PURPOSE: To avoid dielectric breakdown without increasing an insulation thickness by levelling a lower conductive layer on which a conductive layer is further formed.
CONSTITUTION: A lower conductive layer 2 of a required pattern made of conductive copper paste is formed on a board 1. The upper surface of the lower conductive layer 2 is pressed by a roller press 3 or a flat plate to be levelled. At that time, the pressing force of the roller press 3 for levelling the lower conductive layer 2 is, for instance, 5-10kgw. The thickness of the unevenness of the lower conductive layer 2 after levelling is, for instance, smaller than the thickness of the cloth of a screen for screen printing. The lower conductive layer 2 is completed by baking. Then an intermediate insulating layer 4 made of insulating paste is formed on the lower conductive layer. After that, an upper conductive layer 5 of a required pattern is formed on the intermediate insulating layer 4.