A Flip-Chip Packaging Design With Waveguide Output on Single-Layer Alumina Board for E-Band Applications

This paper presents a millimeter-wave (mm-wave) packaging design for E-band long-haul point-to-point communications. A broadband flip-chip interconnect with standard 75 μm pad pitch is developed on an alumina substrate. To meet the application requirement, a microstrip line to WR-12 waveguide (WG) transition is proposed. The transition has no back-short cavity or modified WG involved. A back-to-back transition measurement is conducted to characterize the performance. Results show that the working bandwidth is from 69.5 to 87 GHz and the insertion loss at 77 GHz is less than 0.5 dB. A 40-nm CMOS power amplifier is packaged and measured with the proposed packaging design. The entire packaging loss is only 2.5 dB from pads to WG, including the loss of a 10-mm microstrip line. The simulated and measured results are in good agreement. The gain and peak output power are 13.4 dB and 17.6 dBm. The silicon temperature is measured as 44.4°C after saturated output for 30 min. The performance is close to probe measurement after deembedding the packaging loss. Comparison between bondwire and flip-chip packaging is discussed and both are verified in mm-wave packaging design.