JP3851308B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

  In the method for producing a solid electrolytic capacitor, the present invention is characterized in that a silver paste having a high viscosity is efficiently applied thinly to a capacitor element.

  As shown in FIG. 1, the main body (10) of the solid electrolytic capacitor is formed with a chemical conversion film (2), a solid electrolyte layer (3), and a carbon layer (4) on an anode body (1) made of a valve metal. A capacitor element (11) is prepared by coating the carbon layer (4) of the capacitor element with a silver paste (51), and the silver paste layer (5) is coated with a silver adhesive (52) as shown in FIG. As shown in FIG. 3, the lead frame (6) is adhered, and the whole is covered with a resin outer shell (7), and an aging process is performed.

  However, the completed solid electrolytic capacitor has poor ESR (equivalent series resistance) characteristics, and many defective products occur, resulting in poor yield.

  The applicant has conducted various tests, and as a result, the cause of the poor ERS characteristics is that when the capacitor body (10) is bonded to the lead frame (6), the silver paste layer (51) and the silver adhesive (52) It was concluded that the conductivity was worse.

  This is due to the following reason.

  The silver paste is composed of silver, a binder, and a solvent (volatile component) for dissolving the binder. Here, the binder is a resin component such as an epoxy resin.

  The solid electrolytic capacitor is required to be miniaturized for use. For this reason, the silver paste (51) is coated as thinly as possible.

  In order to form the silver paste layer (5) thinly, it is necessary to apply the silver paste (51) by reducing the viscosity of the silver paste (51) and immersing the capacitor element (11) therein.

  In order to reduce the viscosity of the silver paste (51), it is necessary to increase the ratio of the solvent in the silver paste (51). When the ratio of the solvent is high, the silver and the binder are easily separated, and the binder as the resin component appears on the surface of the silver paste, and the contact resistance with the silver adhesive (52) increases.

  When a silver paste (51) having a low solvent ratio and a high viscosity was applied to the capacitor element (11), the ESR characteristic defects were greatly reduced and the yield was remarkably improved.

  However, a silver paste having a high viscosity is too thick to be applied by dipping, which hinders minimization of the finished product. Applying thinly with a brush is not practical in terms of smear and productivity.

  In view of the above problems, the present invention provides a method for producing a solid electrolytic capacitor capable of improving yield by reducing the discharge rate of defective products due to defective ESR characteristics by applying a high-viscosity silver paste to a capacitor element by an immersion method. It is to clarify.

  The method for producing a solid electrolytic capacitor of the present invention comprises forming a capacitor element (11) by forming a chemical conversion film (2), a solid electrolyte layer (3), and a carbon layer (4) on an anode body (1) made of a valve metal. In a method for producing a solid electrolytic capacitor, comprising the steps of: producing, covering the carbon layer (4) of the capacitor element with a silver paste (51), and bonding a lead frame (6) to the silver paste layer (5) with silver; The covering of the carbon layer (5) with the silver paste (51) is performed by immersing the capacitor element (11) in the silver paste (51) while relatively vibrating the silver paste (51) and the capacitor element (1). The capacitor element (11) is pulled out in the direction of the vibration.

  Specifically, the viscosity of the silver paste (51) is 50 to 300 poise.

  The amplitude of the vibration may be 0.2 to 2 times the length of the capacitor element in the vibration direction.

  More specifically, the frequency may be 20 to 100 Hz.

  Due to the relative vibration between the silver paste and the capacitor element (11), the effective viscosity of the silver paste (51) decreases near the surface of the capacitor element (11). Therefore, even a silver paste (51) having a high viscosity can be thinly applied to the capacitor element (11).

  As in the case where a silver paste having a low viscosity was applied to the capacitor element (11), the poor yield due to poor conductivity could be remarkably improved.

  Moreover, since the silver paste (51) can be applied to the capacitor element (11) by the dipping method, the productivity is excellent.

  Hereinafter, embodiments of the present invention will be described.

As shown in FIG. 1, the body (10) of the solid electrolytic capacitor has a dielectric conversion coating (2) formed on the surface of an anode body (1) formed of valve metal such as Ta, Al, Nb by electrolytic oxidation treatment. A solid electrolyte layer (3) made of an organic solid electrolyte such as an inorganic solid electrolyte of MnO ₂ or a conductive polymer is formed on the dielectric conversion coating (2), and the solid electrolyte layer (3) Are coated with a carbon layer (4) and the carbon layer (4) to form a silver paste layer (5).

  The solid electrolytic capacitor of the present embodiment has a capacitor main body by injection molding by attaching lead frames (6) and (61) to the anode lead wire (60) and the silver paste layer (5) of the capacitor element (11), respectively. (10) and a part of the lead frame (6) (61) are coated with resin to form the outer shell (7), and the lead frame (6) (61) exposed from the outer shell (7) Is completed by folding along the outer shell (7) and then aging.

  In the embodiment, Ta sintered body is used for the valve metal as the anode, and polypyrrole as the conductive polymer is used for the solid electrolyte layer (3) as the cathode.

  The feature of the present invention lies in the step of coating the carbon layer with silver paste, and the other steps are well known in, for example, Japanese Patent Application Laid-Open No. 8-148392, and the description thereof is omitted.

  FIG. 4 shows a coating device (8) for coating the capacitor element (11) with a silver paste (51). The coating device (8) is a tank having an upper surface opening connected to the vibration device (81) ( 82) and a jig (87) for immersing the capacitor element (11) in the silver paste (51) in the tank (82).

  The vibration device (81) pivotally connects the lifting shaft (83) protruding downward on the lower surface of the tank (82) to the eccentric position of the rotating plate (85) via the link (84). ) And a motor (86). The vibration device is not limited to this, and an electromagnetic device may be used.

  The silver paste (51) having a high viscosity of 50 to 300 poise is used.

  The vibrating device (81) vibrates the tank (82), that is, the silver paste (51) in the vertical direction, and leads the capacitor element (11) attached to the jig (87) with the lead wire (60) facing upward. Immerse it to the base end side of the line (60) and pull it up directly, that is, in a direction along the vibration direction of the silver paste (51).

  Here, the length of the capacitor element (11) in the vibration direction was about 3.0 mm. The amplitude of the vibration device in this case is 1.5 mm, but the effect does not change even if the amplitude is increased beyond a certain level (see Table 3). On the other hand, if the amplitude is too large, the depth of the silver paste tank (82) is required, and the required amount of the silver paste (51) increases accordingly, which is not economical. Further, when the amplitude is increased, the power consumption of the vibration device increases, which is not economical.

  Due to the vibration of the silver paste (51), the effective viscosity of the silver paste (51) decreases near the surface of the capacitor element (11). Therefore, even a silver paste (51) having a high viscosity can be thinly applied to the capacitor element (11).

  As in the case where a silver paste having a low viscosity was applied to the capacitor element (11), the poor yield due to poor ESR characteristics could be remarkably improved.

  Moreover, since the silver paste (51) can be applied to the capacitor element (11) by the dipping method, the productivity is excellent.

Example Silver paste Viscosity 200 poise Binder Epoxy resin Solvent n-Butyl carbitol Silver content 82 wt%
Nonvolatile components (silver + binder, etc.) 91 wt%
Silver paste applicator tank frequency 30Hz
Amplitude 1.5mm
The silver paste (51) used was the same as the silver adhesive (52) for bonding the capacitor element (11) to the lead frame (6). Thus, it may be different from the silver adhesive (52) by adjusting the viscosity to be easy to use in the range of 50 to 300 poise.

  The capacitor element (11) whose outer surface was covered with the carbon layer (4) was immersed in a tank (82) containing silver paste (51) under the above conditions, and immediately pulled up in the direction along the vibration direction.

  A silver paste layer (5) having an average thickness of about 40 μm was formed on the capacitor element (11).

  The ESR of the capacitor body (10) on which the silver paste layer (5) was formed was 20 to 35 mΩ.

  The ESR after adhesion of the frame was 25 to 50 mΩ.

  If the ESR of the finished product in FIG. 3 is 80 mΩ as the border line, the ESR is a defective product, and the product is a non-defective product, the yield is about 90%.

Comparative Example Silver paste Viscosity 10 poise Binder Epoxy resin Solvent n-Butyl carbitol Silver content 65 wt%
Nonvolatile components (silver + binder, etc.) 72wt%
When a capacitor element was immersed in the silver paste and a finished solid electrolytic capacitor was manufactured by the post-process, the yield was 30%.

  The table below shows the relationship between the viscosity of silver paste and ESR, the relationship between frequency and average film thickness, and the relationship between amplitude and film thickness.

銀ペースト粘度は、５０〜３００ポイズであれば、完成固体電解コンデンサの歩留まりは８０％以上とすることができた。

When the silver paste viscosity was 50 to 300 poise, the yield of the finished solid electrolytic capacitor could be 80% or more.

  The thickness of the silver paste layer (5) is preferably 40 to 200 μm, and if the frequency of the silver paste (51) is 20 to 100 Hz, it falls within this range. The amplitude of the silver paste (51) is within this range if it is 0.6 to 6 mm. This amplitude corresponds to 0.2 to 2 times the length of the silver paste (51) in the capacitor element (11) in the vibration direction.

  In carrying out the present invention, the tank containing the silver paste (51) may be stationary, and may be extracted from the tank of the silver paste (51) in a direction along the vibration direction while applying vibration to the capacitor element (1).

  The present invention is not limited to the configuration of the above embodiment, and various modifications are possible within the scope of the claims.

It is sectional drawing of the capacitor | condenser element before lead frame attachment. It is a mounting explanatory view of a lead frame. It is sectional drawing of the completed solid electrolytic capacitor. It is explanatory drawing of a silver paste coating device.

Explanation of symbols

(1) Anode body
(10) Capacitor body
(11) Capacitor element
(2) Conversion coating
(3) Solid electrolyte layer
(4) Carbon layer
(5) Silver paste layer
(6) Lead frame
(7) Outer shell
(8) Silver paste applicator
(81) Vibration device

Claims (4)

A capacitor element (11) is produced by forming a chemical conversion film (2), a solid electrolyte layer (3), and a carbon layer (4) on an anode body (1) made of a valve metal, and a carbon layer ( 4) coating a silver paste (51) and bonding the lead frame (6) to the silver paste layer (5). In the method for producing a solid electrolytic capacitor, the carbon layer (5) by the silver paste (51) Covering the silver paste (51) and the capacitor element (11) while relatively vibrating, the capacitor element (11) is immersed in the silver paste (51), the silver paste (51) near the capacitor element surface A method for producing a solid electrolytic capacitor, wherein the capacitor element (11) is pulled out in the direction of the vibration in a state where the effective viscosity is reduced, and the silver paste layer (5) is formed thin. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the frequency is 20 to 100 Hz. The method of manufacturing a solid electrolytic capacitor according to claim 2, wherein the silver paste (51) has a viscosity of 50 to 300 poise. The method for manufacturing a solid electrolytic capacitor according to claim 2, wherein the amplitude of vibration is 0.2 to 2 times the length of the capacitor element (11) in the vibration direction.

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