Perspectives on Repaired Lead-Free Solder Joints


The use of lead-free (LF) solders as a replacement for traditional tin-lead (SnPb) solders in military and high reliability applications has a number of technical challenges unique to the industry. the need for a metallurgically stable solder joint under harsh environmental conditions, high stress and shear loading, and long term storage presents a set of requirements that are significantly different from most commercial applications. It is well documented that processing conditions during soldering can significantly affect the microstructure and reliability of the joint. Due to the low volume and long life cycle of military and aerospace electronic assemblies, repair of components is widely employed. While methods for repairing assemblies using SnPb solders are well established, limited data is available for re -work and repair of LF solder processing, especially when the resulting joint is a combination of SnPb and LF solders. in this study the influence of repair processing conditions on the microstructure of LF solders was investigated. Processing parameters such as soldering conditions and solder composition were used to simulate manufacturing operations. Temperature cycling of components soldered to printed circuit boards between -55°C and +125°C with SnPb, LF, and mixtures of SnPb and LF solders was performed. Analyses of the phases present, chemical composition and microstructure of the solder joints before and after temperature cycling were conducted using optical and electron microscopy to correlate processing conditions to the resulting microstructure. Shear testing of surface mounted capacitors prior to and after temperature cycling demonstrated a significant drop in shear strength after temperature cycling. Implications of processing conditions on the reliability and long term stability of the solder joints will be discussed.


Materials Science and Engineering

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


File Type





© 2024 Emerald Group Publishing Limited, All rights reserved.

Publication Date

01 Dec 2005

This document is currently not available here.