Method for packaging microsensors

Abstract

A method for packaging and protection of sensors, particularly so called microsensors is disclosed. A sensor unit (either a sensor chip or sensor package) is flip chip bonded to a substrate having a through hole, such that the sensing element is placed above the through hole. An underfill material is applied in such a way that due to capillary forces, the entire common area between the sensor and the substrate is completely filled, while the sensing element is not covered by the underfill material. This provides an effective way of sealing the sensing element from the side of the package containing the electronics. For a sensor chip that has been through a first level packaging process, the above mentioned method can still be used for bonding the sensor package to a substrate containing an access hole. For some applications one or multiple layers of protective coatings can be deposited on either one side or both sides of the sensor package for protection against the operating environment. For applications where the sensor is required to operate in a controlled pressure/controlled gas environment, a cavity can be created into the substrate, and the sensor chip can be flip chip bonded (and/or sealed) to the substrate in a controlled environment. An alternative method of packaging is disclosed where the sensor chip is fixed onto the substrate, and a cap is bonded to this substrate using dummy bumps for mechanical strength.