Fine-Pitch Capabilities of the Flat Ultra-Thin Chip Packaging (UTCP) Technology

This paper describes the fine-pitch interconnection capabilities of the ultra-thin chip packaging (UTCP) technology, a technology under development for embedding thin chips in a flexible polyimide (PI) substrate. It allows for fully flexible electronics, as the rigid chips are thinned down to 20-30 ¿m, at which point they become truly flexible themselves. This way, instead of just a flexible substrate with rigid components assembled on top, the entire circuitry can be incorporated inside a 30-40 ¿m thin chip package. The paper briefly introduces the technology's background with a short description of the fabrication process. Building on the developments already achieved, some further optimizations are discussed, and the technology is tested for its fine-pitch interconnection capabilities using test chips with four-point probe and daisy chain patterns, with a pitch down to 40 ¿m. The possibility to package several chips in the same substrate is investigated, as well, and finally an outlook on future experiments is briefly discussed.