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

Direct-write (DW) printing enables the selective deposition and patterning of dielectric and conductive materials in a multilayer fashion to create high-resolution 3-D circuit elements. An embedded p-i-n-diode limiter circuit was demonstrated as an example of a millimeter-wave (mmW) radio frequency (RF) 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 RF 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 micrometer-sized printed features and its use of digitally driven data from CAD files for multiaxis control of the deposition tool and use with different print materials. DC resistance (DCR), return loss and insertion loss were measured and compared to wire-bonded samples up to 20 GHz frequency. The p-i-n-diode 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 RF performance at high frequency without the need for wire tuning and with printed connections being more robust and reliable.