Patent Publication Number: US-2013228670-A1

Title: Photoelectric conversion element unit and image pickup apparatus

Description:
This application is a continuation of application Ser. No. 13/051,473, filed Mar. 18, 2011, the entire disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a photoelectric conversion element unit and an image pickup apparatus. 
     2. Description of the Related Art 
     In order to shorten a wiring length from a photoelectric conversion element package to a drive circuit and a signal processing circuit in an image pickup apparatus, Japanese Laid-Open Patent Application No. (“JP”) 2009-141844 discloses a photoelectric conversion element unit which has an opening of a fixing plate of a photoelectric conversion element package and arranges a drive circuit and a signal processing circuit in the opening. 
     However, JP 2009-141844 arranges the drive circuit and signal processing circuit on the backside of the photoelectric conversion element package, and a thickness of the photoelectric conversion element unit becomes thicker in the optical axis direction. When an electronic component, such as the drive circuit and the signal processing circuit, is thicker than the fixing plate, the thickness becomes larger than a conventional structure that arranges the photoelectric conversion element package on the fixing plate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a photoelectric conversion element unit and an image pickup apparatus, which can provide a good electric characteristic and a small size. 
     A photoelectric conversion element unit according to the present invention includes a package including a photoelectric conversion element configured to perform a photoelectric conversion for an optical image of an object, a substrate mounted with an electronic component that includes a drive circuit configured to drive the photoelectric conversion element and a signal processing circuit configured to process a signal from the photoelectric conversion element, and a fixing plate having an opening, wherein the package and the electronic component are adjacent to each other in a direction orthogonal to an optical axis in the opening, and the package and the substrate are fixed onto the fixing plate. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an image pickup apparatus of this embodiment. 
         FIGS. 2A and 2B  are perspective views of an image pickup unit illustrated in  FIG. 1 . 
         FIG. 3  is an exploded perspective view of image pickup unit illustrated in  FIG. 2 . 
         FIGS. 4A ,  4 B, and  4 C are perspective, plane, and sectional views of a photoelectric conversion element unit illustrated in  FIG. 1 . 
         FIG. 5  is a plane view of a variation of the photoelectric conversion element unit. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is a perspective view of an image pickup apparatus  1 , and reference numeral  2  denotes an image pickup unit that houses an image pickup optical system (not illustrated) configured to form an optical image of an object. The image pickup apparatus  1  of this embodiment is a digital camera, but the present invention does not limit a type of the image pickup apparatus to a digital camera and may be applied to a video camera, etc. 
       FIG. 2A  is a perspective view of a front side of the image pickup unit  2 , and  FIG. 2B  is a perspective view of a backside of the image pickup unit  2 .  FIG. 3  is an exploded perspective view of an image pickup unit  2  illustrated in  FIG. 2B . 
     The image pickup unit  2  includes an image pickup device holder unit in which a barrel unit that houses an image pickup optical system (not illustrated) is attached to a front side of the image pickup device holder unit, and a photoelectric conversion element unit is attached to a backside of the image pickup device holder unit. 
     In  FIG. 3 , reference numeral  104  denotes an attachment portion of the photoelectric conversion element unit located on a rear surface (of the image pickup device holder unit) of the image pickup unit  2  in the digital camera  1 . 
       FIGS. 4A ,  4 B and  4 C are perspective, plane, and sectional views of the photoelectric conversion unit. The photoelectric conversion element unit is a unit in which a fixing plate  103  mounted with a photoelectric conversion element package (simply referred to as “package” hereinafter) is mounted on a flexible substrate  102 . 
     The package  101  houses a photoelectric conversion element  105  illustrated in  FIG. 4C , such as a CCD sensor and a CMOS sensor, configured to perform a photoelectric conversion for an optical image of an object. The package  101  is fixed onto the fixing plate  103 , and mounted on the flexible substrate  102 . 
     An electronic component  106  connected electrically to the photoelectric conversion element  105  is mounted around the package  101  on the flexible substrate  102 . The electronic component  106  includes a drive circuit configured to drive the photoelectric conversion element  105  and a signal processing circuit configured to process a signal from the photoelectric conversion element  105 , and is implemented as an IC or its peripheral circuit component. 
     The fixing plate  103  has a rectangular frame shape and has an opening  103   a  at its center. The package  101  and the electronic component  106  mounted around the package  101  are arranged in the opening  103   a . While the fixing plate  103  of this embodiment is made of metal, it may be made of resin. 
     As illustrated in  FIGS. 4A and 4B , when the package  101  is arranged at the center of the opening  103   a , the electronic component  106  is arranged between the package  101  and a contour of the fixing plate  103  that defines the opening  103   a.    
     The electronic component  106  is arranged around the package  101 , and adjacent to the package  101  in a direction orthogonal to an optical axis. Thus, the electronic component  106  is not laid on the package  101  in the direction parallel to the optical axis unlike JP 2009-141844. An adjacent arrangement between the electronic component  106  and the package  101  provides a good electronic characteristic, and the non-stacking configuration between the electronic component  106  and the package  101  in the direction parallel to the optical axis contributes to a miniaturization of the thickness of the photoelectric conversion unit in the optical axis direction (miniaturization). 
     While the outer circumference frame of the opening  103   a  closes in this embodiment, a U-shaped opening in which an outer circumferential frame is partially absent may be used. 
     In an attempt to fix (adhere) the package  101  onto the fixing plate  103 , the package  101  is positioned relative to the fixing plate  103  using a jig (not illustrated) in the optical axis direction and the direction orthogonal to the optical axis direction of the package  101 . 
     While the package  101  is being positioned, adhesive is flowed in a space between four corners  101   a ,  101   b ,  101   c , and  101   d  and the opening  103   a  of the fixing plate  103  and cured so as to provisional fix the package  101  and the fixing plate  103 . Thereby, the package  101  can be fixed in a well-balanced manner, and deformations after the provisional fixture can be restrained. 
       FIG. 4B  illustrates this state. Since the electronic component  106  is arranged apart from the four corners  101   a  to  101   d  of the package  101 , the package  101  and the fixing plate  103  can be provisionally fixed with a small amount of adhesive. 
     Next, the built-up structure is moved to a bonding jig (not illustrated), and an adhesive agent is flowed in a space between the side surface of the package  101  and the opening  103   a  of the fixing plate  103 , and cured so as to fix the package  101  together with the flexible substrate  102  onto the fixing plate  103 . Since the adhesive also bonds the electronic component  106 , the adhesive area increases and the adhesive strength among the package  101 , the flexible substrate  102 , and the fixing plate  103  increases. 
     As illustrated in  FIG. 4A , the package  101  and the electronic component  106  are arranged in the opening  103   a  of the fixing plate  103 , and stacked on the fixing plate  103  in the thickness direction (optical axis direction). Hence, the thickness of the photoelectric conversion element unit can be made small. 
     The finished photoelectric conversion element unit is attached to the rear surface  104  of the image pickup unit  2  using screws  108   a ,  108   b , and  108   c , as illustrated in  FIG. 2B . Positioning projections  104   a  and  104   b  are provided on the rear surface  104  of the image pickup unit  2 , and positioning holes  103   b  and  103   c  are formed in the fixing plate  103 . The photoelectric conversion element unit is positioned relative to the rear surface  104  of the image pickup unit  2  in the direction orthogonal to the optical axis direction by inserting the positioning projections  104   a  and  104   b  into the positioning holes  103   b  and  103   c.    
     Three concaves are formed on the rear surface  104  of the image pickup unit  2 , and provided with springs  109   a ,  109   b , and  109   c . The springs  109   a  to  109   c  force the fixing plate  103  in the optical axis direction against the screws  108   a  to  108   c . The position in the optical axis direction and the inclination in the direction orthogonal to the optical axis direction of the photoelectric conversion element unit are fine-adjusted relative to the rear surface  104  of the image pickup unit  2  by adjusting a fastening amount of each of the screws  108   a  to  108   c . This configuration provides highly precise positioning (optical adjustment) of the light-receiving surface of the photoelectric conversion element  105  relative to the imaging surface of the image pickup optical system. 
     The present invention precisely positions the package  101  relative to the fixing plate  103 , and closely arranges the package  101  and the electronic component  106  to each other. Thus, a wiring length between the photoelectric conversion element  105  and the electronic component  106  can be shortened, and a good electric characteristic can be obtained. In addition, the electronic component  106  is adjacent to the package  101  in the direction orthogonal to the optical axis, does not overlap the package  101  in the optical axis direction, and is arranged in the opening  103   a  of the fixing plate  103  together with the package  101 . Therefore, the photoelectric conversion element unit can be made thin in the optical axis direction. 
     If the electronic component  106  is mounted on a substrate different from the flexible substrate  102  (or provided outside of the photoelectric conversion element unit), a layout inside of the camera is restricted so as to shorten the wiring length from the package  101  to the electronic component  106 . However, according to this embodiment, the electronic component  106  and the package  101  are mounted on the same flexible substrate  102  (or the electronic component  106  is provided in the photoelectric conversion element unit). As a consequence, no such restraints occur and the design freedom increases. Thereby, a variety of components and a substrate suitable for a miniaturization and a thin profile of the entire camera can be designed. 
       FIG. 5  is a plane view of a variation of the photoelectric conversion element unit. The electronic component  106  is arranged apart from the four sides&#39; centers  101   e ,  101   f ,  101   g , and  101   h  of the package  101 . Provisional fixing of the package  101  to the fixing plate  103  is performed through the four sides&#39; centers  101   e  to  101   h  of the package  101 . Thereby, the package  101  can be provisionally fixed onto the fixing plate  103  with a small amount of adhesive. When the fixing plate  103  is bonded at the four sides&#39; centers of the package  101 , the package  101  can be fixed in a well-balanced manner and the deformations after the provisional fixture can be restrained. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2010-071536, filed Mar. 26, 2010, which is hereby incorporated by reference herein in its entirety.