To prevent the generation of leak phenomenon while lowering connecting resistance, enlarging current capacity at the time of connection and stabilizing connection by having a mean grain size at a specified value, and using metal balls having an aspect ratio less than a specified value and a CV value at a specified value or less and coated with a noble metal.

Metal balls having a mean grain size at 3-50 μm are used, and an aspect ratio of the metal ball is set at a value less than 1.5 and a CV value thereof is set at 10% or less. As a noble metal, Au and Pd are desirably used. This metal ball can be obtained by observing 300 desirable metal balls with an electron microscope, or dispersing the metal balls in the dispersion medium and classifying the metal balls on the basis of the falling speed thereof. In this case, concentration of the metal balls is lowered so as to prevent the generation of a phenomenon that the metal grains are adhered to each other. A surface of the metal ball is provided with a resin layer as an insulating layer so as to prevent the generation of short-circuit between electrodes due to a contact of the conductive fine grains with each other.