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

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.