Overmolded electronic module with underfilled surface-mount components

An overmolded electronic module comprising:

• a heatsink having at least one pedestal;
• a circuit board supported on the heatsink so that a first surface of the circuit board faces away from the heatsink and a second surface of the circuit board faces the heatsink;
• a surface-mount circuit device attached to the second surface of the circuit board with solder bump connections at a first surface thereof, the circuit device being spaced above the second surface of the circuit board by the solder bump connections so as to define a gap therebetween;
• a metal snap-fit retainer mechanically locked to the heatsink so as to enclose the circuit board with the heatsink, the retainer contacting the circuit board so as to bias the circuit device against the heatsink;
• an overmolded body encasing the circuit board and the circuit device with the heatsink to provide a moisture-impermeable seal around the circuit board and the circuit device, the overmolded body having an underfill portion that completely fills the gap between the circuit device and the circuit board so as to underfill the circuit device and encapsulate the solder bump connections, the overmolded body applying a compressive load to the circuit device;
• and
• a connector housing integrally formed in an external surface of the overmolded body, the connector housing comprising input/output pins that extend through the overmolded body and provide electrical connection to the circuit device.

A method of assembling an overmolded electronic module, the method comprising the steps of:

• providing a circuit board having a first surface, an oppositely-disposed second surface, and a surface-mount circuit device attached to the second surface of the circuit board with solder bump connections, the circuit device being spaced above the second surface of the circuit board by the solder bump connections so as to define a gap therebetween;
• supporting the circuit board on a heatsink that thermally contacting a surface of the circuit device oppositely-disposed from the circuit board;
• and
• overmolding the circuit board with an overmold material so as to form an overmolded body that encases the circuit board and the circuit device with the heatsink to provide a moisture-impermeable seal around the circuit board and the circuit device, the overmolded body having an underfill portion that completely underfills the circuit device and encapsulates the solder bump connections.