Substrate unit

A substrate unit, comprising:

• a circuit board;
• a connector portion mounted on the circuit board;
• and
• a case that contains the circuit board;
• wherein the case comprises:
• a lower case having an accommodation section opened upward and accommodating the circuit board;
• an upper cover that covers the accommodation section of the lower case;
• and
• an aperture opened in a side wall of the case, allowing the connector portion to be seated therein;
• and
• wherein the upper cover comprises:
• a ceiling portion including an underside having a board opposing region that opposes the circuit board accommodated in the accommodation section and an outer region bounding a periphery of the board opposing region, the outer region does not oppose the circuit board;
• and
• guide grooves inclined from the board opposing region to the outer region, guide grooves having a water inlet that is flush with the underside of the ceiling portion and an end wall opposite the water inlet, the end wall being generally orthogonal to the underside of the ceiling portion so as to form a water droplet outlet, the water droplet outlet disposed on the outer region of the ceiling portion, the guide grooves guiding water droplets present on the board opposing region to the outer region of the ceiling portion to discharge the water droplets away from the circuit board.