Embedded p-i-n-Diode Die Interconnections With Aerosol-Jet Printing

Direct-Write printing enables the selective deposition and patterning of dielectric and conductive materials in a multi-layer fashion to create high-resolution 3D circuit elements. An embedded PIN diode limiter circuit was demonstrated as an example of a millimeter wave radio frequency circuit element with aerosol jet printed interconnections in place of wire bonding. A hybrid circuit fabrication approach was chosen using conventional low dielectric constant substrates and copper foil circuitry with active die embedded in the substrate. Printed radio frequency elements were placed in the circuit where there was a realizable size-weight-power-cost advantage in terms of better performance, size reduction, or faster build time. Aerosol jet was used because of its micron-sized printed features and its use of digitally driven data from CAD files for multi-axis control of the deposition tool and use with different print materials. DC resistance, return loss and insertion loss were measured and compared to wire bonded samples up to 20 GHz frequency. The PIN diodes circuit limiter was evaluated after exposure to military standard tests including thermal cycling and salt fog testing. Comparing aerosol jet printed connections to wire bonding showed equal radio frequency performance at high frequency without the need for wire tuning and with printed connections being more robust and reliable.