Autocatalytic Laser Activator for Both UV and NIR Lasers: Preparation of Circuits on Polymer Substrates by Selective Metallization

Abstract

In laser-induced selective metallization (LISM), conventional laser activators only work at a single laser wavelength. This study reported a new laser activator (MoO3) very suitable for both 355 nm UV and 1064 nm near-infrared (NIR) lasers for the first time. When applying MoO3 to polymers, the prepared Cu layer on laser-activated polymers showed a good conductivity (2.63 × 106 Ω–1·m–1) and excellent adhesion. Scanning electron microscopy, optical microscopy, and resistance analysis revealed the excellent LISM performance of the polymer/MoO3 composites, and the quality of the Cu layer prepared using the UV laser is much better than that using the NIR laser. The limit width of the copper wire prepared by the UV laser is as narrow as 30.1 μm. We also confirmed the mechanism of MoO3 initiating electroless copper plating after laser activation to be the autocatalytic mechanism, which is very different from the conventional reduction mechanism. The effect of laser activation was only to expose the MoO3 active species to the polymer surface. X-ray diffraction and tube experiments revealed that the activity of α·h-MoO3 was higher than that of α-MoO3. X-ray photoelectron spectroscopy indicated that a part of Mo6+ was reduced to Mo5+ during laser activations, leading to the increase of the oxygen vacancies in MoO3 and possibly further enhancing the activity of MoO3. Besides, the micro-rough structures caused by the laser on the polymer surface provided riveting points for successfully depositing the copper layer. The Ni–Cu, Ag–Cu, and Au–Ni–Cu layers were obtained via the continued deposit of other metals on the Cu layer. The resistances of these metal layers had much better stability than that of the neat Cu layer. Furthermore, the Au layer further enhanced the conductivity of the circuit. The proposed strategy is easy for large-scale industrial applications, which will greatly expand the application scenarios of the LISM field.

Laser-Induced Selective Metallization on Polymers for Both NIR and UV Lasers: Preparing 2D and 3D Circuits

“…This peak is due to the thermal oxidation on the surface at high temperatures during the laser activation . The peak of CO generated by a 1064 nm NIR laser is apparently larger than that produced by a 355 nm UV laser, indicating that the NIR laser’s thermal effect is greater than that of the UV laser, which corresponds to our previous conclusion . Since the NIR laser’s thermal effect is higher than that of the UV laser, the composites’ surface is ablated and vaporized to a greater extent at the moment of NIR laser activation, and therefore, the “pit” generated by the NIR laser is larger and the surface appears darker (Figures a,b, and S5).…”

“…The characterizations revealed that the mechanism of laser activation for copper pyrophosphate was the reduction mechanism, which was entirely different from our previous study. 33 S2. Hemispherical and tileshaped 3D parts were prepared.…”

“…Regardless of the type of laser sensitizers, the above laser sensitizers only can be activated by an NIR laser with 1064 nm. However, with the development of the 355 nm UV laser system, the UV laser gradually shows its unique advantages in LISM . Furthermore, laser sensitizers that can work with both NIR laser and UV laser are urgently needed.…”

“…Therefore, studying laser sensitizers that can work with multiwavelength lasers is necessary and important for the field of LISM. Not long ago, our group reported that MoO 3 could conduct LISM as a laser sensitizer with both 1064 nm NIR and 355 nm UV laser, and its mechanism of laser activation was confirmed as an autocatalytic mechanism . Shortly thereafter, we worked on finding a sensitizer that is suitable to both UV and NIR lasers and belongs to the reduction mechanism, which is the subject and core of this work.…”

“…After NIR and UV laser activation and ECP, excellent 2D and 3D copper patterns (or circuits) were successfully obtained at the laser-activated area of the ABS/Cu 2 P 2 O 7 composite. The characterizations revealed that the mechanism of laser activation for copper pyrophosphate was the reduction mechanism, which was entirely different from our previous study …”