Research
Inkjet Printing of Passive Microwave Circuitry
Project Overview
Fabrication of passive microwave circuitry utilizes repeated cycles of deposit/patternetch processing steps to create multiples layers of patterned conductors. This process is very wasteful since the patterning and etching removes (subtracts) the already deposited material. Inkjet printing provides a more economical and less wasteful approach by allowing the deposition of materials only in the desired areas.
Printing Process
Silver nano-particle ink was deposited on a Corning #7740 glass wafer using the DMC-11610. The glass surface was treated to improve its adhesion properties. After the deposition the ink is sintered from 200¡-300¡C. High sintering temperatures enable conductivity similar to that of bulk silver.
Resolution and Fluid Interaction
The resolution of the DM-11610 on the surface treated glass is 50um but finer resolution can be achieved if the temperature of the glass is raised to 100¡C during print. The figure below shows that there is a considerable thinning at the edges of the CPW line. This is mainly due to the contact angle of the fluid and the glass and may be controlled by the varying the surface treatment.
3D interferometer scan of printed design.
Conclusion
Inkjet printing shows great potential for the fabrication of inexpensive passive microwave circuitry. The results of print silver nano-particle ink shows that resistivity similar to that of plated copper is possible. The RF properties of the print CPW lines also show that improvement of the printing techniques will provide lower conductor losses and thus better passive devices.