Characterization of Thermal Compression Wire Bonds to Thick-Film Conductors on Porcelain Substrates

Four conductor compositions are examined for thermal compression bondability on porcelainized metal substrates. These materials, Thick Film Systems (TFS) 3045 Au, 3106 Pt-Au, 3535 Pt-Pd-Ag, and 3408 Pd-Ag, were evaluated on Alphamet® substrates. The study includes conductors printed on the substrate enamel and on substrates previously printed and fired with the Thick Film Systems 1129 RCB dielectric. Polished cross sections of the TFS 3045 Au conductor on both the enamel and the dielectric are examined with an optical microscope and electron microprobe. Thermal compression bonds are made to each of the four metallizations printed on both the enamel and the dielectric. Pull strengths are measured initially and after storage for 1000 h at 150°C. The effect of storage on electrical performance is also examined. The results obtained show initial mean bond strengths between 5.66 and 6.18 g and between 5.59 and 6.22 g after storage. The change in resistance due to high-temperature storage ranges from -2.4 to +2.2 percent for the various metallization-print surface com- binations.