W2W wafer level vacuum packaging of MEMS devices using solder

With the increasing integration of mechanical and electronic components on the MEMS cavity, the complexity of the system enhances exponentially and thus leads to a need for the larger size package and good process compatibility. Wafer-level vacuum packaging (WLVP) is a promising direction, in this work, Wafer-to-Wafer (W2W) vacuum bonding for MEMS devices by solder sealing were investigated. The wafers with a solder seal ring array on were prepared and W2W bonding was processed in a vacuum bonding system. Then the package units were diced and tested. The shear strength and hermetic test results showed that the vacuum into the samples met the requirements of MIL-STD-883. For further, the relation between the width of the solder ring and the pressure-bearing ability of the device was investigated so as to balance the reliability and size of the MEMS devices.