SBIR Phase I: Ultra-Fine Solder Powder For Electronic Soldering

This Small Business Innovation Research Phase I project will demonstrate the feasibility of limiting surface oxidation of ultra-fine (1-10 micron) solder powder for electronic solder paste. Today, the use of ultra-fine powder for increased resolution of paste printing on printed wiring boards (PWBs) is impeded by the excessive oxide burden on the powder's huge surface area. If this impediment could be removed, and ultra-fine powders were supplied commercially, not only could PWB component population density increase by 10 times or more, but new forms of solder-paste printing, such as Drop-on-Demand, could be innovated. In this project, oxide control will be demonstrated with two approaches: 1) oxygen-barrier coatings applied in the powder-production apparatus and 2) addition of trace amounts of alloying metals which can protect the powder surface. Assay methods that can profile, in nanometer steps, the oxide layer on the solder spheres, will be employed. The ultra-fine powder will be produced by an existing process developed under an NSF/SBIR Phase II award. The commercial application of this project is in the manufacture of printed wiring boards. The world sales of solder paste for surface-mounted components on PWBs is more than $500million/year. Most of the paste is applied by stencil/squeegee printing. That process wastes about 30% of the paste or about $150 million per year. One objective of this project is to reduce waste by higher resolution printing. However, that cannot be achieved unless ultra-fine solder powder is available at a competitive price (about $0.05/g). As components become smaller (e.g., flip chips), the population is controlled by paste-printing resolution, not by component size. Financial implications of these outcomes should be sizeable.