Projects / Thin-film Flex Interconnect (FTI)

Project Overview

The Thin-film Flex Interconnect (TFI) project leverages developments of the HDS design but adds flexibility to MCMs and aims to reduce the overall fabrication overhead and complexity.  Furthermore, the use of polymer-based dielectrics permits the integration of new materials that are incompatible with standard silicon processes.  In parallel, this project is pursuing the embedded integration of passive devices (capacitors, resistors, and inductors) within the flexible layer.  Coupled with the ability to directly integrate depackaged COTS die, this technology offers substantial advantages; however, it has less precision than HDS conductor traces.

Core Fabrication Technologies

Fabrication of prototype flexible systems using bare die begins with the COTS depackaging and hyper-mapping the contacts as provided by the manufacturer.  After accurately mapping all the components, a printed circuit board (PCB) editor, called EAGLE, is used to create the system layout as per a design netlist which is then translated into a microfabrication mask set. 
In order to reduce fabrication overhead, photodefinable polyimide is used to define the interconnect features. 
This is followed with deposition of an adhesion metal and copper seed layer using standardized semiconductor fabrication techniques followed by copper electroplating and polishing to define the conductors.  This process is repeated iteratively in order to create the system power and signal distribution.  Following substrate fabrication and testing, advanced packaging and PCB assembly techniques are employed to complete the system.  In parallel to MCM development, TFI technology is being used to explore development of small-scale passive devices that are enhanced by electromechanical properties of polyimide and its compatibility with new material sets.