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This paper presents benzocyclobutene (BCB) cap packaging of Microelectromechanical systems (MEMS) switches integrated with a thin monolithic microwave integrated circuit (MMIC) wafer. To prevent a possible breakage during BCB bonding process, the 100-μm-thick MMIC wafer is bonded to 680-μm-thick GaAs support before the release of MEMS switches. BCB cap packaging has been performed through BCB cap transfer technique based on antiadhesion monolayered Si carrier wafer. The thick GaAs support wafer has been separated by polymethyl methacrylate (PMMA) sacrificial etching through perforated access holes. The packaged MMIC wafer has been successfully diced using conventional dicing machine. The implemented BCB caps on the target MMIC have the height of 25 μm and the cavity of 12 μm for the housing of MEMS switches. The achieved success rate of BCB caps transfer is ~ 95%. The BCB cap packaging effect to microstrip line has been investigated through the S-parameters measurement before and after the packaging. In addition, the packaged MEMS switch shows the insertion loss of 0.7 dB, the return loss of 25 dB, and the isolation of 20 dB at 30 GHz.