Low cost, rigid to flex interposer using a spray coated intrinsically conductive polymer in a roll to-roll process

We report on a complete roll-to-roll (R2R) processed rigid-to-flex interposer using poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS) doped with ethylene glycol (EG), spray coated onto a plastic polyethylene naphtalate (PEN) substrate with another single-sided adhesive PEN foil acting as a contact stencil mask for the interposer structures. A 355 nm solidstate R2R integrated laser, with a beam width of 20 mu m in focus, is used to cut the pattern of the interposer layer onto the adhesive foil, this foil is then laminated onto the primary substrate foil at 150 degrees C to enable a contact stencil. Multiple layers of the doped PEDOT:PSS is sprayed over the whole surface, then the substrate is processed in an EG bath to improve the conductivity. The PEN masking-layer is then delaminated from the substrate at 65 degrees C, leaving behind only the interposer structures having a sheet resistance of similar to 15 Omega/dagger at room temperature with a 250/150 mu m line/space finger geometry. The resulting structures are robust to flexing, have good current carrying capability (50 mA constant, 100 mA short-duration) and are air stable. The structures also exhibit a positive temperature coefficient of resistance, fair heat dissipation, transparencies of similar to 85% and can be bonded to an IC easily with silver conductive paste or an anisotropic conductive polymer.