High-performance heat exchanger with calibrated bypass

A heat exchanger assembly includes a cooling plate with at least one outer heat transfer surface adapted for thermal contact with one or more heat-generating substrates. A fluid flow path extends from an inlet port to an outlet port, with a plurality of cooling zones spaced apart along the fluid flow path, each cooling zone including a heat transfer element such as a corrugated fin sheet in contact with the inner surface of the first plate wall. Manifold spaces are defined proximate to the inlet and outlet ports, and between adjacent cooling zones. One or more bypass flow passages are provided between upstream and downstream ends of at least one cooling zone, to divert a portion of the heat transfer fluid from flowing through the cooling zone. The volume of fluid flow bypassing one or more cooling zones is calibrated to improve temperature uniformity of the heat-generating substrates.