In an outer lead portion, outer lead wirings are provided on one surface of a base insulating layer and a plurality of metal substrates are provided on the opposite surface thereof. The plurality of metal substrates are provided with predetermined spacings therebetween. The outer lead wirings are not provided on the areas on the surface opposite to the areas on the other surface of the base insulating layer on which the slits are provided between the metal substrates. Metals such as stainless steel, copper or copper alloy can be used for the metal substrates. Coefficient of linear expansion of each metal substrate is preferably equal to that of the base insulating layer.