A new copper based hermetic sealing material: A comparison with AgCu28GeCo0.3
For vacuum brazing applications Hermetic Sealing Materials (HSM) with low partial pressure are widely used to join copper or stainless steel parts. For joining copper AgCu28 is a widespread material, which is well characterized and investigated. For stainless steel, AgCu28Ge2Co0.3 is commonly used if the same brazing temperature as AgCu28 is required. Umicore Technical Materials has developed a new copper-based HSM. The tensile strength of the stainless steel joints on stainless steel is comparable to AgCu28Ge2Co0.3 and the wettability is significantly improved. In this article, the physical properties of the alloy and its brazed joints will be presented in comparison to AgCu28GeCo0.3. However, today the silver content of HSMs is more in focus than in the past decades, because it has the biggest impact on the material prices. To accommodate this trend the total silver content of the new HSM is reduced by almost 44 %.
Brazing: For the engineering technologist
Preface. Brazing fundamentals. Parameters and elements of brazing. Brazing heating methods. Braze filler metal and base material families. Fluxes, atmospheres - types and forms. Joint design, tooling/fixturing, surface preparation, inspection and safety. Applications and future of the process. Appendix. Index.
CONTACT ANGLE HYSTERESIS DUE TO ROUGHNESS IN FOUR METAL/SAPPHIRE SYSTEMS
Reversible advancing and receding contact angles of four metallic liquids (Hg, Sn, Al and Al-Sn4,76at% ) on sapphire were measured by the immersion-emersion tensiometric technique. Alumina cylinders with a mean random surface roughness from a few nanometres to about two micrometres are used. For the non-wetting liquids (Hg, Sn), composite wetting is observed even with roughness as low as 0.5mm. For the wetting liquids (Al and Al-alloy), a residual hysteresis of the contact angle was found at vanishing roughness, a fact that was ascribed to a slight attack of alumina by liquid aluminium, inducing surface anisotropy. Results are described by a single equation which relates the difference between the cosine of advancing and receding contact angles to the surface roughness parameters of the solid.