Volume 5, Issue 1 (January 1977)
Correlation Between Leaking Glass/Metal Seals and Wire Defects in Dry Reed Contacts
Considerable variability in the quality of the surface finish on Remendur (equiatomic iron/cobalt with 2.5 to 3.0% vanadium) wire has been experienced and has seemed to have some relationship with the ability to consistently produce gas-tight, glass-to-metal seals. This paper reports on an attempt to develop a significant and quantitative correlation between relevant surface defects and the tendency to produce leaking seals by using optical cross-sectioning and SEM techniques. Results indicate a significant correlation does exist between surface defects observed in cross section and numbers of leaking seals. However, other factors which contribute to leaking tendency, as well as the limits of resolution of an optical cross-sectioning technique, prevent a quantitative analysis of the data sufficient to predict percentages of leaking seals to tenths of one percent. The approach does have application in detecting wire which is likely to produce greater than 1 to 2% leaking seals from that which is subject only to the vagaries of the sealing machines. Observation of the wire surface with a scanning electron microscope is strictly qualitative and appears to be more difficult to correlate with the tendency to produce leaking seals than cross-sectional evaluation.