Mounting board and semiconductor device

A mounting board comprising:

• an insulating resin layer;
• an electrode pad on the insulating resin layer;
• and
• an insulating protective film covering the electrode pad and the insulating resin layer,
• wherein, in a plan view,
• the electrode pad includes a first side and a second side that run parallel in a first direction,
• the insulating protective film includes an opening including a first opening region and a second opening region that adjoin each other in the first direction, the first opening region lying over the electrode pad to expose a part of the electrode pad, the second opening region exposing a part of the insulating resin layer,
• the first opening region is defined by a third side and a fourth side that are between the first side and the second side in a second direction perpendicular to the first direction and run parallel in the first direction, and
• a maximum dimension of the second opening region in the second direction is greater than a distance between an end of the third side and an end of the fourth side at which the first opening region adjoins the second opening region.