JPS587049B2 - Cotai Denkai Capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a solid electrolytic capacitor having a strong resin exterior and excellent moisture resistance.

Dip packaging has traditionally been used as a packaging method for solid electrolytic capacitors for consumer electronics because it is advantageous in terms of rationalization and mass production, and is less complicated than casting methods.

However, with this dip exterior, pinholes are likely to occur in the resin layer, and there is a risk of poisoning or rash due to diluents and solvents, and an undercoat is required to strengthen the outer shell layer and prevent the occurrence of pinholes. Two coats of the resin layer were required.

For this reason, the resin thickness becomes large, the external dimensions vary widely, sag tends to occur when a large amount of resin is applied at once, and the mechanical shrinkage stress during resin curing is large, easily causing leakage current defects, and many other problems. There are also some problems.

In particular, the occurrence of pinholes has a large effect on moisture resistance properties, so various measures have been taken to prevent this occurrence, such as forming a dense manganese dioxide layer with few bubbles, using an undercoat, and multiple coatings of resin. All of them have advantages and disadvantages, and the methods are difficult, so there are few that can be used as drastic measures.

As shown in Figure 1, the most commonly used exterior case at present is to anodize the valve metal to form a dielectric layer, coat it with manganese dioxide, colloidal graphite, and silver paste, and then weld the anode lead. On the capacitor element 1 obtained by soldering the cathode lead, a low-viscosity thermosetting synthetic resin undercoat layer 2 is formed, and a thermosetting thixotropic synthetic resin 3 and 4 is applied thereon twice. There is a deep exterior with a painted undercoat.

This configuration has the drawbacks that the exterior is thick, the external dimensions vary widely, the thixotropic thermosetting synthetic resin has large mechanical shrinkage stress, and is likely to cause leakage current defects.

The present invention eliminates the thixotropic thermosetting synthetic resin layer that causes large mechanical shrinkage stress, and instead maintains a constant thickness of the exterior part and retains a permeable low-viscosity thermosetting resin, which causes large mechanical stress on the internal capacitor element. SIO2, which can be made smaller and reduce the number of dips without giving shrinkage stress,
We would like to provide a solid electrolytic capacitor that uses an inorganic adhesive mainly composed of an inorganic oxide such as Al203ZrO2, holds a large amount of a permeable, low-viscosity thermosetting resin with excellent moisture resistance, and is heat-cured to form an exterior. That is.

That is, in the present invention, as shown in FIG. 2, a dielectric layer is formed by anodizing the valve metal, and a semiconductor layer such as manganese dioxide, a cathode layer such as colloidal graphite, and a silver paste metal layer are coated thereon. An inorganic adhesive that can form an inorganic porous layer on the capacitor element 5 obtained by welding the anode lead to the anode internal lead and soldering the cathode lead to the metal layer, and has a coefficient of thermal expansion of 0.8X10-5 to 1. 4X10-
It is small, such as 5cm/cm/℃, and has a specific resistance of 106~
1012 to form an inorganic adhesive layer 6 that holds a stable permeable, low viscosity thermosetting synthetic resin, and then 10 to 2
00C. P. A resin exterior is formed by retaining a large amount of thermosetting synthetic resin γ and curing it by heating.

A detailed cross-sectional view of the exterior is shown in FIG.

Next, examples of the present invention will be shown.

A capacitor element 5 is manufactured by anodizing a sintered body of tantalum powder to form a dielectric layer, covering it with a manganese dioxide layer, a colloidal graphite layer, and a silver paste layer, welding an anode lead, and soldering a cathode lead. After dipping in inorganic adhesive 6 and pulling it up 1
Semi-cured at 50°C for 30 minutes, then cured at about 100°C. P
The permeable, low-viscosity epoxy resin 7 was immersed in the resin to maintain sufficient impregnation, then pulled up and cured by heating at 100° C. for 30 minutes.

The results of a comparison of the characteristics of the solid electrolytic capacitor thus obtained and the conventional solid electrolytic capacitor are shown in Table 1, and the results of the moisture resistance test are shown in FIG. 4.

FIG. 5 shows the viscosity range of the permeable, low-viscosity thermosetting synthetic resin when the capacitance change rate was small and favorable as a result of the 500-hour humidity test.

Table 2 shows the difference in dimensions in terms of length l and width d, and Table 3 shows the number of leakage current defects after packaging.

As is clear from the above results, although the solid electrolytic capacitor of the present invention reduces the number of dips, its moisture resistance is improved and leakage current defects are reduced, albeit slightly.

Furthermore, despite the miniaturization, the inorganic adhesive does not have a very high viscosity and does not cause dripping, which reduces external defects.

Regarding the improvement of moisture resistance, materials with excellent moisture resistance such as permeable low-viscosity thermosetting synthetic resins are retained in large quantities in the inorganic porous retention layer compared to those using the conventional undercoat method. This is because it has a remarkable effect of penetrating into the remaining porous voids, eliminating the air, and preventing the generation of voids and pinholes.

In addition, the reduction in leakage current defects is achieved by using inorganic adhesives mainly made of oxides such as Si, Al, and Zr, which are chemically stable and have very low mechanical shrinkage during curing and thermal expansion coefficient during heating. This seems to be due to the use of drugs.

As seen in the examples, it is clear that the time required for the packaging process can be easily shortened because the number of dips is reduced as well as the size is reduced.

Furthermore, since there is no need to use a thixotropic thermosetting resin which has a short pot life, it is also advantageous from the viewpoint of effective utilization of the resin.

As described above, the present invention has many advantages and is attracting attention as being most suitable for the exterior of solid electrolytic capacitors for consumer appliances which require an inexpensive exterior, and its industrial value is extremely large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a solid electrolytic capacitor with an exterior combined with an undercoat, which has been widely used in the past. Figure 2 is a cross-sectional view of an embodiment of the solid electrolytic capacitor of the present invention. Figure 3 is the exterior of the solid electrolytic capacitor shown in Figure 2. Fig. 4 is a characteristic diagram showing the capacitance change rate in the moisture resistance test of the solid electrolytic capacitor obtained by the same example and the conventional solid electrolytic capacitor, Fig. 5 is the osmotic low viscosity thermal FIG. 2 is a characteristic diagram showing the relationship between the viscosity of a curable resin and the rate of change in capacitance during a 500-hour humidity test of a product. 5... Capacitor element, 6... Inorganic adhesive layer, 7
...Permeable low viscosity thermosetting synthetic resin.

Claims (1)

[Claims] 1 A dielectric layer, a semiconductor layer, and a metal layer are formed by anodic oxidation on an anode body made of a valve metal, and an anode lead,
A solid electrolytic capacitor characterized in that a porous inorganic adhesive layer is formed around the outer periphery of a capacitor element to which a cathode lead is connected, and a permeable low-viscosity thermosetting resin is held in this inorganic adhesive layer and cured. .