3D Integrated, Ultra-Thin Functional Microcontroller Device for Wireless, Flexible ECG Systems

This paper presents a technology for the 3D-integration of a TI-MSP430 low-power microcontroller inside conventional double sided flex substrates, for a wearable wireless ECG system. The devices are first thinned down to 25 µm and next integrated as UTCP (Ultra-Thin Chip Package) in between two polyimide layers, resulting in 50-60 µm thin package. These extremely thin, mechanically flexible packages serve as interposers for embedding into conventional multilayer flex substrate, replacing for example the integration of naked dies. Providing a contact fan-out, this approach enables the testing of the device before embedding (solving the KGD issue). It also eliminates the need for precise placement and the use of expensive ultra high density PCBs. Smaller SMD components have been mounted above and below the embedded chip, leading to high density integration. In addition, the embedded thin silicon chip becomes mechanically flexible itself, leading to an increased flexibility of the resulting system.