Development of lead-free interconnection materials in electronic industry during the past decades: Structure and properties

Abstract

During the past decades, series of lead-free solders have been developed rapidly, and are considered as the attractive interconnection materials replacing traditional Sn-Pb solders in electronic industry. In this paper, the interfacial reaction, microstructure evolution, wettability, melting behavior, mechanical properties and reliability of lead-free solders/solder joints bearing alloying elements or particles were systematically reviewed. The effect mechanism of alloying elements and particles on interfacial intermetallic compound (IMC) layers and matrix microstructures were described. What’s more, the reaction precipitation and solid solution precipitation have been demonstrated based on experiments. No obvious change of melting temperature can be found, suggesting that there is no need to change the soldering processing when adopting these novel lead-free solders. About the wettability and mechanical properties of solders or solder joints bearing alloying element and particles, the enhance effect can be found. The reliability assessments including fatigue behavior, drop reliability, humidity environment, electromigration property and whiskers were all analyzed and reviewed, and the influence mechanism of alloying elements and particles on the reliability needs to be further studied systematically, especially for the drop reliability and humidity environment. The reviews can provide the theoretical reference for the investigation of lead-free solders in the future.

Keywords

• Lead-free solder
• Alloying
• Reaction precipitation
• Mechanical properties
• Drop reliability