Low-temperature air-fireable glass-free metallic thick-film electrical conductor materials

Low-temperature air-fireable glass-free metallic thick-film electrical cond uctor materials were developed for interconnections in electronic packaging . The thick film with composition (by weight) 96.60%Ag, 1.38%Cu, 0.28%Al, 0 .35%Ti, and 1.39%Sn used Ti-Al as the active binder. After firing in air at 500 degreesC it exhibited low electrical resistivity (6.2 x 10(-6) Omega . cm), good scratch resistance and strong bonding with the alumina substrate, with no pinholes. The firing caused complete melting of the particles in t he film. Firing in argon rather than air degraded both electrical and bondi ng properties, due to the absence of oxygen, which helped to burn out the v ehicle. The use of Ti rather than Ti-Al as the active binder resulted in ho les in the thick film due to incomplete melting of the Ti-rich particles an d also resulted in poor scratch resistance and weaker bonding to the substr ate. Tin in the composition was important for promoting melting and protect ing the active particles from oxidation during firing.