Encapsulated surface mounting electronic part

An encapsulated surface-mounting electronic part comprising:

• an electronic part element mounted on a resin wiring substrate, said resin wiring substrate having upper and lower surfaces;
• a cover member bonded to said resin wiring substrate so as to cover said electronic part element thereby defining an encapsulation region, said encapsulation region housing said electronic part element and forming an internal cavity;
• an electrically conductive through groove in said resin wiring substrate, said electrically conductive through groove having an interior surface and circumferential peripheries defined by the upper and lower surfaces of said resin wiring substrate;
• a plating layer formed on the interior surface of said electrically conductive through groove, said plating layer further comprising metal layers including at least a Cu layer and an Au layer;
• conductors on the upper and lower surfaces of said wiring substrate connected to the circumferential peripheries of said electrically conductive through groove;
• wherein said Cu layer is also formed on said conductors;
• and
• wherein said metal layers other than said Cu layer are not formed on the conductor on said upper surface of said resin wiring substrate.