Metallized capacitor foil - with aluminium edge strip along selvedge transformed to high resistance fringe

摘要

A foil of insulating material (paper, vinyl acetate, polystyrene, polyethylene, polypropylene or polyamide) for capacitors is coated with a metal film except for a zone along the selvedge. The edge strip of metal (specif. aluminium) has a thickness of =250A degrees and is transformed into high-resistance cpd. by an electrochemical, chemical or thermal process in presence of O2 and/or water. The method eliminates any marginal discharge which leads to the destruction of the capacitor. The edge strip is mechanically stronger than pure aluminium layers of under 100 mu thickness.