SMTA China Conference Proceedings

Failure Analysis Case Study of MLCC Component Crack with Application of FEA and Bend Test

Authors: Henley Zhou, Kerwin Wang, Billy Liu, Jimmy Chen, Apitak Promson, Arnel Camacho, Alex Xie, Michael Sumalinog, Ranilo Aranda, GP Li, RSivam VRajoo, Mike Doiron
Company: Flex
Date Published: 8/28/2017   Conference: SMTA China

Abstract: Multi-Layer Ceramic Capacitors (MLCC) are extensively used as important component for various electric and electronic products. Application range from simple electronic product up to more advance applications such as mobile phones, digital TV, servers and others. Despite the simpleness of the structure of the component, there are several defects that are encountered during its assembly like insufficient solder, tombstoning, dendrites, EOS (electrical overstress) and of course crack which is very common since it is made of ceramic material and are easily breaks even at relatively low mechanical stress. A very small crack defect can make the product operate abnormally or totally non-operational.

Unlike the other MLCC assembly defects, cracks are normally not visible making it difficult to find. The soldering process, raw materials, environment, tools and fixturing are all possible sources of the problem. To narrow down the study, we will be looking into the effect of two major factors on MLCC cracking which is thermally induced stress and mechanical induced stress by board flexing.

This paper will tell a story of a real case failure analysis for 0603 MLCC component crack. The failure was confirmed crack by cross section analysis of the failed unit and suspected to be due to high mechanical stress during the PCBA assembly process. The strain gage testing (SGT) was performed but cannot identify which process contributes to the defect as all strain measured are within the allowable limits. From this, thermal stress was also become a suspect. To simulate the failure, Finite Element Analysis (FEA) was used and correlate the result to the actual defect based on crack pattern and locations. FEA simulation result that the actual crack pattern matched with the mechanically induced stress. Due to different electrode patterns design that each supplier may use, bend test using a simple test vehicle was also done to identify which vendor can supply the most reliable component.

Key Words: 

MLCC, thermal stress, mechanical stress, SGT, FEA, bend test

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