An electronic component unit including a metallic member and an electronic component, such as a semiconductor element, mounted on the metallic member is encapsulated with molding resin such as epoxy resin, thereby forming an electronic package. The electronic component unit is covered with primer made of a material such as resin to increase an adhesive force of the molding resin to the electronic component unit. A glass transition temperature of both of the molding resin and the primer is set to a temperature higher than 200.degree. C. to keep the adhesive force unchanged at least up to the ambient temperature of 200.degree. C. and to secure a reliability of the electronic package. A metallic lead wire connected to the electronic component may be encapsulated together with the electronic component unit. An entire surface of the electronic component unit may be covered with the primer to further improve the adhesive force.