Publications
Radar transmitter and receiver MCM subassemblies implemented in LTCC
The development of transmitter and receiver Multichip Module subassemblies implemented in LTCC for an S-band radar application followed an approach that reduces the number of discrete devices and increases reliability. The LTCC MCM incorporates custom GaAs RF integrated circuits in faraday cavities, novel methods of reducing line resistance and enhancing lumped element Q, and a thick film back plane which attaches to a heat sink. The incorporation of PIN diodes on the receiver and a 50W power amplifier on the transmitter required methods for removing heat beyond what thermal vias can accomplish. The die is a high voltage pHEMT GaAs power amplifier RFIC chip that measures 6.5 mm × 8 mm. Although thermal vias are adequate in certain cases, the thermal solution includes heat spreaders and thermally conductive backplates. Processing hierarchy, including gold-tin die attach and various use of polymeric attachment, must allow rework on these prototypical devices. LTCC cavity covers employ metallic coatings on their exterior surfaces. The processing of the LTCC and its effect on the function of the transmitter and receiver circuits is discussed in the poster session.