Multilayered metallised film capacitor mfg. method - uses local de-metallisations film of sections of dielectric film wound continuously on reels to trim capacitance and to form inactive layers

摘要

The method is used for mfg. multifilm capacitors in which the electrodes are attached by a flow solder technique. Edge sections of metallised film are removed from alternate sides of a strip (45) of metallised dielectric to allow correct connections of electrodes and their external terminal. For at least one pair of top and bottom layers, central sections of metallised film are also removed to electrically isolate them from the electrodes. This prevents shorting of the capacitor in the event of local shorting caused by damage to the end faces of the capacitor. Metallised sections are removed by laser cutting of ribbons of material whilst being wound into large diameter reels. Individual capacitors are then cut from the cylindrical block (41). By selecting the laser wavelength such that it is only absorbed in the metal, and by adjusting the laser power, sections of several layers deep can be removed and the capacitance trimmed to the desired value.