Fabrication methodology for micro cross-flow heat exchangers based on diamond-machined copper foils is presented. Eighty micrometers deep trapezoidal flow channels were cut parallel into foils which are 127 micrometers thick. The foils were vacuum diffusion bonded to form the micro heat exchangers. Hydraulic resistance and thermal performance of the micro heat exchanger were evaluated experimentally in a water to water test apparatus. About 2.64kW of energy was transferred in a cubical heat transfer volume of 1.64cm/sup 3/ with a log-mean- temperature-difference of about 36K. This corresponds to a volumetric heat transfer coefficient of more than 44MW/m/sup 3/-K. The potential applications for the micro heat exchanger are seen in areas where high transfer power are required with little weight and volumes such as aviation, aerospace and microelectronics cooling.