Design and characterization of metal coatings on high temperature polymers for harsh environment electronics board

• Main Author: Ong, Si Hui
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/147763
• Institution: Nanyang Technological University

Commercially, polymers such as polyimide, epoxy and FR-4 are the most commonly used electronic packaging material. However, for high temperature applications such as in the aerospace and marine industries, these polymers are reaching their mechanical and thermal limits. Intensive research has been conducted on an alternative polymer, phthalonitrile (PN), for its thermal conductivity and thermal stability in high temperature applications. However, PN has not been explored as a high temperature printed circuit board (PCB) yet. Previous studies have shown that there exists a special bonding affinity between metals and PN. As PN has excellent thermal and mechanical properties, it exhibits a high potential as a PCB material for high temperature usage in harsh environments. In this study, resorcinol-based PN (rPN) is explored as the high temperature polymer to be used as a PCB. Investigation is carried out to determine the optimum metal coating thickness through tuning of parameters of different metal deposition methods such as sputtering and screen printing. Firstly, the synthesized rPN was characterized through DSC, TGA and FTIR. Then, the metal coatings were deposited on rPN using Physical Vapor Deposition (PVD) sputtering and screen printing. Lastly, the metal coatings on rPN were characterized through four-point probe, cross-hatching adhesion tests, optical microscopy, and scanning electron microscopy (SEM). The DSC results showed that increasing the concentration of catalyst would result in an increased exothermic reaction during polymerization of rPN. TGA analysis revealed that rPN is thermally stable below 500°C. FTIR spectrums indicated that triazine and phthalocyanine absorption peaks were present after post-curing. Silver conductive paint was screen printed on rPN, while copper nanoparticles paste (CuNPs) was screen printed onto a sputtered titanium layer on rPN. Cross-hatching adhesion test showed that CuNPs on rPN had poorer adhesion than silver coating on rPN. Therefore, SEM was used for comparing the surface morphology for both CuNPs and silver ink. Resistivity measurements revealed that heat treatment of silver coating at higher temperature resulted in higher conductivity. In conclusion, the results suggested that it is possible to form metal interconnects on rPN, for usage as PCB material.