The interpretation of the DSC signals of the lead-free solder alloy systems using the CALPHAD approach
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| Year of publication | 2009 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | The knowledge of the phase diagrams and the predictions of the respective liquidus and solidus temperatures are of a great importance. In the present study, the heat flow differential scanning calorimetry (DSC) was used to describe the phase transformations in the lead-free solder systems Sn-Ag-Cu and Sn-Ag-Cu-X (X=Bi, In). We used the Neztsch STA CD/3/403/5/G instrument that enables for the detection of the DSC signal using the heating and cooling rates of down to 0.1 K/min. At these conditions, the samples could be considered to be in the state close to the thermodynamic equilibrium. The DSC heating signal of the materials consisted of two or more different overlapping peaks resulting from the precipitation of secondary phases. The equilibrium state calculations were performed using the CALPHAD approach. The individual phases and their molar Gibbs energies were described by the parameters taken from the COST531 Thermodynamic Database of Lead-free Solders [1]. Since the CALPHAD approach allows for the calculation of thermodynamic functions, the experimental DSC curves could be simulated using the calculated molar enthalpies of the solders (deltaH). The standard molar enthalpies were calculated for different temperatures and for the various lead-free alloys. The respective temperature derivatives were directly and successfully compared with the experimental DSC curves. |
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