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Mechanical Reliability of Aged Lead-­Free Solders
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2012 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

The usage of lead-­free solder joints in electronic packaging is of greatest concern to the electronic industry due to the health and environmental hazards arising with the use of lead. As a consequence, lead is legally prohibited in the European Union and the industry is aiming to produce lead-free products.           

The reliability of solder joints is an important issue as the failure could destroy the whole function of a product. SnAgCu is a commonly used alloy for lead-­free solders. Compared to solders containing lead, tin-­rich solders react more rapidly with the copper substrate. The reaction results in formation of brittle intermetallic compounds and in poor mechanical reliability. The formation can be slowed down by the addition of nickel in the under bump metallization.    

In this project the objective was to evaluate the mechanical reliability of solder joints in high temperature applications. An alloy of nickel and phosphorus was plated on copper plates by electroless plating. The plates were joined together using SnAgCu solder. The samples were then thermally aged at 180°C for different durations (100, 200, 300, 400 and 500 hours). Tensile tests were performed on the samples. The result from the tensile test showed a decrease in mechanical strength with increasing aging duration. The fracture path shifted from being in the bulk solder to being at the interfaced.

Place, publisher, year, edition, pages
Keyword [en]
Solder Joints, Lead-free, Mechanical Reliability
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-98372OAI: diva2:536918
Available from: 2012-08-10 Created: 2012-06-25 Last updated: 2012-08-10Bibliographically approved

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