Green precision manufacturing of ultrathin copper foil leadframes by ultraviolet nanosecond pulsed laser microdrilling

While copper alloy leadframe is the key part for packaging of integrated circuit, developing its clean and precision fabrication technology over wet etching is important for the advancement of sustainable manufacturing. In this work, we propose a novel method for achieving high precision and clean fabrication of leadframes with micron-scale thickness and feature dimensions on 100 μm thinckness copper alloy foil by using nanosecond pulsed laser microdrilling, without the use of etching fluids. Specifically, the multi-pulse laser ablation mechanism of copper alloy is theoretically analyzed by numerical modeling and simulation, based on which a high precision analytical model of ablated material removal rate is established to predict the dependence of micropattern taper, heat damage zone and processing efficiency on utilized laser power. Subsequently, a generalized laser microdrilling method with varying laser power and design dimension scaling is proposed to control the taper and dimensional accuracy of complex micropatterns. And an optical-mechanical coupling laser microdrilling platform is constructed to synchronously control the laser turning on/off, mechanical axis movement and laser processing parameter. Ultimately, one-piece molding of large scale leadframe array, which is composed of high density of burr-free micropatterns with a small taper of 1.7° and high shape accuracy, is achieved on C194 copper alloy foil with a thickness of 100 μm. The present work provides a feasible green solution for the high precision fabrication of leadframes with micron-scale thickness and feature dimensions.