Enhancement of bonding strength of packaging based on BCB bonding for RF devices

This paper presents a Si cap zero-level packaging technique based on a double-layer BCB sealing ring. The BCB ring is defined before the housing cavity etching to achieve high BCB bonding strength. It is found that the non-uniformity of the BCB ring defined on a Si cap with housing cavity prevents the package having high bonding strength. Three different packages have been prepared for shear test; a Si cap without cavity, a recessed Si cap with a conventional BCB ring and a recessed Si cap with pre-defined BCB ring. The three samples for each type of package are measured. The average measured bonding strengths of the test samples are 71, 16 and 42?MPa, respectively, and hence the proposed BCB sealing ring process provides 60?% of bonding strength of Si cap package without cavity for Si cap package with cavity. In addition, the insertion loss change of the packaged CPW is less than 0.1?dB up to 67?GHz while the return loss better than 15?dB at the measured frequency range.