Production of solder microdroplets using a highly parallel and contact-free printing method

This paper reports for the first time on the design and experimental characterization of a highly parallel non-contact dispenser for molten solder micro droplets. The dispenser relies on reusable and exchangeable nozzle plates made from silicon, containing typically 1-25 nozzles of 50mum diameter arranged in an application specific pattern. This enables parallel dispensing while a fast adaptation to different pad layouts is possible. In the presented configuration the non-contact dispenser prints up to 25 solder droplets of 0.5 nl volume simultaneously at a typical droplet velocity of approx. 2 m/s. This leads to well confined and spherical shaped solder bumps of 130 mum size (CV of 4 %) on a gold substrate.