Rework of CSP: the effect on surface intermetallic growth

Abstract

High‐density packaging devices have unique characteristics which make their assembly, test and repair very difficult. The only realistic method of rework is to replace the defective component with a new or re‐balled component. Although a wide range of rework techniques is available, degradation in assembly reliability may accompany the process. The formation of brittle secondary intermetallic compounds following CSP rework can adversely affect the mechanical properties of the joint, particularly when they make up a significant proportion of its thickness. Reports on the effects of different CSP rework techniques on intermetallic layer formation. Two PCB pad‐cleaning methods and three flux/paste deposition methods are investigated. The reworked joints are analysed using optical microscopy to determine the extent of intermetallic growth. Their quality is also assessed using shear strength testing prior to, and after, thermal ageing at 1008C to accelerate the growth of intermetallic compounds and evolution of the solder grain structure.

Citation

Nguty, T.A., Ekere, N.N., Philpott, J.D. and Jones, G.D. (2000), "Rework of CSP: the effect on surface intermetallic growth", Soldering & Surface Mount Technology, Vol. 12 No. 3, pp. 35-38. https://doi.org/10.1108/09540910010347881