The use of boron tri-bromide as a source precursor for low energy boron implantation is studied in this work. Details of gas delivery system, beam purity and running performance have been investigated for a 75keV molecular implant to give an equivalent boron energy of 5keV. The behavior of the Br during thermal processing is compared to that of F derived from a BF2 implant and is seen to be less mobile during post implant rapid thermal annealing with implications to gate oxide performance.