Ultra thin force and acceleration sensor embedded in flexible thin film substrates using thin chip handling, bonding and carrier release technologies

This paper describes a fabrication technology for embedding sensors into flex circuit with a partial glass carrier and the electrical test of the circuit. Two sensors with a device thickness of 20 mm have been embedded into the flex circuit. The total thickness of the flex including semi-additive structured metal layers did not exceed 50mm. To enable the acceleration sensor a degree of freedom to follow the excitation of the sensor a special release sequence was used to obtain a partial rigidness of the flex. With the definition of the overhang of the flex the acceleration sensor sensitivity and its resonance frequency can be adjusted. An FEM simulation has been performed to calculate the resonance frequency of the acceleration sensor and electrical measurement have been performed to validate the performance of the device.