Optimising the interlaminar geometry of ultrasonically additive manufactured metal structures to enable direct embedding of electronic circuitries

Purpose This research aims to exploit the potential of Ultrasonic Additive Manufacturing (UAM) in the embedding of printed electrical materials directly into the interlaminar region of parts during manufacture in order to realise novel multifunctional Metal Matix Composite’s (MMC’s). Design/methodology/approach To ensure the proper electrical insulation between the printed conductor and metal matrices, an insulation layer with sufficient thickness is required to adapt the rough interlaminar surface geometry caused by the transfer of the sonotrode topography during the UAM process. This in turn increases the total thickness of printed circuitries and thereby adversely affects the integrity of the UAM part. This work proposes a unique solution to overcome this rough interlaminar surface through deformation of the UAM substrates via sonotrode rolling or UAM processing. Findings The surface roughness (Sa) of UAM substrates could be reduced from 4.5 μm to 4.1 μm by sonotrode rolling and from 4.5 μm to 0.8 μm by ultrasonic deformation. Peel testing demonstrated that sonotrode rolled substrates could maintain their mechanical strength, whilst the performance of substrates deformed with UAM degraded under same welding conditions (~12% reduction compared with undeformed substrates). This observation was attributed to the work hardening effect of deformation process which was identified via DualBeam FIB-SEM investigation. Originality/value The rolling deformation process (without ultrasonic assistance) was adopted in the further fabrication of multifunctional MMC’s. This method enabled a decrease in the thickness of printed electrical circuitries by ca. 25%.