In recent years, growing types of sensors, processors, power, and energy components are required to be integrated into flexible packaging to diversify the functionality of wearable devices. However, most published work to date has integrated these components in a single layer film, which expanded the projected area of devices and created unbalanced weight distribution, making consumers uncomfortable. In addition, integrating power and batteries components on a single layer and having them close to human skin creates unignorable safety and heat dissipation concerns. Therefore, it is necessary to develop a multilayer stacking technology to optimize the design of flexible packaging. Therefore, in this work, to integrate the flexible batteries and flexible wireless charger on the wearables, as shown in the figure above, a dielet, through-glass vias for multilayer integration of the devices is demonstrated with integration of flexible batteries and flexible wireless charger. The vias consist of 300 um height, 40 um diameter (aspect ratio 8:1) TGV dies on a 1x1 mm2 glass die for power transferring from the 2nd layer to the 1st layer. In addition, on the 1st layer, a front RDL layer is fabricated in a conventional FOWLP process to interconnect vias and functional dies. While on the 2nd layer, a backside RDL layer is fabricated for the interconnection of the 1st and 2nd layer which is designed for wireless chargers and energy storage. In summary, the highly flexible, high electrical and thermal conductive vias can provide a reliable and low form factor interconnection for multilayer integration of wearable electronics. It reduces the projected packaging area and resolves the thermal and safety concern of wearable devices.
