Abstract:
To provide a connection structure of a wiring cable and a connection method of a wiring cable which enable the downsizing of a head part. The connection structure includes: a semiconductor chip having a plurality of imaging elements formed on a front surface and a plurality of connection pads formed on a rear surface; and a wiring cable in which a plurality of wires are integrally formed and from whose end surface the plural wires are exposed, wherein the plural connection pads of the semiconductor chip and the plural wires exposed from the end surface are connected.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of prior International Application No. PCT/JP2013/001988 filed on Mar. 25, 2013; the entire contents of all of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Embodiments described herein relate generally to a connection structure of a wiring cable and a connection method of a wiring cable. 
       BACKGROUND 
       [0003]    Imaging apparatuses include a head-separated imaging apparatus whose head part having an imaging element (for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor) is separated from a main body part which processes an image signal transmitted from the head part. In the head-separated imaging apparatus, the head part and the main body part are connected by a camera cable. Conventionally, the image sensor and the cable have been connected via a substrate, a FPC (flexible printed circuit), TAB (Tape Automated Bonding), and so on. However, recent years have seen a demand for further downsizing of the head part of the head-separated imaging apparatus. 
         [0004]    The present invention was made to solve such a conventional problem, and its object is to provide a connection structure of a cable and a connection method of a cable which enable the downsizing of a head part. 
         [0005]    A connection structure of a cable according to an embodiment includes: a semiconductor chip having a plurality of imaging elements formed on a front surface and a plurality of connection pads formed on a rear surface; and a wiring cable in which a plurality of wires are integrally formed and from whose end surface the plural wires are exposed, wherein the plural connection pads of the semiconductor chip and the plural wires exposed from the end surface are connected. 
         [0006]    The present invention can provide a connection structure of a cable and a connection method of a cable which enable the downsizing of a head part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagram of an imaging apparatus according to an embodiment. 
           [0008]      FIG. 2A  and  FIG. 2B  are schematic views of an image sensor according to the embodiment. 
           [0009]      FIG. 3  is a schematic view of a head part and a camera cable according to the embodiment. 
           [0010]      FIG. 4A  and  FIG. 4B  are schematic views illustrating examples of an alignment mark. 
           [0011]      FIGS. 5A ,  5 B,  5 C, and  5 D are explanatory views of a connection method of the cable to the image sensor according to the embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Hereinafter, an embodiment will be described in detail with reference to the drawings. 
       Embodiment 
       [0013]      FIG. 1  is a schematic diagram of an imaging apparatus  100  according to the embodiment (hereinafter, referred to as the imaging apparatus  100 ).  FIGS. 2A and 2B  are schematic views of a head part  200  and a cable  400 . The imaging apparatus  100  is, for example, an endoscope apparatus, and includes the head part  200 , a CCU (Camera Control 
         [0014]    Unit)  300  (hereinafter, referred to as the main body part  300 ), and the camera cable  400  (wiring cable) connecting the head part  200  and the main body part  300 . 
         [0015]    The head part  200  includes an image sensor  210  (semiconductor chip), a cover glass  220 , and a lens body  230 . A detailed structure of the head part  200  will be described with reference to  FIGS. 2A and 2B  and  FIG. 3 . 
         [0016]    The main body part  300  includes an IF circuit  301 , a memory  302 , a processor  303 , a driver  304 , a controller  305 , and a power supply circuit  306 . 
         [0017]    The IF circuit  301  is an interface for the transmission/receipt of control signals and data to/from the head part  200 . 
         [0018]    The memory  302  is a nonvolatile memory, and is, for example, a serial EEPROM (Electrically Erasable Programmable Read-Only Memory). In the memory  302 , setting data (operation mode) of the head part  200  and correction data are stored. 
         [0019]    The processor  303  is a processor for image processing. The processor  303  performs various kinds of corrections (for example, noise correction, white balance, y correction, and so on) of an image signal transmitted from the head part  200 . The processor  303  outputs the corrected image signal to an external display device  500  (for example, a CRT (Cathode Ray Tube) or a liquid crystal monitor). 
         [0020]    The driver  304  is a drive circuit of the image sensor  210 . The driver  304  changes a drive method and a frame rate of the image sensor  210  based on the control from the controller  305 . Further, the driver  304  outputs pulse signals (for example, pulse signals for vertical synchronization and horizontal synchronization (a transfer pulse signal, a reset gate pulse signal)) to the image sensor  210 . 
         [0021]    The controller  305  reads out the correction data and the setting data from the memory  302 . The controller  305  controls the processor  303  and the driver  304  based on the read correction data and setting data. 
         [0022]    The power supply circuit  306  is connected to an external power source. The power supply circuit  306  converts power from the external power source to a predetermined voltage to supply it to the constituent circuits (the IF circuit  301 , the memory  302 , the processor  303 , the driver  304 , the controller  305 ) of the main body part  300 . Further, the power from the power supply circuit  306  is also supplied to the head part  200  via the camera cable  400 . 
       (Schematic Views of Image Sensor  210 ) 
       [0023]      FIGS. 2A and 2B  are schematic views of the image sensor  210 .  FIG. 2A  is a side view of the image sensor  210 .  FIG. 2B  is a plane view of a rear surface side of the image sensor  210 . Hereinafter, the structure of the image sensor  210  will be described with reference to  FIGS. 2A and 2B . 
         [0024]    The image sensor  210  is a solid-state imaging element such as, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. 
         [0025]    As illustrated in  FIGS. 2A and 2B , the image sensor  210  has a rectangular shape. On a front surface S 1  of the image sensor  210 , an imaging element, a drive circuit of the imaging element, and so on, not shown, are formed. Further, on a rear surface S 2  of the image sensor  210 , a plurality of connection pads P having a rectangular shape are formed. On each of the connection pads P, a solder ball B is provided. The connection pads P are electrically connected to the imaging element, the drive circuit, and so on formed on the front surface S 1 , via not-shown through vias. Further, on the image sensor  210 , an alignment mark AM- 1  for positioning which is used when the image sensor  210  is connected to the camera cable  400  is provided. Note that, in the example illustrated in  FIGS. 2A and 2B , one of corners of the connection pad P on the upper left in the drawing, out of the plural connection pads P formed on the rear surface S 2  of the image sensor  210 , is cut out, and this cutout serves as the alignment mark AM- 1 . 
       (Structure of Head Part  200  and Cable  400 ) 
       [0026]      FIG. 3  is a schematic view of the head part  200  and the cable  400 . Note that in  FIG. 3 , the head part  200  is shown as an exploded schematic view. Hereinafter, the structure of the head part  200  and the cable  400  will be described with reference to  FIG. 3 . 
         [0027]    As described with reference to  FIG. 1 , the head part  200  includes the image sensor  210 , the cover glass  220 , and the lens body  230 . The cover glass  220  is a glass substrate protecting the front surface of the image sensor  210 . The lens body  230  is provided on a front surface of the cover glass  220  (opposite the image sensor  210 ) and forms an image on the image sensor  210 . 
         [0028]    The camera cable  400  is, for example, a wiring cable in which a plurality of wires  410  are integrated by a resin R or the like by molding. The wires  410  of the camera cable  400  are buried in the resin R so as to correspond to positions of the connection pads P formed on the rear surface S 2  of the image sensor  210 , respectively. Further, an end surface E of the camera cable  400  on an image sensor  210  side is a surface cut by laser or the like and the wires  410  are exposed therefrom. 
         [0029]    The end surface E (cut surface) of the camera cable  400  has a rectangular shape agreeing with the shape of the image sensor  210 , and its lengthwise and breadthwise dimensions are also substantially equal to or smaller than those of the image sensor  210 . Further, in the end surface E, an end surface of the resin R and end surfaces of the plural wires  410  are substantially flush with each other. 
         [0030]    The plural wires  410  of the camera cable  400  are used for the transfer of a differential signal of data (image), for power supply, for GND, and so on, for instance. 
         [0031]    Further, an alignment mark AM- 2  for positioning which is used when the camera cable  400  is connected to the image sensor  210  is provided on the camera cable  400 . In  FIG. 3 , part of the camera cable  400  is colored (given a different color) to serve as the alignment mark AM- 2 . Aligning the alignment mark AM- 1  provided on the image sensor  210  and the alignment mark AM- 2  provided on the camera cable  400  at the time of the connection results in the connection of the wires  410  of the camera cable  400  to the correct connection pads P respectively. 
         [0032]    Note that the alignment mark AM- 2  of the camera cable  400  is preferably provided along a longitudinal direction of the camera cable  400 . The alignment mark AM- 2 , if being provided along the longitudinal direction of the camera cable  400 , exists near a cut surface of the camera cable  400  at whichever position the camera cable  400  is cut. Incidentally, the alignment mark AM- 2  may be, for example, a groove V provided in the camera cable  400  (refer to  FIG. 4A ) or a cutout C provided in only one side (refer to  FIG. 4B ). 
       (Connection of Camera Cable  400  to Image Sensor  210 ) 
       [0033]      FIGS. 5A ,  5 B,  5 C and  5 D are views illustrating the procedure for connecting the camera cable  400  to the image sensor  210 . The procedure (method) for connecting the camera cable  400  to the image sensor  210  will be described with reference  FIGS. 5A ,  5 B,  5 C and  5 D. 
         [0034]    First, the image sensor  210  and the camera cable  400  are prepared (refer to  FIG. 5A ). Note that it is assumed that the cover glass  220  for image sensor protection has already been bonded on the front surface of the image sensor  210 . 
         [0035]    Next, the alignment mark AM- 1  of the image sensor  210  and the alignment mark AM- 2  of the camera cable  400  are aligned with each other, and the end surface E of the camera cable  400  is pressed so that the wires  410  of the camera cable  400  abut on the solder balls B provided on the connection pads P formed on the rear surface of the image sensor  210 . Here, the solder balls B have a semispherical shape. Therefore, even if the end surfaces of the wires  410  are slightly set back from the end surface E of the camera cable  400 , it can be ensured that the end surfaces of the wires  410  and the solder balls B abut on each other. 
         [0036]    Next, reflowing (heat treatment) of the solder balls B is performed to electrically join the connection pads P formed on the rear surface of the image sensor  210  and the wires  410  of the camera cable  400  (refer to  FIG. 5B ). Next, the lens body  230  is prepared (refer to  FIG. 5C ). Next, the lens body  230  is aligned by using a positioning jig or the like, and the lens body  230  is joined on the cover glass  220  by using an adhesive for optics (refer to  FIG. 5D ). 
         [0037]    As described above, in this embodiment, at the time of the connection, the end surface of the camera cable  400  from which the plural wires  410  are exposed is pressed against the connection pads P formed on the rear surface S 2  of the image sensor  210 , and therefore, it is possible to easily connect the image sensor  210  and the camera cable  400 . 
         [0038]    Further, the connection pads P are formed on the rear surface of the image sensor  210 , and the camera cable  400  is connected from the rear surface side of the image sensor  210  not via a substrate or the like but directly. Further, the shape and size of the cross section of the camera cable  400  are substantially equal to those of the image sensor  210 . This can downsize the camera head  200 . Further, since a casing covering the image sensor  210  is not provided, it is possible to further downsize the camera head  200 . 
         [0039]    Further, the solder balls B in the semispherical shape are provided on the connection pads P of the image sensor  210 . Therefore, even if the end surfaces of the wires  410  are slightly set back from the end surface of the camera cable  400 , it can be ensured that the end surfaces of the wires  410  and the solder ball B abut with each other. As a result, connection reliability of the image sensor  210  and the camera cable  400  is improved. 
         [0040]    Further, only by the reflowing of the solder balls B, it is possible to connect the plural wires  410  of the camera cable  400  to the image sensor  210  at a time. Therefore, it is possible to easily connect the image sensor  210  and the camera cable  400 . Further, since the number of man-hours necessary for the connection is small, the connection reliability further improves as compared with a case where the wires  410  are connected to the connection pads P of the image sensor  210  one by one. 
         [0041]    Further, since the alignment marks AM- 1 , AM- 2  are provided on the image sensor  210  and the camera cable  400  respectively, aligning the positions of the alignment mark AM- 1  and the alignment mark AM- 2  makes it possible to prevent the connection of the wrong combination of the connection pad P and the wire  410 . 
         [0042]    In the foregoing description, the case where the number of the connection pads P of the image sensor  210  is four is described, but the number of the connection pads P of the image sensor  210  is not limited to four. Further, the number of the wires  410  of the camera cable  400  is not limited to four either, and can be changed according to the number of the connection pads P of the image sensor  210 . Further, the shape of the image sensor  210  is not limited to the rectangular shape and may be a circular shape or a cut circular shape. Further, the cross-sectional shape of the camera cable  400  is not limited to the rectangular shape either and may be a circular shape or a cut circular shape according to the shape of the image sensor  210 . 
       Other Embodiments 
       [0043]    As described above, several embodiments of the present invention are described, but the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. The above-described embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without changing the spirit of the invention.