Patent Publication Number: US-2022238283-A1

Title: Capacitor and method for producing same, and capacitor-mounting method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the U.S. national phase of International Application No. PCT/JP2020/018473 filed May 1, 2020 which designated the U.S. and claims priority to JP Patent Application No. 2019-106568 filed Jun. 6, 2019 and JP Patent Application No. 2020-019994 filed Feb. 7, 2020, the entire contents of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a capacitor mounted on a wiring board such as a circuit board, for example, a chip-type electrolytic capacitor in which as pedestal is disposed on the sealing member side for sealing the metal outer case of the capacitor, and a manufacturing method thereof the mounting method of the capacitor. 
     Description of the Related Art 
     For example, there is a chip-type electrolytic capacitor as one of the capacitors constituting the power storage device constituting the control circuit in the power converter. In the chip-type electrolytic capacitor, an anode lead wire and a cathode lead wire is respectively connected to the anode foil and the cathode foil and wound by interposing a separator therebetween housed in the outer case made of a cylindrical metal with the driving electrolyte, the open end of the outer case sealed by a sealing member to the outer case in which it is configured by caulking, mounting an insulating pedestal having a through hole, penetrating a pair of lead terminals derived from the capacitor body in the through hole, and by bending along the lower surface of the pedestal, this configuration is compatible with surface mounting. Further there is also a method of soldering by through the solder reflow process to the through hole provided on the circuit board, without bending a pair of lead terminals derived from the through hole of the insulating plate. 
     The following literature is known as a referential document disclosing a chip-type electrolytic capacitor having such an insulating pedestal.
     [Patent Document 1] JP 2001-102237   

     Chip type electrolytic capacitor holds the internal driving electrolyte as before described and when exposed to a high temperature state by the solder reflow process, solvent of the driving electrolyte is vaporized to increase the internal pressure of the electrolytic capacitor. Then, with the increase in internal pressure, by the sealing member is expanded to the insulating plate side, when the insulating plate and the capacitor is connected to the circuit board without soldering well become separated, lowering the connection strength causes, there is a problem such as the electrolytic capacitor falls off from the substrate during actual use. 
     In view of the foregoing problems an object of the present invention is to provide a capacitor capable of greatly reducing the occurrence of mounting failure on the circuit board in the solder reflow process. 
     SUMMARY OF THE INVENTION 
     Capacitor of the present invention, characterized in that the open end of the bottomed cylindrical outer case housing the capacitor element is sealed with a sealing member, the lead terminal derived from the capacitor element is formed through the sealing member a capacitor body, the lead terminal is housed in a pedestal having a bottom portion and a side wall formed so as to surround the outer periphery of the capacitor body with a through hole penetrating, a capacitor having a convex portion protruding toward the capacitor body from the inner surface of the side wall, the convex portion is disposed on the caulking portion formed by caulking the side surface of the outer case and a gap portion is provided between the caulking portion and the convex portion. 
     The present invention provides a method of manufacturing a capacitor in which the open end of the bottomed cylindrical outer case housing the capacitor element is sealed with a sealing member, the lead terminal derived from the capacitor element is formed through the sealing member a capacitor body, the lead terminal is housed in a pedestal having a bottom portion and a side wall formed so as to surround the outer periphery of the capacitor body having a through hole penetrating, a method of manufacturing a capacitor having a convex portion protruding toward the capacitor body from the inner surface of the side wall, the caulking portion formed by caulking the side surface of the outer case, characterized in that the step of arranging the convex portion by providing a gap portion between the caulking portion and the convex portion. 
     Capacitor of the present invention, a step of inserting the lead terminal of the capacitor into the through hole filled with solder paste providing in the circuit board and a step of solder reflow connection between the lead terminal and the circuit board. 
     According to the present invention, any of the following effects may be obtained. 
     (1) Capacitor body may be avoided from separating from the pedestal even if the sealing member is expanded for exposure to a high temperature state by solder reflow process. 
     (2) It is possible to suppress the occurrence of mounting failure of the capacitor in the solder reflow process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram showing an example of a capacitor according to the present invention. 
         FIG. 1B  is a diagram showing an example of a capacitor according to the present invention. 
         FIG. 2  is a diagram showing an example of a pedestal of a capacitor according to the present invention. 
         FIG. 3  is a diagram showing an example of a pedestal of a capacitor according to the present invention. 
         FIG. 4  is a diagram showing an example of a capacitor according to the present invention. 
         FIG. 5A  is a diagram showing a cross section of a capacitor before the solder reflow process of the capacitor according to the present invention. 
         FIG. 5B  is a diagram showing a cross section of a capacitor before the solder reflow process of the capacitor according to the present invention. 
         FIG. 6A  is a diagram showing a cross section of the capacitor during the solder reflow process of the capacitor according to the present invention. 
         FIG. 6B  is a diagram showing a cross section of the capacitor during the solder reflow process of the capacitor according to the present invention. 
         FIG. 7  is a diagram showing a cross section of the capacitor after the solder reflow process of the capacitor according to the present invention. 
         FIG. 8  is a diagram showing an example of a pedestal of a capacitor according to another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Capacitor of the embodiment provides an external shape as shown in  FIG. 1A ,  FIG. 1B  and essentially composed of the capacitor body  4  having a lead terminal  22  which is derived through the sealing member  26  for sealing the opening side of the aluminum outer casing for housing the capacitor elements therein and a pedestal  6  disposed on the sealing member  26  side of the capacitor body  4  from which the lead terminal  22  is derived. 
     Capacitor body  4  used in the embodiment, as shown in  FIG. 1A  and  FIG. 1B  is configured like that a bottomed cylindrical aluminum outer case houses the capacitor element therein and after inserting the sealing member  26  to an open end of the case the outer peripheral side surface and the open end in the outer case caulking portion  12  is formed by caulking, thereby the capacitor body  4  is sealed. Lead terminal  22  derived from the capacitor element so as to penetrate the sealing member  26  is provided, the end portion of the lead terminal  22  which is derived to the outside of the sealing member  26  penetrates the through hole formed in the pedestal  6  (not shown). The sealing member  26  is formed of a hardness which exhibits flexibility and elasticity, and for example, ethylene propylene rubber, butyl rubber, silicones rubber, or the like is used. 
     The capacitor element, by interposing a separator between the anode foil and the cathode foil made of a valve metal such as aluminum, is formed by winding and impregnated with electrolytic solution a conductive polymer such as Pothiethylenedioxythiophene as an electrolyte or the conductive polymer may be used as hybrid type for impregnating the electrolyte into the impregnated capacitor element. 
     The pedestal  6  disposed on the sealing member  26  side of the capacitor body  4  is made of a resin having an electrically insulating property of a predetermined thickness, as shown in  FIGS. 1A and 1B , and a side wall  8  extending upward is formed so as to surround the bottom surface portion  20  on which the sealing member  26  side of the capacitor body  4  abuts and the outer peripheral side surface of the capacitor body  4 . The pedestal  6  is a top view substantially rectangular, and notches  10  are formed in a pair of corners adjacent thereto. Thus, it is preferable to form the upper view shape of the pedestal  6  in a substantially rectangular shape, since it is possible to reduce the mounting area of the resulting capacitor to the substrate, the present invention is not limited thereto, top view may be polygonal or circular shape so that the shape of these pedestals  6  may be appropriately selected. Further, a notch  10  is preferably provided in the side wall  8  of the pedestal  6  to conveniently determine the polarity of the lead terminal  22  when the capacitor is mounted to the substrate although free of notches  10  is possible. 
     In the embodiment, the dividing portion  14  for dividing the side wall  8  of the pedestal  6  is formed, to provide a gap between the inner surface and the outer peripheral side surface of the capacitor body  4  of the side wall  8 , so that the outside air from the dividing portion  14  flows efficiently with preferable suppress of the reduction of the heat dissipation effect by the side wall  8  as much as possible, but the present invention is not limited thereto may particularly be formed. 
     A shown in  FIG. 2  and  FIG. 3 , the inner surface of the side wall  8  of the pedestal  6  surrounds the casing side surface of the capacitor and protrudes to the capacitor body  4  side by providing a convex portion  16  disposed in the caulking portion  12  of the outer case is provided. 
     As shown in  FIG. 1B , when the capacitor body  4  is mounted to the pedestal  6  providing the convex portion  16 , the convex portion  16  is disposed in the caulking portion  12  formed by caulking in the side surface of the outer case and a  16  gap portion  34  is provided between the caulking portion  12  and the convex portion. The gap portion  34  is provided on at least one of the upper and lower caulking portions  12  of the convex portion  16  in the axial direction of the capacitor body  4  as shown in  FIG. 5B  and the gap portion  34   b  is provided on the lower side of the gap portion  34   a  and the convex portion  16  on the upper side of the convex portion  16  between the caulking portion  12  and the convex portion  16  in the capacitor  2  of the embodiment and the capacitor body  4  is housed in the axially movable pedestal  6  of the capacitor body  4  through the gap portion  34 . 
     Further, it is preferable to provide the gap portion  34   c  between the caulking portion  12  in the diameter direction of the end portion  21  and the capacitor body  4  of the convex portion  16 . Smooth movement in the axial direction of the capacitor body  4  may be attained by a non-contact of an end portion  21  of the convex portion  16  with the caulking portion  12 . 
     In the embodiment capacitor  2  the caulking portion  12  of the capacitor body  4  is movable in the vertical direction on the base of the convex portion  16  of the pedestal  6 , so that the capacitor body  4  and the pedestal  6  are integrated for movable up and down through the gap  34 . Thus, even if the capacitor body  4  with deformation of the sealing member  26  by the solder reflow process is pushed up from the pedestal  6 , the movement may be allowable in the gap  34  and the convex portion  16  and the caulking portion may be suppressed from coming off with improvement in the reliability of the connection between the lead terminal  22  and the circuit board  28 . 
     Further, as shown in  FIG. 5A  and  FIG. 5B , when the sealing member  26  side of the capacitor body  4  is contacted to the bottom surface portion  20  of the pedestal  6  for housing in the pedestal  6  a gap portion  34   a  it is preferably provided on the convex portion  16  in the axial direction of the capacitor  2 . By providing the gap portion  34   a , the convex portion  16  becomes non-contact with the caulking portion  12  without any application of excessive stress to the caulking portion  12  for sealing the capacitor body  4 . In addition, the gap portion  34   a  allows a fine difference in dimensions of the caulking portion  12  of the individual capacitors with enhancement reliably of accommodation of the capacitor body  4  to the bottom portion  20  of the pedestal  6 . 
     Further, the convex portion  16  is formed in a tapered portion  15  toward the bottom from the opening side of the pedestal  6 . Thus it is possible to assist the storage of the capacitor body  4  in the pedestal  6 . Furthermore, a locking portion  19  for suppressing undesired escape of the capacitor body  4  housed is formed on the convex portion  16 . 
     Thus, the capacitor body  4  with deformation of the sealing member  26  by the solder flow may be suppressed from movement in the direction in which the caulking portion  12  comes out contact with the locking portion even when spaced from the pedestal  6 . 
     The convex portion  16  may be formed at least one location on the inner surface of the side wall  8 . In the embodiment, the convex portions  16  as shown in  FIG. 3  are formed at two positions perpendicular to the upper surface when observed with respect to the central axis of the capacitor body  4 . When a plurality of convex portions  16  are arranged, it is preferable not to form at a position opposed to each other via the central axis of the capacitor body  4 . If the pedestal  6  disposed so as to face the convex portions  16  through the central axis of the capacitor body  4 , the convex portions  16  are narrowed with respect to the diameter of the capacitor housing portion cracking or damage is likely developed in the pedestal  6  when attempting to accommodate the capacitor body  4  to the pedestal  6 . 
     Further, as shown in  FIG. 3 , provision is made of an opening  18  in the bottom surface portion  20  of the pedestal  6  located below the axial direction of the capacitor of the convex portion  16  provided on the side wall  8 . The convex portion  16  along the tapered portion  15  when the capacitor body  4  in contact with the capacitor body  4  is inserted into the pedestal  6  to the convex portion  16  is elastically deformed in the radial direction as a stress is applied to the pedestal  6 . Therefore, by forming the opening  18  in the bottom surface portion  20  of the pedestal  6  located below the axial direction of the capacitor of the convex portion  16  provided on the side wall  8 , the stress escapes to the peripheral portion of the opening  18  so that possible cracking and breakage of the pedestal  6  may be relieved. 
     Further, as shown in  FIG. 2 , the ribs  17  projecting inwardly over the vertical direction are provided at four positions at equal intervals on the inner surface of the side wall  8 . The separation width between the tips of the pair of ribs  17  positioned so as to face each other is formed so as to be slightly shorter than the diameter of the capacitor body  4 . 
     The rib  17  may be formed above the axial direction of the capacitor body  4  of the convex portion  16 . Thus, when the capacitor body  4  is accommodated to the pedestal  6 , the rib  17  serves to guide the capacitor body  4  and stably housed in the pedestal  6  and the convex portion  16  is formed below the axial direction of the capacitor body  4  of the rib  17  for continuous guide from the rib  17  and the convex portion  16  is disposed with a gap portion  34  to the caulking portion  12  provided in the capacitor body  4 . 
     Thus in this embodiment, the rib  17  is formed over the vertical direction of the inner surface of the side wall  8 , the outer peripheral side surface of the capacitor body  4  is supported over the top and bottom of the side wall  8 , the oscillation of the capacitor body  42  it is preferable because it is possible to more effectively suppress, the present invention is not limited thereto, it may be formed on at least a portion of the inner surface of the side wall  8 . 
     Although the upper surface view shape of the rib  17  is preferably formed in a semicircular shape, the present invention is not limited thereto, the shape as long as at least the tip is formed so as to be in contact with the outer peripheral side surface of the capacitor body  4 . 
     Further, the ribs  17  are provided at four positions at equal intervals on the inner surface of the side wall  8 , and is formed so as to be a position facing each other, so that the capacitor body  4  is uniformly sandwiched, and more stably supported, notwithstanding the present invention is not intended to be limited thereto, the capacitor body  4  is provided on the side wall  8  as long as it is adapted to be sandwiched between the ribs  17  and the number as well as the formation position may be appropriately selected. 
     In the capacitor  2  thus constructed, by mounting the capacitor body  4  inside the rib  17  provided on the inner surface of the side wall  8 , the tip of the rib  17  is pressed against the outer peripheral side surface of the capacitor body  4  and elastically deformed on the side wall  8  side and the outer peripheral side surface of the capacitor body  4  by its elastic repulsive force as sandwiched strongly with the tips of the ribs  17 , so that an oscillation of the capacitor body  4  even during excitation, breakage of the lead terminal  22  due to oscillation of the capacitor body  4  may be suppressed. Further, since the rib  17  is configured integrally with the side wall  8  for excellent strength with reduction of the manufacturing cost of the side wall  8 . 
     Furthermore, the capacitor body  4  is supported by the ribs  17 , so that the gap is formed between the outer peripheral side surface and the side wall  8  of the capacitor body  4 , lowering of the heat dissipation of the capacitor body  4  by providing the side wall  8  may be suppressed as much as possible. 
     Further, as shown in  FIG. 4 , it may be connected by a solder reflow process inserted into the through hole  30  without bending a pair of lead terminals  22  derived from the capacitor body  4 . Thus, it is possible to avoid the concentration of stress on the lead terminal  22  that occurs when the lead terminal  22  is bent. 
     Further since the lead terminal  22  is fixed in the through hole  30 , the capacitor and the circuit board  28  as compared with a general surface-mounted product that does not insert the lead terminal  22  into the through hole  30  and may be firmly connected. 
     In the embodiment, it is preferable to provide an auxiliary terminal  24  for stronger connection between the pedestal  6  and the circuit board  28  on the lower surface of the pedestal  6 , notwithstanding the present invention is not limited thereto, it may not be particularly formed. 
     Further, according to another embodiment using the auxiliary terminal as shown in  FIG. 8  including a virtual line L 1  connecting a pair of lead terminals derived from the capacitor body and a virtual line L 2  connecting a pair of auxiliary terminals disposed on the lower surface of the pedestal  6 , the contact point of the angle may be arranged auxiliary terminals so as to have a relationship substantially perpendicular. The direction of the imaginary line L 1  may ensure a high vibration resistance as fixed to the substrate at two points by a pair of lead terminals. Similarly, the direction of the virtual line L 2  ensures a high vibration resistance as fixed to the substrate at two points by a pair of auxiliary terminals. It is possible to ensure high vibration resistance to vibration from a plurality of directions by arranging the auxiliary terminals so that the respective virtual lines are arranged in different directions (e.g., perpendicular direction). 
     Capacitor  2  configured as described hereinbefore is connected by soldering to a predetermined position of the circuit board  28 . A through hole  30  provided in the circuit board  28  is filled with solder paste, and the lead terminal  22  of the capacitor is inserted into the through hole  30 . When sufficiently inserted the sealing member  26  side of the capacitor body  4  and the bottom portion  20  of the pedestal  6  are made in contact to determine the height and the gap portion  34   b  are provided the gap portion  34   a  above and below the convex portion  16  in the axial direction of the capacitor body  4 . As shown in  FIG. 5A  and  FIG. 5B , the convex portion  16  as shown in  FIG. 5B  is disposed above the caulking portion inner region occurring between the pedestal  6  and the caulking portion  12  and the gap portion  34   b  is provided below the caulking portion  12  as a space portion for allowing the movement of the capacitor body  4  due to the deformation of the sealing member  26 . 
     As shown in  FIG. 5A  and  FIG. 5B , when the solder reflow process is started a slight individual difference by the capacitor  2  as shown in  FIG. 6A  diagram  FIG. 6B  is developed like that the sealing member  26  with the internal pressure rise of the capacitor  2  is expanded to push up the capacitor body  4  in a direction away from the bottom surface portion  20  of the pedestal  6  ( FIG. 6A  arrow direction). However, since the convex portion  16  is controlled in the caulking portion  12  of the capacitor body  4  with upward movement of the caulking portion  12  by the gap portion  34   b  disposed below the convex portion  16  in the axial direction of the capacitor body  4 , separation of the capacitor from the pedestal  6  may be suppressed. Thus as shown in  FIG. 6A  and  FIG. 6B  the capacitor body  4  is pushed up, the convex portion  16  is positioned below the caulking portion inner area. Further, the height of the pushed up capacitor provides the gap portion  34   a  above the convex portion  16 . Although the height of the capacitor body  4  pushed up by the expansion of the sealing member  26  is slightly different according to the individual difference of the capacitor  2 , as shown in  FIG. 6B , the capacitor body  4 , when housed in the pedestal  6  is made into contact with the bottom surface portion  20  of the pedestal  6  by deformation of the sealing member  26  caused due to the solder reflow process and the capacitor body  4  is spaced apart from the bottom surface portion  20  of the pedestal  6  providing the lengths and when housed in the pedestal  6  by contacting the capacitor body  4  shown in  FIG. 5B  to the bottom surface portion  20  of the pedestal  6  providing, the length b of the gap portion  34   b  provided under the convex portion  16  in the axial direction of the capacitor in order to design the position of the convex portion  16  or the caulking portion as the formula a□b. Thus, it is possible to positively allow the movement of the capacitor  4  in association with the solder reflow process with the caulking portion  12 . 
     Further, when the capacitor body  4  shown in  FIG. 5B  is housed in the pedestal  6  by contacting with the bottom surface portion  20  of the pedestal  6 , the length b of the gap portion  34   b  provided under the convex portion  16  in the axial direction of the capacitor  2  is preferably about 0.2 mm˜3.0 mm, more preferably about 0.5 mm˜2.0 mm and it may appropriately be designed according to the size of the capacitor body  4  and the depth of the caulking portion  12 . 
     When the condenser  2  is cooled in the cooling step of the solder reflow process, the sealing member  26  involving the is slight individual difference by the condenser  2  expanded is contracted as shown in  FIG. 7  and the condenser body  4  is lowered by its own weight for the height in the amount of contraction the sealing member  26 . The solder solidifies and is mechanically and electrically interconnected. At this time, depending on the degree of adhesion between the rib  17  provided in the capacitor body  4  and the side wall  8  may connect the lead terminal  22  to the circuit board  28  in a state where the capacitor body  4  is provided with a slight clearance without descending to the bottom surface portion  20  of the pedestal  6  free of influence for the mounting operation on the circuit board  28 . 
     As hereinbefore described, although an example of the present invention has been described with drawings, specific feature is not limited to those examples, and any change and addition in the range which does not deviate from the summary of the present invention shall be included in the present invention. 
     For example, in the present embodiment, the method of implementing the capacitors  2  on the circuit board  28  after insertion of the lead terminal  22  of the condenser body  4  into the through-hole  30  provided on the circuit board  28  and the molding method to be carried out by rubber reflow processing with sufficient pushing into contact with the encapsulating member  26  side and the base  20  of the seat  6  of the condenser body  4  are described, notwithstanding the present invention shall not be limited to those. After insertion of the lead terminal  22  of the condenser body  4  into the through-hole  30  provided on the circuit board  28  as the method of implementing the capacitors may be carried out by a rubble reflow process with previous separation of the encapsulating member  26  side of the condenser body  4  and the base  6  and the base  20  of the base. Specifically the capacitor body is pulled upward within a range in which the convex portion  16  provided in the pedestal  6  is disposed in the caulking portion  12  provided in the capacitor body  4  and the convex portion  16  may be disposed under the inner region of the caulking portion  12 . 
     Thus, the sealing member  26  side and the pedestal  6  of the capacitor body  4  is spaced apart in advance to expand the gap or provide a gap between the sealing member  26  and the pedestal  6  for deformation of the sealing member  26  by applying the solder reflow process thereby the deformation is absorbed into the gap. As compared with the solder reflow process in a state where the bottom surface portion  20  of the sealing member  26  and the pedestal  6  are made into contact, it is possible to eliminate or reduce the movable distance above the capacitor body. The shorter movable distance upward of the capacitor body  4  with the solder reflow process may reduce the load on the lead terminal  22 . That is, the gap portion  34  provided between the convex portion  16  of the caulking portion  12  and the pedestal  6  of the capacitor body  4  may move the capacitor body  4  in the vertical direction. The size and the sealing member  26  of the capacitor  2  material, depending on the mounting equipment or the like, the distance between the capacitor body  4  and the pedestal  6  during the solder reflow process may be appropriately selected. 
     According to the present invention, it is possible to significantly reduce the occurrence of mounting failure on the circuit board  28  in the solder reflow. 
     IDENTIFICATION OF REFERENCE NUMERALS 
     
         
         
           
               2  Capacitor 
               4  Capacitor body 
               6  Pedestal 
               8  Side wall 
               10  Notch 
               12  Caulking part 
               14  Division part 
               15  Tapered portion 
               16  Convex part 
               17  Rib 
               18  Opening 
               19  Locking part 
               20  Bottom part 
               22  Lead terminals 
               24  Auxiliary terminal 
               26  Sealing member 
               28  Circuit boards 
               30  Through hole 
               32  Solder paste 
               34  Gap