The Harmfulness of Re‐working Cosmetically Defective Solder Joints

Abstract

The loss of reliability of a PTH soldered joint caused by unnecessary re‐working after wave soldering is considered. Standardised joints are re‐worked under conditions that closely control the temperature of the soldering iron tip, the time of contact of the tip to the joint, the angle and the contact pressure of the soldering iron, the amount of flux and the amount of extra solder applied. The service life of the joints is assessed using accelerated thermal cycling between ‐20°C and +100°C. In all cases, the service life of these test joints is degraded by re‐working. The effect becomes worse when the temperature and time of re‐work are increased. The degradation of fatigue performance is associated with changes in the solder fillet microstructure. The effects on fatigue performance of changing the fillet size by adding extra solder during re‐work are complex, but explainable in general terms. The results obtained from the controlled laboratory rework tests are corroborated by test assemblies re‐worked to companies' in‐house workmanship standards and by field data.

Citation

Lea, C. (1990), "The Harmfulness of Re‐working Cosmetically Defective Solder Joints", Soldering & Surface Mount Technology, Vol. 2 No. 2, pp. 4-9. https://doi.org/10.1108/eb037712