A Low-Loss Microstrip Surface-Mount K-Band Package

This paper presents a hermetic-compatible surface mount package for microstrip structures designed for K-band applications. The microstrip lines, fabricated on a 250 mum-thick alumina substrate are packaged using a 280 mum-thick silicon cap wafer and gold-gold thermo-compression bonding. A 130 mum cavity is etched in the cap wafer to allow ample space for RF MEMS devices, surface- or bulk-wave acoustic filters, power amplifiers, or multi-chip assemblies. A via-hole transition is used to connect the microstrip line inside the package to the coplanar waveguide (CPW) line on the back side of the alumina wafer. The gold sealing ring is connected to the microstrip ground using via-holes through the alumina wafer to eliminate any parasitic resonance modes and to improve the isolation between the input and output ports. A packaged microstrip line with total dimensions of 2.6 mm has a measured insertion loss and return loss of less than 0.5 dB and 18 dB, respectively, at DC-23 GHz