Nanosecond pulsed laser irradiation of metal for processing microgroove with vertical sidewalls

Laser processing is widely used in the manufacture of surface patterns. However, it faces new challenges under some industrial demands. For example, the fine cladding circuit requires that the metal layer is precisely etched in depth for slight damage to the substrate and the formed conductive tracks have vertical sidewalls for higher precision. The former can be achieved by a reasonable control of the process parameters, but the latter is difficult to realize by conventional laser milling since the energy distribution of the spot is Gaussian. In this situation, a new laser processing method, pre-etching then sidewall trimming, is proposed to reduce the taper angle of the etched edge. It features an additional trimming process in which the laser process parameters are planned orderly for their relatively independent effect, and the multiaxis machining technology is introduced to realize the etching with oblique incidence. To control the etching depth in pre-etching, the ablation result of microgroove is predicted by building the laser ablation model at vertical incidence. Furthermore, the laser ablation model at oblique incidence is developed and the planning method of process parameters for the sidewall trimming is researched. The operation of the proposed processing method is completed through a five-axis laser processing machine tool. It is demonstrated that the prepared microgroove has the taper angle less than 3° (decrease degree > 90%). The research achievements improve the sloping sidewalls caused by the inherent characteristic of laser, which has practical application value for manufacturing the surface pattern with high-quality edge.