Fabrication of adhesion-enhanced and highly reliable copper circuits onto flexible substrates via a scribing–seeding–plating process

Abstract

In this study, a novel scribing–seeding–plating (SSP) process for the fabrication of copper circuits with a strong adhesion strength of 39.68 N cm⁻¹ and a high conductivity of 4.69 × 10⁷ S m⁻¹ (about 82.33% of bulk copper) onto flexible sandpaper substrates was developed. Specifically, a simple 450 nm blue laser pulse was firstly employed to scribe and modify the sandpaper surface, which caused the in situ generation of hydrophilic groups and ablated grooves. Then, Au catalytic nanoparticles were seeded on the laser direct scribing zones and subsequently catalyzed the electroless copper plating. The processing parameters were optimized by the Box–Behnken response surface methodology to obtain the optimal adhesion strength, and the best local maximum was found to be at 610.56 # for the mesh number of the sandpaper, a laser fluence of 15.38 J cm⁻², a scanning speed of 300.00 mm s⁻¹, and a scanning line interval of 13.21 μm. Remarkably, the optimized sandpaper-based Cu circuits maintained good anti-oxidation performance, favorable adhesion and reliable flexibility even after over 1000 bending or folding cycles. This environmentally friendly and effective SSP process for fabricating copper circuits onto sandpaper has great potential applications in flexible printed circuits and low-cost RFID tags.