A study related to the improvement of the continuous ultrasonic tacking process of thermoplastic PEEK and PEKK carbon fibre unidirectional tapes. The project consisted of two interrelated research topics; a microstructural characterization of unidirectional tapes and an extensive tacking parameter study. By using a Voronoi Tesselation algorithm it was found that the microstructures of tapes analysed are not consistent and far from homogeneous. The distribution of fibres and resin is related to the ability of processing the tape with the ultrasonic tacking technology. Besides, the consistency in bond line of tacked samples was analysed, what was found to be in relation with the degree of consistency and homogeneity of the microstructure. A central composite design statistical model was utilised to study the effect of the tacking parameters to the bond strength of tacked samples. Implementation of results of the interrelated research topics showed potential for process optimization. A velocity increase of roughly 40% was achieved.