Semiconductor module having a solder-bonded cooling unit

A semiconductor module comprising:

• an insulated circuit substrate that includes a substrate, a circuit layer arranged on a front surface of the substrate, and a metal layer arranged on a back surface of the substrate;
• a semiconductor element that is electrically connected to the circuit layer;
• a cooling unit that includes a ceiling board with a uniform thickness and a flat surface bonded to the metal layer, a bottom board arranged opposite the ceiling board, a side wall that connects a periphery of the ceiling board and a periphery of the bottom board, and a fin that connects the ceiling board and the bottom board, where the thickness of the ceiling board is greater than or equal to 0.5 mm and less than or equal to 2.0 mm and a total thickness of the ceiling board and the bottom board is greater than or equal to 3 mm and less than or equal to 4 mm;
• and
• a solder bonding layer that bonds an entire back surface of the metal layer to the ceiling board, the solder bonding layer having a functional melt temperature of less than or equal to 350° C., said solder bonding layer not melting below 200° C.;
• wherein a thickness of the bottom board is greater than or equal to two times the thickness of the ceiling board and less than three times the thickness of the ceiling board.