This paper presents the combination of an innovative assembly and packaging process utilising Solid Liquid Inter Diffusion (SLID) Cu-Sn interconnects within bespoke ceramic substrates that have been produced using Additive Manufacturing (AM). The resultant process chain supports the integration and packaging of power electronics for harsh environment applications. In this work, we investigate how the bond strength and mechanical integrity of Cu-Sn SLID interconnects are affected after being exposed concurrently to vibration and thermal loading (“shake and bake test”) . Test vehicles were exposed simultaneously to thermal loading up to 300 °C and mechanical loading in terms of high random frequency vibration between 1 Hz and 2000 Hz, which is closely associated with the aerospace and oil & gas industries maximum operating conditions. In parallel micro-extrusion printing methods in which high viscosity ceramic pastes are dispensed through cylindrical fine nozzles (2-250µm) using CNC controlled motion has enabled complex 3D geometries to be fabricated. Additional secondary conductor deposition after firing the ceramic substrate enables the electronic circuitry to be generated without dedicated tooling, masks or templates. This work presents the first fully 3D printed ceramic based electronic substrates. To demonstrate the applications of this printing method a 555 timer circuit with flashing LED has been printed and the components surface mount assembled. The resultant ceramic substrates are dense, mechanically robust and the reflowed circuit functions exactly as intended.