RESIN MULTILAYER SUBSTRATE AND METHOD FOR MANUFACTURING RESIN MULTILAYER SUBSTRATE

A metal foil layer includes a metal foil layer upper main surface, a metal foil layer lower main surface with a surface roughness greater than that of the metal foil layer upper main surface, and a metal foil layer side surface that is a surface of the metal foil layer excluding the metal foil layer upper main surface and the metal foil layer lower main surface. The metal foil layer upper main surface is in contact with an upper resin layer. The metal foil layer lower main surface is in contact with a lower resin layer. A portion of a lower main surface of the upper resin layer and a portion of an upper main surface of the lower resin layer are in contact with each other to define a layer interface. In a cross section of the metal foil layer, the metal foil layer side surface includes an outer point and an inner point where the upper resin layer is in contact with the side surface, and the inner point is below the outer point and inward of the outer point.