Patent Publication Number: US-2016224061-A1

Title: Electrical device and method of producing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-018237, filed on Feb. 2, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to an electrical device and a method of producing the same. 
     BACKGROUND 
     Mobile electrical devices such as a smartphone and a tablet terminal, which may be referred to as mobile terminals hereinafter, are widely used in these years. The mobile terminal has various functions such as a voice call function, WiFi, a Global Positioning System (GPS), a near field communication (NFC) function, and a television function, which use a wireless communication technology. 
     The mobile terminal includes a specific antenna for each of the functions such as a voice call function, WiFi, GPS, an NFC function, and a television function. The antenna is made of a metal thin plate, for example, and disposed on a side surface of a housing of the mobile terminal. Technologies related to this are disclosed in Japanese Laid-open Patent Publication No. 2001-22910 and Japanese Laid-open Patent Publication No. 2010-114559. 
     SUMMARY 
     In accordance with an aspect of the embodiments, an electrical device includes a first unit including an electrode; a second unit having a hole at a position corresponding to the electrode of the first unit; a probe pin having a smaller diameter than the hole and configured to be elastically deformed, the probe pin being disposed in the hole such that a front end thereof is in contact with the electrode of the first unit; and an adhesive connecting the first unit and the second unit to each other and filling the hole so as to fix the probe pin. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and/or other aspects and advantages will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawing of which: 
         FIGS. 1A and 1B  are plan views illustrating an example of an electrical device according to a first embodiment; 
         FIG. 2  is a cross-sectional view taken along a line II-II in  FIG. 1B ; 
         FIGS. 3A and 3B  are cross-sectional views illustrating a structure of a probe pin; 
         FIG. 4  is a view indicating one step in a method of producing the electrical device according to the first embodiment; 
         FIG. 5  is a view indicating one step in the method of producing the electrical device according to the first embodiment; 
         FIG. 6  is a view indicating one step in the method of producing the electrical device according to the first embodiment; 
         FIG. 7  is a view indicating one step in the method of producing the electrical device according to the first embodiment; 
         FIGS. 8A and 8B  are schematic cross-sectional views illustrating a first modification; 
         FIGS. 9A and 9B  are schematic cross-sectional views illustrating a second modification; 
         FIG. 10  is a plan view illustrating an electrical device according to a second embodiment; 
         FIG. 11  is a cross-sectional view taken along a line XI-XI in  FIG. 10 ; 
         FIG. 12  is a view indicating one step in a method of producing the electrical device according to the second embodiment; 
         FIGS. 13A and 13B  are views indicating one step in the method of producing the electrical device according to the second embodiment; 
         FIG. 14  is a plan view illustrating an electrical device according to a third embodiment; 
         FIG. 15  is a cross-sectional view taken along a line XV-XV in  FIG. 14 ; 
         FIG. 16  is a view indicating one step in a method of producing the electrical device according to the third embodiment; 
         FIG. 17  is a view indicating one step in the method of producing the electrical device according to the third embodiment; and 
         FIG. 18  is a view indicating one step in the method of producing the electrical device according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments are described with reference to the drawings. 
     First Embodiment 
       FIGS. 1A and 1B  are plan views illustrating an example of an electrical device according to a first embodiment.  FIG. 2  is a cross-sectional view taken along a line II-II in  FIG. 1B . In this embodiment, an electrical device is a mobile terminal such as a smartphone. 
       FIG. 1A  illustrates a display panel  10 .  FIG. 1B  illustrates a housing  20 . The mobile terminal is assembled by connecting peripheral portions of the display panel  10 , which is illustrated in  FIG. 1A , and the housing  20 , which is illustrated in  FIG. 1B , with an adhesive. The display panel  10  is an example of a first unit, and the housing  20  is an example of a second unit. 
     The display panel  10  is a thin plate and includes a plurality of pixels in a display area  15  for displaying characters and images, for example. As illustrated in  FIG. 1A , a plurality of antennas  11   a  to  11   e,  which are metal thin plates, are disposed on the peripheral portion of the display panel  10 , more specifically, on a rear surface of a portion outside the display area  15 . 
     The length of each of the antennas  11   a  to  11   e  is determined depending on its function such as a voice call function, WiFi, GPS, an NFC function, or a television function. The antennas  11   a  to  11   e  each have a circular pad (electrode)  12  on each end thereof. 
     The housing  20  has a U-shaped cross section having a space in which a circuit board (not illustrated), for example, is disposed. As illustrated in  FIG. 1B , the peripheral portion of the housing  20 , which is referred to as a side wall  23  hereinafter, includes a plurality of recesses  24  in an upper surface thereof. The recesses  24  are located at positions corresponding to the pads  12  on the display panel  10 . 
     As illustrated in  FIG. 2 , a probe pin  21  is disposed in each recess  24 . The probe pin  21  includes a coil spring therein, which is described later, and elastically stretches (deforms) in an axial direction thereof. The probe pin  21  has a smaller diameter than the recess  24 . The probe pin  21  and the inner surface of the recess  24  define a space to be filled with an adhesive, which is described later. 
     The diameter of the probe pin  21  and the diameter of the recess  24  may be suitably determined. The diameter of the probe pin  21  may be in a range of 0.2 mm to 2 mm, and the diameter of the recess  24  may be in a range of 1.2 mm to 6 mm. 
       FIG. 3A  is a cross-sectional view illustrating a structure of the probe pin  21 . As illustrated in  FIG. 3A , the probe pin  21  includes a cylindrical portion  21   a,  a coil spring  21   b,  a contact portion  21   c,  and an insertion portion  21   d.  The probe pin  21  is made of metal. 
     The cylindrical portion  21   a  has a cylindrical shape, and the coil spring  21   b  is disposed in the cylindrical portion  21   a.  The contact portion  21   c  has a bar shape. The contact portion  21   c  has a lower portion positioned in the cylindrical portion  21   a  and an upper portion protruding upward from the cylindrical portion  21   a.  The contact portion  21   c  is biased upward by an elastic force of the coil spring  21   b.    
     The insertion portion  21   d  is a protrusion extending from the lower end of the cylindrical portion  21   a.  As illustrated in  FIG. 2 , a probe pin connecting portion  22   a  of a connection terminal  22  is disposed on a bottom of the recess  24 . When the insertion portion  21   d  is inserted into a hole in the probe pin connecting portion  22   a,  the probe pin  21  and the connection terminal  22  are electrically and mechanically connected to each other. 
     The probe pin  21  may have a flat front end as illustrated in  FIG. 3A  or may have a pointed front end as illustrated in  FIG. 3B . 
     As illustrated in  FIG. 2 , the connection terminal  22  includes the probe pin connecting portion  22   a,  which is disposed on the bottom of the hole  24 , a pad  22   b,  which is disposed inwardly from the side wall  23  and connected to the circuit board, and a connection  22   c,  which extends between the probe pin connecting portion  22   a  and the pad  22   b.    
     The probe pin connecting portion  22   a,  the pad  22   b,  and the connection  22   c  are formed of metal as one component. The connection terminal  22  is integrated with the housing  20  by an insert molding process, for example. 
     Hereinafter, a method of producing an electrical device (mobile terminal) in the first embodiment is described with reference to  FIG. 1 , and  FIG. 4  to  FIG. 7 . 
     The display panel  10  and the housing  20  illustrated in  FIGS. 1A and 1B  are formed first. The antennas  11   a  to  11   e  and the pads  12 , which are metal thin films, are formed on the peripheral portion of the display panel  10 . 
     A copper foil coated film is punched out or etched to form antenna blanks and pad blanks, for example. Then, the obtained blanks are attached to the peripheral portions of the display panel  10  to form the antennas  11   a  to  11   e  and the pads  12 . Alternatively, a conductive paste may be printed on the peripheral portion of the display panel  10  to form the antenna blanks and the pad blanks. Then, the obtained blanks may be plated with copper to form the antennas  11   a  to  11   e  and the pads  12 . 
     The housing  20  is formed by the insert molding process, for example, in which a resin material and the connection terminal  22  are integrated. A circuit board is disposed in the housing  20  such that a terminal of the circuit board is in contact with the connection terminal  22 . Thus, the circuit board and the housing  20  are electrically connected to each other. 
     Then, as illustrated in a plan view of  FIG. 4 , an adhesive  25  is applied to an upper surface of the side wall  23  of the housing  20 . At the same time, the hole  24  is filled with the adhesive  25 . The type of the adhesive  25  is not limited. An adhesive that contracts in volume as curing thereof proceeds, which is referred to as a cure shrinkable adhesive hereinafter, is preferably used. The cure shrinkable adhesive preferably has a shrinkage rate, or a shrinkage rate in a thickness direction, in a range of about 3% to about 8%. 
     Then, as illustrated in  FIG. 5 , the housing  20  is disposed in a housing fixture jig  31 . The housing fixture jig  31  includes stop blocks  32  having a predetermined height at positions around the housing  20 . 
     The reference numeral  27  in  FIG. 5  denotes a circuit board disposed in the housing  20 . The circuit board  27  includes an electronic circuit for activation of the display panel  10 . The reference numeral  28  in  FIG. 5  denotes a terminal of the circuit board  27 . 
     Then, the display panel  10  is sucked by a suction tool  33  of a vacuum suction transport machine, for example, and disposed above the housing  20 . Then, as illustrated in  FIG. 6 , the suction tool  33  is moved down until the suction tool  33  comes in contact with the stop block  32 . The distance between the upper surface of the side wall  23  and the display panel  10  is made substantially constant by the contact between the suction tool  33  and the stop blocks  32 . Thus, an adhesive layer having a uniform thickness is obtained. 
     In the specification, the adhesive positioned between the display panel  10  and the side wall  23  is referred to as an adhesive layer. The thickness of the adhesive layer is in the range of 0.2 mm to 0.4 mm, for example. 
     Then, the adhesive  25  is cured. The contact portion  21   c  and the pad  12  are kept in contact with each other under a substantially constant pressure due to the elastic force of the coil spring  21   b  until the adhesive  25  is cured. Then, the contact portion  21   c  and the pad  12  are fixed to each other due to the curing of the adhesive  25  with the contact pressure being maintained. Since the cured adhesive  25  fixes the contact portion  21   c,  the probe pin  21  loses its stretchability (elasticity). In other words, the adhesive  25  attached to the probe pin  21  fixes the shape of the probe pin  21 . 
     Then, an electrical device (mobile terminal) including the housing  20  and the display panel  10  connected together is removed from the housing fixture jig  31  after the adhesive  25  is sufficiently cured.  FIG. 7  illustrates a cross-sectional view of the electrical device  30  removed from the housing fixture jig  31 . The electrical device  30  is produced in this way. 
     As described above, in this embodiment, since the front end (contact portion  21   c ) of the probe pin  21  comes in elastic contact with the pad  12 , the probe pin  21  reliably comes in contact with the pad  12  even if the adhesive layer has a non-uniform thickness. 
     In addition, in this embodiment, since the stretchability of the probe pin  21  is lost when the adhesive  25  is cured, creep deformation of the adhesive layer does not occur even when the electrical device is used for a long period of time. Thus, the connection obtained by the adhesive  25  has long-term reliability. 
     In this embodiment, the probe pin  21  and the connection terminal  22  are electrically and mechanically connected when the insertion portion  21   d  of the probe pin  21  is inserted into the hole of the connection terminal  22 . However, the probe pin  21  and the connection terminal  22  may be connected by soldering or with a conductive adhesive, for example, or may be connected with a screw or by welding. 
     First Modification 
       FIGS. 8A and 8B  are schematic cross-sectional views illustrating an electrical device according to a first modification. In the first modification, the side wall of the housing  20  includes protrusions, which are not included in the first embodiment, on the upper surface thereof so as to limit the thickness of the adhesive layer. The other configurations are substantially identical to those in the first embodiment and are not described in detail. In  FIGS. 8A and 8B , components identical to those in  FIG. 2  and  FIG. 7  are assigned the same reference numerals as those in  FIG. 2  and  FIG. 7 . 
     As illustrated in  FIG. 8A , in the first modification, protrusions  41  are disposed at predetermined positions on the upper surface of the side wall  23  of the housing  20 . As illustrated in  FIG. 8B , when the display panel  10  is connected to the housing  20  with the adhesive  25 , the display panel  10  is brought into contact with the top of each protrusion  41 . This enables the adhesive layer to have a uniform thickness. The height of the protrusion  41  may be suitably determined. In this modification, the height of the protrusion  41  is in a range of 0.2 mm to 0.4 mm. The height of the protrusion  41  corresponds to the thickness of the adhesive layer. 
     In the first modification, since the thickness of the adhesive layer is made uniform by the contact between the protrusions  41  and the display panel  10 , the housing fixture jig  31  including the stop blocks  32  as illustrated in  FIG. 5  is unnecessary. In addition, the adhesive layer has more uniform thickness. 
     In the above-described modification, the housing  20  includes the protrusions  41 . However, the display panel  10  may include the protrusions  41 . 
     Second Modification 
       FIGS. 9A and 9B  are schematic cross-sectional views illustrating a second modification. In  FIGS. 9A and 9B , components identical to those in  FIG. 2  are assigned the same reference numerals as those in  FIG. 2 . 
     In the second modification, as illustrated in  FIG. 9A , a plate spring is used as the probe pin  42 . The lower end of the probe pin  42  is connected to the connection terminal  22 , and the upper end thereof protrudes upward a little from the side wall  23  of the housing  20 . 
     As illustrated in  FIG. 9B , when the display panel  10  and the housing  20  are connected with the adhesive  25 , the pad  12  of the display panel  10  presses the probe pin  42  such that the probe pin  42  elastically curves or bends. Thus, the front end of the probe pin  42  and the pad  12  are in contact with each other under a substantially constant pressure. 
     Then, when the adhesive  25  is cured, the adhesive  25  in the hole  24  fixes the shape of the probe pin  42 , and thus the elasticity of the probe pin  42  is lost. 
     In the second modification, the advantages identical to those in the first embodiment are obtained. 
     Second Embodiment 
       FIG. 10  is a plan view illustrating a housing  50  of an electrical device of a second embodiment.  FIG. 11  is a cross-sectional view taken along a line XI-XI in  FIG. 10 . In the second embodiment, the electrical device is a mobile terminal such as a smartphone as in the first embodiment. Components identical to those in the first embodiment are not described. 
     The housing  50  has a U-shaped cross section having a space in which a circuit board (not illustrated), for example, is disposed. Probe pins  51  and protrusions  54 , which regulate the thickness of the adhesive layer, are disposed at predetermined positions on a side wall  53  of the housing  50 . 
     The probe pin  51  of this embodiment is a bar and does not have stretchability, although the probe pin  21  in the first embodiment has stretchability (elasticity). In addition, although the housing  20  in the first embodiment has the space (holes  24 ) to be filled with the adhesive around the probe pin  21 , the housing  50  in this embodiment does not have such a space. 
     Only a front end portion of the probe pin  51  protrudes upward from the side wall  53 , and the remaining portion is in the side wall  53 . The front end portion of the probe pin  51  protrudes by an amount substantially identical to or more than the value obtained by subtracting the thickness of the pad  12  from the height of the protrusion  54 . 
     As illustrated in  FIG. 11 , the probe pin  51  has a pointed front end. The lower end of the probe pin  51  is connected to the connection terminal  22 . 
     The probe pin  51  and the connection terminal  22  may be integrally formed. As in the first embodiment, the probe pin  51  and the connection terminal  22  may be electrically and mechanically connected by the insertion of the lower end portion of the probe pin  51  into the hole of the probe pin connecting portion  22   a  of the connection terminal  22 . 
     Hereinafter, a method of producing the electrical device (mobile terminal) of the second embodiment is described with reference to  FIG. 12  and  FIGS. 13A and 13B . 
     As illustrated in a plan view of  FIG. 12 , an adhesive  56  is applied to an upper surface of the side wall  53  of the housing  50 . A cure shrinkable adhesive, which contracts in volume as curing thereof proceeds, is preferably used as the adhesive  56 , although the type of the adhesive  56  is not limited. 
     Then, the display panel  10  is sucked by a suction tool of a vacuum suction transport machine, for example, and disposed above the housing  50  as illustrated in  FIG. 13A . The suction tool is moved down until the display panel  10  comes in contact with the protrusions  54  as illustrated in  FIG. 13B . 
     This enables the front end of the probe pin  51  to stick into the pad  12 , establishing an electrical connection between the probe pin  51  and the pad  12 . 
     Then, the adhesive  56  is cured to maintain the connection between the probe pin  51  and the pad  12 . A force that draws the display panel  10  toward the housing  50  is generated by the cure shrinkable adhesive used as the adhesive  56 . Thus, the probe pin  51  and the pad  12  are reliably connected, further improving the reliability of the electrical connection. The electrical device according to the second embodiment is produced in this way. 
     As described above, in this embodiment, the thickness of the adhesive layer is made uniform by contacting the display panel  10  with the protrusions  54  on the side wall  53  of the housing  50 . This reduces unevenness in the thickness of the adhesive layer, leading to a reliable connection between the probe pin  51  and the pad  12 . 
     In this embodiment, the probe pin  51  has a pointed front end so as to stick into the pad  12 . With this configuration, the electrical connection between the probe pin  51  and the pad  12  is more reliably established. 
     In addition, since the probe pin  51  in this embodiment does not have elasticity, creep deformation does not occur in the adhesive layer even when the electrical device is used for a long period of time. 
     Third Embodiment 
       FIG. 14  is a plan view illustrating a housing  60  of an electrical device according to a third embodiment.  FIG. 15  is a cross-sectional view taken along a line XV-XV in  FIG. 14 . In the third embodiment, the electrical device is a mobile terminal such as a smartphone as in the above-described embodiments. Components identical to those in the first embodiment are not described. 
     The housing  60  has a U-shaped cross section having a space in which a circuit board (not illustrated), for example, is disposed. Probe pins  61  are disposed at predetermined positions on the side wall  63  of the housing  60 . The probe pin  61  of this embodiment is a bar and does not have stretchability as in the second embodiment. In addition, as in the second embodiment, the housing  60  in the third embodiment does not have a space to be filled with the adhesive around the probe pin  61 . 
     Only a front end portion of the probe pin  61  protrudes upward from the side wall  63 , and the remaining portion is in the side wall  63 . The length of the front end portion of the probe pin  61  protruding from the side wall  63  is determined depending on a preferable thickness of the adhesive layer. The probe pin  61  has a pointed front end, and the lower end thereof is connected to the connection terminal  22 . 
     Hereinafter, a method of producing the electrical device (mobile terminal) according to the third embodiment is described with reference to  FIG. 16  to  FIG. 18 . 
     As illustrated in a plan view of  FIG. 16 , an adhesive  66  is applied to an upper surface of the side wall  63  of the housing  60 . A cure shrinkable adhesive, which contracts in volume as curing thereof proceeds, is preferably used as the adhesive  66 . However, if a thermosetting shrinkable adhesive, which is cured by heat, is used, the adhesive needs to be heated at a temperature of 80° C. or more so as to be cured. This may deteriorate characteristics of the display panel  10  and characteristics of a semiconductor, for example, mounted in the circuit board. 
     In view of the above, in the third embodiment, a cure shrinkable adhesive other than the thermosetting shrinkable adhesive, which is referred to as a non-thermosetting shrinkable adhesive hereinafter, is used. Examples of the non-thermosetting shrinkable adhesive include a one-component epoxy adhesive, a two-component epoxy adhesive, a moisture curing silicone adhesive, a reactive urethane adhesive, and a two-component acrylic adhesive. 
     Then, as illustrated in  FIG. 17 , the housing  60  is placed in the housing fixture jig  31 . The housing fixture jig  31  includes the stop blocks  32  having a predetermined height at positions around the housing  60 . 
     Then, the display panel  10  is sucked by the suction tool  33  of the vacuum suction transport machine, for example, and disposed above the housing  60 . The suction tool  33  is moved down until the suction tool  33  comes in contact with the stop block  32  as illustrated in  FIG. 18 . 
     As described above, the distance between the upper surface of the side wall  63  and the display panel  10  is made substantially constant by the contact between the suction tool  33  and the stop blocks  32 . Thus, the adhesive layer has a uniform thickness. In addition, the probe pin  61  has the pointed front end so as to stick into the pad  12 . With this configuration, the electrical connection between the probe pin  61  and the pad  12  is reliably established. 
     Then, the adhesive  66  is cured. The electrical device according to the third embodiment is produced in this way. 
     As described above, in the third embodiment, the cure shrinkable adhesive is used as the adhesive  66 . With this configuration, the display panel  10  comes closer to the housing  60  as the curing of the adhesive  66  proceeds even if the probe pin  61  and the pad  12  are not sufficiently in contact with each other immediately after the connection between the display panel  10  and the housing  60  with the adhesive  66 . Thus, the probe pin  61  and the pad  12  sufficiently come in contact with each other, and the electrical connection between the probe pin  61  and the pad  12  is established. 
     In the third embodiment, the probe pin  61  has a pointed front end so as to stick into the pad  12 . With this configuration, the electrical connection between the probe pin  61  and the pad  12  is more reliably established. 
     In addition, since the probe pin  61  in this embodiment does not have elasticity, creep deformation does not occur in the adhesive layer even when the electrical device is used for a long period of time. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.