| abstract |
The present invention relates to a thick film formed of a mixture of metal powders and metallo-organic decomposition (MOD) compounds in an organic liquid vehicle and a process for advantageously applying them to a substrate by silk screening or other printing technology. The mixtures preferably contain metal flake with a ratio of the maximum dimension to the minimum dimension of between 5 and 50. The vehicle may include a colloidal metal powder with a diameter of about 10 to about 40 nanometers. The concentration of the colloidal metal in the suspension can range from about 10 to about 50% by weight. The MOD compound begins to decompose at a temperature of approximately about 200 DEG C. to promote consolidation of the metal constituents and bonding to the substrate which is complete at temperatures less than 450 DEG C. in a time less than six minutes. The mixtures can be applied by silk screening, stencilling, gravure or lithography to a polymer-based circuit board substrate for producing rigid and flexible printed wiring boards in a single operation with negligible generation of hazardous wastes. The same mixtures can be used in place of solder to assemble circuits by bonding electrical components to conductors as well as to make the conductors themselves. |