COST531 Joint WG1/2 meeting SGTE/ NPL Database Activities 13 June 2003 Alan Dinsdale NPL Materials Centre NPL, UK

Scope of presentation  SGTE  NPL / SGTE database  Conclusions from Paris meeting  Uses of the database  Specific calculations and assessments  Prediction of surface tension

COST531: Working groups  Thermodynamics and Phase Diagrams  Literature search and selection of key systems  Optimised phase diagrams  Creation of critically assessed thermodynamic database  Also estimation of surface tension, wettability, electrical properties  Physical properties  Measurement of wettability, surface tension, viscosity, mechanical behaviour …  Chemical properties  Oxidation behaviour, toxicity, environmental aspects  Reliability  Thermal shock, overload failure, age hardening ….  Processing and Packaging  Flip chip technique etc.

SGTE Members  Canada ThermFact, Montreal.  France Institute National Polytechnique, Grenoble. (LTPCM) Association THERMODATA, Grenoble. IRSID, Maizières-les-Metz. Université Paris Sud, Chatenay-Malabry. (LCPMB)  Germany RWTH, Aachen. (Department of Materials Chemistry) Max Planck Institut für Metallforschung, Stuttgart. (PML) GTT Technologies, Hertzogenrath.  Sweden Royal Institute of Technology, Stockholm. (Department of Materials Science and Engineering) Thermo-Calc Software AB Stockholm.  United Kingdom National Physical Laboratory, Teddington. (Materials Centre) AEA Technology, Harwell.  USA The Spencer Group, Ithaca

Possible future members  NIST  Tohoku University  NASA

Landolt-Börnstein Numerical Data and Functional Relationships in Science and Technology New Series / Editor in Chief: W. Martienssen Group IV: Physical Chemistry Volume 19 Thermodynamic Properties of Inorganic Materials compiled by SGTE Subvolume B Binary Systems Phase Diagrams, Phase Transition Data, Integral and Partial Quantities of Alloys Part 1 Elements and Binary Systems from Ag-Al to Au-Tl

Contents of the NPL / SGTE database  Designed for use in the calculation of phase equilibria involving solders and other low melting alloy systems.  Covers the following 12 elements Ag, Al, Au, Bi, Cu, Ge, In, Pb, Sb, Si, Sn, Zn Contains data for  Binary systems (all 66 except Au-Zn)  Ternary systems (15 systems specifically assessed) Ag-Bi-Sn, Ag-Cu-Pb, Ag-Cu-Sn, Ag-Pb-Sn, Al-Cu-Si, Al-Sn-Zn, Au-In-Pb, Bi-In-Pb, Bi-In-Sn, Bi-In-Zn, Bi-Pb-Sn, Bi-Sn-Zn, Cu-Pb-Sn, In-Pb-Sn, In-Sn-Zn  Predictions can be made of thermodynamic properties of phase equilibria for wide range of compositions in that 12 component system

Agreement between SGTE and COST531  SGTE to provide a preliminary database for  use within COST531  internal research  SGTE, in return, will be able to use COST531 data.

Database management  Need to agree on  Scope of the database  Unary data  Key binary (and ternary ?) data  Models

Paris meeting: July 2002

Conclusions from Paris meeting  Concentrate on: Ag-Bi-Cu-Sn  with the addition of Au, In, Ni, P, Pd, Sb, Zn  Plus (?) Al, Pb Possible initial scope of database: Ag-Bi-Cu-Pb-Sn with (Ni-P) and Pd

Other datasets available (not in SGTE solders database)  Ag-Ni, Ag-Pd  Cu-Ni, Cu-P  Ni-P, Ni-Pd, Ni-Sn  Pb-Pd  Pd-Sn

Missing systems  Binary systems: Ag-P, Bi-Ni, Bi-P, Bi-Pd, Cu-Pd, P-Sn, Ni-Pb, P-Pb  Ternary systems: Ag-Bi-Cu, Bi-Cu-Sn, Ag-Cu-Ni, Ag-Ni-Sn, Ag-Cu-P, Ag-P-Sn, Cu-P-Sn, Ag-Cu-Pd, Ag-Pd-Sn, Cu-Pd-Sn

Unary data  Based on CALPHAD 1991, 15(4),  Updated version for CALPHAD 2003 (?)  Major changes for solders relate to: Snhcp_a3 fcc_a1 tetragonal_a6 In fcc_a1 tet_alpha1 bct_a5 rhombohedral_a5 biin_epsilon hcp_zn

Key papers from CALPHAD conference  Ursula Kattner: “Thermodynamic assessment of the Sn- Cu-Ni and Sn-Ag-Cu-Ni system”  Zbigniew Moser: “Physical, electrical and mechanical studies of (Sn-Ag_eut+Cu=Pb-free soldering materials”  Ales Kroupa: “Database for calculation of lead free solders”  Nele Moelans: “Thermodynamic optimization of the lead- free solder system Bi-In-Sn-Zn”

Types of properties covered  Enthalpies  Vapour pressures  Specific heat  Phase diagrams  Liquidus and solidus temperatures  Molar volumes and densities

Uses of the database  To calculate the liquidus and solidus temperatures of a solder  To calculate the effect of contamination of a new lead free solder with a conventional Pb-Sn solder  To calculate the enthalpy release on solidification of a solder  To calculate the volume changes in a solder on solidification and during thermal cycling  Calculation of surface tension

Specific calculations  Binary phase diagrams  Ternary phase diagrams  Isopleths  Effect of pressure  Constant composition vs temperature  Mass phase  Heat capacity  Volume  Enthalpy  Prediction of surface tension

Prediction of surface tension  Based on the approach of Tanaka  Using the Butler equation to estimate the surface tension from bulk thermodynamic properties  Tested with success for metallic and ionic melts  Assumes an equilibrium between the bulk liquid and the surface liquid  Generalised and extended in this project to cover multicomponent systems  Tested in detail for solder systems  Uses the new database for solders  Makes use of Brian Keene’s review of experimental surface tension data for tin and lead free solders (1993)  Provides good basis for virtual measurement system for solders

Model for surface tension (1)  As originally presented:  This relates the surface tension of the binary alloy to the surface tension of the pure components and the thermodynamic properties of the bulk and the surface monolayer

Model for surface tension (2)  These equations can be transformed into:  and expresses that the chemical potential of the components is equal in the bulk and surface layer  The thermodynamic properties of the bulk are well represented by standard thermodynamic models

Model for surface tension (3)  The thermodynamic properties of the surface layer is given by:  Where A 1 is the surface area of component 1,  1 is the surface tension of component 1  N 0 is the Avogadro number and V 1 the molar volume of component 1

Model for surface tension (4)  There is an empirical relationship between G mix, the excess Gibbs energy of mixing, for the surface and G mix for the bulk  Gibbs energy of surface layer given by:  The surface tension, , is calculated to be the value which just brings the surface into equilibrium with the bulk.  This allow the model to be generalised to any number of components

Sample calculations: Bi-Sn 608 K

Surface composition: Bi-Sn 608 K

Ag-Sn 1273 K

Ag-Sn 40%Sn : effect of temperature

Sn-Ag-Cu: variation with temperature

Surface tension of pure Sn

Surface tension of pure Pb