MicroConnex: Taking flex circuitry fabrication to the next level
(Image courtesy of MicroConnex)
MicroConnex (Snoqualmie, Wash.) and the University of Washington (UW) are developing low-cost flexible circuit fabrication processes using roll-to-roll (R2R) printing for high volume production. Also known as web processing reel-to-reel processing, R2R is the process of creating electronic devices on a roll of flexible plastic or metal foil.
Medical ultrasound happens to be a major market for MicroConnex’s flex circuits, and it’s not hard to imagine other healthcare applications.
While R2R printing isn’t new, it still poses some technical challenges, according to Steve Leith, vice president of engineering and technology at MicroConnex. Manufacturers have trouble ensuring that the circuit sticks to the plastic, assuring that they control accurate circuit widths and thicknesses, and fabricating circuits with sufficient electrical conductivity to be useful, Leith said.
MicroConnex and UW are evaluating the interactions and results of using different inks, different substrates and a range of clean and ink application processes to identify the best print conditions for adhesion.
Given the trend toward increasing electronic complexity and miniaturization, MicroConnex is focusing on printing very narrow circuits in a high-density design. The challenge is due in part to the relatively poor electrical properties of circuits made from printed conductive inks. To compensate, designers must use wide and thick circuit dimensions to carry enough current in the circuit. But wide and thick circuit dimensions limit how many electrical lines can be printed on a given area of substrate, Leith said.
MicroConnex and UW are working to develop a two-step “hybrid” printing process in which fine circuit patterns in silver are first printed using an R2R process to create narrow circuits in high-density designs. The second step adds copper, a high conductivity metal, to the circuit.
“The result of the hybrid process is a circuit that achieves a commercially viable combination of small dimensions, good adhesion and acceptable electrical properties,” Leith said. “Silver ink and electroplated copper provide the best balance of cost-to-performance versus alternatives.”
The MicroConnex-UW team received nearly $500,000 from NextFlex to buy experimental materials and to fund staff time to focus on designing, performing, analyzing and reporting results.
“The funded project was initiated in April, so we are really just getting started down the long path that will lead to demonstrating production volume capability,” Leith said. “The initial focus — and the primary deliverable on the grant — is to take incremental and well-defined steps to first develop a foundational understanding at lab and prototype volumes that can eventually be applied and scaled to production levels. We need to learn how to walk before we run.”
