JP4775972B2 - Manufacturing method of chip-type solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a method for manufacturing a chip-type solid electrolytic capacitor, and more particularly, to a method for manufacturing a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are formed by a lead frame and is packaged with a mold exterior resin.

  2. Description of the Related Art In recent years, electronic components applied to electronic devices have become increasingly demanding for high reliability of electronic components as they become smaller and thinner. For this reason, even a chip-type solid electrolytic capacitor has been improved in reliability by reducing defective outer packaging and leakage current.

  An example of a conventional chip-type solid electrolytic capacitor will be described with reference to FIGS. FIG. 5 is a schematic cross-sectional view of a conventional solid electrolytic capacitor. 1 is an internal element (capacitor element), 2 is a lead frame serving as an anode terminal and a cathode terminal, 3 is a mold exterior resin, and 16 is a crusher. Filler 18 is a resin containing a flame retardant. Moreover, FIG. 6 is a figure which shows the preparation method of mold exterior resin in a prior art example.

  In this example, as shown in FIG. 5, an anode take-out wire is embedded and planted in a valve action metal powder such as Ta or Nb, and after pressure forming, sintering is performed to form an anode body. Thereafter, an oxide film is formed on the anode body by chemical conversion, and a solid electrolyte, a graphite layer, a silver layer, and a cathode layer are sequentially formed to form the internal element 1. Then, the internal element 1 is attached to the lead frame 2 for taking out the positive and negative electrodes, and then a mold exterior, deburring, and terminal molding are performed to produce a chip-type solid electrolytic capacitor. At this time, as shown in FIG. 6, the type of the constituent filler of the mold exterior resin c (indicated by reference numeral 3 in FIG. 5) has one type and one type of average particle diameter.

  That is, as shown in FIG. 6, for example, a crushing filler a (65 to 75% by weight) having an average particle diameter of 14 μm and a resin b (25 to 35% by weight) containing a flame retardant are prepared to produce a mold exterior resin c. To do. By using this as the mold exterior resin 3 of FIG. 5, a conventional solid electrolytic capacitor is produced.

  In the technique disclosed in Patent Document 1, an inorganic filler composed of one kind of particle system is contained in the exterior resin.

JP 2002-252150 A

  Conventionally, when one type of filler is used as described above, a thin burr of the mold exterior resin remaining on the lead frame is generated if the filler having a small particle size is increased in a crushed shape or the like. If the particle size is increased to increase the amount, resin shortage (resin deficiency on the surface of the exterior resin) occurs due to insufficient fluidity of the exterior mold exterior resin. Therefore, there has been a problem that it is necessary to prevent the resin package from being short while preventing the thin burr of the mold exterior resin.

  In addition, as an important failure mode of solid electrolytic capacitors using valve metals, capacitor burnout due to deterioration of leakage current (LC) characteristics and voltage drop of the circuit due to it may occur. When there are many crushing fillers, there was a problem in the LC deterioration at the time of mounting due to more stress generated by the anchor effect due to the difference in thermal expansion coefficient between the exterior mold exterior resin and the internal element due to heat.

  In this situation, an object of the present invention is to provide a manufacturing method of a chip-type solid electrolytic capacitor that can prevent the occurrence of thin burrs and resin shortage at the time of mold exterior and can prevent deterioration of leakage current characteristics at the time of mounting. It is in.

  In order to achieve the above object, a particle-type filler having three kinds of average particle diameters is used as a mold exterior resin for sheathing an internal element of a solid electrolytic capacitor using a valve metal, and the largest filler is a sphere. The shape is composed of an average particle size of 20 to 40 μm, and the second largest filler is smaller than the first filler and has an irregular crushed shape and an average particle size of 20 to 30 μm, and the third size. A mold exterior material (mold exterior resin) prepared with an irregular crushing shape and an average particle diameter of 10 to 20 μm and having a particle diameter sufficient to fill the gap between the largest fillers is used. .

That is, in the manufacturing method of the chip-type solid electrolytic capacitor of the present invention, an anode take-out wire is embedded and planted in a valve-acting metal powder, and after pressure forming, sintering is performed to form an anode body. An oxide film is formed by chemical conversion, and a cathode layer is formed in the order of a solid electrolyte layer, a graphite layer, and a silver layer to produce an internal element. After mounting this internal element on a lead frame for taking out a positive cathode, a mold exterior In the method of manufacturing a chip-type solid electrolytic capacitor in which resin molding and terminal molding are performed, the mold exterior resin contains at least three types of particle fillers having different average particle diameters, and the first particle filler is spherical. filler chromatography, filler crushed filler der of the second and third particle system is, I formulated fillers and third particle-based filler of the second particle system Characterized by formulating a filler and filler of the first particle system.

  The first particle-based filler has a spherical shape and an average particle size of 20 to 40 μm, and the second particle-based filler has an irregular shape by crushing and has an average particle size as compared with the first particle-based filler. The diameter is small and in the range of 20-30 μm, the third particle filler has an irregular shape by crushing, the average particle size is smaller than the second particle filler, and is in the range of 10-20 μm. Good.

  A filler obtained by blending the second particle filler and the third particle filler may be blended with the first particle filler. If it carries out like this, it will become easy to arrange | position the 2nd and 3rd particle type filler so that the clearance gap between the 1st particle type fillers may be filled in mold exterior resin.

  As described above, according to the present invention, (1) by combining a filler with a large crushing shape and a filler with a small crushing shape, the distance between the fillers can be reduced and the fillers can be chained together. Blocks entry into the gap of the frame, and even if it enters, it does not spread any further, can prevent the occurrence of thin burrs in the mold exterior resin that can be formed in the gap between the mold and the lead frame, and (2) Crush by inclusion of spherical filler By reducing the amount of the filler, the anchor effect between the crushing filler and the internal element is reduced, and the flow of the mold exterior resin is improved, so that the resin flow shortage of the mold exterior resin can be prevented. Moreover, (3) LC deterioration at the time of board | substrate mounting resulting from the stress generation | occurrence | production by the anchor effect of a crushing filler and an internal element by the difference in the thermal expansion coefficient of mold exterior resin and an internal element by heat | fever can be prevented.

  That is, according to the present invention, there is no thin burr of the mold exterior resin in the lead frame part, there is no resin shortage due to insufficient fluidity of the resin at the time of molding, and the mold resin that can further improve the leakage current (LC) characteristics It is possible to provide a method for manufacturing an exterior chip type solid electrolytic capacitor.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to the present invention. FIG. 2 is a diagram showing a method for preparing a mold exterior resin in one embodiment of the present invention, with emphasis on filler materials to be used, their preparation ratio, and preparation order.

  In the chip-type solid electrolytic capacitor, as shown in FIG. 1, an anode wire is embedded and planted in a valve metal such as Ta or Nb, and after pressure forming, sintering is performed to form an anode body. Thereafter, the anode body is subjected to chemical conversion to form an oxide film, and a solid electrolyte, a graphite layer, a silver layer, and a cathode layer are sequentially formed to form the internal element 1. Then, the internal element 1 is attached to the lead frame 2 for taking out the positive and negative electrodes, and thereafter molding, deburring of the mold exterior resin, and terminal molding are performed.

  The mold exterior resin used in the mold formation will be described. As shown in FIG. 2, the types of constituent fillers have three or more types of average particle diameters, the first (first particle filler) is a spherical filler g, and the average particle diameter is 20 to 40 μm. The second (second particle filler) is an irregular shaped crushed filler e, with an average particle size of 20-30 μm, and the third (third particle filler) is an irregular crushed filler d. The mold exterior resin j is produced by preparing the particles having a particle diameter of 10 to 20 μm and including them in a resin containing a flame retardant and a coupling agent. In addition, about the material of a spherical filler and a crushing filler, a silica, an alumina, etc. can be used.

  The blending ratio and blending order of these filler materials are as shown in FIG. First, 2.5 to 5.0% by weight of crushed filler d and 95.0 to 97.5% by weight of crushed filler e are prepared to obtain crushed filler f. Next, 2.5 to 10.0% by weight of crushed filler f and 90.0 to 97.5% by weight of spherical filler g are prepared to obtain final filler h. Next, 80 to 85% by weight of the final filler h and 15 to 20% by weight of a resin i containing a flame retardant are prepared to obtain a mold exterior resin j.

  By the way, the reason why the average particle size of the spherical filler g (first particle filler) is set to 20 to 40 μm is that thin burrs are likely to occur when the particle diameter is less than 20 μm, and insufficient resin occurs on the exterior resin surface when the particle diameter exceeds 40 μm. This is because there is an inconvenience that it is easy to do.

  Further, the reason why the average particle size of the crushed filler e (second particle filler) is 20 to 30 μm is that thin burrs are likely to be generated if it is less than 20 μm, and that the leakage current characteristics are likely to be deteriorated if it exceeds 30 μm. Because there is. It is more preferable that the average particle size is limited to 23 to 27 μm.

  The reason why the average particle size of the crushed filler d (third particle filler) is 10 to 20 μm is that if it is less than 10 μm, the chain with the crushed filler e (second particle filler) is not sufficient, and the thin burrs are thin. On the other hand, if the thickness exceeds 20 μm, the gap between the fillers having a larger particle size cannot be filled, and there is a disadvantage of deterioration of leakage current. The average particle size is more preferably limited to 11 to 15 μm.

  In addition, when the average particle size of the crushing filler d composed of the crushing filler d and the crushing filler e is adjusted to 18 to 22 μm, the crushing fillers having a large particle size and a small particle size are well chained, thin burr, resin shortage and This is preferable in that the effect of preventing leakage current deterioration is recognized.

  The mold exterior resin j thus prepared is used as the mold exterior resin 4 in FIG. 1, and the internal element 1 is molded using a known mold to complete a chip-type solid electrolytic capacitor. That is, the mold exterior resin 4 includes a spherical filler 5 (spherical filler g in FIG. 2), a smaller crushed filler 6 (crushed filler e in FIG. 2), and a smaller crushed filler 7 (crushed filler d in FIG. 2). ) And a resin 8 containing a flame retardant, a coupling agent, and the like.

  EXAMPLES Next, an Example is given and this invention is demonstrated further.

  The method for producing the mold exterior resin of this example is the same as that of FIG. 2 already described, and the structure of the chip-type solid electrolytic capacitor of this example is also the same as that of FIG. Also refer to the example description.

  In the production of a chip-type solid electrolytic capacitor, as shown in FIG. 1, an anode wire is embedded and planted in valve action metal powder such as Ta and Nb, and after pressure forming, sintering is performed to form an anode body. . Thereafter, an oxide film formed by chemical conversion is formed on the anode body, and a solid electrolyte, a graphite layer, a silver layer, and a cathode layer are sequentially produced to obtain the internal element 1. Then, the internal element 1 is attached to the lead frame 2 for taking out the positive and negative electrodes, and thereafter molding, deburring of the mold exterior resin, and terminal molding are performed.

  At this time, as a filler material for producing a mold exterior resin to be used for molding, a pulverized filler obtained by melting crystalline silica and pulverizing it after cooling, and applying a burner heat treatment to make it spherical by surface tension during cooling The spherical filler obtained was used.

  Referring to FIG. 2, an irregular shaped crushing filler d having an average particle diameter of 13 μm is 3.8 wt%, and an irregular crushing filler e having an average particle diameter of 25 μm is prepared at a ratio of 96.2 wt%. An irregular crushed filler f having an average particle diameter of about 20 μm is obtained.

  The final crushed filler f is blended at a ratio of 6.2% by weight, and the spherical filler g having an average particle diameter of 30 μm is blended at a ratio of 93.8% by weight to obtain the final filler h.

  The final filler h is 82.5% by weight, and the resin i containing a coupling agent, a flame retardant, and the like is blended at a ratio of 17.5% by weight to prepare a mold exterior resin j. As shown in FIG. 1, the molded outer packaging resin j is used as the molded outer packaging resin 4 of the internal element 1 to produce a solid electrolytic capacitor.

  On the other hand, as a conventional product, as shown in FIG. 6, an irregular shaped crushing filler a having an average particle diameter of 14 μm is made 70% by weight, and a resin b containing a coupling agent, a flame retardant, etc. is made 30% by weight. A solid electrolytic capacitor was produced using the mold exterior resin 3. The leakage current value (LC) and the appearance defect rate related to the mold exterior of the conventional product and the inventive product of the example were compared with 2500 samples. FIG. 3 is a diagram comparing the leakage currents of the inventive product and the conventional product, and is expressed as a relative value where the average value of the leakage current (μA) in the conventional product is 1. FIG. 4 is a diagram comparing the appearance defect rates of the inventive product and the conventional product, and is expressed as a relative value where the appearance defect rate (%) of the conventional product is 1.

  As shown in FIG. 3, the leakage current (LC) of the example could be reduced to about 0.57 times the conventional value. Moreover, as shown in FIG. 4, the external appearance defect rate regarding the mold exterior resin of the Example could be reduced to 0.46 times the conventional value.

  As mentioned above, although embodiment and Example of this invention were described, this invention is not restricted to the form of FIG. 1, FIG. 2, Even if there is a design change of the range which does not deviate from the summary of this invention, It is included in the present invention. That is, it goes without saying that various modifications and corrections that can be made by those skilled in the art are included.

  The present invention can be applied not only to a solid electrolytic capacitor but also to an electrical component molded with a mold exterior resin.

The typical sectional view of the solid electrolytic capacitor concerning the present invention. The figure which shows the preparation method of mold exterior resin in one embodiment of this invention. The figure which compares and shows the leakage current of an invention product and a conventional product. The figure which compares and compares the appearance defect rate of an invention product and a conventional product. The typical sectional view of the solid electrolytic capacitor in a conventional example. The figure which shows the preparation method of mold exterior resin in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal element 2 Lead frame 3, 4 Mold exterior resin 5 Spherical filler (1st particle type filler)
6 Crushed filler (second particle filler)
7 Crushing filler (3rd particle filler)
8, 18 Resin 16 Crushing filler a, d, e, f Crushing filler b, i Resin c, j Mold exterior resin g Spherical filler h Final filler

Claims (2)

An anode wire is embedded and planted in the valve action metal powder, and after pressure forming, sintering is performed to form an anode body, and an oxide film is formed by chemical conversion on this anode body, and a solid electrolyte layer, a graphite layer, An internal element is formed by forming a cathode layer in the order of the silver layer, and after mounting the internal element on a lead frame for taking out the positive and negative electrodes, a chip-type solid electrolytic capacitor that performs molding of the mold exterior resin and terminal molding in the manufacturing method, the mold package resin contains at least three kinds of filler particle system different average particle sizes from each other, the first particle type of the filler is spherical filler over, filler of the second and third particle system crushed filler der is, and characterized in that the filler and the third formed by compounding a filler of particles based filler of the second particle system is formulated with filler of the first particle system Manufacturing method of that chip type solid electrolytic capacitor.   The first particle-based filler has a spherical shape and an average particle size of 20 to 40 μm, and the second particle-based filler has an irregular shape by crushing and has an average particle size as compared with the first particle-based filler. The diameter is small and in the range of 20-30 μm, the third particle filler has an irregular shape by crushing, the average particle size is smaller than the second particle filler, and is in the range of 10-20 μm. The method for producing a chip-type solid electrolytic capacitor according to claim 1, wherein:

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