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 %.
Measurement of contact angle and work of adhesion at high temperature
A critical review is given of the present state of knowledge and future perspectives in high-temperature contact angle measurement. Experimental results obtained by the different versions of the sessile drop method and by various procedures are given in order to illustrate the two main sources of scatter in wettability data, the first being related to the quality of the substrates and the second to control of the furnace atmosphere.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.