Applicable Business AreasFCCL manufacturers, Flexible printed circuit (FPC) manufacturers, Communication component manufacturers, Mobile device manufacturers, Base station equipment manufacturers
Target ApplicationsFCCLs used in high frequency circuit fabrication
To accommodate the rapid increase in data traffic driven by high resolution video streaming and the widespread use of generative AI, the communications industry is moving toward the utilization of gigahertz and higher frequency bands. Because transmission loss
increases as signal frequency rises, various design approaches are required to minimize loss in high frequency circuits, which serve as the transmission paths.
One well known approach is to reduce dielectric loss by selecting substrate materials with low dielectric constant (Dk) and low dielectric dissipation factor (Df). Liquid crystal polymers (LCPs) are widely used in flexible printed circuits (FPCs) for this purpose. However, LCPs exhibit a large coefficient of thermal expansion (CTE) mismatch with copper foil, which creates challenges in dimensional stability as circuit patterns continue to become finer.
To address this, Resonac proposes a polyimide resin that offers low Dk and low Df comparable to LCPs, while significantly reducing the CTE mismatch with copper foil.
By directly coating our polyimide resin solution onto copper foil, flexible copper clad laminates (FCCLs) can be fabricated (Fig. 1). As the thermal expansion behavior of our polyimide closely matches that of copper foil, it contributes to improved dimensional stability in high frequency FPC circuits, where patterning density and multilayer structures continue to advance.
(a) Fabrication Process
(b) Fabrication Examples
Films made from our polyimide resin were compared with conventional LCP films across several key properties.
Resonac’s polyimide demonstrated a lower Dk than LCP and a comparable Df (Fig. 2). This indicates that high frequency circuits using our polyimide can be expected to exhibit reduced dielectric loss originating from the substrate.
(a) Comparison of Dk
(b) Comparison of Df
Note: The data shown are representative examples of measurement and calculation results and do not guarantee product quality.
While LCP exhibits a large CTE difference from copper foil across the entire temperature range, our polyimide shows copper like thermal expansion behavior from room temperature up to approximately 300°C. As a result, FCCLs fabricated by coating our polyimide onto copper foil exhibit reduced warpage and improved dimensional stability in high frequency circuits.
Updated: March 19, 2026
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