Defect Description
Solder joints at which severe corrosion process(es) has/have taken place that mechanical strength of the joint is weakened but electrical contact remains or partially remains that make them undetectable as a defective contact. It is possible that corroded products can consolidate the mechanical contact but the list of tests below only cover a weakened contact.
(Can be irrelevant since it is uncommon for corroded products to be formed in new products)
Defect Formation Process(s)
Different corrosion processes could have taken place depending on the type of materials and the ambient condition of the solder joint. One example of solder joint corrosion can be the presence of Ag3Sn in SAC solders accelerates the dissolution of tin from solder matrix into corrosive medium because of galvanic corrosion mechanism, which forms a loose Ag3Sn structure in the corroded region that yields a weaken mechanical strength [1].
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List of Tests to Precipitate this Defect |
Failure Acceleration |
Likelihood to Precipitate this Defect (condition) |
Failure Mechanism(s) |
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• Cyclic thermal mechanical stress accelerates crack initiation or growth of the weak solder joint • Thermal mechanical stress causes fracture of the weak solder joint |
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Thermal Faitgue Thermal mechanical Overstress |
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• Random Vibration accelerates fatigue cracking of the weak solder joint • Random Vibration can cause fracture of the weak solder joint |
✔/✇ |
Mechanical Fatigue Mechanical Overstress |
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• Combination of Thermal Shock and Random Vibration |
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Combination of Thermal Shock Random Vibration |
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• Bending can cause fracture of the weak solder joint |
(Defect at a location with significant strain due to bending) |
Mechanical Overstress |
References
[1] Song, Fubin, and S. W. Lee., “Corrosion of Sn-Ag-Cu Lead-free Solders and the Corresponding Effects on Board Level Solder Joint Reliability.” Proceedings of Electronic Components and Technology Conference, pp. 891-898, 2006
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