A predominantly theoretical study is presented of the impact and solidification of molten solder droplets on a multi-layer substrate. This problem is of central importance to the novel micromanufacturing process called solder jetting, in which picoliter-size solder droplets are dispensed for the attachment of microelectronic components. The theoretical model is based on a Lagrangian formulation, and accounts for a host of thermal-fluid phenomena, including surface tension and heat transfer with solidification. Deforming finite elements with integrated automatic mesh generation are utilized to accommodate the large deformations which develop during the computations. An experimental investigation is also presented in which deposits produced by a prototype solder jetting apparatus are analysed using scanning electron microscopy. Results of simulations are presented in which variations of the initial droplet temperature, impact velocity, thermal contact resistance and initial substrate temperature are studied to demonstrate their impact on droplet spreading, on final deposit shapes and on the times to initiate and complete freezing. In many cases, non-intuitive results are observed, such as the non-monotonic dependence of the solidification time on variations of many of the parameters considered. Detailed study of the final solidified shapes, as well as the droplet configuration and flow filed at the onset of phase change, indicate strong coupling between the droplet dynamics and the freezing behavior.