Multi-substrate circuit assembly

A circuit assembly comprising:

• a casing comprising first and second casing members;
• a ceramic substrate having a first surface and a periphery defining a lateral surface surrounding the first surface, the ceramic substrate having a second surface oppositely-disposed from the first surface and in thermal contact with the first casing member of the casing;
• a power integrated circuit chip on the first surface of the ceramic substrate, the power integrated circuit chip dissipating more than five watts;
• an organic substrate comprising at least one circuit component on a first surface thereof and a periphery defining a lateral surface surrounding the first surface, a portion of the lateral surface of the organic substrate abutting and contacting a portion of the lateral surface of the ceramic substrate so as to define an interface therebetween, the thickness of the ceramic substrate in a direction perpendicular to the first surface thereof being shorter than a length of the first surface thereof in a direction perpendicular to the interface, the organic substrate having a coefficient of thermal conductivity that is lower than the coefficient of thermal conductivity of the ceramic substrate;
• and
• at least one conductor common to both the ceramic and organic substrates so as to physically connect the organic and substrates together, the conductor bridging the interface between the ceramic and organic substrates;
• a first heatsink pedestal defined by the second casing member and in thermal contact with a surface of the power integrated circuit chip on the ceramic substrate;
• and
• a second heatsink pedestal defined by the second casing member and in thermal contact with a surface of the circuit component on the organic substrate.