Abstract: A method is provided for transferring a graphene sheet to metal contact bumps of a substrate that is to be used in a semiconductor device package, i.e. a stack of substrates connected by said contact bumps, e.g., copper contact bumps for which graphene forms a protective layer. An imprinter device can be used comprising an imprinter substrate, said substrate being provided with cavities, whereof each cavity is provided with a rim portion. The imprinter substrate is aligned with the substrate comprising the bumps and lowered onto said substrate so that each bump becomes enclosed by a cavity, until the rim portion of the cavities cuts through the graphene sheet, leaving graphene layer portions on top of each of bumps when the imprinter is removed. The graphene sheet is preferably attached to the substrate by imprinting it into a passivation layer surrounding the bumps.