•A novel ultra-thin vapour chamber manufacturing process was developed.•Vapour chambers that were 0.55-mm thick were fabricated and investigated.•The effects of liquid-filling ratios on the thermal performance were studied.•The effects of test states on the thermal performance were investigated. With the increasing heat flux required in portable electronic devices, ultra-thin vapour chambers (UTVCs) have attracted increasing attention as efficient phase-change heat-transfer components. In this work, a sintered copper powder wick fabricated through a screen-printing process is proposed, providing a novel method for manufacturing large-area and complex-shaped UTVCs. UTVCs with a thickness of 0.55-mm and printed copper powder wicks were fabricated, and the copper powder paste preparation and UTVC manufacturing processes are described in detail. The copper powder paste was made by mixing dipropylene glycol monomethyl ether and copper powder with a particle size of 65–75 μm in a 5:1 ratio. The thickness of the copper layer after sintering was 0.2 mm and its porosity was 59.7%. The heat transfer performance of UTVCs under different liquid-filling ratios and test states was investigated. The results showed that the optimal liquid-filling ratio of the presented UTVCs is 43.2% and that its maximum heat-transfer capability is 6.5 W with a thermal resistance of 0.46 °C/W in the horizontal state. The thermal resistance of the UTVC in the anti-gravity state is more than twice that of the UTVC in the horizontal state. The proposed manufacturing process provides a new solution for the research of the thinner VC and the patterned wick structures.