Author: H.C. Peebles Company: F2 Associates Date Published: 4/28/1997
Surface Mount International
Abstract: This paper describes the design and initial test results for a magneto-hydrodynamically (MI-ID) driven solder jetting device capable of on demand delivery of small droplets of molten solder. The design consists of a solder reservoir, a magneto-hydrodynamic (MI-ID) drive chamber, a permanent magnet and a small jetting orifice. An electric current is passed through the tie chamber in the presence a magnetic field generating a Lorentz force on the molten solder in the chamber. The pressure created by this form drives solder out of the jetter orifke. Ondemmxl generation of single drops of 610 pm diameter 63 ‘/0 Sn-Pb solder at 230° C was demonstrated using single 130 usec wide square wave current pulses with an amplitude of 40 A. Solder droplet generation under these conditions was found to be highly reproducible. Trajectories tended to cluster around a single, near vertical direction with a standard deviation of +0. 16°. The diameter of the emitted droplets varied by no more than ± 2’Yo.