Precision adjustment of spring contacts using laser forming

Small-lot, precision electrical contact-containing devices frequently require manual adjustment of their contact gaps under a microscope; a time consuming, skilled operator-dependent procedure. Laser forming has been shown effective in bending ∼mm-thick, low strength, flat steel alloy stock and is evaluated herein as a high productivity, high precision alternative. The application discussed uses thin, high reflectivity, high conductivity, and high strength Neyoro-G^™. Since laser forming requires thermal-gradient-induced non-homogeneous plastic strain, size-scale and material properties were of concern. Calculations employing simple models from the literature and a non-linear, transient finite element analysis (FEA) were used to evaluate feasibility and suggest laser processing parameters. The FEA model employed temperature-dependent mechanical properties; modeled both a scanned-spot and stationary bar-shaped source equal to the contact width; and used heat inputs chosen to promote through-thickness thermal gradients with peak temperatures at the Neyoro-G^™ final heat treatment temperature (to avoid softening). Material properties, process parameters and initial and final material conditions are discussed and related to bi-directional bending behaviour. The bar-shaped heat source was found to be more effective both by modelling and in reality.