Abstract: A circuit board includes an insulating layer including first and second insulator films, a first wiring layer embedded in the first insulator film and including pads and first wiring patterns exposed from the first insulator film, and a second wiring layer including second wiring patterns formed on the second insulator film and via wirings penetrating the insulating layer and electrically connecting the second wiring patterns to the first wiring layer. The first insulator film is made of a reinforcement-free resin that includes no reinforcing member. The second insulator film is made of a reinforcing member impregnated with a resin.

Abstract: An electronic device includes a first wiring substrate including a component mounting area, a second wiring substrate stacked on the first wiring substrate, in which an opening portion is provided in a part corresponding to the component mounting area, and connected to the first wiring substrate via solder bumps which are arranged on a periphery of the component mounting area, a frame-like resin dam layer formed between the solder bumps on the periphery of the component mounting area, and surrounding the component mounting area, and an electronic component mounted on the component mounting area of the first wiring substrate, wherein a sealing resin is filled between the first wiring substrate and the second wiring substrate such that the component mounting area is formed as a resin non-forming area by the resin dam layer.

Abstract: A conductive ball mounting method of the present invention, includes a step of, arranging a mask in which an opening portion is provided, on a substrate including a connection pad, arranging a conductive ball on the connection pad through the opening portion of the mask by supplying the conductive ball onto the mask, separating the substrate and the mask, in the step, an extra conductive ball left on the mask drops through the opening portion of the mask, thereby a surplus ball is mounted on the substrate, and removing the surplus ball on the substrate by making the surplus ball adhere onto an adhering head.