  13  is fixed to the holder  11 , with the image sensor chip  133  facing the lens module  12 . 
     In the digital camera module  100 , the top surface of the bottom layer  131  peripherally surrounded by the frame layer  132  must contain the top pads  1311  and the image sensor chip  133  together, and sufficient space should be provided between the image sensor chip  133  and an inside wall of the frame  102  for movement of wire bonding tools used to connect the wires  134  with the chip pads  1331  and the top pads  1311 . Therefore, package volume for packaging the chip  12  is a lot larger than that taken up by the chip  12 , which results in a relative larger volume of the digital camera module  100 . As such, the digital camera module  100  is not suitable for slim, compact electronic products. 
     What is needed, therefore, is a digital camera module with small size, high reliability and high image quality. 
     SUMMARY OF THE INVENTION 
     In one embodiment thereof, a digital camera module includes a lens holder, a lens module received in the lens holder, and an image sensor chip package mounted to the lens holder. The lens module includes a lens barrel movably engaged in the lens holder and at least one lens received in the lens barrel. The image sensor chip package includes a base, an image sensor chip mounted on the base, a transparent cover, and an adhesive positioning the transparent cover with respect to the image sensor chip. The adhesive and the transparent cover cooperatively seal the image sensor chip therein. 
     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present digital camera module can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the digital camera module. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic, cross-sectional view of a typical digital camera module; 
         FIG. 2  is a schematic, cross-sectional view of a digital camera module according to a first embodiment of the present invention, and 
         FIG. 3  is a schematic, cross-sectional view of a digital camera module according to a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 2 , a digital camera module  200  in accordance with a first embodiment of the present invention is shown. The digital camera module  200  includes a lens holder  20 , a lens module  30  and an image sensor chip package  40  both mounted on the lens holder  20 . 
     The lens holder  20  has a front end  201 , a rear end  203  opposite to the front end  201 , and a receiving cavity  205  penetrating through the lens holder  20  from the front end  201  to the rear end  203 . An internal thread  207  is formed on an inner periphery surface the lens holder  20 . 
     The lens module  30  includes a barrel  301  and at least one lens  302 . The barrel  301  is a hollow cylinder for receiving the at least one lens  302  therein, and has an external thread  3011  formed on an external surface thereof. One end of the barrel  301  is covered by a plate  303  which has a transparent region  3031  formed in a central portion thereof. The transparent region  3031  aligns with an optical axis of the lens  302  allowing light to be transmitted to the lens  302 . 
     The image sensor chip package  40  includes a base  401 , an image sensor chip  402 , a plurality of wires  403 , an adhesive means  404  and a transparent cover  405 . 
     The base  401  is made of a material such as a plastic, a ceramic or a fibrous composite. The base  401  has a top surface  4011 , a bottom surface  4012  on an opposite side of the base  401  to the top surface  4011 , a plurality of top pads  4014  and a plurality of bottom pads  4015 . The top pads  4014  are arranged in a circular pattern on the top surface  4011  of the base  401 . The bottom pads  4015  are arranged in a circular pattern on the bottom surface  4012 . Each bottom pad  4015  corresponds to and electrically connects with a respective top pad  4014 . It is to be understood that the top pads  4014  could also be embedded in the base  401  as shown in  FIG. 2 , with a surface exposed to outside from the top surface  4011 , and the bottom pads  4015  also could be embedded in the base  401  with a surface exposed to outside from the bottom surface  4012 . The bottom pads  4015  are used to electrically connect with other electronic elements such as a PCB. 
     The image sensor chip  402  is adhered to the top surface  4011  of the base  401 , surrounded by the top pads  4014 . A top side of the image sensor chip  402  is arranged with a photosensitive area  4021  and a plurality of chip pads  4022  around the photosensitive area  4021 . 
     The wires  403  are made of a conductive material such as gold or aluminum alloy. One end of each wire  403  is connected/joined with a respective chip pad  4022  of the image sensor chip  402 , and the other end of the wire  403  is connected/joined with a respective top pad  4014  of the base  401 . 
     The adhesive means  404 , such as a silicone, epoxy, acrylic, or polyamide adhesive, is applied peripherally around the image sensor chip  402 , over the wires  403 . The adhesive means  404  covers the wires  403  and junctions of the wires  403  and the pads  4014 ,  4022 , in order to protect the wires  403  from crack from metal fatigue and to ensure the connections between the ends of the wires  403  and pads  4014 ,  4022 . It is to be understood that the adhesive means  26  could be applied to the peripheral edge of the image sensor chip  402 , over the wires  403 , therefore the adhesive means  404  covers part of each wire  403  and junctions between the wires  403  and the chip pads  4022 . 
     The cover  405  is laid over the image sensor chip  402  which receives light transmitted through the cover  405 . A bottom surface of the cover  405  touches the top of each wire  403 , thereby being supported by the wires  403 . The cover  405  is adhered to the adhesive means  404  and therefore seals the photosensitive area  4021  of the image sensor chip  402  together with the adhesive means  404 . 
     In assembling the digital camera module  200 , firstly, an adhesive means  50  such as glue is applied on the rear end  203  of the lens holder  20 . Secondly, the lens holder  20  with the adhesive means  50  is located on the base  401  of the image sensor chip package  40 , with the rear end  203  of lens holder  20  adhered to the top surface  4011  of the base  401  and containing the top pads  4014  of the base  401  therein. Thereafter, the adhesive means  50  is cured to fix the lens holder  20  to the image sensor chip package  40 . Thirdly, the lens module  30  is inserted into the receiving cavity  205  of the lens holder  20  from the front end  201  of the lens holder  20 , with the lens barrel  301  threadingly engaging with the lens holder  20 , then the lens module  30  is adjusted until it is properly focused on the image sensor chip  402 . Lastly, the adhesive means  50  is applied to the front end  201  of the lens holder  20  and cured peripherally around the outside surface of the lens barrel  301  exposed to outside from the front end  201  of the lens holder  20 , so as to secure the lens barrel  301  to the lens holder  20 . 
     It is to be understood that the lens holder  20  and image sensor chip package  40  could be connected to each other via other connecting assembly such as guiding holes (not shown) and guiding poles (not shown) corresponding to the guiding holes. For example, a plurality guiding holes could be defined in the rear end  203  of the lens holder  20 . Accordingly, a plurality guiding of poles would be disposed on the top surface  4011  of base  401  of the image sensor chip package  40 , respectively inserted in and engaging with a corresponding guiding hole. The adhesive means  50  would be applied on the top surface  4011  of the base  401 , around the periphery of the lens holder  20 , in order to enforce the connection between the lens holder  20  and the base  401  of the image sensor chip package  40 . 
     In a second embodiment of the present invention as shown in  FIG. 3 , a digital camera module  300  has a similar structure to the digital camera module  200 . The digital camera module  300  includes a lens holder  22 , a lens module  32  and an image sensor chip package  42 . The lens holder  22  includes a front end  221 , a rear end  223 , a hole  225  and an internal thread  227 . The lens module  32  is configured to have a lens barrel  321  having an external thread  3211 , at least one lens  322  and a plate  323  having a transparent region  3231  formed at a central portion of the plate  323 . The image sensor chip package  42  includes a base  421  having a top surface  4211 , a bottom surface  4212 , a plurality of top pads  4214  and a plurality of bottom pads  4215 , an image sensor chip  422  including a photosensitive area  4221  and a plurality of chip pads  4222 , a plurality of wires  423 , an adhesive means  424  and a transparent board  425 . 
     The difference between the image sensor chip package  300  and the image sensor chip package  200  is that the rear end  223  of the lens holder  22  has a stepped shape including a first step surface  2231  and a second step surface  2232 . An inner periphery of the first step surface  2231  has a dimension slightly larger than that of the outer periphery of the cover  425 . An inner periphery of the second step portion  2232  has a dimension smaller than that of the outer periphery of the cover  425 . The second step surface  2232  of the lens holder  22  connects with the periphery of the cover  425 , via an adhesive means  52 , so that the lens holder  22  is secured to the image sensor chip package  42 . 
     In the present invention, the image sensor chip is adhered on the top surface of the base without a side wall, thus there is no space restriction on the wire bonding tools&#39; movements. Accordingly, the size of the base can be sufficiently minimized to a size approaching that of the image sensor chip, and the volume of the image sensor chip package can also be minimized which results in a relatively smaller volume for the digital camera module. In addition, the photosensitive area of the image sensor chip is sealed by the adhesive means and the cover. Since the adhesive means and the cover together form a space therebetween which is relatively small to contain relatively little dust and particles therein, the pollution and/or contamination of the photosensitive area is reduced and the quality and reliability of the digital camera module is much improved. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.