From zero- to second-level packaging of RF-MEMS devices

This paper reports the full packaging and assembly of RF-MEMS devices for operation below 6GHz, comprising 0-level, 1-level and 2-level packaging. The fabrication process for the RF-MEMS devices is based on the Philips PASSI™ process, which is adapted to accommodate the packaging. The 0-level assembly is based on solder bonding, and is realized on a flip-chip aligner/bonder under atmospheric pressure, at 240°C. The 1-level package comprises a chip-scale-package (CSP) in which the 0-level packaged device is directly equipped with solder balls for the interconnect. The individual 1-level assemblies are then flip-chip mounted on a RF-board at 240°C, completing the 2-level packaging. RF measurements of a 2nd-level packaged series switch showed an increase of the insertion loss of about 0.1 dB after 0-level packaging, increasing to about 0.5dB after 2nd-level packaging. Preliminary evaluation of the 0-level package hermeticity using switches configured as mechanical resonators indicates an hermetic seal.