High-temperature variable melting point Sn-Sb lead-free solder pastes using transient liquid-phase powder processing

Abstract

During this investigation, a high-temperature, variable melting point (VMP) Sn-Sb solder paste was developed. The solder was created by mixing pure Sn and Sb powders together with a flux to form a paste. The proper choice of flux composition and Sn powder size resulted in a Sn-10wt.%Sb solder paste that had an initial melting point of 232°C and solder ball formation at peak temperatures as low as 241°C. This represents a significant reduction in the process temperature that would normally be required for a prealloyed solder with a melting point of 250°C. When this solder paste is reheated, significant remelting does not take place until a temperature above 241°C is reached. In this way, the solder exhibits a VMP. Experiments indicate that this VMP behavior is due to isothermal solidification (or freezing) at the solder temperature owing to the partial transient liquid-phase (TLP) behavior of the solder powder paste.

Phase Equilibria of the Sn-Sb Binary System

“…[1][2][3][4][5][6] Step soldering refers to the circumstance that soldering processes occur at various steps because more than one soldering process is needed for some electronic products. [1][2][3] To avoid remelting of the earlier solder joints in the later soldering processes, solders with different melting points are used.…”

“…The melting points of Sn-Sb alloys are higher than that of conventional eutectic Sn-Pb solder and they have been used as high-temperature solders in step soldering processes. [4][5][6] In addition, various Sn-Sb-based alloys have been developed as high-temperature solders in compliance with recent Pb-free requirements 7 for electronic products.…”

Evaluation of Microstructures and Mechanical Properties of Sn-10Sb-Ni Lead-Free Solder Alloys with Small Amount of Ni Using Miniature Size Specimens

“…It is possible that the Sn-Sb solder alloys which have highest melting temperature range among existing lead-free solder alloys, are able to replace the Pb-rich solder alloys [7][8][9][10][11][12][13][14]. It has been reported that the Sn-Sb solder alloys have low electric resistivity and good mechanical properties [7,15].…”

Solidification properties and microstructure investigation of the as-cast Sn-rich alloys of the Sn-Sb-Zn ternary system

“…Several studies of Pb-free high-temperature solder alloys have been performed [3][4][5][6]. It was concluded that among various lead-free solders, Sn-Sb based alloys are promising candidates for the replacement of the high-melting-point Sn-95 wt.% Pb alloy [3][4][5][6]. In those studies authors investigated the phase diagram, *Corresponding author: tel.…”