Anti-reflection Layer-Sputtered Transparent Polyimide Substrate with Reliable Adhesion Strength to the Copper Layer

Abstract

Parameters of DC-reactive magnetron sputtering are optimized to deposit anti-reflection (AR) layers on transparent polyimide (PI) substrates, followed by the deposition of the conductive copper layer, to fabricate practically reliable composite films as advanced flexible circuits. When the deposition thickness is controlled and the gas composition during sputtering is adjusted, the resultant AR layer-coated PI film exhibits low reflectance and reveals improved adhesion strength to the copper layer. The adhesion reliability tests confirm that the peel strength between the PI film and the deposited layers could be further improved after thermal processing due to the formation of a worm-like morphology for better mechanical interlocking with layers. The facile sputtering process successfully fabricates a reliable substrate material with low reflectance and sufficient adhesion strength to copper for application as flexible printed circuits.

Sputtered anti-reflection layer on transparent polyimide substrate improves adhesion strength to copper layer: effects of layer thickness and sputtering power

“…According to our previous work, the presence of primer layer on fluorinated PI significantly improves the adhesion strength. 8 Therefore, the transparent PI films (thickness = 25 ± 1 μm) coated with a thin layer of primer (thickness = 1.1 ± 0.1 μm) provided by Pomiran Metalization Research Co., Ltd. were selected as the substrates in this work.…”

“…Therefore, an anti-reflective (AR) layer is often fabricated between colorless PI and electronic circuits to hide the electronic circuits. 1,8–10…”

“…From our previous work, the deposition of AR layers on colorless PI substrates successfully enhances the adhesion strength between PI and the copper (Cu) layer, which mimics the electronic circuits. 8 By adjusting the parameters, such as gas composition, of DC reactive magnetron sputtering, the AR layer-coated transparent PI substrates not only exhibit high adhesion strength to the Cu layer but low reflectance, indicating its potential as advanced flexible printed circuit material. In this work, we further investigate the effects of the AR-layer thickness and the sputtering power on the adhesive and optical properties of PI composite films.…”

Progress of research on the bonding-strength improvement of two-layer adhesive-free flexible copper-clad laminates

“…Tsai et al 116 deposited an antireflective (AR) layer on a PI film by optimizing the parameters of direct-current magnetron sputtering, reducing the reflectivity of the sheet and improving its bonding strength with copper foils. With the heat-treated PI film, the interface developed a worm-like morphology, the mechanical interlocking of the layers deepened, and the peel strength of the layers increased ( Fig.…”