Analysis of laser metal-cut energy process window

Metal fuses for laser redundant links have been used for years in laser repair application. Nonetheless, reliability problems have occurred for laser metal cut structures, such as the material leftover remaining at the bottom of the cut site or the formation of a lower corner crack. In this paper, a special finite element Two-Stage Laser Cut Simulation Model (TSLCSM) is proposed to study the cut process. Compared with other simulation methods for similar purposes, the proposed model not only includes the stress-relief effect caused by cracking and breakthrough of passivation caused by upper corner cracks, but it also explains the laser-cut mechanism ignoring the metal underlayer. It proves earlier experimental results that a laser-energy window exists for each cut structure under a specified laser pulse. Different laser cut structures and different laser parameters are considered in the simulation, and useful guidelines are obtained for a maximum laser-energy process window. Experimental observations consistent with simulation results show that the differential between upper corner stress and lower corner stress is temporarily dependent on the passivation breakthrough caused by upper corner cracks. Also, it is shown that lower corner cracks can be formed at much lower laser energies than previously expected.