Patent Publication Number: US-2011075391-A1

Title: Electronic Apparatus and Circuit Module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. 2009-228937 filed on Sep. 30, 2009, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     One embodiment of the invention relates to an electronic apparatus and a circuit module. 
     2. Description of the Related Art 
     In recent years, portable electronic apparatuses have various functions such as a projector function. In such electronic apparatuses, various measures are taken to downsize the apparatus as well as to implement the various functions. For example, JP-A-2004-63569 describes a semiconductor device in which semiconductor chips are stacked, and a conductive layer is formed on a side face of each of the semiconductor chips so as downsize the semiconductor device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
         FIG. 1  is an exemplary perspective view of a projector according to a first embodiment of the invention; 
         FIG. 2  is an exemplary top view of a video signal generating unit and a lens unit of the projector of  FIG. 1 ; 
         FIG. 3  is an exemplary perspective view of the projector which is partially cut away to illustrate the video signal generating unit and the lens unit of  FIG. 2 ; 
         FIG. 4  is an exemplary sectional view of a portion of the projector around the lens unit of  FIG. 3 ; 
         FIG. 5  is an exemplary side view illustrating how the projector of  FIG. 1  is used; 
         FIG. 6  is an exemplary diagram of a circuit module housed inside the video signal generating unit according to the first embodiment; 
         FIG. 7  is an exemplary perspective view of the circuit module according to the first embodiment; 
         FIG. 8  is an exemplary diagram of a flexible wiring board according to the first embodiment; 
         FIG. 9  is an exemplary diagram of a modified example of a circuit board according to the first embodiment; 
         FIG. 10  is an exemplary diagram of a modified example of the circuit module according to the first embodiment; 
         FIG. 11  is an exemplary diagram of a modified example of the flexible wiring board according to the first embodiment; and 
         FIG. 12  is an exemplary diagram of a circuit module housed in a video signal generating unit according to a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, an electronic apparatus has a circuit module. The circuit module includes a first circuit board having a first side end face on which a first circuit pattern is formed, a second circuit board having a second side end face on which a second circuit pattern is formed, and a flexible wiring board which is in contact with the first side end face and the second side end face to electrically connect the first circuit pattern and the second circuit pattern. 
       FIG. 1  illustrates a projector  1  according to a first embodiment as an example of an electronic apparatus. The projector  1  will be described below with reference to  FIGS. 1 to 5 . As shown in  FIG. 2 , the projector  1  has a body  10  (a housing) defining an outer shape, a video signal generating unit  11 , a mirror  12 , a bearing unit  13 , a lens unit  14 , a counter weight  15 , and an attenuator  16 . 
     The body  10  has a top wall  10   a , a bottom wall  10   b  which is opposed to the top wall  10   a  and whose surface serves as a placement surface when the body  10  is placed on something, and a peripheral wall  10   c  which connects the top wall  10   a  and the bottom wall  10   b . The peripheral wall  10   c  has a front wall  10   d  to which the lens unit  14  is attached, a rear all  10   e  which is opposed to the front wall  10   d , and side walls  10   f ,  10   g  each of which connects the top wall  10   a  and the bottom wall  10   b  and also connects the front wall  10   d  and the rear wall  10   e . A plurality of inner surfaces and inner walls are provided in the body  10 . The inner surfaces and inner walls include inner surfaces of the top wall  10   a , the bottom wall  10   b , the front wall  10   d , the rear wall  10   e , and the side walls  10   f ,  10   g  and walls of housed components. 
     The video signal generating unit  11  has a top wall  11   a , a bottom wall  11   b  which is opposed to the top wall  11   a  and the bottom wall  10   b  of the body  10 , and a peripheral wall  11   c  which connects the top wall  11   a  and the bottom wall  11   b . The walls  11   a ,  11   b ,  11   c  serve as inner walls of the body  10 . The peripheral wall  11   c  has a front wall  11   d , a rear wall  11   e  which is opposed to the front wall  11   d , and side walls  11   f ,  11   g  each of which connects the top wall  11   a  and the bottom wall  11   b  and also connects the front wall  11   d  and the rear wall  11   e.    
     The video signal generating unit  11  incorporates a circuit module  111  which is provided with circuit boards  112 ,  113  and a flexible wiring board  114  which is electrically connected to the circuit boards  112 ,  113 . The circuit module  111  is composed of electronic components that function as a control section etc. of the video signal generating unit  11 . The circuit module  111  will be described later with reference to  FIGS. 6-8 . 
     The video signal generating unit  11  incorporates an LED(s) as a light source(s), a display device, a mirror, etc. The video signal generating unit  11  is either of a type using one white LED or of a type using three LEDs (red, green, and blue LEDs). The video signal generating unit  11  emits light carrying a projection image that is formed by the display device. 
     The mirror  12  is disposed on a light emitting axis L 1  of a light beam emitted from the video signal generating unit  11  and reflects (deflects) the light beam by approximately 90°. The bearing unit  13  is composed of a first bearing  131  and a second bearing  132  whose axes coincide with the light emitting axis L 1 . The first bearing  131  is disposed between the video signal generating unit  11  and the mirror  12 . The second bearing  132  is disposed on the opposite side of the mirror  12  to the first bearing  131 . The bearing unit  13  supports the mirror  12  so that it is rotatable about the light emitting axis L 1 . 
     The lens unit  14  incorporates lenses including a collimation lens and an angle-of-view adjustment lens. The lens unit  14  is disposed on a light projecting axis L 2  of a light beam reflected by the mirror  12  in such a manner that the individual lenses are arranged with their axes coincident with the light projecting axis L 2 . The lens unit  14  is attached to the bearing unit  13  in such a manner as to rotate together with the mirror  12 . A tip portion  141  of the lens unit  14  is inserted in a hole  101  of the body  10  and exposed from the body  10  as shown in  FIG. 1 . As shown in  FIG. 5 , a projection image M is projected from the lens unit  14  toward a projection surface S which is provided outside the body  10 . 
     The counter weight  15  is attached to the bearing unit  13  on the opposite side of the light emitting axis L 1  to the lens unit  14 . The counter weight  15  has such mass as to allow the bearing unit  13  to approximately balance it with the lens unit  14 . The attenuator  16  attenuates an angular deviation of the lens unit  14  with respect to the body  10  that is caused when the body  10  is inclined so as to rotate about the light emitting axis L 1 . For example, as shown in  FIGS. 3 and 4 , the attenuator  16  is has coil springs  161 ,  162  which hold the counter weight  15  from both sides in the rotation direction of the bearing unit. 
     The coil springs  161 ,  162  may have either the same spring constant or different spring constants. Instead of using the coil springs  161 ,  162 , the counter weight  15  may be supported by a leaf spring or the bearing unit  13  may be provided with a spiral spring. It is also preferable to provide another damper in addition to the coil springs  161 ,  162 . The additional damper may be friction that is set in each of the first bearing  131  and the second bearing  132 . In the projector  1 , the mirror  12  and the lens unit  14  can rotate freely about the light emitting axis L 1 . Therefore, even if the body  10  is rotated (moved in the vertical direction) as a result of a rotation of a forearm A about the elbow E, the mirror  12  and the lens unit  14  maintain their postures because of their inertia, that is, they rotate in the direction that is opposite to the rotation direction of the body  10 . As a result, in the projector  1 , the simple structure that the mirror  12  and the lens unit  14  are supported rotatably by the bearing unit  13  can prevent an event that a projected image M is moved to a large extent because of a hand-movement-induced shake of the projector  1 . 
     Next, the circuit module  111  according to the embodiment will be described with reference to  FIGS. 6-8 .  FIG. 6  shows the circuit module  111  which is housed in the video signal generating unit  11  used in the embodiment.  FIG. 7  is an exemplary perspective view of the circuit module  111  according to the embodiment.  FIG. 8  shows the flexible wiring board  114  used in the embodiment. 
     As shown in  FIGS. 6 and 7 , the circuit boards  112 ,  113  are electrically connected to each other by the flexible wiring board  114 . The flexible wiring board  114  bridges the circuit boards  112 ,  113 . The circuit boards  112 ,  113  have respective end portions  112   a ,  113   a  which are opposed to each other. 
     The circuit board  112  has a surface  112 A which is opposed to the front wall  11   d  (an inner wall of the body  10 ) of the video signal generating unit  11  and is mounted parallel with the front wall  11   d . The circuit board  112  has circuit patterns  112   c  which are formed on a side face  112   b  of the end portion  112   a . The circuit patterns  112   c  are terminals which extend from wiring patterns (not shown) that are formed on or inside the circuit board  112 . 
     The circuit board  113  has a surface  113 A which is opposed to the front wall  11   f  (an inner wall of the body  10 ) of the video signal generating unit  11  and is mounted parallel with the side wall  11   f . The circuit board  113  has circuit patterns  113   c  which are formed on a side face  113   b  of the end portion  113   a . The circuit patterns  113   c  are terminals which extend from wiring patterns (not shown) that are formed on or inside the circuit board  113 . 
     As shown in  FIG. 8 , two end portions of the flexible wiring board  114  are provided with respective terminal portions  114   a ,  114   b . The terminal portion  114   a  of the flexible wiring board  114  is in contact with the side face  112   b  of the end portion  112   a  of the circuit board  112 . The terminal portion  114   b  of the flexible wiring board  114  is in contact with the side face  113   b  of the end portion  113   a  of the circuit board  113 . The flexible wiring board  114  is opposed to a corner portion  11   h  which connects the front wall  11   d  and the side wall  11   f  of the video signal generating unit  11  and is part of the peripheral wall lie (an inner wall of the body  10 ). The corner portion  11   h  is formed with a hole to be used when the video signal generating unit  11  is mounted using connection members such as screws. 
     The terminal portion  114   a  is electrically connected to the circuit patterns  112   c  which are formed on the side face  112   b  of the end portion  112   a  of the circuit board  112 . On the other hand, the terminal portion  114   b  is electrically connected to the circuit patterns  113   c  which are formed on the side face  113   b  of the end portion  113   a  of the circuit board  113 . 
     With the above structure, the embodiment realizes high-density mounting of the housed components. Since the circuit module  111  is provided parallel with the front wall  11   d  and the side wall  11   f  of the video signal generating unit  11 , the space occupied by the circuit module  111  in the video signal generating unit  11  can be made small. 
     In the embodiment, the circuit board  112  has the circuit patterns  112   c  which are formed on the side face  112   b  of the end portion  112   a . The circuit board  113  has the circuit patterns  113   c  which are formed on the side face  113   b  of the end portion  113   a . The end portions  112   a ,  113   a  are opposed to each other, the terminal portion  114   a  of the flexible wiring board  114  is in contact with the side face  112   b , and the terminal portion  114   b  of the flexible wiring board  114  is in contact with the side face  113   b . With this configuration, the length of the flexible wiring board  114  can be made shorter than in a case that the flexible wiring board  114  is connected to conductive paths that are formed on the surface  112 A of the circuit board  112  and the surface  113 A of the circuit board  113 . This realizes cost reduction and also enables high-density mounting because the end portions  112   a ,  113   a  can be connected to each other electrically by a short member. 
     In the embodiment, the side face  112   b  is substantially parallel to the said wall  11   f  of the video signal generating unit  11 , the side face  113   b  is substantially parallel to the front wall  11   d  of the video signal generating unit  11 , and the flexible wiring board  114  is disposed along the corner portion  11   h  of the video signal generating unit  11 . To provide a space for, for example, screwing of a screw, the corner portion  11   h  projects inward than other portions of the peripheral wall  11   c . Conventionally, it is difficult to dispose housed components in an area in the vicinity of such a projection (a projected/recessed portion) and such a space is rendered a dead space. In contrast, the structure of the embodiment makes it possible to dispose the circuit module  111  so as to flexibly cope with the projected/recessed portion of the peripheral wall  11   c  and thereby enables high-density mounting. 
     Next, modified examples of the circuit boards  112 ,  113  will be described with reference to  FIG. 9 .  FIG. 9  illustrates a modified example of the circuit board  112 . To simplify the description, the structure of only the circuit board  112  will be described below. However, the same structure can also be applied to the circuit board  113 . 
     As shown in  FIG. 9 , according to the modified example of the circuit board  112 , the circuit patterns  112   c  formed on the side face  112   b  of the end portion  112   a  are conductive layers formed on inner surfaces of grooves. For example, through-holes  112   d  are formed through a circuit board, and the circuit board is then cut at a plane L-L′ which passes through the respective through holes  112   d , whereby the end portion  112   a  is fowled which has terminals on the side face  112   b.    
     With the above structure, in the modified circuit board  112 , conductive terminals can easily be formed on the side face  112   b . Where circuit patterns are formed on the side face  112   b , the circuit patterns becomes more likely to be peeled or scraped off as the circuit board  112  becomes thinner. In contrast, according to the modified example, since the conductive patterns can be formed at positions that are secluded from the side face  112   b , they can be prevented from being peeled or scraped off. The physical durability is thus increased. 
     Next, modified examples of the circuit module  111  and the flexible wiring board  114  will be described with reference to  FIGS. 10 and 11 .  FIG. 10  illustrates a modified example of the circuit module  111 .  FIG. 11  illustrates a modified example of the flexible wiring board  114 . 
     As shown in  FIGS. 10 and 11 , in the modified examples, projections  114   c  are formed on the terminal portion  114   a , and projections  114   d  are formed on the terminal portion  114   b . For example, the projections  114   c ,  114   d  are conductive bumps that are electrically connected to the conductive paths on the flexible wiring board  114 . The projections  114   c  are provided along a perimeter of the terminal portion  114   a  which is in contact with the side face  112   b  of the circuit board  112 . The projections  114   d  are provided along a perimeter of the terminal portion  114   b  which is in contact with the side face  113   b  of the circuit board  113 . 
     With the above structure, in the modified circuit module  111 , the projections  114   c ,  114   d  make it possible to clearly recognize those portions of the flexible wiring board  114  which are to be joined to the circuit boards  112 ,  113  and to thereby facilitate a process of joining the flexible wiring board  114  to the circuit boards  112 ,  113 . 
     The projections  114   c ,  114   d  are conductive bumps. Therefore, the projections  114   c ,  114   d  can be electrically connected to conductive patterns that are formed on surfaces, other than the side faces  112   b ,  113   b , of the circuit boards  112 ,  113 . More reliable electrical connections can thus be realized. 
     Furthermore, the projections  114   c  are provided so as to surround that region of the terminal portion  114   a  which is in contact with the side face  112   b  of the circuit board  112  and the projections  114   d  are provided so as to surround that region of the terminal portion  114   b  which is in contact with the side face  113   b  of the circuit board  113 . Therefore, the circuit boards  112 ,  113  are held in place being sandwiched between the arrays of projections  114   c  and the arrays of projections  114   d , respectively. With this structure, the circuit boards  112 ,  113  can be fixed to the flexible wiring board  114  in a stable manner. 
     Next, a circuit module  211  according to a second embodiment of the invention will be described with reference to  FIG. 12 . The circuit module  211  according to the second embodiment is different from the circuit module  111  according to the first embodiment in the structures of the circuit board  112  and the flexible wiring board  114 . Therefore, the different portions will mainly be described below and the common portions will not be described by using the same reference symbols. A projector incorporating the circuit module  211  has the same appearance as the projector of  FIG. 1  according to the first embodiment. 
       FIG. 12  shows the circuit module  211  which is housed in the video signal generating unit  11  according to the second embodiment. 
     As shown in  FIG. 12 , the circuit boards  112 ,  113  are electrically connected to each other by the flexible wiring board  114 . The flexible wiring board  114  bridges the circuit boards  112 ,  113 . The circuit boards  112 ,  113  have respective end portions  112   a ,  113   a  which are opposed to each other. 
     The circuit board  112  has a surface  112 A which is opposed to the side wall  11   g  (an inner wall of the body  10 ) of the video signal generating unit  11  and mounted parallel with the side wall  11   g . The circuit board  113  has a surface  113 A which is opposed to the side wall  11   f  (an inner wall of the body  10 ) of the video signal generating unit  11  and mounted parallel with the side wall  11   f . The flexible wiring board  114  is opposed to the front wall  11   d  (an inner wall of the body  10 ) of the video signal generating unit  11  and mounted parallel with the front wall  11   d.    
     With the above structure, the second embodiment realizes high-density mounting of the housed components. Since the circuit module  111  is provided parallel with the front wall  11   d  and the side walls  11   f ,  11   g  of the video signal generating unit  11 , the space occupied by the circuit module  111  in the video signal generating unit  11  can be made small. 
     According to the second embodiment, the length of the flexible wiring board  114  can be shortened and the cost can be reduced. And the end portions  112   a ,  113   a  can be connected to each other electrically by a short member. 
     The invention is not limited to the foregoing embodiments but various changes and modifications of its components may be made without departing from the scope of the present invention. Also, the components disclosed in the embodiments may be assembled in any combination for embodying the present invention. For example, some of the components may be omitted from all the components disclosed in the embodiments. Further, components in different embodiments may be appropriately combined. 
     An electronic apparatus to which the invention is applicable to is not limited to a projector. For example, the invention is also applicable to various electronic apparatus such as a portable computer, a digital camera, a video camera, a personal digital assistant, etc.