Single-pulse Conduction Limited Laser Welding Using A Diffractive Optical Element

Abstract

Conduction limited laser welding is commonly used in electronic and battery applications, where a high width-to-depth ratio weld is desirable. A laser beam with Gaussian or top-hat distributions is often used to produce conduction limited spot welds. Both these energy distributions result in a higher proportion of the laser beam energy being introduced towards the centre of the welded spot and consequently, a reduced penetration weld towards the circumference of the beam spot. The use of diffractive optical elements to tailor the energy distribution of the laser beam has been evaluated. An incident laser beam with an energy distribution in the shape of a ring or C-shape was projected onto the material, which results in heat propagating towards the centre, producing a shallow weld with a consistent depth of penetration across the entire overlapped joint. The results confirmed a corresponding thermal model which predicted an even distribution of heat at the joint interface.