Demonstration of integral passives on double sided polyimide flex

Understanding that integral passives can offer significant performance and cost leverages, the General Electric Research and Development Center, Schenectady, NY, has teamed with Rensselaer Polytechnic Institute (RPI), Arizona State University (ASU), Sheldahl, and the Mayo Foundation on the development of thin film deposition processes for the fabrication of passive elements on polyimide films. This program was targeted at developing manufacturing processes for the fabrication of integral resistors, capacitors and inductors to be used in digital and mixed mode (combined analog/digital) applications operating in the GHz regime. To demonstrate the developed technology, multichip modules were fabricated that included a microwave frequency down converter circuit (shifting the input signal from 5 GHz to 500 MHz), a biphase demodulator, a 500 MHz filter, a 5 GHz filter, and a splitter. The design and fabrication methodology implemented a novel double sided flex approach positioning the thin film capacitors on one side and the resistors and inductors on the reverse side. The capacitor material set consisted of tantalum oxide (Ta 2 O 5 ) and diamond like carbon (DLC). Spiral geometric patterns of electroplated Cu formed the inductors, while the resistors used reactively sputtered tantalum nitride (Ta 2 N). The high yield (>95%) of integral passive components on the fully functional multichip modules demonstrate the feasibility of incorporating thin film passive components with the manufacture of polyimide flex circuitry.