This Small Business Innovation Research (SBIR) Phase I project will develop an innovative process for fabricating, assembling and soldering millions of micron-sized silicon chips (microChips) into a display backplane with high-throughput and yield. Solder technologies for micron-sized devices are fundamentally different than those for bulk chip die-casting, due to increased surface tension and decreased device-thermal-load, providing an opportunity for innovation and value creation. This project leverages a manufacturing platform for fabricating and assembling micron-sized LEDs (microLEDs), each with a single integrated "solder bump" that automatically bonds the microLED into the backplane upon transfer. To extend this approach to multi-terminal devices such as silicon integrated circuits, we will demonstrate feasibility of forming multiple solder connections within a single microChip. We will screen alloy compositions and process parameters against detailed microChip thermal models, and develop a MEMS process for patterning the selected alloys. We will study the wetting characteristics of the solder under our assembly conditions to control spreading. We will use these results to demonstrate a simple microChip circuit in Phase 1, and use the technologies and design-rules developed here to build a pixel-level driver in Phase 2 (the fundamental element needed to replace the TFT backplane in flat-panel displays). The broader impact/commercial potential of this project stems from development of an innovative microLED display product that consumes less energy than state-of-the-art LCDs, extending battery life in portable applications, and potentially saving 0.86 Quads of U.S. energy per year in stationary applications. The TFT backplane in these products is the primary cost-driver (particularly for larger displays). Success in Phase 1 will prove the feasibility of an approach to eliminate the TFT backplane, with significant long-term benefits in the form of reduced manufacturing costs and reduced minimum manufacturing scale and capital equipment costs. Lower manufacturing cost will drive rapid market penetration, increasing the economic and environmental impacts of this technology. Lower capital costs and manufacturing scale will enable economic domestic manufacturing. The growth of a U.S. display manufacturing industry would lead to increased manufacturing jobs and gross national product, as well as enhanced national security through a domestic supply of display products to the Defense Department. The ability to integrate multi-terminal devices into this manufacturing platform will also allow this innovative manufacturing equipment to expand into new industries in the future
