Technologists in Belgium have slimmed down a chip package to less than 60 µm and integrated it onto a low-cost, flexible substrate. The resulting ultrathin chip package (UTCP) with embedded microcontroller could pave the way to inexpensive, unobtrusive wearable electronics for monitoring the heart and body functions. The new 3-D integration process was presented during the Smart Systems Integration Conference in Brussels this week by researchers from the Interuniversity Microelectronics Centre (IMEC) in Leuven, Belgium, and its associated laboratory at Ghent University. IMEC is Europe’s largest independent nanoelectronics and nanotechnology research center.The Interuniversity Microelectronics Centre’s flexible, wireless system monitors the heart and other vital body parameters with an embedded microcontroller chip. (Photo: IMEC) First the chip was thinned down to 25 µm and embedded in a flexible UTCP. Next, the package was embedded in a standard double-layer flex printed circuit board (PCB) using standard flex PCB production techniques. After the chip is embedded, other components can be mounted above and below it. IMEC said the integration process uses UTCP interposers that solve the “known good die” issue by enabling easy testing of the packaged thin dies before embedding. Expensive high-density flexible substrates can be avoided by the fan-out UTCP technology that relaxes the interconnection pitch from 100 µm or lower to 300 µm or more, compatible with standard flex substrates. IMEC demonstrated the integration technology with a prototype flexible wireless monitor that measures the heart rate (electrocardiogram) and muscle activity (electromyogram). The system consists of an embedded ultrathin chip for the microcontroller and analog-to-digital converter, an ultralow-power biopotential amplifier chip and a radio transceiver. By thinning down the chips for UTCP embedding, the technologists made them mechanically flexible, so the complete system is more flexible, making it unobtrusive and comfortable to wear. For more information, visit: www2.imec.be/imec_com/