Patent Publication Number: US-2007105456-A1

Title: Press-fit fixing terminal, and electronic component having the same terminal

Description:
FIELD OF THE INVENTION  
      The present invention relates to a press-fit fixing terminal to be inserted into a through-hole of a wiring board in order to mount various electronic components to the wiring board, and the press-fit fixing terminal connects the component mechanically and electrically to the wiring board. The present invention also relates to electronic components having the same terminals.  
     BACKGROUND OF THE INVENTION  
      Methods of mounting electronic components onto a wiring board have focused on streamlining the mounting jobs, and also on alleviating the environmental load as a lead-free soldering. Under such a climate, a press-fit fixing terminal is employed to some mounting methods instead of soldering.  
      This conventional press-fit fixing terminal is described with reference to  FIG. 6 - FIG. 8 .  FIG. 6  shows a front view of the conventional terminal, and  FIG. 7  shows a lateral view of the terminal shown in  FIG. 6 .  FIG. 8  shows a schematic sectional view cut along line  8 - 8  of  FIG. 6 , namely, a schematic sectional view illustrating the press-fit fixing terminal mounted to a wiring board. In  FIG. 6 , press-fit fixing terminal  301  is attached to electronic component  302 , and terminal  301  is formed symmetrically with respect to a center axis of an inserting direction to the wiring board.  
      Press-fit fixing terminal  301  has hollow section  303  formed by blanking along the outline thereof Terminal  301  is formed of two lines, and each one of the lines includes extending section  304  linearly extends from the root of electronic component  302 , straddling section  305  which flares gradually from extending section  304  to ridges  306 , and terminal segments  307  which tapers off from ridges  306  to tip of terminal  301 .  
      As shown in  FIG. 7 , the one line formed of straddling section  305  and terminal segment  307  is bent, thereby forming a V-shaped wedge, the other line formed of straddling section  305  and terminal segment  307  is bent in the same way, so that the two lines are spaced out widest at ridges  306 .  
      Press-fit fixing terminal  301  discussed above is press-fitted into through-hole  308  provided to wiring board  309  as shown in  FIG. 8 . The inner diameter of through-hole  308  is slightly smaller than the maximum width between two ridges  306  in order to maintain the mechanical and electrical connections of terminal  301 .  
      Prior art related to the present invention is disclosed in, e.g. Unexamined Japanese Patent Publication No. 2003-257526.  
      As shown in  FIG. 8 , conventional press-fit fixing terminal  301  has two ridges  306  which are brought into contact with through-hole  308  at the insertion, and ridges  306  are the cut-faces or the corners produced by blanking press-fit terminal  301  out of the material metal plate, so that the ground of the material contacts through-hole  308 . In order to get stable electrical contact, terminal  301  undergoes a plating process after the blanking. The plating process incurs an additional cost and sometimes invites deformation.  
     SUMMARY OF THE INVENTION  
      The press-fit fixing terminal of the present invention is mountable to a wiring board by being inserted into a through-hole of the wiring board, the terminal comprises the following elements:  
      a flat plate section made of metal thin plate and double-backed such that its end is placed on a root side and a bent point works as an insertion tip when the terminal is inserted into the through-hole; and  
      two resilient contacting sections sandwiching a double-backed portion of the flat plate section and placed symmetrically with respect to the double-backed portion, and respective ridges of the resilient contacting sections facing outward viewed from the double-backed portion, i.e. each one of the resilient contacting sections forming a V-shape including an obtuse angle.  
      The resilient contacting section of the terminal is formed this way: a center part of the flat plate section is cut out to form a long and narrow shape, and a first end of the long and narrow shape remains solid with the flat plate section, and a second end thereof is left free. In other words, the flat plate section is cut at its center part along the longitudinal direction such that the center part is hold between narrow parts on both sides. The narrow parts are namely borders of the flat plate section in the width direction.  
      Electronic components of the present invention are equipped with press-fit fixing terminals mountable to a wiring board by being inserted into through-holes. The terminals have the structure discussed above.  
      This construction allows the press-fit fixing terminal to be made of thin material in thickness, so that the terminal can be resistant to plastic deformation and stable in contact. On top of that, the surface of original material not have been cut can be used as a contacting face, so that electrical contact becomes stable. The material undergone a plating process can be used, so that an inexpensive press-fit fixing terminal excellent in contact stability is achievable, and an electronic component equipped with this press-fit fixing terminal is obtainable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a front view of a press-fit fixing terminal in accordance with an embodiment of the present invention.  
       FIG. 2  shows a lateral view of the press-fit fixing terminal shown in  FIG. 1 .  
       FIG. 3  shows vertical sectional view illustrating the press-fit fixing terminal, shown in  FIG. 1 , being press-fitted into a through-hole of a wiring board.  
       FIG. 4  shows a horizontal sectional view taken along line  4 - 4  of  FIG. 3 .  
       FIG. 5  shows an external appearance of another press-fit fixing terminal having a different structure.  
       FIG. 6  shows a front view of a conventional press-fit fixing terminal.  
       FIG. 7  shows a lateral view of the press-fit fixing terminal shown in  FIG. 6 .  
       FIG. 8  shows a schematic sectional view taken along line  8 - 8  of  FIG. 6  and illustrating the press-fit fixing terminal, shown in  FIG. 6 , being mounted to a wiring board. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
      An exemplary embodiment of the present invention is demonstrated hereinafter with reference to the accompanying drawings.  FIG. 1  shows a front view of a press-fit fixing terminal in accordance with the embodiment of the present invention.  FIG. 2  shows a lateral view of the press-fit fixing terminal shown in  FIG. 1 .  FIG. 3  shows vertical sectional view illustrating the press-fit fixing terminal, shown in  FIG. 1 , being press-fitted into a through-hole of a wiring board.  FIG. 4  shows a horizontal sectional view taken along line  4 - 4  of  FIG. 3 .  
      In  FIG. 1  and  FIG. 2 , press-fit fixing terminal  11  of the present invention is mountable to a wiring board by being press-fitted into a through-hole of the wiring board, and terminal  11  includes flat plate section  14  and resilient contacting section  17 .  
      Flat plate section  14  is made of metal thin plate and double-backed, so that end  12  is placed near the root, and bent point  20  works as insertion tip  13  when terminal  11  is press-fitted into a through hole. Two resilient contacting sections  17  sandwich double-backed section  30  of flat plate section  14 , and are placed symmetrically with respect to double-backed section  30 . Both ridges  18  face outward viewed from double-backed section  30 , so that each one of the resilient contacting sections  17  forms a V-shape including an obtuse angle.  
      Resilient contacting section  17  is formed this way: a center part of flat plate section  14  is cut out to form a long and narrow shape, and first end  31  of the long and narrow shape remains solid with flat plate section  14  and second end  32  of the long and narrow shape is left free. In other words, flat plate section  14  is cut at its center part along the longitudinal direction such that the hole left after the cut is held between narrow parts  15  on both sides. Narrow parts  15  are namely borders of flat plate section  14  in the width direction.  
      Press-fit fixing terminal  11  in accordance with this embodiment is further detailed hereinafter with reference to  FIG. 1 - FIG. 4 . In  FIGS. 1 and 2 , terminal  11  is integrated into electronic component  2 , and made of resilient metal thin plate including copper alloy having undergone a well electrically conductive plating process. The metal thin plate is double-backed such that end  12  of flat plate section  14  led out from electronic component  2  is placed near the root extending from component  2 . The metal thin plate is thus double-backed, so that double-backed section  30  is formed. The bent point i.e. turn  20  works as insertion tip  13  when the terminal is inserted into a through hole of a wiring board.  
      Press-fit fixing terminal  11  is cut at its center part along the longitudinal direction such that the center part forms a long and narrow shape, narrow parts  15  on both sides of the center part remain solid with flat plate section  14 , and the center section remains solid with (connecting to) flat plate section  14  only at its lower end, i.e. on the side of insertion tip  13 .  
      This long and narrow shape is processed into resilient contacting section  17  forming a V-shape including an obtuse angle this way: the shape is provided to both the faces of double-backed section  30  such that the shape becomes symmetrically on both sides, and both ridges  18  face outward viewed from double-backed section  30 , so that the long and narrow portion forms a V-shape including an obtuse angle.  
      In other words, resilient contacting section  17  is cut out at its center section held between narrow parts  15  on both sides, which are borders of flat plate section  14  in the width direction, and first end  31  of the long and narrow portion remains solid with (connecting to) flat plate section  14 , and second end  32  is left free.  
      Two resilient contacting sections  17  are punched out like “shearing off” free from tailings when they are punched out from flat plate section  14 . The free end on the opposite side of connecting section  16 , namely, second end  32  of resilient contacting section  17  forms wider section  19  having a greater width along the width direction than first end  31 . Wider section  19 , i.e. second end  32  can be bent away from flat plate section  14  in a regular status without any load.  
      Wider section  19 , i.e. second end  32  is rolled to become much wider, so that second end  32  has a greater width than that of slit hole  141  left behind punching out resilient contacting section  17  from flat plate section  14 . Ridges  18  of two resilient contacting sections  17  protrude outward at their centers, so that a roughly spherical shape is formed on respective sides in the sectional view cut along the width direction.  
      Press-fit fixing terminal  11  discussed above is press-fitted into a through hole of a wiring board. This status is described hereinafter with reference to  FIGS. 3 and 4 , in which terminal  11  is press-fitted in through-hole  8  provided to wiring board  9 .  
      Two resilient contacting sections  17  are bent such that the space between two ridges  18  of two V-shaped resilient contacting sections  17  becomes somewhat greater than the diameter of through-hole  8 . This structure allows each one of the free end, i.e. wider section  19  formed on the upper end of contacting section  17 , to resiliently slide upward on the surface of flat plate section  14 , and when the space between two ridges  18  becomes narrow enough due to the slide for two ridges  18  to fit into through-hole  8 , resilient contacting sections  17  are press-fitted into through-hole  8  and urge against the inner wall of through-hole  8 .  
      Since resilient contacting section  17  is bent into a V-shape including an obtuse angle, its free end, i.e. wider section  19 , is brought into contact with slit hole  141  having a narrower width than that of a hole left behind punching out wider section  19  from flat plate section  14 . Wider sections  19  thus will not fall into slit hole  141  in the regular status or when resilient contacting section  17  is press-fitted. Yet, in this embodiment, wider section  19  is rolled to be much wider, so that wider section  19  is positively prevented from falling into slit hole  141 . As a result, the press-fit into through-hole  8  can be done smoothly.  
      The free end, namely, wider section  19 , is bent away from flat plate section  14  in regular status. The cut edge of the free end thus becomes farther away from the surface of flat plate section  14 . The bent point of wider section  19  slides smoothly on the surface of flat plate section  14  with a little contact resistance, so that terminal  11  can be inserted with ease and a stable contacting pressure can be expected.  
      As shown in  FIG. 4 , ridges  18  form roughly spherical surfaces of which center parts moderately protrude outward, so that the contacting portions to the inner wall of through-hole  8  become close to area contact. The previous discussion proves that the cut edge of terminal  11  is not used as the contacting portion, so that terminal  11  provides stable electrical contact.  
      This embodiment proves that the material face prior to the process can be used as contacting face of resilient contacting section  17 , so that the contacting face resiliently contacts through-hole  8 . Therefore, well-conductive material such as silver can be used as plated material, so that inexpensive press-fit fixing terminals are obtainable.  
      Two resilient contacting sections  17  confronting each other allow terminal  11  to secure sufficient contacting pressure although the material is metal thin plate, so that stable mechanical connection is obtainable. On top of that, since plated material can be used, an electrical contacting function can be integrated into the inside (not shown) of electronic component  2 .  
      Resilient contacting section  17  which works as a mechanical connector as well as an electrical connector to through-hole  8  is formed by cutting out (shearing off) the center portion in width direction of flat plate section  14  of terminal  11 , so that terminal  11  needs only a narrow width and scrapped material can be thus minimized.  
      In this embodiment, the free end of resilient contacting section  17 , namely, wider section  19 , is rolled to be wider than the width of slit hole  141 , however, narrow parts  15  of flat plate section  14  can be crushed to form projection  142  for narrowing the width of slit hole  141 . This structure prevents wider section  19  from falling into slit hole  141 , and allows ridges  18  to contact through-hole  8  mechanically and electrically in stable manner. Although this is not illustrated, narrow parts  15  can be pushed inside laterally along the width direction to deform for narrowing the width of slit hole  141 . This preparation also produces an advantage similar to what is discussed previously.  
      Wider section  19  is not always needed, because the width of the resilient contacting section can be flared from the border between the flat plate section and the resilient contacting section toward the free end. This structure can also prevent the resilient contacting section from falling into the slit hole.  
      The press-fit fixing terminal of the present invention is useful product because it can be used in variable resistors, encoders, switches, and antennas.  
      According to the present invention, an original face of flat plate of the material can be used as a contacting face, so that the material having undergone plating process can be used, which allows providing inexpensive press-fit fixing terminals having stable contact with through-holes.  
      In the case of using the resilient contacting section punched out (sheared off) from the flat plate section, a press-fit fixing terminal having a narrow width is obtainable, so that scrapped material can be minimized and a through-hole having a smaller diameter can receive the terminal. As a result, electronic devices using this terminal can be downsized.  
      The resilient contacting section, forming a V-shape with an obtuse angle inclusive and having a second end wider than a first end, can prevent the free end (second end) from falling into the slit hole of the flat plate section, so that stable contacting pressure is obtainable.  
      The resilient contacting section, of which free end (second end) is bent away from the flat plate section, allows the free end to confront the flat plate section when the terminal is inserted into a through-hole, so that contact resistance is reduced and the resilient contacting section tends to be resiliently deformed. As a result, the terminal is easy to press-fitted, and a stable contact pressure can be expected.  
      The resilient contacting section having the second end (free end) wider than the width of the slit hole formed by punching out the resilient contacting section from the flat plate section prevents the free end from falling into the slit hole, so that stable contact pressure is obtainable.  
      The resilient contacting section having a ridge, of which center protrudes outward and forms roughly a spherical surface in a sectional view cut along the width direction, allows contacting the through-hole with generally a spherical face, so that stable contact is obtainable.  
      Press-fit fixing terminals of the present invention can employ plated material, so that stable contact and an inexpensive cost can be advantageously expected. The terminals thus can be employed as terminals of electronic components which are to be mounted to wiring boards by press-fitting the terminals into the through-holes.