3D-printed solder droplet circuit boards research

Tom's research contract gave to a mech eng colleague to attempt 3D-printed PCBs. Motorola and Intel also tried; everyone gave up because of surface tension (developed quantitatively in §7).

Some of the early attempts were at metals. In fact I had a research contract — I didn't need the money, so I gave it to someone over in mechanical engineering who wanted to do 3D printing of printed circuit boards.

Tom's collaboration with Prof. Sonin (MIT mechanical engineering) on jetting lead-tin solder droplets to print circuit boards. Used to illustrate how Young's equation breaks down outside equilibrium and simple geometry. "Tens and hundreds of millions of dollars" of industry effort have failed at this for twenty years.

Twenty years ago I was providing funding for Professor Sonin in mechanical engineering, who's retired now. Professor Sonin is an excellent mathematician, fluid-flow analyst. We were trying to do — sort of pre-3D-printed — printing of circuit boards. You could make one-of-a-kind circuit boards by shooting out little drops of lead-tin solder. People have been doing this with polymers; why couldn't we do it with liquid metal? Tens and hundreds of millions of dollars have been spent trying to do this with liquid metals, and it has not yet been perfected after twenty years.