Characterization of thermal fatigue properties of lead-free Sn–Cu–Al–Mg solder alloy produced by powder metallurgy method

Abstract

In the present study, lead-free Sn–Cu–Al–Mg-based solder alloys for electronics packaging were produced. Effects of thermal shock and thermal stress on the crack formation in the Sn-based solder alloys were investigated. Lead-free quaternary Sn–Cu–Al–Mg-based solder alloys were produced by using mechanical alloying and powder metallurgy route. Soldering involves using a molten filler metal to wet the surfaces of a joint. Wave soldering is a method for mass assembly of printed circuit boards involving through holes, surface. Lead-free solder alloys must show high wettability, suitable mechanical properties, electrical conductivity, high electrochemical corrosion resistance, and low cost. Mechanical alloying and powder metallurgy method were used in order to prevent formation of intermetallics and formation of voids. Mechanical alloying–powder metallurgy method could reduce the micro/macro-segregation and provide homogeneous microstructure. Initially, elemental metal powders were mechanically alloyed in a ball mill by using zirconia balls in order to produce alloy powders. Then, the alloy powders were compacted at 300 MPa and then the green specimens were sintered at 180 °C for 60 min. Nondestructive ultrasonic tests and eddy current tests were used for characterization of the solder alloy specimens. Elastic modulus of the Sn alloys was determined by ultrasonic measurements. Electrical conductivity of the specimens was determined by using eddy current tests. Microstructure was studied by scanning electron microscope. Effects of thermal shock and thermal stress on the crack formation in the alloys were investigated by heat treatment cycles in a chamber furnace. Heating cycles for thermal stress consist of heating to 150 °C and slow cooling. Heating cycles for the thermal shock consist of heating and quenching. In addition, electrochemical corrosion behaviour of the Sn solder alloys was investigated in NaCl solution.