Capacitor apparatus incorporating fuse

Abstract: A capacitor apparatus incorporating a fuse comprises: a capacitor device (1) having a first electrode and a second electrode; a fuse (2) whose one end is connected to said first electrode; a first lead terminal (5) connected to the other end of said fuse (2); a second lead terminal (4) connected to said second electrode; and resin (3) in which said capacitor device (1), fuse (2), and a part of said first and second lead terminals (4,5) are molded. Both ends (2a,2b) of said fuse are wide and a central portion thereof (2c) is narrow. According to such a feature, fuming and ignition of the capacitor device due to an excessive current therethrough can be prevented without fail.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor apparatus, and more particularly, to a capacitor apparatus incorporating a fuse. 2. Description of the Prior Art A tantalum capacitor apparatus has conventionally been used where a fuse is incorporated to prevent fuming and ignition of the tantalum capacitor due to an excessive electric current and to prevent a peripheral circuit from catching fire from the tantalum capacitor apparatus . A capacitor apparatus of this type is constructed by molding a capacitor device and a fuse in resin. A plus electrode of the capacitor device is connected to a first lead terminal. A minus electrode thereof is connected to a second lead terminal through the fuse. The fuse employed for the capacitor apparatus is either a cylindrical type with a diameter  of 0.12mm as shown in Fig. 1 or a type with a width w of from 0.5mm to 1.0mm and a thickness t of from 0.05mm to 0.07mm as shown in Fig. 2. In the above-described conventional capacitor apparatus having a fuse where a cylindrical or band-shaped fuse is used, it takes a long time for the fuse to melt when an excessive current flows therethrough, so that there is still a possibility that fuming and ignition of the capacitor apparatus occur. EP-A-0 306 809 discloses a capacitor apparatus comprising a capacitor device having a first electrode and a second electrode; a fuse whose one end is connected to said first electrode; a first lead terminal connected to the other end of said fuse; a second lead terminal connected to said second electrode; a silicone or bubbled silicone resin applied to a periphery of said fuse, and a epoxy resin in which said capacitor device, fuse, silicone and a part of said first and second lead terminal are molded. IBM TECHNICAL DISCLOSURE BULLETIN, vol. 25, no. 8, January 1983, page 4081: J.J.BUTERA ET AL.: "OVERCURRENT PROTECTION FOR ALUMINIUM ELECTROLYTIC CAPACITORS" discloses an aluminium electrolytic capacitor with a fuse as integral part of the positive terminal. The fuse has a necked area that will open when a predetermined overcurrent flows and may be encapsulated in silicone or other suitable material to contain arcing. SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitor apparatus incorporating a fuse where the fuse immediately melts when an excessive current flows therethrough and where fuming and ignition of the capacitor can sufficiently be prevented. In accordance with the object, a capacitor apparatus according to the present invention is provided as defined in appended claim 1. BRIEF DESCRIPTION OF THE DRAWINGS This and other objects and features of this invention will become clear from the following description taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which: Fig. 1 is a perspective view of a fuse employed for a conventional capacitor apparatus incorporating a fuse; Fig. 2 is a perspective view of another fuse employed for a conventional capacitor apparatus; Fig. 3 is a plan view of a fuse employed for the present invention; Fig. 4 is a cross-sectional view of a part of a capacitor apparatus which is an embodiment of the present invention; and Fig. 5 is a structural and cross-sectional view of a tantalum capacitor employed for the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In this embodiment, as shown in Fig. 4, one end of a fuse 2 is connected to a minus electrode which forms a periphery of the capacitor device 1. The other end of the fuse is connected to a lead terminal 5 which is provided separately from a lead terminal 4 connected to a plus electrode of a capacitor device 1. While both of end portions 2a and 2b of the fuse 2 are comparatively wide as shown in Fig. 3, a central portion 2c thereof is very thin; a width W1 thereof is 0.01mm, within a range P. Because of this, current density is high at the central portion 2c, so that the fuse 2 easily melts. The wide end portions 2a and 2b enable easy connection and reduce resistance at connection portions. The end portion 2a is connected to the lead terminal 5. The end portion 2b is connected to the minus electrode of the capacitor device 1. The fuse 2 is made of an alloy of lead, tin, and silver. A melting point thereof is comparatively high. This characteristic is advantageous in bringing a current carrying capacity of the fuse 2 as close to that at which the capacitor device 1 is broken as possible. The fuse 2 is of thin, plate-like shape. The shape and that the fuse 2 is made of the above-described alloy provide flexibility to the fuse 2. Hence, when there is a difference in height between two connection portions as shown in Fig. 4, the fuse 2 can be bent into an appropriate form to be connected. All the above-described members of the capacitor apparatus other than a part of the lead terminals 4 and 5 are molded in epoxy resin 3. Silicone resin 6 is applied to a periphery of the fuse 2. The silicone resin 6 is previously applied to the fuse 2 before the members are molded in the epoxy resin 3. The silicone resin 6 is applied so as to surround at least the central portion 2c. To apply the resin 6 as described above makes melting of the fuse 2 easier. That is, at a temperature at which the central portion 2c of the fuse 2 melts, the resin 6 melts and a volume thereof decreases to decrease a space occupied by the resin 6. Consequently, the melted fuse is more easily dispersed, which helps the melting of the fuse 2. As described above, according to the present invention, since the thin portion provided on the central portion 2c immediately melts when a current value of the current flowing therethrough becomes a predetermined excessive current value, fuming and ignition of the capacitor device can be prevented without fail. Fig. 5 schematically shows a structure of a tantalum capacitor which is an embodiment of the capacitor device 1. The tantalum capacitor consists of, from the center to the periphery, tantalum (Ta) constituting the plus electrode, tantalum pentoxide (Ta 2 O 5 ) forming a dielectric layer, manganese dioxide (MnO 2 ), carbon (C), and silver (Ag). The layers of manganese dioxide, carbon, and silver constitute the minus electrode. The silver layer forms the periphery, to which the end portion 2a of the fuse 2 is connected. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims: A capacitor apparatus comprising a capacitor device (1) having a first electrode and a second electrode; a fuse (2) whose one end is connected to said first electrode; a first lead terminal (5) connected to the other end of said fuse (2) ; a second lead terminal (4) connected to said second electrode; a first resin (6) applied to a periphery of said fuse (2), and a second resin (3) in which said capacitor device, fuse, first resin and a part of said first and second lead terminal are molded, characterized in that a fuse (2) having wide ends (2a,2b) and a narrow central portion (2c) is used as said fuse (2) and that the first resin (6) is applied so as to surround at least the narrow central portion (2c) of the fuse (2) and the first resin (6) melts at a temperature at which the narrow central portion (2c) melts. A capacitor apparatus according to claim 1, wherein said fuse (2) is made of an alloy of lead, tin, and silver. A capacitor apparatus according to claim 1, wherein said capacitor device (1) is a tantalum capacitor where a plus electrode is provided in a center thereof and a periphery thereof is a minus electrode, and said one end of said fuse (2) is connected to said minus electrode. A capacitor apparatus according to claim 1, wherein said fuse (2) is of thin, plate-like shape and has flexibility.

Inventors: KURIYAMA CHOUJIROU C O ROHM CO, TANAKA EISAKU C O ROHM CO LTD, KURIYAMA, CHOUJIROU, C/O ROHM CO., LTD., TANAKA, EISAKU, C/O ROHM CO., LTD.
Applicants: ROHM CO LTD, ROHM CO., LTD.
Application year: 1991
Main classification: H01G9
IPC codes: H01G9, H01H85, H01G2