Osaka, Japan – The amount of digital communication supporting our daily lives continues to increase. This means there is a constant need to improve hardware, including optimizing the performance of printed wiring boards (PWBs). Researchers from Osaka University have demonstrated a method for strongly combining polytetrafluoroethylene (PTFE) and smooth cooper foil. They presented their findings at the INTERFINISH2020 congress.
Because the digital information being transported through communication systems is increasingly complex, the frequency of transmissions must increase. However, as the frequency increases so too does the loss of transmission from the conduction component of the circuit. Therefore, materials must be continually improved to create future-ready PWBs.
Copper is the go-to wiring material for PWBs because it is highly conductive, and thus efficiently transports information to its destination. There is currently nothing superior to copper for this task, so the focus for improvement is to decrease transmission loss from the support material.
PTFE is ideal for this role because it has both low relative dielectric constant and low dielectric loss tangent; however, PTFE does not like to stick to things. An intermediate layer is often used between PTFE and copper to improve the adhesion, but using these layers is a tradeoff because they increase insertion losses.
In this study, the researchers have created an adhesive-free method of sticking commercially available PTFE to copper foil with high adhesion strength, thus dispensing with the need for a middle layer.
“Our technique involves what is known as heat-assisted plasma (HAP) treatment,” explains first author Misa Nishino. “We subjected the PTFE to a HAP to make the surface stickier, and then pressed the two layers together at a high temperature to ensure they were strongly bonded.”
The research team examined pure PTFE and a cloth woven from glass and PTFE and found that both showed significantly increased adhesion to copper foil after HAP treatment. In addition, the very smooth surface of the copper foil meant that the transmission could have an obstruction free pathway, minimizing the losses.
“Our method is both simple and environmentally friendly, making it a highly attractive option for large scale processes,” says study corresponding author Yuji Ohkubo. “We expect our findings will be used to make high-frequency PWBs that will contribute to the enhancement of digital devices for the 5G world and beyond.”
The study, “Adhesive-free strong adhesion between heat-assisted-plasma (HAP)-treated polytetrafluoroethylene (PTFE) and copper foil,” is presented at the INTERFINISH2020 congress from Sep. 6-8th in 2021.
About Osaka University
Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Method of Research
Subject of Research
Adhesive-free strong adhesion between heat-assisted-plasma (HAP) -treated polytetrafluoroethylene (PTFE) and copper foil