A review: On the development of low melting temperature Pb-free solders

• Published in: Microelectronics and reliability Vol. 54; no. 6-7; pp. 1253 - 1273
• Main Authors: Kotadia, Hiren R., Howes, Philip D., Mannan, Samjid H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2014; Elsevier
• Subjects: Applied sciences; Complex systems; Cross-disciplinary physics: materials science; rheology; Design. Technologies. Operation analysis. Testing; Electronics; Exact sciences and technology; Integrated circuits; Interconnections; Interface reactions; Interfacial reactions; Intermetallic compounds; Lead (metal); Lead-free solder; Legislation; Materials science; Microelectronic fabrication (materials and surfaces technology); Nanocomposite solders; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soldering; Solders; Tin; Europe; Nanocomposite solders; Lead-free solder; Intermetallic compounds; Soldering; Interfacial reactions; Nanoparticle; Legislation; Complex system; Metallizing; Common base; Solder metal; Alloying element; Coatings; Solidification; Prospective; Integrated circuit bonding; Additive; Microelectronic fabrication; Interconnection; Soldered joint; Integrated circuit; Lead free soldering; Interface reaction; Low temperature
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2014.02.025

Pb-based solders have been the cornerstone technology of electronic interconnections for many decades. However, with legislation in the European Union and elsewhere having moved to restrict the use of Pb, it is imperative that new Pb-free solders are developed which can meet the long established benchmarks set by leaded solders and improve on the current generation of Pb free solders such as SAC105 and SAC305. Although this poses a great challenge to researchers around the world, significant progress is being made in developing new solder alloys with promising properties. In this review, we discuss fundamental research activity and its focus on the solidification and interfacial reactions of Sn-based solder systems. We first explain the reactions between common base materials, coatings, and metallisations, and then proceed to more complex systems with additional alloying elements. We also discuss the continued improvement of substrate resistance to attack from molten Sn which will help maintain the interface stability of interconnections. Finally, we discuss the various studies which have looked at employing nanoparticles as solder additives, and the future prospects of this field.