Sacrificial microchannel sealing by glass-frit reflow for Chip Scale Atomic Magnetometer

This paper reports on a novel and simple packaging technique to enhance the atmosphere controllability of the microfabricated alkali vapor cell used for CSAMs (Chip Scale Atomic Magnetometers), in which sacrificial microchannels at the bonded interface are utilized as gas feedthrough for evacuation and filling, subsequently sealed by glass-frit reflow. By applying the proposed method, a 10 mm³ potassium vapor cell with 0.1 MPa helium buffer gas was fabricated. Sealing of the microchannels by glass-frit reflow were successfully demonstrated adopting the optimized parameters as 460-480°C at bonding pressure of more than 250 kPa. The leak rate of less than 3.1×10^-14 Pa·m³/s, which is required sealing quality for CSAM, was verified through a high resolution helium leak test.