Evidence that Visual Inspection Criteria for Soldered Joints are no Indication of Reliability

Abstract

Exemplary data are given that demonstrate unequivocally the inapplicability of commonly used visual inspection criteria for judging the long‐term service reliability of soldered joints. The data are obtained from a controlled model system. Plated‐through hole (PTH), wave soldered joints are used in this work, having a controlled degree of voiding, blowholing and solder blowout, covering the full range of normal visual assessment, from perfect to very bad, for this particular type of visible fault. The joint performance is assessed in terms of its joint pull strength, thermal shock, mechanical high frequency fatigue, low cycle thermal fatigue and propensity as a corrosion initiation site. No evidence was found that the visible outgassing faults degraded the solder joint performance. Indeed, in all the fatigue tests, the visually unacceptable solder joints performed significantly better. Furthermore, in a related research project, manual reworking of joints has been found to be demonstrably detrimental to solder joint reliability.

Citation

Lea, C. (1991), "Evidence that Visual Inspection Criteria for Soldered Joints are no Indication of Reliability", Soldering & Surface Mount Technology, Vol. 3 No. 3, pp. 19-24. https://doi.org/10.1108/eb037765