Copper Clad Laminate for High Frequency Printed-circuit Board in 5G era

With the rapid development of the communication industry, the demand for
hardware is constantly growing. However, traditional epoxy resin copper clad
laminate (CCL) cannot meet the high frequency requirement of 5G (fifthgeneration
wireless systems) environments.
PTFE is an excellent dielectric material with a low dielectric constant and minimal
dielectric loss. It can thus be widely used in mobile communication equipment,
radio receivers, transfer devices, base station antennae, and household appliances,
and CCL made from PTFE has many applications.
The main purpose of this project was to investigate the use of PTFE to replace
epoxy resin. There are several obvious problems with this, such as poor mechanical
properties (bending strength, hardness, and so on), the large coefficient of thermal
expansion, and the poor bonding force between the copper foil and matrix resin.
Those problems greatly affect the promotion of this technique.
To solve the issues with poor mechanical properties, this project investigated the
use of different reinforcing materials such as glass fabrics and glass fibre mats
while simultaneously seeking and testing a suitable silane coupling agent to
increase the fibre strength and the binding forces between the resin and any
reinforcing materials.
Alongside investigating a silane coupling agent, this project also researched
various copper foil and bonding layer, as these two things are the most important
elements affecting bonding force and fulfilling the various purposes of CCL. Based
on experiments and comparisons, electrolytic copper foil and FEP film were the
technologies selected in this project.
In order to explore the performance of copper foil and a bonding layer, this project
utilised the process of hot-pressing and copper cladding. The coefficient of thermal
expansion of PTFE is much larger than that of epoxy resin, as the hot-pressing of
PTFE board and copper cladding cannot be done together. The pressure curve and
temperature must thus normally be designed separately. In this project, an
integrated technological approach was designed and tested.