Embedding thinned chips in flexible PCBs

Abstract

Autonomous systems for healthcare and sports applications benefit largely from a small form factor, as minute dimensions result in maximal mobility and comfort. By embedding a commercially available IC in a flexible circuit board (FCB), the overall size of a system can be reduced. This work presents the process of thinning and packaging an IC in a flexible interposer, and the embedding thereof in a FCB. To illustrate the potential of this technology towards miniaturization, a commercially available RF transceiver ZL70102 was packaged and embedded, thus realizing a volume reduction of 60%. I ntroductionResearch in the field of healthcare and sport monitoring tends to focus on the development of smart devices, where the output of multiple sensors is combined with the functionality of a microcontroller, memory and an RF transceiver for wireless communication to a base station or other nodes in the Body Area Network (BAN). The picture is often completed with a battery or energy harvester, thus providing an autonomous solution which enables the user or patient to monitor his/her health with a higher effectiveness and precision. Conventional technology often results in bulky solutions, and miniaturization of these systems only seems to be possible at the expense of functionality, autonomy and comfort.This paper reports on the development of a versatile packaging technology which allows integrating commercially available ICs into a miniature package by embedding the chip into a flexible circuit board (FCB). This action then allows rerouting the passives on top of the IC, which results in a system with a smaller form factor, breaking the boundaries imposed by SMD technology and fine pitch packages.

High-Yield Fabrication Process for 3D-Stacked Ultrathin Chip Packages Using Photo-Definable Polyimide and Symmetry in Packages

“…However in mass production of the UTCP packages, the yield will be lower. The yield ƞ of the process flow for individual UTCP packages, as described in the above section has been verified to be higher than 85%, based on the measurement of the functionality of several commercially available off-the-shelf ICs (MSP430F1611, nRf24L01, in-house ASIC design, etc) [11]. When N UTCP-packages are stacked, one single non-functional UTCP will result in a nonfunctional stack.…”