JPS629207B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to leadless aluminum electrolytic capacitors. Recent advances in electronic circuits and systems have created a need for the development of leadless capacitors that have the maximum capacitance per unit volume by minimizing the number of external terminals and have an external shape that allows automatic mounting on circuit boards. . Conventionally, tantalum solid electrolytic capacitors and ceramic capacitors have been put into practical use as capacitors with the above-mentioned characteristics, but in the case of aluminum electrolytic capacitors in which a paste-like driving electrolyte is soaked into the capacitor element, Since the driving electrolyte adheres to the surface of the capacitor element, it is extremely difficult to mold it with synthetic resin.
In addition, high heat of 150 to 200 degrees Celsius is directly applied to the capacitor element during molding, which causes deterioration of the dielectric oxide film and permeability of the exterior resin, which causes permeation loss of the driving electrolyte and makes the electrical characteristics of the capacitor unstable. Become. Furthermore, since aluminum electrolytic capacitors are impregnated with driving electrolyte, if a solderable metal such as a tantalum solid electrolytic capacitor is used as a terminal, it will corrode and cannot be used. Therefore, in order to convert an aluminum electrolytic capacitor into a leadless type capacitor, the exterior structure and terminal derivation remain issues. Also, recently opened in 1988.
12341, a leadless type in which a capacitor element is housed in an insulating cylinder, a terminal cap is fitted into openings at both ends of the insulating cylinder via an elastic member, and a part of the terminal cap is caulked. Aluminum electrolytic capacitors have also been proposed, but the assembly of the capacitors is complicated and time-consuming, which increases costs.In addition, if the terminal caps are made of a valve metal such as aluminum to prevent corrosion from the driving electrolyte, it may cause damage to the board. If the terminal cap is made of a solderable metal such as copper, it will be corroded by the drive electrolyte, and in the worst case, the connection between the terminal cap and the internal terminal wire may peel off and break. There are drawbacks. There is also a proposal by the present inventor as in Japanese Utility Model Application Publication No. 56-121250, in which a terminal cap made of clad material is attached to the outside of the opening of the container by crimping, fitting, or welding. As a result, the terminal cap attachment may become loose due to solder heating during mounting on the board, vibration or heat shock applied to the device after mounting, and the sealing performance deteriorates, and in extreme cases, the terminal cap may become detached from the container opening. There were some drawbacks. The present invention has been made in view of the above-mentioned circumstances, and is a pipe made of tetrafluoroethylene-hexafluoropropylene copolymer, in which a capacitor element impregnated with a driving electrolyte is provided with grooves in the length direction from both ends. The thickness of the outer circumferential ring of a terminal cap made of a cladding material of a solderable metal and a valve metal, to which the electrode lead wire led out from the capacitor element is connected, is that of the total length of the container. 1/4 each
Capacitors with a depth equal to or slightly thicker than the inner groove with a length of ~2/5 are fitted into the inner groove and sealed, allowing automatic mounting and soldering to the board without corrosion. It is an object of the present invention to provide a leadless aluminum electrolytic capacitor that is extremely easy to assemble, has good sealing properties, and has stable characteristics. An embodiment of the present invention will be described below with reference to the drawings. That is, as shown in FIG. 1, it is made of a pipe made of tetrafluoroethylene-hexafluoropropylene copolymer, and a middle groove 1 is provided from both ends in the length direction of the pipe thickness, and a partition wall 2 in the middle part connects the middle groove 1 to 2. In the hollow interior of the divided container 3, as shown in FIG. 2, an aluminum anode foil whose surface area has been expanded by roughening and a dielectric oxide film formed by anodization, and a separator made of paper or porous plastic film are placed. The capacitor element 4 is made of a laminate formed by laminating aluminum cathode foils or a wound body formed by winding these layers, and accommodates a capacitor element 4 impregnated with a driving electrolyte. The length of the inner groove 1 is set to be 1/4 to 2/5 of the total length of the container 3, respectively. Electrode lead wires 5 are led out from both positive and negative electrode foils to the capacitor element 4, and the electrode lead wires 5 are welded to terminal caps 6 that seal the openings at both ends of the container 3 and serve as external terminals. Connecting. The terminal cap 6 has a cylindrical shape with a bottom and is made of a clad material in which a solderable metal and a valve metal are bonded in a low-temperature solid state, and has an outer peripheral ring 7.
The outside, that is, the side to be soldered to the board, is Cu,
The inner side, that is, the side that contacts the driving electrolyte and connects the electrode lead wire 5, is made of a solderable metal such as Ni, Fe, or Sn, and a valve metal such as Al or Ti. The cladding material is, for example, Al--Cu,
This is a low-temperature solid phase welding of Al-Fe, Al-Ni, Ti-Ni, etc. Next, the outer circumferential ring 7 of the terminal cap 6 is press-fitted into the inner groove 1 of the container 3, and the openings at both ends of the container 3 are closed and hermetically sealed. In this case, in order to increase the fitting strength and improve the sealing performance, the thickness of the outer peripheral ring 7 of the terminal cap 6 is made equal to or somewhat thicker than the depth of the inner groove 1, and the outer ring 7 of the terminal cap 6 is press-fitted into the inner groove 1. It is also effective to interpose an adhesive such as silicone rubber or epoxy resin between the outer ring 7 of the terminal cap 6 and the inner groove 1. In addition, the tetrafluoroethylene-hexafluoropropylene copolymer that makes up the container 3 has excellent heat resistance, cold resistance, and chemical resistance, with a particularly high melting point of 250-290°C (depending on the copolymer composition). , because it has little deterioration during solder heating and also has good adhesion to metal.
The sealing performance between the outer ring 7 of the terminal cap 6 and the inner groove 1 is also good. As described above, the leadless aluminum electrolytic capacitor of the present invention has a terminal cap made of a cladding material of a solderable metal and a valve metal.
The outside part that is soldered to the board is made of solderable metal, and the inside part that comes into contact with the driving electrolyte is made of valve metal, so solderability is good and there is no corrosion. Also, when assembling the capacitor, use the terminal cap 6.
It is only necessary to make the thickness of the outer circumferential ring 7 equal to or slightly thicker than the depth of the inner groove and press fit into the inner groove 1, which is extremely easy and suitable for mass production. Furthermore, the length of the inner groove 1 is 1/4 of the total length of the container 3.
It is relatively long and has a large joint area of ~2/5, and because the peripheral ring 7 of the terminal cap 6 is press-fitted, good sealing performance and stable characteristics can be maintained. Next, Table 1 shows a comparison between the examples of the present invention, comparative examples, and conventional reference examples. Examples B, C, D,
E. Comparative Examples A and F were made by press-fitting the outer ring of a terminal cap made of clad material into the inner groove of a container with a diameter of 5.0 mm and a length of 9.0 mm made of tetrafluoroethylene-hexafluoropropylene copolymer. It is a leadless aluminum electrolytic capacitor with a rating of 16WV-4.7μF,
Reference example G is a leadless aluminum electrolytic capacitor with the same rating as disclosed in Japanese Utility Model Application No. 56-121250, in which terminal caps made of clad material are fitted around the outer periphery of both ends of a container of the same size made of polyphenylene oxide. 1, each of these samples was heated to 85℃,
Capacitance change rate and vibration test after applying rated voltage for 1000 hours in 95% humidity (vibration frequency 10-55Hz, full amplitude
1.5mm, sweep method 10-55-10Hz for 1 minute, and two
The figure shows the values of the dielectric loss tangent and leakage current after applying the dielectric material for 3 hours in each direction for 6 hours.

[Table] From Table 1, Examples B, C, D, and E are Comparative Examples A and F.
Compared to Reference Example G, both the capacitance change rate and the dielectric loss tangent and leakage current after the vibration test showed stable values.
Its stability is even more remarkable. Also, among the above samples, life test of Example C and Reference Example G (temperature 85°C, humidity 95%RH, rated voltage applied)
FIG. 3 shows the capacitance change rate, and FIG. 4 shows the change in dielectric loss tangent. From FIG. 3 and FIG. 4, it can be seen that Example C has better sealing performance than Reference Example G, has less change, and has a longer life. As detailed above, according to the present invention, a capacitor element impregnated with a driving electrolyte is placed in a container made of a tetrafluoroethylene-hexafluoropropylene copolymer pipe with grooves extending from both ends in the longitudinal direction. The thickness of the outer circumferential ring of the terminal cap made of a cladding material of a solderable metal and a valve metal, which houses the terminal cap and connects the electrode lead wire led out from the capacitor element, is as follows:
By fitting into and sealing the inner grooves, each having a length of 1/4 to 2/5 of the total length of the container with a depth equal to or slightly thicker, no corrosion occurs and no damage to the substrate is achieved. It is possible to provide a leadless aluminum electrolytic capacitor that can be soldered automatically and is extremely easy to assemble, and has good sealing performance, long life, and stable characteristics.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a container according to an embodiment of the present invention, FIG. 2 is a side sectional view showing a leadless aluminum electrolytic capacitor according to an embodiment of the present invention, and FIGS. 3 and 4 3 shows a comparison of characteristics in a life test between Example C of the present invention and conventional Reference Example G, and FIG. 3 is a curve diagram showing the capacitance change rate.
FIG. 4 is a curve diagram showing changes in dielectric loss tangent. 1... Middle groove, 2... Partition wall, 3... Container, 4...
Capacitor element, 5... Electrode lead wire, 6... Terminal cap, 7... Outer ring.

Claims (1)

[Claims] 1. A capacitor element impregnated with a driving electrolyte and from which an electrode lead wire is led out, a container consisting of a pipe of tetrafluoroethylene-hexafluoropropylene copolymer that houses the capacitor element, and the length of the pipe thickness of the container. A solder having a middle groove having a length of 1/4 to 2/5 of the total length of the container, which is divided into two by a partition wall in the middle part in the width direction, and an outer peripheral ring that connects the electrode lead wire and fits into the middle groove. A leadless terminal comprising a terminal cap made of a cladding material of an attachable metal and a valve metal, and the outer circumferential ring has a thickness equal to or slightly thicker than the depth of the inner groove and is press-fitted. Aluminum electrolytic capacitor.