Heraeus Electronics has developed a new thick film gold conductor paste that avoids lead and cadmium. Specially matched ingredients also ensure a denser fired film and excellent bond strength with the ability for etching.
The thick film gold conductor paste can be used for high-reliability applications, such as medical devices as well as high-frequency circuits for communications. Those applications require high performance at high and low temperatures, in chemically aggressive environments, or extremely humid conditions. The paste performs well on dielectrics and on oxide substrate compositions even when multiple firing steps are required.
For the paste, specially matched ingredients are used. First, the specific gold powder ensures a higher and tighter bond distribution. Second, a vehicle formation that ensures maximum densification. Third, a special material combination achieves an excellent bond strength when etched on aluminum oxide. Regulations in the electronics industry have called for the elimination of hazardous substances in thick film pastes for quite some time, but exemptions are in place for critical applications. These exemptions are expected to expire in the next few years.
“Demands for dense, defect-free, etchable gold films that deliver equivalent or improved performance to their lead containing counterparts have been increasing dramatically” says Dean Buzby, Global Product Manager Thick Film. “Continuing trends towards circuit miniaturization and higher packaging density result in greater complexity. Therefore, the thick film gold properties become increasingly critical.”
It can screen print and resolve fine features down to 100 micron-size lines and spaces. The paste also has the ability to be etched using methods like photolithography processes. This results in even higher density circuit designs down to 25–50 micron-size lines and spaces. Wirebond adhesion of both thin gold and aluminum wire is excellent when fired directly onto ceramic as well as on dielectrics.