Patent Publication Number: US-2011063450-A1

Title: Camera module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. divisional application filed under 37 USC 1.53(b) claiming priority benefit of U.S. Ser. No. 12/289,471 filed in the United States on Oct. 28, 2008, which claims earlier priority benefit to Korean Patent Application No. 10-2008-0077148 filed with the Korean Intellectual Property Office on Aug. 6, 2008, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a camera module. 
     2. Description of the Related Art 
     Recently, camera modules are mounted on IT devices such as mobile terminals, PDAs (Personal Digital Assistant), MP3 players and so on. With the development of technology, the resolution of the camera modules changes from 300,000 pixels (VGA) to several million pixels, and the reduction in size and thickness of the camera modules are being performed depending on mounting targets. Further, the camera module provides various additional functions, such as auto-focusing (AF) and optical zoom. 
     The camera modules are manufactured by using main parts of charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensors. Incident light transmitted through the lens is condensed by the image sensor and is stored as data in a memory. The stored data is displayed as an image through a display medium, such as liquid crystal display (LCD) or PC monitor. 
     Typical camera modules are manufactured by a chip-on-film (COF) method, a chip-on-board (COB) method and the like. The COB method will be described with reference to drawings. 
       FIG. 1  is an exploded perspective view of a conventional camera module manufactured by the COB method, and  FIG. 2  is a cross-sectional view of the conventional camera module. 
     In the conventional camera module  10 , a printed board  11  having a CCD or CMOS image sensor  12  mounted thereon through wire bonding is coupled to a lower end portion of a housing  13  formed of plastic, and a lens barrel  16  having a cylindrical body  14   a  extending downward is coupled to a lower end portion of a barrel  13   a  extending upward from the housing  13 . 
     In the camera module  10 , the housing  13  and the lens barrel  14  are coupled to each other by coupling a female screw portion  13   b  formed on the inner circumferential surface of the barrel  13   a  to a male screw portion  14   b  formed on the outer circumferential surface of the cylindrical body  14   a.    
     Further, an IR filter  15  is interposed between a lens  14   c  mounted in the lens barrel  14  and the image sensor  12  attached on the upper surface of the printed board  11  so as to cut off excessive long-wavelength infrared rays incident on the image sensor  12 . 
     In the camera module assembled in such a manner, while light incident from a specific object passes through the lens  14   c , an image is inverted so that the focus is adjusted on the surface of the image sensor  12 . At this time, when a focus is optimally adjusted while the lens barrel  14  screwed to the upper end of the housing  13  is rotated, an adhesive is injected between the barrel  13   a  of the housing  13  and the lens barrel  14  such that the housing  13  and the lens barrel  14  are bonded to each other. Then, the camera module is finalized. 
     In the camera module manufactured by the COB method, the lens barrel  14  is inserted into the upper opening of the housing  13  such that the lens barrel  14  and the housing  13  are closely coupled to each other through the screw coupling using the female and male screw portions  13   b  and  14   b  formed on the inner and outer circumferential surfaces of the housing  13  and the lens barrel  14 . As height adjustment is performed by rotating the lens barrel  14  at the upper end portion of the housing  13 , focus adjustment between the lens  14   c  within the lens barrel  14  and the image sensor  12  mounted on the printed board  11  is achieved. 
     Therefore, in the conventional camera modules manufactured by the above-described assembling method, when the housing  13  and the lens barrel  14  are vertically coupled, and if the female and male screws  13   b  and  14   b  are engaged at a distorted angle, screw threads may be broken or the coupling portion may be worn away by the friction between the female and male screws  13   b  and  14   b . Then, foreign matters such as minute particles may occur, thereby degrading the assembling property. 
     Further, the particles occurring between the housing  13  and the lens barrel  14  inevitably fall onto the upper surface of the IR filter  14  or the light receiving region of the image sensor  12 , because the housing  13  is rocked left and right when the focus adjustment is performed by rotating the lens barrel  14  mounted on the upper end portion of the housing  13 . Therefore, when an image is reproduced by the image sensor  12 , the particles have a large effect on the image. 
     Further, since the housing  13  and the lens barrel  14  are coupled though the male and female screws, the lens may be tilted along a spiral angle formed in the lens barrel  14  when the lens barrel  14  is rotated along the spiral contact surface. 
     Once foreign matters fall onto the lens  14   c  or the image sensor  12 , they cannot be simply removed. Therefore, the camera module  10  in which the foreign matters have occurred should be discarded as a whole. As a result, the expensive lens  14   c  or the image sensor  12  is also discarded. 
     Further, since the housing  13  having the IR filter  15  coupled thereto is mounted on the printed board  11  after the image sensor  12  is wire-bonded to the printed board  11 , movable foreign matters may fall into the housing  13 , or specifically onto the upper end portion of the image sensor  12  such that defects frequently occur. Furthermore, since passive elements (not shown in  FIG. 1 ) are mounted around the image sensor  12 , flux or other foreign matters frequently occur. 
     Further, in order to quickly respond to users&#39; request which changes day by day, a sample manufacturing schedule needs to be reduced by standardizing a camera module. 
     SUMMARY 
     An advantage of the present invention is that it provides a camera module which adopts a holder assembly which has an image sensor and an IR filter mounted therein and is formed of a ceramic material, thereby minimizing defects caused by foreign matters. Since the holder assembly is previously manufactured, it is possible to quickly respond to users&#39; requests. Further, as a reflow process is adopted, it is possible to simplify the manufacturing process. Further, when defects occur in the camera module, a rework operation can be easily performed, and the manufacturing cost can be reduced. 
     Another advantage of the invention is that it provides a method of manufacturing a camera module. 
     Additional aspect and advantages of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     According to an aspect of the invention, there is provided a method of manufacturing a camera module, the camera module including a housing that includes one or more lenses which are sequentially fixed and coupled and of which the focus does not need to be adjusted; a holder assembly that is coupled to a lower end portion of the housing; and a main substrate that is coupled to a lower end portion of the holder assembly. The method comprises providing bonding media for bonding the main substrate through a reflow process such that the bonding media are disposed on a lower surface of a holder substrate composing the lower end portion of the holder assembly, and fixing an image sensor on an upper surface of the holder substrate through wire bonding; mounting a holder formed of a ceramic material so as to surround the image sensor wire-bonded to the holder substrate; mounting an IR filter on the holder so as to seal an internal space of the holder, which is defined by the holder substrate and the holder and in which the image sensor is included, thereby completely manufacturing the holder assembly; bonding the holder assembly to the main substrate through a reflow process; and performing fine focus adjustment while sliding the housing into the housing mounting portion formed at the upper end portion of the holder body coupled to the main substrate. 
     The housing may include a support portion which extends from an inner lower end of the housing so as to come in contact with the upper end portion of the holder assembly. The support portion may be provided so as to be disposed on an upper end portion of the IR filter. 
     The method further comprises providing passive elements on the holder substrate such that the passive elements are positioned outside the holder, before the bonding of the holder assembly to the main substrate. 
     According to another aspect of the invention, a camera module comprises a housing that includes one or more lenses which are sequentially fixed and coupled and of which the focus does not need to be adjusted; a holder assembly that is coupled to a lower end portion of the housing; and a main substrate that is coupled to a lower end portion of the holder assembly through a reflow process. The holder assembly includes a holder including: a housing mounting portion that is formed on an upper end portion of the holder such that fine focus adjustment can be performed in a sliding manner when the holder assembly is coupled to the lower end portion of the housing; and a filter mounting portion that is formed in such a manner that an internal space of the holder is sealed by an IR filter, the holder being formed of a ceramic material on which a reflow process can be performed; the IR filter that is mounted on the filter mounting portion formed in the holder; and a holder substrate that is coupled to a lower end portion of the holder and includes an image sensor fixed on an upper surface thereof through wire bonding and bonding media for bonding the main substrate through a reflow process, the bonding media being provided on a lower surface of the holder substrate. 
     The housing may include a support portion which extends from an inner lower end of the housing so as to come in contact with the upper end portion of the holder assembly. The support portion may extend so as to be disposed on an upper end portion of the IR filter. 
     The filter mounting portion may be formed on an inner surface of the upper end portion of the holder. 
     The filter mounting portion may be formed on an inner surface of a middle portion of the holder. 
     The camera module further comprises passive elements that are provided on the holder substrate so as to be positioned outside the holder. 
     The bonding media formed on the lower surface of the holder substrate may be solder balls or pads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is an exploded perspective view of a conventional camera module manufactured by the COB method; 
         FIG. 2  is a cross-sectional view of the conventional camera module; 
         FIG. 3  is a cross-sectional view of a holder assembly according to a first embodiment of the invention; 
         FIG. 4  is a cross-sectional view of a camera module  40  according to a second embodiment of the invention; 
         FIG. 5  is a cross-sectional view of a camera module  50  according to a third embodiment of the invention; 
         FIG. 6  is a cross-sectional view of a camera module  60  according to a fourth embodiment of the invention; and 
         FIGS. 7A to 7G  are process diagrams sequentially showing a method of manufacturing a camera module according to the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. 
     Hereinafter, a camera module and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings. 
     Camera Module 
     First Embodiment 
       FIG. 3  is a cross-sectional view of a holder assembly according to a first embodiment of the invention. 
     The hold assembly  30  shown in  FIG. 3  includes a holder  31 , a holder substrate  32 , an image sensor  33 , an IR filter  34 , and bonding media  35  for a reflow process. 
     First, the holder  31  formed in a cylindrical shape is mounted so as to surround the image sensor  33  fixed on the holder substrate  32  through wire bonding. In the first embodiment, when a housing (not shown in  FIG. 3 ) including a lens is coupled to the holder assembly  30 , a lower end portion of the housing and an upper end portion of the holder assembly  30  are coupled in a sliding manner. Therefore, a housing mounting portion  36  is formed along the circumferential surface of the upper end of the holder  31 . 
     Further, a stepped filter mounting portion  37  is formed along the inner circumferential surface of the upper end of the holder  31 , and the IR filter  34  is mounted on the filter mounting portion  37 . For example, the IR filter  34  is fixed to the holder  31  through an adhesive such as ultraviolet (UV) bond. Therefore, the depth of the filter mounting portion  37  within the holder  31  corresponds to the height of the IR filter  34 . 
     The IR filter  34  serves to cut off excessive infrared rays incident on the image sensor  33  and to ‘seal’ the holder assembly  30 . In other words, the IR filter  34  serves as a cover glass for protecting the image sensor  33  within the holder assembly  30  from external contaminants which may occur during a variety of processes to be subsequently performed, even though it will be described below in a method of manufacturing a camera module. 
     Meanwhile, the lower end portion of the holder  31  is coupled to the holder substrate  32 . The image sensor  33  is fixed on the upper surface of the holder substrate  32  through wire bonding, and the bonding media  35  for bonding a main substrate  41  (refer to  FIG. 4 ) are provided on the lower surface of the holder substrate  32 . For example, solder balls or pads are provided as the bonding media  35  for a reflow process. 
     In the first embodiment, the main substrate  41  and the holder assembly  30  are previously bonded to each other through a reflow process before the housing  42  (refer to  FIG. 4 ) is coupled. In the conventional COB method, the process for bonding the camera module to the main substrate is separately performed. In the reflow process according to the invention, however, the bonding media  35  are previously mounted between the holder assembly  30  and the main substrate  41  such that a plurality of holder assemblies  30  can be bonded to a plurality of main substrates through one process. Therefore, it is possible to simplify the manufacturing process. 
     However, since a general reflow process is performed at a high temperature of about 250° C., it was difficult to apply the reflow process to a camera module which is manufactured by the COB method and uses a housing formed of plastic such as PVC. 
     Therefore, in this embodiment, the holder  31  is formed of a ceramic substrate on which the reflow process can be performed. Accordingly, only the holder assembly  30  can be attached to the main substrate  41  through the reflow process, before the housing  42  including lenses  42   a  is installed. 
     Further, passive elements  38  such as a capacitor, an inductor, and a resistor are mounted on the holder substrate  32  so as to be disposed outside the holder  31 . When the passive elements are mounted around the image sensor  33 , foreign matters may have an effect upon the image sensor  33 . In this embodiment, however, since the passive elements  38  are isolated from the image sensor  33  within the holder  31 , it is possible to minimize the contamination of the image sensor  33  caused by the occurrence of foreign matters. 
     According to this embodiment, a standardized and commonly-used module can be previously manufactured as the holder assembly  30  so as to be mounted on the main substrate  41  depending on a user&#39;s request, which makes it possible to quickly respond to the user&#39;s request. Therefore, it is possible to reduce the manufacturing time. 
     Further, in the conventional camera module, individual components were sequentially assembled. In this embodiment, however, since the holder assembly  30  is previously manufactured, the manufacturing process can be simplified. Further, a rework operation can be easily performed when defects occur in the camera module, and the lenses or image sensor can be reused. 
     Second Embodiment 
       FIG. 4  is a cross-sectional view of a camera module  40  according to a second embodiment of the invention. 
     In this embodiment, the descriptions of the same technical construction as that of the first embodiment will be omitted, and like reference numerals will be attached to the same components. 
     The camera module  40  according to the second embodiment includes a main substrate, a housing  42 , and the holder assembly  30  described in the first embodiment. 
     First, the holder assembly  30  is mounted on the main substrate  41 , and a reflow process is then performed. In general, since the reflow process is performed at a high temperature of about 250° C., the reflow process is performed before the housing formed of plastic such as PVC is mounted on the holder assembly  30 . 
     After the holder assembly  30  is bonded to the main substrate  41 , the housing  42  is mounted on the upper end portion of the holder assembly  30 . The housing  42  includes one or more lenses  42   a  which are sequentially fixed and coupled and of which the focus does not need to be adjusted. At this time, the housing  42  is inserted into the housing mounting portion  36  of the holder  31  while being adjusted in a sliding manner. Therefore, the depth of the housing mounting portion  36  is designed in such a manner that a focal distance (that is, a distance from the lower end of the lens to the upper end of the image sensor) can be adjusted. 
     In the conventional camera module manufactured by the COB method, since the lens barrel and the housing are coupled through the screw portions, the screw adjustment should be performed so as to adjust a focal distance. Accordingly, foreign matters may occur during the screw adjustment. In this embodiment, however, since the housing  42  is adjusted in a sliding manner, it is possible to minimize foreign matters. 
     Third Embodiment 
       FIG. 5  is a cross-sectional view of a camera module  50  according to a third embodiment of the present invention. 
     In this embodiment, the descriptions of the same technical construction as those of the first and second embodiments will be omitted, and like reference numerals will be attached to the same components. 
     The housing  42  further includes a support portion  42   b  which extends from an inner lower end of the housing  42  so as to come in contact with the upper end of the holder assembly. That is, the housing  42  further includes the cylindrical support portion  42   b  formed at the inner lower end thereof. The support portion  42   b  may be disposed on the upper end of the IR filter  34 . 
     As the support portion  42   b  is adopted, the housing  42  and the holder assembly  30  can be coupled more reliably. Further, when the housing  42  is coupled, the housing  42  can be inserted into the holder  31  without a separate height adjustment process. In other words, the height of the support portion  42   b  is determined after a desirable focal distance is previously calculated. Then, the housing  42  can be inserted into the holder  31  without a separate height adjustment process. Therefore, it is possible to prevent an image error caused by ‘tilting’ when the image sensor module and the housing are coupled. 
     Fourth Embodiment 
       FIG. 6  is a cross-sectional view of a camera module  60  according to a fourth embodiment of the invention. 
     In this embodiment, the descriptions of the same technical construction as those of the first to third embodiments will be omitted, and like reference numerals will be attached to the same components. 
     First, a filter mounting portion  37   a  is formed on the inner surface of a middle portion of the holder  31  of the holder assembly  30 . 
     For the bonding media  35 , pads may be used instead of solder balls. Like the solder balls, the pads reliably bond the holder assembly  30  to the main substrate  41 , while an adhesive provided on the lower ends of the pads is molten during a high-temperature reflow process. Therefore, it is possible to simplify the manufacturing process, as in the reflow process using the solder balls. 
     Method of Manufacturing Camera Module 
     Hereinafter, a method of manufacturing a camera module according to an embodiment of the present invention will be described. 
     In this embodiment, the descriptions of the same technical construction as those of the first to fourth embodiments will be omitted, and like reference numerals will be attached to the same components. 
     First, a holder assembly  30  is manufactured. Then, a main substrate  41  is bonded to the holder assembly  30  through a reflow process, and a housing  42  is mounted on the upper end portion of the holder assembly  30 . Since a general reflow process is performed at a high temperature of about 250° C., the housing formed of plastic such as PVC is mounted on the holder assembly  30  after the reflow process. 
     The holder assembly  30  is manufactured by the following process. 
     First, bonding media  35  for bonding the main substrate  40  through a reflow process are provided on the lower surface of a holder substrate  32  composing the lower end portion of the holder assembly  30 , and an image sensor  33  is mounted on the upper surface of the holder substrate  32  (refer to  FIG. 7A ) and is fixed through wire bonding (refer to  FIG. 7B ). For the bonding media  35 , solder balls or pads may be used. 
     Then, a holder  31  formed of a ceramic material having thermal resistance is mounted on the holder substrate  32  so as to surround the image sensor  33  wire-bonded on the holder substrate  32  (refer to  FIG. 7C ). Since the holder  31  is formed of a ceramic material, it can endure high-temperature heat generated during a reflow process. 
     Next, a housing mounting portion  36  on which a housing  42  is to be mounted is provided on the upper end portion of the holder  31  along the circumferential surface of the holder  31 . Further, a filter mounting portion  37  on which an IR filter is to be mounted is provided along the inner circumferential surface of the upper end portion of the holder  31 . When the IR filter  34  is mounted, an adhesive such as UV bond may be used. 
     As the upper end portion of the holder  31  is sealed by the IR filter  34 , the IR filter  34  may serve as a cover glass for protecting the expensive image sensor  33  from external contaminants which may occur during a variety of processes to be subsequently performed (refer to  FIG. 7D ). 
     Before the holder assembly  30  is bonded to the main substrate  41 , passive elements  38  are provided on the holder substrate  32  so as to be positioned outside the holder  31  (refer to  FIG. 7E ). The passive elements  38  may be provided on the upper end portion of the holder  31  as well as the holder substrate  32  (not shown). 
     The holder assembly  30  constructed in such a manner is bonded to the main substrate  41  through a reflow process (refer to  FIG. 7F ). At this time, since a plurality of holder assemblies can be bonded to a plurality of main substrates through one process, it is possible to simplify the manufacturing process. Further, since the holder assembly  30  is previously manufactured, it is possible to quickly respond to users&#39; requests, thereby reducing the manufacturing time. That is because, since a proper quantity of main substrates  41  are bonded through the reflow process in accordance with users&#39; requests, mass production can be achieved. 
     After the holder assembly  30  and the main substrate  41  are bonded to each other, the housing  42  is mounted on the housing mounting portion  36  of the holder assembly  30  in a sliding manner. While the housing  42  is slowly slid into the housing mounting portion  36  of the holder assembly  30 , fine focus adjustment is performed (refer to  FIG. 7G ). Therefore, it is possible to minimize foreign matters which have occurred during the screw adjustment in the conventional screw coupling method. 
     According to the present invention, defects caused by foreign matters can be minimized. Further, since the holder assembly is previously manufactured, it is possible to quickly respond to users&#39; requests. Further, since the reflow process is adopted, the manufacturing process can be simplified, and throughput can be enhanced. Further, when defects occur in the camera module, a rework operation can be easily performed, and the image sensor can be reused, which makes it possible to reduce the manufacturing cost. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.