An electrical connector assembly is disclosed having an electrical connector positionable over an opening in a wall to form an airtight seal and an electrical connection between the inside and an outside of the wall. The electrical connector has an insulating board made of insulating material. The insulating board includes a first surface facing the wall, a second surface on the side opposite to the first surface, and a side surface extending from a peripheral edge of the first surface to a peripheral edge of the second surface. An electrical connection portion made of electrically conductive material extends from the first surface through the insulating board to the second surface to electrically connect the first surface to the second surface. A surface roughness region provided at the peripheral edge of the first surface.