Abstract: A module device on a first substrate includes a power module, a housing, a pair of locking structures. The housing covers the power module. The locking structures are installed on a pair of opposite sides of the housing, and the locking structure includes a main body, a locking ring, a pair of ribs and anchoring portions. The locking ring extends from a side toward an inner side of the main body, and is a double-ring structure, which includes an inner and an outer ring. A first side of the outer ring is connected to the main body, a second side of the outer ring is connected to the inner ring. The ribs extend along a normal direction of the top surface of the main body. The anchoring portions are disposed at the end of the ribs, and an extending direction is perpendicular to an extending direction of the rib.