Multilayer resin substrate, and method of manufacturing multilayer resin substrate

A multilayer resin substrate comprising:

• a base material including:
• a first resin layer including:
• a first surface;
• and
• a second surface opposed to the first surface;
• and
• a second resin layer including:
• a third surface;
• and
• a fourth surface opposed to the third surface;
• a first conductor pattern on the first surface of the first resin layer;
• a second conductor pattern between the second surface of the first resin layer and the third surface of the second resin layer;
• an interlayer connection conductor in at least the first resin layer;
• a first opening portion in the first resin layer;
• and
• a second opening portion in the first resin layer;
• wherein
• the first resin layer and the second resin layer are stacked on each other in a stacking direction;
• the base material includes a fifth surface including a concave portion;
• the fifth surface includes the first surface and is located on an outermost surface of the base material;
• the concave portion includes the first opening portion;
• the first opening portion is located on each of the first surface and the second surface;
• an area of the first opening portion on the first surface is larger than an area of the first opening portion on the second surface, when viewed in the stacking direction;
• the interlayer connection conductor is provided by a metal material in the second opening portion;
• the second opening portion is located on each of the first surface and the second surface;
• an area of the second opening portion on the first surface is smaller than an area of the second opening portion on the second surface, when viewed in the stacking direction;
• the first opening portion includes an end portion on the first surface;
• and
• the end portion is not in contact with the first conductor pattern.