Abstract: A solar collector device having a plurality of parallel collector tubes mounted between a pair of header members through which a heat carrying liquid flows. The collector tubes each have a plane surface exposed to the solar rays and extending laterally substantially equal to the maximum diameter of the respective tubes. The edges of adjacent tubes abut each other to form a substantially continuous planar collector surface. The tubes are moreover, made of a highly efficient conductor of thermal energy, namely a specialized copper alloy. A method of forming such tubes with planar surfaces for use in solar energy collectors is also disclosed.