GB2123610A - Casing of solid electrolyte capacitor - Google Patents

Abstract

A solid electrolyte chip capacitor having anode and cathode terminals 1, 2 of L-shaped cross-section disposed at opposite ends for enabling application to a printed circuit board, and a flat smooth resin plate 7 fixed to the top surface of encapsulating resin 8 for facilitating the use of "vacuum chuck" handling in automatic assembling of printed circuit structures. The plate 7 may cover only part of the resin surface. <IMAGE>

Description

SPECIFICATION Solid electrolyte capacitor This invention relates to a solid electrolyte capacitor designed for application to printed circuit boards, and especially to an improved chip capacitor for facilitating automatic assembling of printed circuit structures.

Many kinds of such capacitors have been proposed for application to printed circuit boards.

Such capacitors have their anode and cathode terminals on the bottom surface so as to enable direct contact with corresponding conductors on the printed circuit board. Examples of this type of capacitor are discloased in United States Patent Nos. 3,855,505 and 4,247,883.

Recently, automatic processes have been developed for assembling'printed circuit structures and a so-called "vacuum chuck" technique has been introduced for conveniently transferring capacitors to specified locations on the board. The "vacuum chuck" is a device for attracting an object to a sucking port thereof, which is connected to a reduced pressure or "vacuum" source, to transfer it to anywhere desired. For successfully effecting a "vacuum chucking" operation, the attracted surface of the capacitor, which is generally the top surface thereof, must be flat and smooth.

However, prior art capacitors are generally unsuitable for this purpose since they have been manufactured without taking this matter into account. Although the capacitor of the abovementioned U.S. Patent No. 4,247,883 is shown as having a "flat and smooth" top surface, such resin-filled surface in practice includes small undulations which may result in insufficient chucking. Though a smooth surface can be obtained by resin-moulding the capacitor with a metal mould, the cost of manufacture rises considerably.

Another United States Patent No. 3,550,228 discloses a chip capacitor having a cap whose top surface is flat and smooth. Although this capacitor seems suitable for use with a "vacuum chuck", it is complicated in structure and therefore very expensive.

Therefore, an object of this invention is to provide an improved solid electrolyte chip capacitor having a flat and smooth top surface for perfect vacuum chucking, and a simple structure for avoiding unwanted increase of manufacturing costs.

According to this invention there is provided a capacitor comprising a solid electrolyte capacitor element, two terminal members having L-shaped cross-sections and connected respectively to the anode and cathode of said capacitor element, said members being arranged to have first portions thereof facing each other and second portions thereof in a common plane underneath said capacitor element, an electrically insulating synthetic resin mass filling the space between said two terminal members to embed said capacitor element therein and a thin synthetic resin plate adhered to the top surface of said resin mass.

In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawing, in which; Figure 1 is a perspective view of an embodiment of a capacitor according to this invention; Figure 2 is a sectional side view of the embodiment of Figure 1; and Figure 3 is a sectional side view of another embodiment of a capacitor according to this invention.

Throughout the drawings, like reference numerals are given to corresponding structural components.

Referring to Figures 1 and 2, a capacitor includes a pair of channel type metal terminal members 1 and 2 having L-shaped cross-section.

The terminal members 1 and 2 are arranged, as shown, to have their vertical portions facing towards each other and their horizontal portions in a common plane. An anode conductor 4 of a capacitor element 3 is welded to the terminal member 1 and a cathode layer 5 of the element 3 is bonded to the terminal member 2 with solder or electrically conducting adhesive 6. The capacitor element 3 is embedded in insulating synthetic resin 8 filling a space between the two terminal members 1 and 2, and a thin synthetic resin plate 7 is adhered to the top surface of the resin 8.

The terminal members 1 and 2 may be made from a solderable metal plate, such as of copper, nickel or nickel silver, or a suitable metal plate plated with solderable metal, such as solder, tin or gold. The capacitor element 3 may be prepared in conventionai manner. For example, suitable powdered valve metal, preferably tantalum, is press-formed and sintered to form an anode body, and an oxide layer, a semiconductor layer and a cathode layer are sequentially deposited in this order on the anode body. "Valve metal" is a metal such as tantalum, aluminium, zirconium, titanium, niobium or the like, which exhibits "valve action", that is, unidirectional electric conductivity between the metal and its oxide coating.The resin 8 may be selected from suitable electrically insulating air-hardening, radiation hardening or thermo-hardening adhesive resins, such as epoxy resin. The resin plate 7 may preferably be made of polyimide resin, polyethylene fluoride resin or glass-filled epoxy resin. The resin plate 7 is preferably adhered to the resin surface by the adhesive force of the resin 8 itself before it cures, although it may instead be adhered with a separate adhesive agent after curing of the resin 8. The thickness of the plate 7 can be very small, such as 0.2 millimetre, for example, so long as any possible undulation of the surface of the resin 8 does not appear on the surface of the plate 7.

In Figure 3, the resin plate 7 covers only a part of the surface of the resin 8. The shape of the plate 7 may be rectangular; but alternatively any other suitable shape may be substituted.

Capacitors in accordance with this invention can be manufactured efficiently, in similar manner to that shown in the aforementioned U.S. Patent No. 4,247,883, by arranging a pair of long electrode channels having L-shaped crosssections in parallel, connecting a plurality of capacitor elements to both channels to form a ladder-like structure, pouring hardening resin between the channels to embed'the capacitor elements therein, putting a thin plastics strip on the top surface of the resin to adhere it thereto and, after curing of the resin, separating the discrete capacitors by sawing.

As described above, the capacitor of this invention has a simple structure and can be manufactured readily at low cost, while keeping its top surface highly flat and smooth.

Claims (3)

Claims

1. A capacitor comprising a solid electrolyte capacitor element, two terminal members having L-shaped cross-sections and connected respectively to the anode and cathode of said capacitor element, said members being arranged to have first portions thereof facing each other and second portions thereof in a common plane underneath said capacitor element, an electrically insulating synthetic resin mass filling the space between said two terminal members to embed said capacitor element therein, and a thin synthetic resin plate adhered to the top surface of said resin mass.

2. A capacitor according to claim 1, wherein said synthetic resin plate is sized and shaped to cover only a part of said top surface of the resin mass.

3. A capacitor substantialiy as herein described with reference to and as illustrated in Figures 1 and 2 or Figure 3 of the accompanying drawing.