JP2007273867A - Capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor with superior reliability that can sufficiently withstand mechanical stress of curvature, bending, etc., of a substrate after the substrate is mounted. <P>SOLUTION: When the capacitor is soldered to be mounted on the substrate by joining a terminal electrode plate to a flank of the capacitor, joining a heat-resisting member forming a gap with the terminal electrode plate to a bottom surface of a capacitor body, and then folding the terminal electrode plate along a bottom surface of the heat-resisting member; the space is formed between the terminal electrode and heat-resisting member to prevent the heat-resisting member which has extended along the width owing to a difference in thermal expansion between the capacitor body and heat-resisting member, from pressing and spreading the terminal electrode plate in contact with the terminal electrode plate, and then mechanical stress applied to the capacitor body can be eliminated to prevent cracking. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a capacitor, particularly a capacitor structure.

  Capacitors are used in a wide range of electronic devices, but in recent years, larger capacities have been demanded. In particular, a ceramic capacitor having a large capacitance has a large number of stacked layers in order to further increase the capacitance. When these ceramic capacitors are surface-mounted directly on a circuit board by solder or the like, problems such as cracks occur due to expansion and contraction of the board during soldering. Further, since it is directly fixed on the substrate, it cannot adapt to the warp or bend of the substrate, resulting in defects such as cracking of the capacitor or peeling off of the soldered portion.

In order to solve these problems, for example, there is a method (means) disclosed in Japanese Utility Model Laid-Open No. 63-187320. That is, a capacitor is manufactured by providing an insulating rubber block on the bottom surface of the capacitor and providing a metal terminal connected to the external electrode on the side surface of the insulating rubber block. (Patent Document 1)
Japanese Utility Model Publication No. 63-187320

  Thereby, generation | occurrence | production of the crack by the curvature or bending of a board | substrate etc. can be suppressed, and reliability can be improved.

  However, in the method proposed in Patent Document 1, since the insulating rubber block is provided on the bottom surface of the capacitor, the stress can be relieved with respect to mechanical stress caused by warping or bending of the substrate. However, in ceramic capacitors, the coefficient of thermal expansion of the insulating rubber block is larger than the coefficient of thermal expansion of the capacitor, so the difference in thermal expansion between the capacitor body and the insulating rubber due to the heat of the solder when mounting on the board causes the capacitor body to There is a problem that the stress is directly applied and the reliability of the capacitor is lowered due to the occurrence of cracks. Alternatively, there may be a problem that the metal terminal is peeled off from the capacitor body.

  The technical problem of the present invention is to provide a capacitor having excellent reliability free from cracks caused by soldering when mounted on a board.

  In the capacitor of the present invention, a terminal electrode plate is bonded to the side surface of the capacitor, and a heat-resistant member that forms a space portion between the terminal electrode plate and the terminal electrode plate is bonded to the bottom surface of the capacitor body. It is characterized by being folded along the bottom surface. As a result, in soldering when mounting the capacitor on the substrate, a space portion is provided between the terminal electrode plate and the heat-resistant member for the expansion of the heat-resistant member caused by the difference between the thermal expansion of the capacitor body and the heat-resistant member. By preventing the heat resistant member extending in the width direction from spreading the terminal electrode plate while contacting the terminal electrode plate, the mechanical stress applied to the capacitor body can be eliminated, and the occurrence of cracks can be prevented. .

  The shape of the heat-resistant member is a plate-like member. By installing the heat-resistant member as a plate on the bottom surface of the capacitor body, when the solder for joining the capacitor body and the terminal electrode plate is dissolved in the soldering for joining the substrate and the terminal electrode plate, the capacitor body is dropped. Can be prevented. Furthermore, it is possible to prevent the capacitor body from being directly soldered during dipping soldering.

Further, the distance from the top surface of the substrate to the bottom surface of the capacitor body is preferably set to 0.2 mm or more in consideration of an appropriate height as an electronic component, and is small as long as the appropriate height can be maintained. Is preferred.
The space formed between the terminal electrode plate and the heat-resistant member, and the distance from the bottom surface of the terminal electrode plate folded along the bottom surface of the heat-resistant member to the bottom surface of the capacitor body should be 0.2 mm or more. Therefore, when the substrate is warped or bent, the spring is bent so that the portion of the terminal electrode plate in contact with the space expands outward according to the warp or bend of the substrate, or bends so as to be narrowed inward. By acting as described above, mechanical stress applied to the capacitor body can be relaxed. Also, when the substrate expands with respect to the capacitor body in a temperature cycle due to temperature rise or cooling of the substrate, the terminal electrode plate opens outward, and conversely, when the substrate contracts with respect to the capacitor body, the terminal electrode plate Since the mechanical stress applied to the capacitor body can be relieved by bending inward, cracks can be prevented from occurring in the capacitor body.

The side surface of the capacitor body and the terminal electrode plate are joined by low melting point solder. In this case, the low melting point solder is preferably a solder having a melting point of 220 ° C. or less, and Sn or Pb is used as a base material and Zn, Cu, Ag or the like is added.
By joining the side surface of the capacitor body and the terminal electrode plate with a low melting point solder, it is possible to prevent the external electrodes of the capacitor body from being broken during high temperature soldering. In addition, since the low melting point soldering temperature can be lower than the high temperature solder, the difference in thermal shrinkage between the capacitor body and the solder metal that occurs when the solder solidifies and cools after soldering is reduced. Therefore, since the stress applied to the capacitor body is relieved, damage to the capacitor body can be reduced.

  The heat-resistant member bonded to the bottom surface of the capacitor body is an insulating member having a melting point of 270 ° C. or higher. By setting the melting point of the heat-resistant member bonded to the bottom surface of the capacitor body to 270 ° C. or higher, it is possible to withstand the heat at the time of soldering at the time of board bonding, particularly soldering by reflow in a far-infrared furnace.

The capacitor of the present invention is a capacitor in which a plurality of capacitor bodies are laminated, and the heat-resistant member is joined to the lowermost part of the laminated capacitor bodies. By using a capacitor in which a plurality of capacitor bodies are stacked, the effect of the invention can be maintained as it is, and a large-capacity capacitor can be obtained with the same mounting area.
Furthermore, by stacking and integrating a plurality of capacitors having different temperature characteristics and joining each external electrode to the terminal electrode plate, a capacitor having a temperature characteristic suitable for the purpose of use can be obtained according to the combination of the stacked capacitors. .

  A terminal electrode plate is joined to the side surface of the capacitor body, and a heat-resistant member that forms a space with the terminal electrode plate is joined to the bottom surface of the capacitor body, and the terminal electrode plate extends along the bottom surface of the heat-resistant member. By folding, when soldering when mounting the capacitor on the substrate, the expansion of the heat-resistant member caused by the difference between the thermal expansion of the capacitor main body and the heat-resistant member, the space between the terminal electrode plate and the heat-resistant member By providing, it is possible to prevent the heat stress member extending in the width direction from spreading the terminal electrode plate while contacting the terminal electrode plate, thereby eliminating the mechanical stress on the capacitor body and preventing the occurrence of cracks it can.

  EXAMPLES Examples are given below to describe the capacitor of the present invention in detail with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention.

  First, plate-like terminal electrode plates 4 are bonded to both side surfaces of the capacitor body 1 with low melting point solder 6. Next, the heat-resistant member 2 having a width narrower than that between the terminal electrode plates 4 is placed between the terminal electrode plate 4 and the bottom surface of the capacitor body so that the widths of the space portions 7 on both sides thereof are substantially the same. The member 2 is joined with an adhesive.

  Furthermore, the lower end portions of both terminal electrode plates 4 are folded inward along the bottom surface of the heat-resistant member 2 while maintaining the width of the space portion 7 to form the folded holding portion 4-1, thereby forming the capacitor of the present invention. Is created.

  The heat-resistant member 2 is a plate-like member having a constant thickness, and the material of the member is a plate material having a melting point of 270 ° C. or higher so that it can withstand the temperature of the solder when mounted on the board.

  Moreover, the space | interval from the board | substrate upper surface to the bottom face of the said capacitor | condenser main body 1 became a space | interval of 0.2 mm or more because the folding holding | maintenance part 4-1, the heat-resistant member 2, and the adhesive agent 3 intervened.

  The capacitor body 1 and the heat-resistant member 2 are bonded with an adhesive having heat resistance against soldering when mounting on the board.

  FIG. 2 is a perspective view showing a capacitor in which a plurality of capacitor bodies according to the second embodiment of the present invention are stacked.

  The external electrodes 5 of the plurality of capacitor bodies 1-1 and 1-2 are aligned and stacked, and the capacitor bodies 1-1 and 1-2 are joined using an adhesive 3-1. Next, the terminal electrode plates 4 are joined to the both side surfaces of the capacitor main bodies 1-1 and 1-2 with low melting point solder 6, respectively. Further, the heat-resistant member 2 is joined to the lowermost part of the capacitor body so that the space 7 is formed on both sides between the both terminal electrode plates 4 and the heat-resistant member 2. Next, the lower end portion of each terminal electrode plate 4 is bent inward along the bottom surface of the heat-resistant member 2 so that the width of the space portion 7 is maintained, thereby forming the folding holding portion 4-1. A capacitor according to a second embodiment of the invention is created.

  In Example 1, first, a ceramic capacitor having a capacitor size of 3.2 mm in length and 2.5 mm in width was used. As the terminal electrode plate, a metal plate having a thickness of 0.1 mm and a material of 42 Alloy was used, and the terminal electrode plate was joined to the side surface of the capacitor body with a low melting point solder (Sn-3.0Ag-0.5Cu). Next, the heat-resistant member to be joined to the bottom surface of the capacitor body is a heat-resistant polyamide resin plate (trade name; manufactured by Genesta, Kuraray Co., Ltd.) having a thickness of 0.5 mm. The space between the heat-resistant member and the terminal electrode plate The width is 10 μm on each of the left and right sides, and the width is 20 μm in total. The dimensions in the width direction are the same as the dimensions of the capacitor. This heat-resistant member was adhered to the bottom surface of the capacitor body with an epoxy adhesive, and the terminal electrode plate was folded inward at right angles along the bottom surface of the heat-resistant member while maintaining the width of the space portion to form a folded holding portion. .

  Note that the width of the space between the heat-resistant member and the terminal electrode plate may be a size that does not contact the terminal electrode plate when the heat-resistant member thermally expands in the width direction. And the coefficient of thermal expansion of the heat-resistant member, and the soldering temperature when mounting the board, and are not limited to the dimensions of this embodiment.

  Next, it mounted on the aluminum substrate using the solder, and the temperature cycle test was implemented in the temperature range of -55 degreeC-+125 degreeC. The occurrence of defects such as a decrease in appearance, capacitance, and insulation resistance was not observed up to 1000 cycles.

  Further, this capacitor was mounted on a substrate made of glass epoxy using solder, and a substrate bending resistance test (based on the former JIS C6429) was performed. Although the appearance at a bending amount of 2 mm was confirmed by pressurizing the center of the substrate, no occurrence of defects was observed, and it was confirmed that no crack was generated even when the bending amount was bent to 8 mm due to the substrate bending resistance.

  (Comparative example) The ceramic capacitor used in Example 1 was directly mounted on an aluminum substrate using a solder, and a temperature cycle test was performed in a temperature range of -55 ° C to + 125 ° C. It was observed that cracks occurred in the capacitor.

In addition, when the ceramic capacitor used in the comparative example was directly solder-mounted on a substrate and a substrate bending resistance test was performed, it was confirmed that the capacitor would crack when the bending amount was bent to 3 mm in the substrate bending resistance test. It was.

It is sectional drawing which shows the capacitor | condenser by 1st embodiment of this invention. FIG. 6 is a perspective view of a plurality of stacked capacitors according to a second embodiment of the present invention. It is sectional drawing of the capacitor | condenser which uses the insulating rubber block in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1-1,1-2 Capacitor main body 2 Heat-resistant member 3,3-1,3-2 Adhesive 4 Terminal electrode board 4-1 Folding holding part 5 External electrode
6 Solder part 7 Space part

Claims (2)

A terminal electrode plate is joined to the side surface of the capacitor body, and a heat-resistant member that forms a space with the terminal electrode plate is joined to the bottom surface of the capacitor body, and the terminal electrode plate extends along the bottom surface of the heat-resistant member. Folded capacitor. The capacitor according to claim 1, wherein a plurality of the capacitor main bodies are stacked, and the heat-resistant member is joined to a lowermost portion of the stacked capacitor main bodies.

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