Multilayer plastic substrate for electronics

This work demonstrates the making of four-layer wiring design on a flexible plastic substrate by laminating together individual printed sheets. Overmolding of the device into plastic is also experimented. In printed electronics, multilayer wiring is often avoided because of the technological difficulties in making several conductor layers. Yet many electrical designs require multiple layers and are therefore out of reach for printed and plastic electronics. In this work, multilayer wiring in the form of four-layer laminated structure was studied. Via filling in plastic foils was studied with different silver based pastes and it was found that most pastes fill vias well while simultaneously printing the wiring. Method for making multilayer boards by laminating polymer sheets together was explored by testing a range of plastic materials for their lamination adhesion and then producing a test structure on polyethylene terephthalate (PET) with wiring running through the substrate. Finally, this demo device with LED components was overmolded with thermoplastic polyurethane (TPU) to form a sealed structure with integrated lenses for LEDs. The final structure is sealed, flexible and transparent, which is desirable for example in display applications.