Isothermal heat sink with converging, diverging channels

A fluid-cooled electronic apparatus, comprising:

• an electronic device;
• a heat sink member with a surface for making thermal contact with said electronic device;
• wherein said heat sink member has a plurality of generally parallel channels for carrying coolant fluid, said plurality of channels comprising a first group of channels and a second group of channels, said first group of channels and said second group of channels being positioned generally alternately across the member so that coolant flow alternates direction across said member;
• and
• wherein at least one channel of said first group of channels and said second group of channels has a channel cross-section that varies over a length thereof to enhance a heat transfer coefficient of said coolant fluid within said at least one channel at a selected section of said at least one channel and thereby produce a more uniform temperature at said surface of said heat sink member when making thermal contact with said electronic device.