Patent Publication Number: US-7217153-B2

Title: Electronic circuit apparatus and production method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-130722 filed on Apr. 28, 2005. 
     FIELD OF THE INVENTION 
     The present invention relates to an electronic circuit apparatus and a production method thereof, for example, in a vehicular electronic key system. 
     BACKGROUND OF THE INVENTION 
     A conventional electronic circuit apparatus such as a communicating apparatus in a vehicular electronic key system has a casing to contain a battery and a circuit board on which electronic components are mounted (Patent Document 1). 
     Patent Document 1: JP-2004-52471 A 
     A main body of the casing is formed of a flat card-shaped box having a bottom to include a circuit-board containing portion and battery containing portion, which contain the circuit board and battery, respectively. The circuit board and battery are hermetically enclosed in the main body of the casing using a covering sheet, i.e., a lid. Each terminal, an end portion of which is soldered on the circuit board, is extended into the battery container to be pressed to contact the battery; therefore, each terminal is previously deformed to bend towards a battery position where the battery is to be inserted. 
     In the conventional electronic circuit apparatus, both the front and rear surfaces of the circuit board are enclosed within the casing, increasing the thickness of the casing or the apparatus to possibly worsening portability. 
     To decrease the thickness of the apparatus, the following method can be adopted: one surface of a circuit board, on which an electronic component is mounted, is sealed with resin to form a casing; the other surface of the circuit board having no electronic component mounted is used as an outer surface of the casing. Here, when the casing is molded with resin, a mold for forming a battery containing space is required. 
     However, since the above terminal needs to be previously deformed to bent towards the battery position, the mold for forming the battery containing space cannot be a slide type mold, which will be prevented from moving by the bent terminal. Consequently, the mold becomes complicated. 
     Each terminal needs to be soldered on the circuit board at its end portion and to contact the battery at the other end portion; therefore, the terminal is considerably extended from the circuit board where the end portion is soldered. This makes it difficult for the circuit board to securely support the terminal. Consequently, the terminal is soldered on the circuit board by hand, instead of being automatically mounted. The number of production processes for producing the electronic circuit apparatus increases, posing a problem. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electronic circuit apparatus and a production method thereof to help solve the above problem. Namely, a structure of the apparatus allows a production method to use a slide type mold in forming a casing by sealing a circuit board with resin, decreasing the number of production processes and the thickness of the apparatus. 
     To achieve the above object, an electronic circuit apparatus, to which a battery of a button type is to be inserted as a power source, is provided with the following: An electronic component is included; a positive terminal is included for contacting a positive electrode of the battery; a negative terminal is included for contacting a negative electrode of the battery; a circuit board is included for including a recess line portion, wherein the electronic component and both end portions of each of the positive terminal and the negative terminals are attached to a first surface of the circuit board; and a casing is included for including the circuit board by sealing, using resin, the circuit board in addition to the electronic component and the both end portions of each of the positive terminal and the negative terminal. A second surface opposite to the first surface of the circuit board is included as a part of an outer surface of the casing. The casing further includes a battery containing space, which is surrounded by the recess line portion of the circuit board, for detachably containing the battery. A part of each of the positive terminal and the negative terminal appears within the battery containing space. When the battery is not inserted, a distance between the positive terminal and the negative terminal in a direction of a thickness of the battery that is to be inserted is shorter than the thickness of the battery. 
     Under the above structure, in a molding process where the casing is molded with resin to include the circuit board, a mold for forming the battery containing space can be inserted to a gap between both the terminals from an opening portion facing the recess line portion of the circuit board. Namely, a slide type mold can be used in the production method of the electronic circuit apparatus, decreasing the number of production processes. 
     In this case, a pressing process can be applied subsequently after the molding process is completed. Namely, the pressing process can be applied after the molding process to enable the terminals to contact the battery with pressure, i.e., to cause a distance between both the terminals in a direction of a thickness of the battery to be shorter than the thickness of the battery. 
     Furthermore, under the above structure, the second surface of the circuit board where no component is mounted can be used as a part of the outer surface of the casing. This can eliminate the necessity of an additional separate outer surface wall of the casing, decreasing the thickness of the electronic circuit apparatus. 
     In contrast, a production method for producing the electronic circuit apparatus described above is provided with the following processes: filling the cavity with a liquid of the resin; solidifying the liquid of the resin within the cavity; releasing off the mold the casing, which has been formed after the solidifying the liquid of the resin; and applying a pressing process to the positive terminal and the negative terminal within the battery containing space to cause the distance between the positive terminal and the negative terminal in the direction of the thickness of the battery to be shorter than the thickness of the battery. 
     Under the above production method, when before the casing is molded with resin to include the circuit board, the terminals still have flat shapes parallel to each other without having been deformed. Therefore, a slide type mold to be inserted into a gap between the terminals can be used for forming the battery containing space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a plan view of an electronic key communicating apparatus according to an example embodiment of the present invention; 
         FIG. 2  is a sectional view taken from a line II to II in  FIG. 1 ; 
         FIG. 3  is a sectional view taken from a line III to III in  FIG. 2 ; 
         FIG. 4  is a sectional view of a metal mold used for producing the example embodiment shown in  FIG. 1 ; and 
         FIG. 5  is a sectional view taken from a line V to V in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A communicating apparatus (transmitting/receiving apparatus) of a vehicular electronic key system as an electronic circuit apparatus according to an example embodiment will be explained below. As shown in  FIGS. 1 ,  2 , an electronic key communicating apparatus  1  is constructed mainly of a casing  4 . The casing  4  includes a circuit board  2 , a circuit component  3 , and positive and negative terminals  5 ,  6 . The circuit component  3  is mounted on a first surface (e.g., front surface or mounting surface) of the circuit board  2 ; two end portions of each of the positive and negative terminals  5 ,  6  are mounted on the first surface of the circuit board  2 . Then, the casing  4  is formed by sealing with resin the circuit board  2  in addition to the mounted circuit component  3  and the end portions of each of the terminals  5 ,  6 . Here, the casing  4  includes a battery containing space B for containing a battery  7  of a button type as a power source of the apparatus  1 . This battery is to be inserted into the battery containing space B; then a battery cover (not shown) is to be attached to cover the battery  7 . 
     The circuit board  2  is, e.g., a printed circuit board, in which an electrically conductive material such as copper foil is formed on, e.g., a glass epoxy board, ceramic board, etc. 
     The circuit component  3  mounted on the circuit board  2  includes various devices or units such as a resistor, capacitor, diode, transistor, IC, or antenna. As explained above, these devices or units are only mounted on the first surface  21  of the circuit board  2 . A second surface  22  (e.g., rear surface) opposite to the first surface  21  is a flat surface without any mounted devices. 
     As shown in the plan view in  FIG. 1 , the circuit board  2  includes a recess line portion  23  for forming an area to contain the battery  7 . The positive and negative terminals  5 ,  6  are arranged to appear or be viewed (vertically in  FIG. 1 ) to cross (or bridge) the battery containing space B and further the recess line portion  23 ; both ends of each of the terminals  5 ,  6  are soldered on wiring patterns (not shown) formed on the mounting surface  21  in vicinity of the concave line portion  23 . Thus, the positive and negative terminals  5 ,  6  are to contact a positive and negative electrodes of the battery  7  within the battery containing space B, respectively. 
     In this mounting structure of each terminal  5 ,  6 , both ends of each terminal  5 ,  6  can be stably placed in given positions; therefore, the both ends of each terminal  5 ,  6  can be soldered simultaneously when the circuit component  3  is mounted by automatic soldering in the mounting process. 
     Each terminal  5 ,  6  is formed of flexible conductive material such as beryllium copper plate overlaid with gold. The battery  7  (shown as chain double-dashed line in  FIG. 1 ) can be inserted into a gap between the terminals  5 ,  6  to contact the terminals  5 ,  6  at both sides of the battery  7 , respectively. The gap or distance between the terminals in a direction of a thickness of the battery  7  is defined to be a distance d 1  a little larger than a thickness t of the battery  7  near each end potion. In contrast, the terminals  5 ,  6  have central bent portions to come close to each other around a central portion of the battery containing space B to have a distance d 2  smaller than the thickness t of the battery  7 . 
     Thus, when the batter  7  is inserted into the gap between the terminals  5 ,  6 , the central bent portions of the terminals  5 ,  6  are elastically deformed to spread upward and downward (in  FIG. 3 ), respectively; this elastic force allows the terminals  5 ,  6  to be pressed to contact the positive and negative electrodes of the battery, respectively. Thus, the battery  7  can provide the circuit component  3  on the circuit board with an electric power. 
     The casing  4  is formed by sealing the mounting surface  21  of the circuit board  2  along with the circuit component  3 , and the end portions of the terminals  5 ,  6  and their vicinity, as shown in  FIG. 2 . In other words, the circuit component  3  and terminals  5 ,  6  are mounted on the mounting surface (first surface) of the circuit board  2  at a mounting process; the circuit board  2  after the mounting process is placed in a given position within a cavity of a metal mold while the second surface  22  of the circuit board  2  is closely attached to a wall of the metal mold; then, an insert molding process is applied to the placed circuit board  2  using resin material to form or the casing  4 , to which the circuit board  2  is inserted. This causes the second surface  22  of the circuit board  2  to be exposed on a surface of the casing  4 . In detail, the second surface  22  of the circuit board  2  and an adjacent surface of the resin portion of the casing  4  are smoothly joined to each other to form a single surface. In other word, the second surface  22  of the circuit board  2  is included as a part of an outer surface of the casing  4 . 
     After the casing  4  is formed, the mounting surface  21  of the circuit board  2 , the mounted circuit component  3 , and the mounted end portions of the terminals  5 ,  6  are entirely enclosed within the resin of the casing  4 . Electric circuitry within the casing  4 , except portions of the terminals  5 ,  6  within the battery containing space B, is completely sealed, enabling the electronic key communicating apparatus  1  to be waterproof. 
     The casing  4  is designed to have a card type shape that is easily carried or held by a user. For instance, this card type shape can have a planar size (i.e., height and width in the plan view in  FIG. 1 ) similar to that of a credit card (i.e., height and width of ID- 1  type specified in an ISO/IEC 7816-1 standard). 
     The resin material of the casing  4  can be thermoset resin such as epoxy resin for this example embodiment. When the thermoset resin is used for molding, a temperature of the metal mold is necessary to be maintained to be suitable for thermosetting temperature of the resin. In this example embodiment, the circuit component  3  and terminals  5 ,  6  are mounted on the circuit board  2  by soldering, so that the temperature of the metal mold is sufficiently lower than a melting point (melting temperature) of the soldering material used. For instance, in this example embodiment, the melting point of the soldering material is 240 degrees Celsius and the thermosetting reaction temperature of the resin is 170 degrees Celsius. 
     The epoxy resin of the thermoset resin forming the casing  4  excels in a heat-resistance property and mechanical strength, which can enhance reliability of the electronic key communicating apparatus  1  that is required to be always held by a driver. 
     The resin material can be replaced with any other thermoset resin material without limited to the epoxy resin as long as a condition that a melting temperature of the soldering material is less than a thermosetting reaction temperature of the used resin material. 
     Next, a production method for producing the above electronic key communicating apparatus  1  will be explained with reference to  FIGS. 4 ,  5 , in particular, regarding a molding process for molding the casing  4  using resin. 
     At first, a structure of a metal mold  100  will be explained. The metal mold  100  includes an upper metal mold  101 , a lower metal mold  102 , and a slide core  103  of a slide type mold, as shown in  FIG. 4 . When the metal mold  100  is tightened up, the slide core  103  is caused to move from left to right in  FIG. 4  by an incline pin or the like (not shown) and then stop at a position shown in  FIG. 4 . The slide core  103  defines a cavity  104  jointly with the upper and lower metal molds  101 ,  102 . The cavity  104  is to be filled with the epoxy resin to constitute a body of the casing  4 . 
     The upper metal mold  101  includes a sprue (hole)  105  as a passage for feeding resin via a gate  106  into the cavity  104 . The lower metal mold  102  includes a knockout pin  107  and a vacuum hole  108 . The knockout pin  107  is arranged to contact the second surface  22  of the circuit board  2  after the metal mold  100  is tightened up; the knockout pin  107  is used for releasing off the metal mold  100  the casing  4  as a molded object after the molding. The vacuum hole  108  is linked through a pipe (not shown) with an external vacuum pump to control a pressure of the vacuum hole  108  as need, thus sucking the circuit board  2  with negative pressure to support the circuit board  2  within the cavity  104 . 
     Next, placing the circuit board  2  will be explained below, provided that the circuit component  3  and the terminals  5 ,  6  have been already mounted on the circuit board  2 . 
     Before the metal mold  100  is tightened up, i.e., when the upper and lower metal molds  101 ,  102  are staying away from each other (vertically in  FIG. 4 ) and the slide core  103  is staying leftward in  FIG. 4  while contacting the lower metal mold  102 , the circuit board  2  as an inserted object is placed within the cavity  104 . 
     For instance, the second surface  22  of the circuit board  2  is arranged at a given position within the cavity  104  to closely contact a surface of the lower metal mold  102 , while the negative terminal  6  is engaged in a groove  102   a  provided on the lower metal mold  102 , as shown in  FIG. 5 . At the same time, a positioning pin  102   b  provided on the lower metal mold  102  for positioning is inserted to the through-hole  61  of the negative terminal  6 , thus allowing the circuit board  2  to be arranged in the given position within the cavity  104 . 
     The depth (vertical dimension in  FIG. 5 ) of the groove  102   a  is designed to accord with a plate thickness of the negative terminal  6 . After the circuit board  2  is placed in the cavity  104 , both the lower metal mold  102  and the negative terminal  6  (engaged in the groove  102   a ) form a flat surface, as shown in  FIGS. 4 ,  5 . 
     The height of the positioning pin  102   b  of the lower metal mold  102  is slightly smaller than the plate thickness of the negative terminal  6 . After the circuit board  2  is placed in the cavity  104 , the tip of the positioning pin  102   b  does not protrude towards the cavity  104  from the surface of the negative terminal  6 , allowing the slide core  103  to smoothly move. 
     In this example embodiment, two pairs of the through-hole  61  and positioning pin  102   b  are provided for enhancing positioning accuracy; however, the number of pairs can be any number as needed without limited to two. 
     Thus-arranged metal mold  100  is then tightened up; namely, the lower metal mold  102  and slide core  103  are moved upward in  FIG. 4  to contact the upper metal mold  101  while the positive terminal  5  is engaged in a groove  101   a  on the upper metal  101 . 
     The depth (vertical dimension in  FIG. 5 ) of the groove  101   a  is designed to accord with a plate thickness of the positive terminal  5 . After the metal mold  100  is tightened up, both the upper metal mold  101  and the positive terminal  5  engaged in the groove  101   a  form a flat surface, as shown in  FIGS. 4 ,  5 . This also allows the upper metal mold  101 , the slide core  103 , and the lower metal mold  102  to closely contact one another. 
     The slide core  103  moves through a gap between the terminals  5 ,  6  from the left side to the right side in  FIG. 4  and then stops at the position shown in  FIG. 4  while contacting the terminals  5 ,  6 . Subsequently, the pressure within the vacuum hole  108  is decreased to suck the circuit board  2 , allowing the circuit board  2  to closely contact the surface of the lower metal mold  102 . Thus, a supporting process for supporting the circuit board  2  within the cavity  104  is completed as shown in  FIG. 4 . 
     Then, a temperature of the metal mold  100  is increased to a temperature suitable for thermosetting reaction of the epoxy resin, i.e., 170 degrees Celsius in this example embodiment. 
     After the temperature of the metal mold  100  becomes stable at 170 degrees Celsius, a nozzle of an injection unit (not shown) is joined at an upward end of the sprue  105  of the upper metal mold  101 ; then, liquefied epoxy resin is injected via the gate  106  to fill the cavity  104 . When the resin pervades the cavity  104  and then sprue  105  is filled with the resin, injecting the resin is stopped to end the filling process. 
     The resin filling the cavity  104  is subjected to a thermosetting reaction within the metal mold  100 , resulting in solidification of the resin to end the solidifying process. 
     Subsequently, the lower metal mold  102  and slide core  103  are caused to move downward in  FIG. 4  to depart from the upper metal mold  101  while the slide core  103  moves leftward to be separated at the same time. 
     Applying the negative pressure to the vacuum hole  108  is then stopped to return the pressure of the vacuum hole  108  to atmosphere pressure; then, the knockout pin  107  is caused to move upward in  FIG. 4  to release the casing  4  off the lower metal mold  102 , ending the releasing process and all the molding process. 
     Next, a pressing process is applied to the terminals  5 ,  6 ; namely, the pressing is applied to, of each terminal  5 ,  6 , a portion exposed to the battery containing space B to obtain a shape shown in  FIG. 3  where a minimum distance d 2  (in a direction of a thickness of the battery  7 ) of the gap between the terminals  5 ,  6  is formed to be smaller than a thickness t of the battery  7 . To applying the pressing process to each terminal  5 ,  6 , each terminal  5 ,  6  required to be fixedly supported at a portion near the casing  4  for preventing damage during the pressing process. For instance, force is applied around a central portion of each terminal  5 ,  6  and transmitted towards the casing  4  and circuit board  2  to cause a possible damage of the casing  4  or possible peeling of the soldering between each terminal  5 ,  6  and the circuit board  2 . The pressing process ends to terminate the production process of producing the electronic key communicating apparatus  1  of this example embodiment. 
     As explained above, the electronic key communicating apparatus  1  of this example embodiment is formed as below. The casing  4  is formed with an insert molding process, i.e., by sealing using resin the circuit board  2  along with the mounted circuit component  3  and end portions of the positive and negative terminals  5 ,  6  mounted on the board  2 . Here, the circuit component  3  and end portions of the terminals  5 ,  6  are mounted on one (first) surface of the circuit board  2 ; the second surface  22  of the circuit board  2  is included as a part of an outer surface of the casing  4 . Furthermore, the recess line portion  23  is provided in the circuit board  2  for surrounding the battery  7 ; the terminals  5 ,  6  pass through an area or space formed by the recess line portion  23  and are attached or mounted on the circuit board  2  at both end portions of the terminals  5 , 6 . 
     This structure of the apparatus  1  can remove one of surface walls of a casing included in a conventional apparatus, making the thickness of the apparatus  1  smaller than that of the conventional apparatus. 
     Furthermore, in the insert molding process where the circuit board  2  is inserted within the casing  4 , a mold for forming the battery containing space B can be inserted between both the terminals  5 ,  6  via an opening of the recess line portion  23  of the circuit board  2 , allowing the structure of the metal mold  100  to be simple and enhancing the productivity. Therefore, the slide core (slide type mold)  103  can be adopted to decrease the number of production processes and, in addition, the thickness of the apparatus  1 . 
     Furthermore, the terminals  5 ,  6  are exposed within the battery containing space B included in the casing  4 , so that the pressing process can be easily applied to the terminals  5 ,  6  after the molding process. This allows the terminals  5 ,  6  to have shapes to contact, with pressure, both the electrodes of the battery  7 , respectively. 
     Furthermore, the through-hole  61  is provided in, of the negative terminal  6 , the portion present within the battery containing space B; in the molding process, the through-hole  61  is engaged with the positioning pin  102   b  provided in the lower metal mold  102  so as to position the circuit board  2  within the cavity  104 . 
     The positioning of a circuit board within a cavity of a metal mold can be achieved by, e.g., engaging a positioning pin provided in a lower metal mold with a hole provided in the circuit board; however, this hole visible after the production process deteriorates appearance of the casing, requiring an additional process to fill the hole with resin or the like and then shaping a surface into a flat one. This poses a problem such as increasing a cost. 
     In contrast, positioning using the through-hole  61  provided in the negative terminal  6  allows the through-hole  61  to eventually become invisible as appearance since the through-hole  61  is hided by the battery cover (not shown) attached to the casing  4  after the battery is inserted. Thus, the above positioning in the example embodiment allows the circuit board  2  to be accurately arranged within the cavity  104  of the metal mold  100  without increasing the cost due to the additional process, which enhances the productivity of the apparatus  1 . 
     Furthermore, in the above production process of the casing  4 , the vacuum hole  108  provided in the lower metal mold  102  is sucked with negative pressure to support the circuit board  2  within the cavity  104 ; however, this vacuum hole or sucking process can be eliminated. In this case, the circuit board  2  is accurately placed at the given position by engaging the positioning pin  102   b  with the through-hole  61  in the negative terminal  6 . 
     Furthermore, the example embodiment as an electronic circuit apparatus is adapted to the vehicular electronic key communicating apparatus  1 ; however, it can be adapted to any one without limited to the above. For instance, it can be adapted to other types of electronic circuit apparatuses. Yet furthermore, without limited to an application for vehicles, it can be adapted to an electronic circuit apparatus for a consumer use. 
     It will be obvious to those skilled in the art that various changes may be made in the above-described example embodiments of the present invention. However, the scope of the present invention should be determined by the following claims.