Printed electronics by inkjet offers enormous potential since it is an additive process allowing accurate deposition of liquids at high speed and without waste. However, one of the challenges in inkjet is the optimization of printing parameters as well as the surface energy between different deposited inks and interfaces. In this paper, an in-line process for the realization of multilayer resistors by drop-on-demand inkjet printing is described. This process is developed within a home-build 'JETPAC' prototype system allowing the printing of both metals and dielectrics. This prototype is used to realize 3D series resistors that were stacked on a top of each other through a passivation layer. Here, the first printing level optimization process includes the tuning of inkjet-printed parameters and the surface energy between the Kapton substrate and both silver and hydrophobic UV dielectric inks. The second printing level optimization process includes the setting of the accurate parameters for the selective microwave sintering of silver nanoparticles. Finally, the resistors printed on a top of each other were interconnected in series via contact pads after alignment step. Results shows that different value of resistors can be achieved in 2x2 mm² surfaces with total thickness of 30 µm. This work shows a unique opportunity of in-line printing and the subsequent selective sintering of silver ink to produce multilayer passive devices and to offset the surface limitation involved in RFID and smart packaging applications.