Flexible Hybrid Electronics Including Ultrathin Strain Sensors or Radio Frequency Identification Dies Manufactured on Wafer Silicon Carrier

Flexible hybrid electronics (FHEs) is becoming a disruptive technology in the packaging of electronic components. Indeed, thanks to the thinness and flexibility of devices, it is conceivable to add a function to any object without changing its aspect. However, this approach faces critical issues, such as the management of ultrathin components from different sources and the cost of individual operations. In this article, a wafer-level packaging (WLP) process for integrated silicon dies coming from various foundries in a flexible label is presented. The process is performed in a microelectronic component manufacturing line on a 200-mm temporary wafer carrier, thus achieving a high level of integration. The purpose of this article is to present results for different hybridization methods of ultrathin silicon dies inside a flexible label. In addition, the process was applied to two demonstrators. The first comprises an ultrathin silicon strain sensor based on a doped crystalline (100) silicon piezoresistive effect that is embedded in a flexible label and bonded to a printed circuit board. When the printed circuit board is mechanically stressed, the die resistances are changed as a result of the piezoresistive effect, and a Wheatstone bridge circuit is used to measure the change in resistance. The second demonstrator is a heterogeneous flexible system including an ultrathin radio frequency identification (RFID) dies integrated within a small flexible label and bonded to a flexible antenna. The functionality of the two demonstrators has been successfully demonstrated.