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Influence of Ni addition on the thermal parameters during directional solidification of Sn-Cu solder alloys

Grant number: 11/06694-9
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): May 01, 2011
Effective date (End): April 30, 2012
Field of knowledge:Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
Principal Investigator:José Eduardo Spinelli
Grantee:Giovana Lima Ghiraldelli
Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Nowadays the traditional Sn-Pb brazing alloys have been replaced by alternative solder alloys. This is due to the recognized hazardousness of lead, whose complete market exclusion is predicted as unavoidable in few years. The brazing process is widely used to connect microelectronic devices. The eutectic Sn-Pb presents adequate properties to be applied in brazing and soldering processes, such as low melting point (183°C), good wettability, good fluidity and sufficient mechanical properties. The cooling rates obtained along soldering processes are directly affected by physicochemical affinity between molten alloy and metallic substrate. Although Sn-Cu lead-free alloys may be considered a possible alternative, research efforts are still necessary in order to improve the wettability of these alloys against different metal surfaces. Additions of minor alloying elements like nickel seem to be a feasible solution to improve the mentioned property once such modification is not enough to change the alloy melting point and only small costs increments may be attached to the process. Hence, the ternary Sn-Cu-Ni alloys seem to be promising materials to encompass such demand, although detailed studies of solidification under equilibrium and non-equilibrium conditions remain scarce in literature. The present study aims to examine the influence of Ni additions on thermal and microstructure developments of directionally solidified Sn-Cu alloys. Different metallic substrates will be evaluated against molten alloys, such as copper, low carbon steel and AISI 304 stainless steel.