JP2522405B2 - Chip type solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a chip-type solid electrolytic capacitor, and more particularly to a cathode / cathode terminal structure with improved connection reliability, component mountability, and volume efficiency of the cathode / cathode terminal.

[Conventional technology]

Conventionally, this type of chip-type solid electrolytic capacitor has, for example, as shown in FIG. 3, an anode lead derived by connecting an external cathode terminal 14 with a conductive adhesive to a capacitor element having a silver paste layer formed by a known technique. After connecting the external anode terminal 13 to the wire by welding, the mold exterior 15 including a part of the positive and negative terminals is formed, and the external positive and negative terminals are respectively bent into an L shape. There is a chip type solid electrolytic capacitor. . Further, as proposed in Japanese Utility Model Publication No. 62-14673, after forming a cathode conductor layer such as silver paste by a known technique as shown in FIG. 4 in order to enhance the volumetric efficiency,
The element is covered with an insulating resin layer, and a part of the upper part of the cathode conductor layer is removed to expose the exposed cathode conductor layer, the anode lead wire, and the surrounding insulating resin layer. There is a resin-coated chip type solid electrolytic capacitor in which a conductor layer 16 coated with is formed, a plating layer 17 and a solder layer 18 are further formed thereon, and an anode lead wire is projected.

[Problems to be Solved by the Invention]

However, the above-mentioned chip type solid electrolytic capacitor has the following drawbacks.

In other words, the chip-type solid electrolytic capacitor packaged with a mold has an external cathode terminal connected to the device with a conductive adhesive and then packaged with a mold. A certain distance is required between the element and the bent part of the external cathode terminal in order to reduce the mechanical stress applied to the element when the terminal is bent along the side of the mold resin. And miniaturization were difficult. Further, because of the mold exterior, there are disadvantages that the leakage current is deteriorated by the pressure at the time of resin injection, and an expensive mold die must be prepared when changing the design.

Further, there are problems such as an increase in cost due to bonding the external cathode terminal and the element with an expensive conductive adhesive, and connection reliability due to variations in the amount of conductive adhesive applied.

On the other hand, the chip-type solid electrolytic capacitor coated with resin is
Thinner than molded type because electrode terminals are directly formed on both ends of the element without using external lead terminals.
Although the size can be reduced, the protruding portion of the anode lead wire is long, so that when a component is mounted on a printed wiring board or the like by using a component mounting machine, there is a disadvantage that the component of the mounting machine causes the component to be ejected. Further, since the conductor layer 16 made of silver paste or the like and the anode lead wire are connected by the binder resin contained in the silver paste or the like, when heat stress is applied,
Since the binder resin and the anode lead wire have different coefficients of thermal expansion, there is a problem that the connection reliability is impaired and the open failure of the anode terminal occurs. There is also a drawback that the capacitor becomes large by the thickness of the conductor layer.

[Means for solving the problem]

The chip-type solid electrolytic capacitor of the present invention comprises an anode body made of a valve metal having an anode lead wire, an element formed of an oxide film layer, an electrolyte layer, and a cathode conductor layer formed on the surface of the anode body, and an anode. A chip-type solid consisting of an insulating resin layer formed on the peripheral surface of the element so that the opposite surface of the lead wire lead-out surface is exposed, and a positive / cathode terminal formed on the anode lead wire lead-out surface and the exposed cathode conductor layer. The electrolytic capacitor is characterized in that at least one terminal includes a plating catalyst metal, a plating layer, and a solder layer, which are sequentially formed, and metal particles of the plating catalyst metal are separated from each other.

〔Example〕

Next, the present invention will be described with reference to the drawings. First
FIG. 1 is a sectional view of an embodiment of a chip type solid electrolytic capacitor according to the present invention.

Anode lead 1 made of tantalum is planted on anode body 1 in which tantalum powder, which is one of the metals having a valve action, is pressure-molded and vacuum-sintered, and an oxide film layer (illustrated in the figure) is formed on the outer peripheral surface of anode body 1. (Omitted) and the semiconductor oxide layer 3 are formed, and the first graphite layer 4 is formed on the outer side thereof except the anode lead planting surface. A coating resin layer 5 is formed by applying and heating polyptadiene resin on the anode lead planting surface of the anode body 1. Further, a second graphite layer 6 containing a metal catalyst powder, for example, palladium powder, for example, a first plating layer 7 made of an electroless nickel plating layer is sequentially formed on the outer peripheral surface of the anode body other than the anode lead planting surface.

Next, after the insulating resin layer 8 is formed on the entire outer peripheral surface of the anode body other than the opposing surface of the anode lead planting surface, the third surface containing the metal catalyst powder, for example, palladium powder, on the opposing surface of the anode lead planting surface. A cathode terminal composed of the graphite layer 9, the second plating layer 11 made of, for example, an electroless nickel plating layer, and the solder layer 12 is formed. Further, on the insulating resin layer 8 on the anode lead planting surface and on the anode lead 2, a plating catalyst metal 10 made of, for example, palladium powder, a second plating layer 11 made of an electroless nickel plating layer, and an anode terminal made of a solder layer 12 are formed. Is formed, and finally the anode lead 2 is cut to form a chip type solid electrolytic capacitor.

That is, the terminal of the present invention comprises a plating layer formed by adhering a plating catalyst metal on the exterior resin without using a conductive paste, and a solder layer formed on the plating layer and a solder layer. .

Next, a manufacturing process of the chip type tantalum solid electrolytic capacitor having such a configuration will be described.

First, the pressure-molded tantalum powder is vacuum-sintered at a high temperature, and the anode lead 1 made of tantalum material is planted.
Is anodized in a phosphoric acid aqueous solution at a formation voltage of 100 V to form a tantalum oxide film on the entire outer peripheral surface, is then immersed in a manganese nitrate solution, and is pyrolyzed in an atmosphere of 250 to 300 ° C after the manganese nitrate is attached. A manganese layer is formed. This dipping and pyrolysis is performed multiple times to obtain a uniform manganese dioxide layer. Next, the anode body 1 having the manganese dioxide layer formed thereon is immersed in a graphite solution in which graphite powder is suspended in an aqueous solution of a water-soluble polymer material,
The first graphite layer 4 is formed by drying in an atmosphere of ° C.

Next, polyptadiene resin is applied to the anode lead planting surface by a dispenser and then dried in an atmosphere of 150 to 200 ° C. to form a coating resin layer 5.

Next, epoxy resin 20-50%, graphite powder 5-
30%, inorganic filler 20-50%, palladium powder 1-10%
Are mixed in a weight ratio and diluted with butyl cellosolve to a position where they come into contact with the coating resin layer, and the temperature is 150 to 200 ° C.
The second graphite layer 6 is formed by being thermally cured in the atmosphere. The palladium powder in the second graphite layer has a function as a plating catalyst, and the inorganic filler has an effect of forming irregularities on the surface to increase the adhesion of the plating film by the anchor effect.

Furthermore, 2% in a hydrochloric acid aqueous solution containing 10% palladium by volume.
After immersing for about 3 minutes to activate the palladium surface, it is washed with pure water to perform electroless plating. Since the peripheral portion of the anode lead 2 excluding the second graphite layer 6 is covered with the coating resin layer 5, the manganese dioxide layer and the oxide film are protected from the gas during the reaction. As the plating solution, for example, an electroless nickel plating solution (pH = 6.7 at room temperature) using dimethylaminoborane as a reducing agent is used, and plating is performed at 65 ° C. for 40 minutes to form a nickel plating layer 7 of about 4 to 5 μm. To be done. After plating, the whole is thoroughly washed with water and placed in a constant temperature bath at 120-150 ° C.
It is left to evaporate water. Next, powdery epoxy resin is electrostatically coated on the outer peripheral surface of the element while masking the surface opposite to the anode lead planting surface, and temporarily cured in an atmosphere of 100 to 200 ° C for about 30 minutes, then masked. Remove and heat in an atmosphere of 100 to 200 ° C for 30 to 60 minutes to completely cure the insulating resin layer 8
To form. Next, the surface of the anode lead is roughened by spraying alumina powder having an average particle size of about 40 to 50 μm.

Next, a butyl acetate solution of an amine compound of palladium is applied on the insulating resin layer 8 and the anode lead 2 on the surface where the anode lead is set up, and is thermally decomposed at 200 ° C. for 30 minutes to deposit a palladium powder having a particle size of about 0.1 micron. Then, the plating catalyst metal 10 is attached. Further, since the surface opposite to the anode lead planting surface is masked, the insulating resin layer is not formed and the first plating layer 7, that is, the electroless nickel plating layer is exposed.
Epoxy resin 20 ~ 50%, graphite powder 5 ~
30%, inorganic filler 20-50%, palladium powder 1-10%
Were mixed in a weight ratio and dissolved in a small amount of butyl carbitol acetate.
The third graphite layer 9 is heat-cured in the atmosphere of 00 ° C.
To form.

Next, the device was immersed in the electroless nickel plating solution described above up to the anode lead 2 under the conditions of 65 ° C. for 45 minutes, and the third graphite layer 9 and the anode lead planting surface and the anode lead 2 on which the palladium powder was adhered. A second plating layer, that is, an electroless nickel plating layer is formed on the top. At this time, electroless nickel plating does not deposit on the third graphite layer 9 and on the insulating resin layer 8 other than the anode lead planting surface to which the palladium powder is adhered, because there is no palladium powder serving as a plating catalyst.

Further, the element is dipped in the flux and then dipped in a eutectic solder bath at 260 ° C. to form the solder layer 12 on the second plating layer to complete the anode terminal and the cathode terminal.

Finally, the excess anode lead 2 is cut to form a chip type solid electrolytic capacitor.

In this example, polybutadiene resin was used as the material of the coating resin layer formed on the anode lead embedding surface, but this material is used to protect the oxide film and the manganese dioxide layer from hydrogen generated during the plating reaction. Therefore, resins such as epoxy, acrylic, polyester, polyvinyl chloride, polypropylene, etc., and mixed resins thereof may be used.

Further, although an electroless nickel plating layer is used as the plating layer in this embodiment, since this material is the base of the solder layer, electroless copper plating may be used. In this case, use a high-speed plating bath that uses EDTA as the chelating agent.
Perform at 50 ℃ for 40 minutes.

FIG. 2 is a vertical sectional view of another embodiment of the present invention. In the present embodiment, while the above-mentioned embodiment carried out electroless nickel plating after thermally decomposing the organic compound of the plating catalyst metal at the time of deriving the anode terminal, this method was also used at the time of deriving the cathode terminal. Perform using. That is, after the insulating resin layer 8 is formed, a butyl acetate solution of an amine compound of palladium is applied to the anode lead, the anode lead embedding surface and the surface opposite to the anode lead and thermally decomposed at 200 ° C. for 30 minutes to deposit palladium powder. Next, the anode lead 2 for 40 minutes in the above-mentioned 65 ° C electroless nickel plating solution.
The electroless nickel layer, that is, the second plating layer 11 is formed by immersing.

In this embodiment, since the third graphite layer 9 used in the above-mentioned embodiments is not used, the cathode terminal can be thinned, and there is an advantage that the chip type solid electrolytic capacitor can be further downsized.

The amine compound of palladium, which acts as a catalyst for electroless plating, has a higher deposition rate as the concentration increases, but the cost is high because a lot of expensive palladium metal is used.
get up. As a result of the examination, when the concentration of the palladium amine compound was 1%, the plating reaction started within 1 minute, and after 30 minutes, the nickel plating thickness of 3 μm was applied to the entire surface of the palladium amine compound butyl acetate solution-coated portion. Was formed. Considering plating depositability and cost, the concentration of the amine compound of palladium is preferably 0.1 to 5%. Even if the concentration of the amine compound of palladium is 5%, the palladium layer formed after thermal decomposition has no conductivity. This is 5
This is because at a concentration of about%, the precipitated palladium particles are not densely formed so that they can be electrically conducted. However, it plays a sufficient role as a catalyst for electroless plating.

FIG. 5 shows the results of evaluating the reliability of the anode terminal connection when changing the anode cutting dimension of the chip tantalum capacitor thus produced. As a comparative example, FIG. 6 shows the evaluation results of a chip tantalum capacitor formed by using a conductor layer of silver paste or the like disclosed in Japanese Utility Model Publication No. 62-14673 as a plating catalyst. Temperature cycle test is -55 ℃ 125 ℃,
The tangent of the dielectric loss (hereinafter abbreviated as tan δ) was measured as a scale for evaluating the connection reliability between the anode lead wire and the anode terminal layer by performing 100 cycles under the condition of standing in each atmosphere for 30 minutes. In the example of the present invention, the cutting dimension of the anode lead wire is 0.
Although tan δ was not deteriorated at all even if it was cut short to 1 mm, the capacitor manufactured by the method disclosed in JP-B-62-14673 showed deterioration at a cutting dimension of 0.4 mm and 0.2
When the cutting dimension was less than mm, n = 50 all open defects occurred. When the defective product was analyzed, it was found that the interface between the anode lead wire and the silver paste was separated. With the conventional product, if the cutting dimension is shortened, the connection between the anode lead wire and the anode terminal layer interface becomes the connection between the anode lead wire and the silver paste layer.
Since the product of the present invention is a connection between the anode lead wire and the nickel plating layer via the palladium particles and is a metal-to-metal connection having almost the same thermal expansion coefficient, it is considered that the stability due to thermal shock is enhanced. On the other hand, the silver paste layer, which is the plating catalyst of the conventional product, and the anode lead wire are kept connected by the binder resin contained in the silver paste, which has a thermal expansion coefficient much larger than that of the metal. Is likely to peel off, resulting in an open defect. When the cutting dimension of the conventional product is lengthened, as can be seen from FIG. 4, the anode lead wire and the anode terminal layer have two connecting portions, that is, the anode lead wire and the silver paste layer, and the anode lead wire and the nickel plating layer. It is considered that tan δ did not deteriorate in the thermal shock test because the connection reliability between the anode lead wire and the nickel plating layer was high.

As the plating catalyst, a copper amine compound was applied instead of the palladium amine compound to form a plating catalyst metal. Butyl butyrate was used as the solvent, and 10% by weight of the amine compound of copper was dissolved. The plating reaction started 5 minutes after immersion in the plating solution, and the plating deposition rate was slower than that of palladium, but tan δ deterioration in the temperature cycle test was not observed. Other than this, it has been found that simple substances, alloys, and mixed powders of gold, silver, iron, nickel, tin, etc. are effective as the catalyst metal. In addition to amine compounds, organic acid compounds such as phenol and benzoic acid may be used.

〔The invention's effect〕

As described above, the present invention has the following effects because it does not use a binder resin as a plating catalyst but uses a solution in which an organic compound of a catalyst metal is dissolved.

(1) Since the connection strength between the anode lead wire and the anode terminal is increased, the cutting length of the anode lead wire can be shortened, and when mounting the component with the automatic mounting machine, the tab of the mounting machine may cause the component to skip. Disappear.

(2) Since the anode terminal layer is formed of a plating layer or a solder layer having high adhesion strength to the anode lead wire, the problem of peeling of the anode terminal layer in a thermal shock test or the like is eliminated.

(3) Since the amount of catalyst metal added is smaller than that of silver paste or the like, the material cost can be reduced.

(4) Since the plating catalyst metal particles are 0.1 micron or less, the anode and cathode terminals can be made thin.

(5) Since the catalyst metal is formed by thermally decomposing the organic compound solution of the plating catalyst metal, it is not necessary to immerse the catalyst metal in a strong acid solution as compared with the conventional sensitization-activation method or the like, so that the product is not deteriorated.

As described above, according to the present invention, the plating layer and the solder layer are directly formed on the terminal formation surface layer without using the conductive paste when forming the positive and negative terminals, so that the thickness of the positive and negative terminals can be reduced. Therefore, the chip-type solid electrolytic capacitor can be further downsized and the volume efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention, FIG. 2 is a vertical sectional view of another embodiment of the present invention, and FIGS. 3 and 4 are examples of conventional chip type solid electrolytic capacitors. FIG. 5 and 6 are characteristic evaluation diagrams showing the characteristics of the present invention and the conventional example, respectively. 1 ... Anode body, 2 ... Anode lead, 3 ... Semiconductor oxide layer, 4 ... First graphite layer, 5 ... Coating resin layer,
6 ... second graphite layer, 7 ... first base metal layer,
8 ... Insulating resin layer, 9 ... Third graphite layer, 10 ...
Plating catalyst metal, 11 ... second plating layer, 12 ... solder layer, 13 ... anode terminal, 14 ... cathode terminal, 15 ... exterior resin layer, 16 ... conductor layer, 17 ... plating layer , 18 …… Solder layer, 19 …… Anode terminal, 20 …… Cathode terminal.

Claims (2)

(57) [Claims] 1. An anode body made of a valve metal having an anode lead wire, an element comprising an oxide film layer, an electrolyte layer and a cathode conductor layer formed on the surface of the anode body, and an anode lead wire leading surface. A chip type having an insulating resin layer formed on the peripheral surface of the element so that the cathode conductor layer on the opposite surface of the element is exposed, and a positive / cathode terminal formed on the anode lead-out surface and the exposed cathode conductor layer. In a solid electrolytic capacitor, at least a terminal of an anode is formed by sequentially forming a plating catalyst metal, a plating layer, and a solder layer, and metal particles of the plating catalyst metal are separated from each other. . 2. The chip type solid electrolytic capacitor according to claim 1, wherein the plating catalyst metal is formed by depositing an organic compound solution of the catalyst metal and then thermally decomposing it.