Materials and Manufacturing in Electronics Prof. Dr.-Ing. Jürgen Villain University of Applied Sciences Augsburg, Germany Department of Electrical Engineering COST 531 Meeting Berlin

Lectures and Team Lectures Materials Science for Engineers Manufacturing in Electronics Packaging Design and Strength of Materials Team in the Lab Dipl.-Ing. T. Qasim (material science) Dipl.-Ing. Ch. Weippert (crystallography) Dipl.-Ing. (FH) A. Svetly (mechanical engineering) J. Pahl (material test) E. Hundt (measuring technique) Students, candidate for a doctor`s degree

Topics of Research Influence of structure on the mechanical behaviour of metals Determination of mechanical properties of small specimens depending on temperature and strain rate Size effect on mechanical properties of metals in electronics Vapour-phase soldering of lead-free solder materials Creep behaviour of solder materials Formation of intermediate phases in small solder volumes

Equipment of the Lab Macro and micro tension test machines (0.5 N – 500 N, -55 °C/250 °C) Pull- and Shear-Test Creep Test (RT/200 °C) Laser extensometer Special clamping jaws for small specimens Micro-hardness tester SEM with EDX (tension and creep tests inside possible) X-ray fluorescent analysis Thermal shock Vapour-Phase soldering Wetting tester Ovens

Special clamping jaws for small Cu-Foils (10 µm µm) Tensile module for small specimens (part of SEM) Tools for small specimens

Material parameters describing exactly the material behaviour of electronic devices under working conditions are necessary for thermo-mechanical simulations. Elongation at rupture of Sn43Bi57 for different temperatures and strain rates Tensile strength of Sn43Bi57 for different temperatures and strain rates Determination of mechanical properties of small specimens depending on temperature and strain rate

Size Effect on Mechanical Properties of Copper Foils The smaller the tested volume the lower the ductility !

Manufacturing and Reliability of Lead-Free-Solders Topics: Manufacturing parameters, shear and tensile strength, creep- behaviour, migration, intermediate compounds Solder materials: Sn91Zn9, Sn43Bi57, Sn96.5Ag3.5, Sn93.5Ag3.8Cu0.7Bi2(4)

Phase Formation in Small Solder Volumes (intermediate phases) Sn43Bi57, device Sn, Pad: Cu/Ni/Au Sn91Zn9, device Sn, Pad: Cu/Ni/Au Small solder volumes are out of thermodynamic equilibrium and consist mainly of intermediate phases (3 – 5 elements) with almost completely unknown material properties.

60Sn40Pb, Q m = 0.73 eV 43Sn57Bi, Q m = 0.76 eV 91Sn9Zn, Q m = 1.01 eV 96.5Sn3.5Ag, Q m = 0.87 eV Lowest homologoues temperature, highest homologoues stress Creep behaviour of solder materials The creep behaviour of solder materials at high homologous temperatures can be described using a viscoplastic equation.  (t,T,  )=  o J(t) a  a 

Comparison of Activation Energies and Time-Temperature Shift-Factor Round phases Dendritic or scorched phases

Sn60Pb40, stress 5 N/mm 2, same structure, same strain rate. The smaller the tested volume the lower the creep resistance. Size Effect on Creep Behaviour of a Solder Material

Further investigations Analysis of metallic and intermediate phases of small solder volumes Determination of the mechanical behaviour of eutectic and non eutectic solder materials with regard to structure and tested volume under experimental and numerical view