Abstract:
The invention involves an image sensor camera module and a method of fabricating the image sensor camera module. The image sensor camera module uses a single-body type lens holder defined by a hollow cylindrical body having a shoulder protruding radially inwardly from an inner surface thereof. First and second lenses therein are spaced apart by a first spacer and a filter therein is spaced from the second lens by a second spacer. An image sensor is adhered to a lower rim of the body, and the filter is adhered to an upper rim thereof. All optical elements within the lens holder thus are affixed in fixed relative position compatible with a predefined focal length and axis. Moreover, the adhesively sealed interior of the body of the image sensor camera module prevents particulate contamination.

Description:
[0001]     This application claims the priority of Korean Patent Application No. 2004-61957, filed on Aug. 6, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a camera module applied to a mobile phone or a digital camera, and more particularly, to a lens holder structure of an image sensor camera module and a method of fabricating the same.  
         [0004]     2. Description of the Related Art  
         [0005]     Use of digital cameras is increasing along with internet video communication and the like. Also, with the increasing popularity of next generation mobile communication, compact camera modules are increasingly required to use compact personal digital assistants (PDAs) in video communication or the like. In other words, there is a greatly increasing demand for subminiature camera modules directly and indirectly related to high- and multi-function digital cameras.  
         [0006]     In particular, cameras adapted in mobile phones used for mobile communication employ compact camera modules.  
         [0007]      FIG. 1  illustrates a conventional image sensor camera module. Referring to  FIG. 1 , a barrel  30  in which a lens  80  is mounted is attached to a lens holder  20 . The barrel  30  is inserted into the lens holder  20  using a matching threading of the lens holder  20  and the barrel  30 . By rotating the threaded barrel  30  within the threaded lens holder  20 , a distance between the lens  80  and an image sensor  70  attached on a circuit board  10  is adjustable. This distance is then used to adjust the focus of the lens  80 . However, in a case where an axis  60  of the lens  80  does not coincide with a central axis  50  of the image sensor  70 , an image with a high resolution cannot be obtained via the lens  80 , and the phase of the image is also not clear. Thus, the barrel  30  is necessarily adjusted to allow the axis  60  of the lens  80  to coincide with the central axis  50  of the image sensor  70 , i.e., a length distance between the lens  80  and the image sensor  70  is necessarily adjusted.  
         [0008]     In other words, the conventional image sensor camera module is completed by separately assembling the lens holder  20  into which the barrel  30  is inserted, and the image sensor  70  is attached on the circuit board  10 . Both the accuracy and reliability of the conventional image sensor camera module are poor because the axis  60  of the lens  80  will often not coincide with the central axis  50  of the image sensor  70 . Another shortcoming of the conventional image sensor camera module is that the barrel and lens holder threads may cause particles to be generated during a rotation of the barrel  30 . The particles may contaminate the image sensor  70 , which may affect the operation of the image sensor  70 .  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides an image sensor camera module which can be assembled without adjusting a focal length between a lens and an image sensor.  
         [0010]     In one aspect, an image sensor camera module comprising: a lens holder defined by a single generally cylindrical body having an opening extending axially therethrough; a first lens installed inside the lens holder; an image sensor comprising an upper surface directly adhered to an inner surface of the cylindrical body; and a circuit board electrically coupled to terminals of the image sensor.  
         [0011]     In another aspect, the present invention also provides a method of fabricating an image sensor camera module by which a process of assembling the image sensor camera module can be simplified, and a contamination of the image sensor camera module due to particles can be prevented.  
         [0012]     According to an embodiment of the present invention, there is provided an image sensor camera module including: a lens holder; a lens installed inside the lens holder; an image sensor including an upper surface directly adhered to an inner surface of the lens holder; and a circuit board electrically coupled to terminals of the image sensor.  
         [0013]     According to another embodiment of the present invention, there is provided an image sensor camera module including: a single body type lens holder into which first and second lenses are inserted to be spaced apart from each other via a spacer; a filter adhered to an inner surface of the lens holder above the second lens to be exposed to the outside of the lens holder; an image sensor including an upper surface, the upper surface being adhered to the inner surface of the lens holder under the first lens; and a circuit board electrically coupled to terminals of the image sensor under the lens holder.  
         [0014]     According to still another embodiment of the present invention, there is provided a method of fabricating an image sensor camera module, including: providing a single body type lens holder; inserting a lens on a protrusion formed inside the lens holder; inserting a spacer on the lens; inserting a filter into an end of the lens holder; and adhering an image sensor to a lower surface of the protrusion; and electrically coupling terminals of the image sensor to a circuit board.  
         [0015]     According to yet another embodiment of the present invention, there is provided a method of fabricating an image sensor camera module, including: providing a single body type lens holder into which first and second lenses are inserted to be spaced apart from each other via a spacer and to which a filter is adhered on the second lens to be exposed to the outside of the lens holder; adhering an upper surface of an image sensor to an inner surface of the lens holder under the first lens; electrically coupling terminals of the image sensor to a circuit board under the lens holder; and filling a filling adhesive between the image sensor and the circuit board. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The above and other features and advantages of the invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.  
         [0017]      FIG. 1  is a cross-sectional view of a conventional image sensor camera module.  
         [0018]      FIG. 2  is a cross-sectional view of an image sensor camera module, according to one embodiment of the invention.  
         [0019]      FIG. 3  is a flowchart of a method of fabricating the image sensor camera module of the present invention.  
         [0020]      FIGS. 4 through 9  are cross-sectional views illustrating a method of fabricating the image sensor camera module of the one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.  
         [0022]      FIG. 2  is a cross-sectional view of an image sensor camera module, according to an embodiment of the present invention. Referring to  FIG. 2 , a first lens  140  is inserted on (or placed flush against) an inner protrusion or shoulder  120  of a single body type lens holder  100 . Those of skill in the art will appreciate that shoulder  120  represents a generally planar substantially contiguous peripheral inward protrusion that, because of the uniform dimensions of the holder and the shoulder integrally formed therewith supports the first lens  140  and an image sensor  240  in a fixedly predetermined position defining a fixed focal length or distance and a fixed focal axial alignment. It will also be appreciated that the preferably integrally molded holder and shoulder properly fixedly align an optional second lens and an optional filter in identical, fixed focal axial alignment and focal length.  
         [0023]     Thus, in accordance with one embodiment of the invention, a second lens  180  is inserted above the first lens to be spaced apart from the first lens  140  via a first spacer  160 . The inner protrusion or shoulder  120  is formed to extend circularly, circumferentially around an inner surface of the lens holder  100  to support the first lens  140 . Also in accordance with one embodiment of the invention, a filter  200  is mounted above the second lens  180  to be adhered to the inner surface of the lens holder  100  to be exposed to the outside. Here, the filter  200  is preferably adhered to the inner surface of the lens holder  100  (at an upper extreme end thereof referred to herein as a rim) using an adhesive  220  to seal the interior of the lens holder  100  against particulate contaminants. As shown in  FIG. 2 , a second spacer  300  may be further included to maintain a desired distance between the second lens  180  and the filter  200 .  
         [0024]     The lens holder  100  can be made of a material intercepting radio waves such as a plastic material or a metallic material, and the first and second lenses  140  and  180  and the filter  200  may be made of any suitable glass, plastic or other optical quality material.  
         [0025]     An upper surface (a surface opposite the surface that includes the connection terminals) of an image sensor  240  is directly adhered to the inner surface of the lens holder  100  under the first lens  140 . The image sensor  240  may be adhered to an underside of the shoulder  120  using an adhesive  130  as shown in  FIG. 2 . The image sensor  240  is also electrically coupled to a circuit board  280  under the lens holder  100 . A filling adhesive  320  is filled between the lens holder  100  and the circuit board  280  to which the image sensor  240  is adhered. The image sensor  240  will be understood to be an image sensor in which an image sensor chip is mounted on a board. A passivation layer (not shown) such as silicon nitride, polyimide, or glass may be formed on part of or the entire surface of the image sensor chip.  
         [0026]     Here, the image sensor  240  may be a suitable Charge Coupled Device (CCD) or a Complementary Metal-Oxide-Semiconductor (CMOS) image sensor. The image sensor  240  may be packaged in the form of a chip scale package, for example, ball grid array (BGA), or quad flat nonlead (QFN), to make the image sensor module compact. In  FIG. 2 , the image sensor  240  includes terminals  260  that protrude from the lower opposite surface of the image sensor  240  as in the case of a BGA. However, in the case of the QFN, the terminals  260  do not protrude outside the image sensor  240 . Instead, portions of the image sensor  240  itself are exposed to the exterior of the sensor and perform the electrical interconnect function of the terminals  260 .  
         [0027]     As described above, in the image sensor camera module according to the present invention, the single-body type lens holder  100 , in which the first and second lenses  140  and  180  are spaced apart from each other via the first spacer  160 , is adhered to the image sensor  240 . Thus, when the image sensor camera module is assembled, a focal length between the first and second lenses  140  and  180  and the image sensor  240  does not need to be adjusted as in the prior art. As a result, a process of assembling the image sensor camera module can be greatly simplified, and the accuracy and reliability of the image sensor camera module can be greatly improved. Also, since the lens holder  100  is directly adhered to the image sensor  240 , the probability of error or inaccuracy in fabricating the image sensor camera module is low when compared to that of the conventional image sensor camera module.  
         [0028]      FIG. 3  is a flowchart of a method of fabricating the image sensor camera module of the present invention.  FIGS. 4 through 9  are cross-sectional views illustrating the method of fabricating the image sensor camera module of the present invention.  
         [0029]     The method of fabricating the image sensor camera module of the present invention will now be described in detail with reference to  FIGS. 3 through 9 .  
         [0030]     As shown in  FIG. 4 , in operation S 1 , the first lens  140 , the first spacer  160 , the second lens  180 , and the second spacer  300  are inserted into the single body type lens holder  100 . In operation S 2 , the filter  200  is inserted into the lens holder  100 . In operation S 3 , the interior of the lens holder  100  is sealed with the adhesive  220  and then treated using ultraviolet (UV) radiation. The completed lens holder  100  is turned upside down as shown in  FIG. 4 .  
         [0031]     The lens holder  100  includes the shoulder  120  extending in a circle around the inner surface thereof. The first lens  140  is inserted and placed flush against the shoulder  120  so that the shoulder  120  supports the first lens  140 . The first spacer  160  is inserted and placed flush against the first lens  140 , and then the second lens  180  is inserted and placed flush against the first spacer  160 . Next, the second spacer  300  is inserted and placed flush against the second lens  180 . Next, the filter  200 , e.g., an infrared (IR) or ultraviolet (UV) or other desired camera-quality filter, is inserted on the second spacer  300 . Thereafter, the adhesive  220  is inserted between an end or rim of the inner surface of the lens holder  100  and the filter  200  so that the filter  200  is adhered to the rim of the inner surface of the lens holder  100  and so that an outer surface of the filter  200  is exposed.  
         [0032]     The first spacer  160  is inserted so that the first lens  140  is spaced apart from the second lens  180 , and the second spacer  300  is inserted so that the second lens  180  is spaced apart from the filter  200 . Thus, the first and second spacers  160  and  300  must be designed to obtain an optimum resolution in consideration of the focal length of the first and second lenses  140  and  180  and an image sensor that will be adhered in a subsequent process. An adhesive, e.g., a UV adhesive, is preferably coated on a surface of the shoulder  120  inside the lens holder  100  to securely adhere the first lens  140  to the shoulder  120 . If necessary, an O-ring made of a rubber material may be inserted on a surface of the first lens  140  opposite the shoulder  120 . The first spacer  160  is preferably a singular, hollow, cylindrical structure or it can be a spacer made of several pieces. The filter  200  filters UV light irradiated from the outside, and the side of the filter  200  is sealed with the adhesive  220  to adhere the filter  200  to the lens holder  100 . The adhesive  220  preferably contains an ingredient that hardens, i.e. is activated, by UV radiation.  
         [0033]     In operation S 4 , the image sensor  240  is adhered to the lens holder  100 . As shown in  FIG. 5 , for the adhesion of the image sensor  240  to the lens holder  100 , an adhesive  130  is coated on a horizontal second shoulder region of the inner surface  120  of the lens holder  100 . Referring to  FIG. 6 , a surface of the image sensor  240  opposite that which includes the terminals  260  is adhered on the adhesive  130 . As shown in  FIG. 7 , the resultant structure includes the image sensor  240  adhered to the lens holder  100 .  
         [0034]     The adhesive  130  is any suitable adhesive and preferably is a thermosetting adhesive that is used at a temperature between approximately 100° C. and 150° C. Because the image sensor  240  is directly adhered to the lens holder  100 , an image sensor camera module compatible focal lengths of the first and second lenses  140  and  180  and the image sensor  240  is possible. In this process, the adhesive  130  can contribute to reducing any error between the focal lengths of the first and second lenses  140  and  180  and the image sensor  240  to less than 20 micrometers. Thus, a resolution of the image sensor camera module can be preserved. In addition, when an adhering process is performed after the entire upper surface of the image sensor  240  is passivated by the passivation layer (not shown), contamination of the image sensor camera module, for example, by airborne particles (or by particles inadvertently, frictionally produced while screwing a prior art lens holder into a prior art threaded barrel—see  FIG. 1 ) is further reduced.  
         [0035]     In operation S 5 , the image sensor  240  is adhered to the circuit board  280 . Referring to  FIG. 8 , the image sensor  240  is adhered to the lens holder  100  and also is electrically connected and adhered to the circuit board  280  via the terminals  260 . The terminals  260  of the image sensor  240 , e.g., solder balls, are electrically coupled to a corresponding circuit pad (not shown) representing electric signals of the circuit board  280 , as will be understood by those of skill in the art.  
         [0036]     Referring to  FIG. 9 , in operation S 6 , the filling adhesive  320  is filled between the circuit board  280  and the image sensor  240 . The filling adhesive  320  strengthens the adhesion of the lens holder  100  to the circuit board  280  and prevents impurities from permeating between the lens holder  100  and the circuit board  280 . Those of skill in the art will appreciate that the filling adhesive  320  can, for example, be a thermosetting adhesive that is capable of readily being hardened, e.g., the application of heat or UV radiation.  
         [0037]     Although not shown, in a subsequent process, the circuit board  280  adhered to the lens holder  100  may be separated from other such image sensor modules (e.g., a regular, plural array of such modules) using a sawing or routing or machining or laser process to singularize or individuate each image sensor camera module. Alternatively, a single circuit board  280  may be adhered to a single lens holder  100  to obviate the separation process described above. However, it is preferable that a plurality of lens holders be adhered to a single circuit board having a corresponding regular array of individual or group camera module circuit patterns. Then the circuit board can be readily separated or divided into sections, each section having one or more lens holders.  
         [0038]     As described above, according to embodiments of the present invention, there is provided the lens holder  100  in which the first and second lenses  140  and  180  are inserted and spaced apart from each other via the first spacer  160 , and the filter  200  is adhered to the inner surface of the lens holder  100  above the second lens  180  to be exposed to the outside of the lens holder  100 . Next, the upper surface of the image sensor  240  is adhered to the inner surface of the lens holder  100  under the first lens  140 . As a result, a process of fabricating the image sensor camera module can be simplified and rendered more accurate and repeatable. Further, particulate contamination of the image sensor camera module can be prevented.  
         [0039]     An image sensor camera module according to embodiments of the present invention can use a single-body type lens holder. Thus, the costly process of adjusting focal lengths of the image sensor and its respective one or more lenses can be omitted. Also, the distance between the lenses and the image sensor can be rendered more uniform. As a result, the highest accuracy and resolution of the image sensor camera module can be maintained.  
         [0040]     Also, a method of fabricating the image sensor camera module according to embodiments of the present invention results in a greatly simplified process of assembling the image sensor camera module. As the single-body type lens holder is directly adhered to the image sensor, any undesirable change of focal lengths of the lenses and the image sensor can be minimized. Also, any error in fabricating the image sensor camera module can be minimized or avoided altogether. Finally, the image sensor camera module can prevent particles from permeating the sealed body and its adhered contents.  
         [0041]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.