Flexible circuit substrates are the foundation for building highly reliable and performance flexible circuits or flex circuits for flexible electronics. Traditional flexible circuit substrates are based on polyimide and polyimide with acrylic-type adhesive. More recent use of high-temperature thermoplastics liquid crystal polymers such as PEEK and modified PTFE for specific enhanced performance.
While traditional polyimide-based and more recently adopted modified PTFE and LCP polymers have been evolved over time with proven performances, there are still limitations that are inherent in the substrate material characteristics.
- Low thickness copper flexible circuit substrates with polyimide are typically produced with vacuum deposition methods that are inherently high in costs for production and limited in high volume availability. Thus, the delivery time tends to be long and not very reliable.
- The use of acrylic adhesive on polyimide or modified PTFE while solving the production limitation, the inherent material properties of acrylic-based adhesive tend to lower the performance of the resulting flexible circuits and flexible electronics.
- Polyimide, acrylic-polyimide, and LCP polymers are inherently higher dielectric constant and higher moisture absorption for the millimeter-wave and microwave electronics at 5G and 6G frequencies.