Effect of heat-affected zone on the nanosecond pulsed laser scanning ablation of Ag nanoparticle layer

Pulsed laser ablation can be used in printed electronics to remove silver (Ag) nanoparticle (NP) inks from undesired locations. Removing Ag NP involves a scanning ablation process, in which laser beams are irradiated on spots irradiated by a previous laser beam. In this study, that the heat-affected zone (HAZ), which is the peripheral area of the ablation crater where NPs are not ablated but are affected by heat, greatly influences the ablation aspects. Ablation failure was observed in short laser beam displacements, where the irradiated laser energy per unit length increased. Additional experimental investigation and thermal analysis concluded that property variations, such as increased reflectivity and thermal conductivity, suppressed the temperature increase and made it more difficult for the HAZ and nearby Ag NP to be ablated. Moreover, the ablated lines formed by a higher laser beam fluence and shorter laser beam displacement were not as ablated as the lines formed with a relatively lower laser beam fluence and longer laser beam displacement. Through detailed analysis, we deduced that the local fluence of the second laser beam irradiated on the HAZ was a more critical parameter than the peak fluence of the laser beam. We suggest that in the case of a Gaussian laser beam, the laser beam displacement should be equal to the radius of the ablation crater and HAZ to maximize the local fluence irradiated on the HAZ and minimize the adverse effects of the HAZ. The results can provide a guideline for future manufacturers to perform Ag NP layer ablation while considering the influence of the HAZ.