US6476332: Conductor Systems for Thick Film Electronic Circuits
This patent documents a method that uses non-toxic lead-free solder to create conductors for thick film electronics. After inks are applied to a ceramic substrate, the substrate is then dried and fired in a furnace, which allows the conductor to form. Palladium silver solder paste is then applied to the conductor pads, and electrical components are placed on top. By using silver solder instead of lead, conductors for thick film electronics are able to bond without a toxic medium. The substrate is then placed in a reflow furnace, where the solder can melt and then eventually solidify. Thick film technology is essential to many electronic products, including vehicles. The automotive industry uses thick film products because these electronic circuits are durable and remain unaffected by the extreme operating environment inside of a car's engine compartment. While thick film methods and techniques have been successful for quite some time, the lead (Pb) in the tin (Sn) lead solder has been known to be exceptionally damaging to the environment. Therefore, the importance of the invention described in this patent cannot be understated.
Link to Official Patent: Conductor Systems for Thick Film Electronic Circuits
Keyword: Thick Film