Packaging method for RF MEMS devices using LTCC capping substrate and BCB adhesive bonding

Abstract

In this paper, we reported a packaging method utilizing LTCC (low temperature co-fired ceramic) substrates and BCB (benzocyclobutane) sealing rim for RF MEMS devices. The LTCC substrate is used as a capping substrate and Ag via holes implanted in LTCC substrates are used as RF feedthrough vertical interconnection. BCB layers play a role in bonding of the MEMS device and LTCC capping substrate. We also measured the RF characteristic of the packaged CPW line, and compared with the RF performance before and after packaging. The Measured value of the only CPW line without a packaging has an insertion loss of 0.047 dB at 2 GHz, and 0.092 dB at 20 GHz, respectively. After packaging, the insertion loss of the packaged CPW is 0.091 dB at 2 GHz and 0.312 dB at 20 GHz, respectively. A leak test has been performed using both IPA soaking and He-based leak tester. Most of the samples show no leakage in IPA test, and the measured He-based leak rate is 10/sup -6/ Pa/spl middot/L/s. The shear strength of the package was measured to be 25/spl sim/35 MPa. The proposed packaging shows less than 0.22 dB in insertion loss over DC-20 GHz, and, it also shows an acceptable value in hermitic test and mechanical shear strength.