Technical Note: Cu-Be Stress Corrosion Cracking in Ammonia⁽¹⁾

Cu-Be is used for spring contacts in high reliability connectors and related electrical components. It is a very strong material with good electrical conductivity. Phenolic resins are commonly used as insulating material in electrical components, and when these resins are formed by using a NH₄OH catalyst, NH₃ is liberated if the resin is heated. Ammonia outgassing levels as high as 4000 ppm have been observed at this laboratory for some resin heat treatments. Several investigations¹ –⁶  have shown that Cu-Be is susceptible to stress corrosion cracking (SCC) in ammoniacal environments, but quantitative data on the environmental conditions required for cracking are not available. Therefore, an investigation was undertaken to define the conditions required for cracking. This note will briefly discuss the effect of NH₃ and H₂O concentrations and stress intensity (K) on crack propagation in Cu-Be. The effects of O₂ and...