Package quality testing using integrated pressure sensor

An integrated thermal pressure sensor is used to characterize the sealing quality of hermetic packages. The fully CMOS-compatible sensor is obtained by maskless sacrificial layer etching. The sensor consists of a laterally clamped dielectric membrane with integrated heater, sepa rated from the supporting chip by a μm-thin gap. The device monitors the thermal conductivity and, thus, the pressure of the gas filling the gap. It has maximum responsivity in the range from 1 mbar to 10 bar. Two pressure microsensors and reference structures were cointegrated with a CMOS thermoelectric infrared detector. The systems were mounted into hermetic and leaky TO-5 packages. To test their hermeticity, the packages were pressurized in helium (He) at 4 bar for 4 hours. Changes of the atmosphere inside the packages were measured during the pressurization using the integrated pressure sensors. A model was fitted to the data and the results were compared with standard fine and gross leak testing. A clear correlation between the results of standard leak testing and the new method was found.

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