We report a micro heat exchanger microfabricated from a bulk aluminium alloy substrate. The device is comprised of two 18 cm long microchannels, one on each side of an aluminium chip, capped on both sides with a thin self-adhesive polymer film. In spite of a cheap and facile fabrication method, initial experiments with the device show promising results. Area densities from 25000 m-1 to 45000 m-1 have been achieved. Compared to our previous work on aluminium microfluidic devices produced with a similar technology but from a different, less pure alloy, in this study the etched surfaces are significantly smoother, and present less photoresist delamination.