Numerous studies have concluded that improved high power density cooling methods are required for future avionics due to the trends in increasing heat dissipation, device miniaturization and higher packaging density. A high flux heat exchanger (HFHE) has been designed to optimally meet the thermal performance and envelope requirements selected as appropriate for future avionics, at a minimum impact to the host aircraft. This paper summarizes the design and fabrication of the prototype HFHE. The HFHE has been successfully performance tested with results included in Part II of this paper.Design objectives for the HFHE included a local heat flux capability of 100 W/cm2 (at 20 one-cm2 sites), a total SEM-E size module heat load of 2,000 W, and a maximum device junction temperature of 90°C with PAO coolant at not less than 0°C. An aluminum frame coldplate with a laminated copper heat transfer insert was designed and fabricated which met all of these performance requirements. The coldplate uses multiple-plate/multiple-jet impingement cooling in a stack of thin photo-etched and diffusion bonded laminations for extremely low coldplate-to-coolant thermal resistance.