The objective of the activity is to design, manufacture and evaluate test samples in order to derive acceptance criteria of defectsand ageing effects in high voltage printed circuit boards of Electronic Power Conversion (EPC) and Power Processing Units (PPUs) with voltages exceeding 500 V. Targeted Improvements:Establish acceptance criteria for defects and ageing effects for high voltage (>500 V) circuit boards not existing today. Description: High voltage printed circuit boards (PCB) are critical building blocks used in telecommunication electric propulsion equipment (PPUs) and power supplies (EPCs) for travelling wave tubes. Unwanted high voltageeffects can limit the lifetime of such PCBs, making their procurement very demanding in order to guarantee best quality and a defect-free PCB. This leads to exhaustive screening requirements with an impact on time, effort and yield. Furthermore, the very conservative rules limit the optimisation and further size/mass reduction of high voltage designs. Finally, there remains always the risk ofundetected issues. This activity will address the following key topics, paving the way towards an advance of double and multilayer high voltage PCB procurement and design:- study the effects using a theoretical approach and conduct associated verification tests,- derive rules for screening and acceptance and develop screening methods,- predict and verify ageing effects, life limiting-factors and the impact on screening yield.- derive pass fail criteria for acceptance of defects- develop techniques to inject reproducible defects for test purposesExisting approaches for optimised PCB procurement and design rules for low voltage PCBs shall serve asa starting point. Considering high voltage specific requirements and problem areas, hardware high voltage PCB samples/breadboards will be designed and manufactured to carry out verification testing, including testing in vacuum. The outputs of this activity will be made available for future potential updates to relevant standards. Footnote: On Delegation Request activities will only be initiated on the explicit request of at least one National Delegation.