The market for printed electronics is growing continuously. Its low-cost fabrication process, large-area scalability and short processing time makes it interesting for researchers, even though the performance is lower as compared to conventional electronics. Popular printing technologies such as screen printing and inkjet printing are well established, but the upcoming maskless meso-scaled aerosol printing technique promises unique advantages. It allows the direct printing of finer 2D-3D structures, using a wide range of materials with viscosity between 1-1000 cP, while resolving the exhaustive problem of nozzle clogging. However, the implementation of printed electronics in consumer electronics remains a challenge, as device performance has to be improved. New techniques such as aerosol jet printing require additional research to fulfill their promise. This thesis investigates the implementation of fully printed structures using aerosol jet printing, focusing on devices in the fields of optoelectronics and semiconductor packaging.
The system components and operation mechanism of the aerosol jet printing system are described and a methodology for process optimization is proposed. Four distinctive regions for process optimization are identified: ink selection, surface treatment, process control and postprocessing. In the preliminary work, the possibilities of the aerosol jet printing process control is explored, such as achievable line width, film thickness, material compatibility and sintering possibilities. Test structures are produced in order to test the fabrication workflow, and to observe the interaction and compatibility of multiple printed layers. The challenges associated with aerosol jet printing are identified, including wetting, alignment, overspray and satellite deposition.
A fully printed ultraviolet photodetector with a nanoporous morphology is investigated. Presynthesized Zinc Oxide crystals are printed to reduce the post-annealing temperature. At a temperature of < 150 ◦C, the solvent is evaporated, resulting in a porous structure having high surface area-to-volume ratio. A fully printed photodetector that has comparable performance to the state-of-the-art is demonstrated, while the low-temperature fabrication process maintains compatibility with large area flexible plastic substrates.
Next, a fully printed microstrip transmission line with SU-8 as dielectric and silver as conductor is proposed, which can provide high-bandwidth interconnections in packaged semiconductor dies. The metal and dielectric materials are characterized at microwave frequencies upto 18 GHz. It is shown that a good correspondence is reached between the simulated design parameters and the printed structure, which results in good characteristic impedance matching and low transmission losses. The transition of the printed transmission line to a microwave integrated circuit is demonstrated, thereby validating the concept of aerosol jet printed transmission lines inside the package.
Lastly, the SU-8 based printed transmission lines are extended into microwave ring resonators, with applications in high frequency sensing. It is envisioned to directly print these structures inside the package, directly connected to a microwave integrated amplifier for high-Q sensing. Therefore, these ring resonator are designed for microwave center frequencies ranging from 15.5 to 21.5 GHz for reduced size which can be integrated inside a package. The material characterization of metal and dielectric materials are carried out up to 26 GHz. The simulated results showed good correspondence with the measured results in terms of center-frequency, insertion loss and Q-factor
