Importance

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Abstract

A solid electrolytic capacitor has an anode body (1) and an anode wire (2) and lead out connections (8, 3). In series with the connections and the body is a fusable link (6) formed of a composite of low melting point conductive plastics metal matrix. The fusable link (6) is in the form of a pad of this material. In a preferred form this material is made by compressing into sheets metal-coated polymer particles. The sheet is cut into pads and inserted into the capacitor assemblies to act as a combined thermal and electrical fuse. Preferably the pads are less than 1 mm thick and coated on both sides with solder and approximately 1 mm square. The pads can be reflow soldered between the anode and the lead frame or negative wire termination. Alternatively it can be reflow soldered between the anode wire and the positive wire termination. As the current reaches high level if a fault develops in the capacitor, the metal layer will melt and also melt the plastics. The metal will then disperse in the liquid plastics and on cooling will not re-establish conduction because it is no longer in the same physical form. Alternatively the fusible link comprises metal-coated polymer particles dispersed in a resin binder and applied as a conductive paste.

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First Claim