Werkstofforientierte Grundlagenforschung bleifreier Zinnlegierungen

Translated title of the contribution: Fundamental research on lead-free tin alloys with focus on the materials

Stefanie Scheiber

Research output: ThesisDoctoral Thesis

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Abstract

The European Union defined restrictions on hazardous elements due to environmental and health reasons. One of the limited metals is lead. The maximum content in diverse applications is fixed to 0.1 wt.-%. Therefore, new lead-free alloys have to be tested as substitute for eutectic Sn40Pb. This material is commonly used for low melting soldering in electric and electronic industry. There are various research activities, which focus on Pb-free eutectic compositions. Usually, ternary or quaternary elements are added to Sn-based matter. The additives should improve the material properties. Especially, the experiments intend to reach a melting temperature similar to Sn40Pb. This prevents expensive investments in new facilities. Additionally, the companies could continue using approved soldering techniques. The literature research of this thesis showed a number of publications on lead-free solders during the last decades. Unfortunately, a systematic overview about the effects of a wide range of alloying elements is completely missing. The aim of this work is to define ten material systems based on tin. For the design of experiments the software MODDE® Pro 12 is applied. Consequently, tin is melted in an induction furnace at the Chair of Non-Ferrous Metallurgy. The alloying elements silver, bismuth, copper, nickel as well as zinc are added with respect to the test planning. Lead impurities should be avoided. The base metal contains already 0.1 wt.-% Bi. In order to use the produced materials as solders the microstructural, thermic and mechanical properties have to be examined. After metallographic preparation scanning electron microscopy with energy dispersive x-ray spectroscopy is applied to investigate the intermetallic compounds, eutectics and matrix phase. The affinities of added elements to each other are showed. The results are compared to thermodynamic calculations using FactSage™ 7.2. Furthermore, these allow the evaluation of the solidus and liquidus temperatures of alloys. For experimental determination of melting behaviour dynamic differential scanning calorimetry is applied. Hardness measurements with Brinell’s method are executed for estimation and comparison of mechanical properties. Finally, the obtained values are added into the software MODDE® Pro 12 for calculation of statistical models. These can be used for prediction of material qualities within the selected borders of alloy systems for the application in diverse areas.
Translated title of the contributionFundamental research on lead-free tin alloys with focus on the materials
Original languageGerman
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Antrekowitsch, Helmut, Assessor A (internal)
  • Clemens, Helmut, Assessor B (internal)
Publication statusPublished - 2019

Bibliographical note

no embargo

Keywords

  • alloy development
  • Sn
  • lead-free
  • thermodynamics
  • DSC
  • hardness measurment
  • SEM/EDX
  • statistic modelling

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