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Effects of high current density on lead-free solder joints of chip-size passive SMD components

Effects of high current density on lead-free solder joints of chip-size passive SMD components The purpose of this paper is to present a novel approach on investigating critical current densities in the solder joints of chip-size surface mounted device (SMD) components. The investigation involves a numerical approach and a physical validation with selected track-to-pad connections and high current loads (CXs).Design/methodology/approachDuring the investigations, shape of solder fillets was calculated in Surface Evolver, and then the current densities were calculated accordingly in the given geometry. For the verification, CX tests were performed on joints at elevated temperatures. The joints were qualified with X-ray microscopy, cross-section analysis and shear tests.FindingsThis study ascertained that the inhomogeneity in current density depends on the track-to-pad structure of the joint. Also this study found that the heavy CX decreases the mechanical strength, but the degradation does not reach the level of electromigration (EM)-induced voiding.Practical implicationsThe heavy CX significantly affects joint reliability and the results point out to EM-induced failure-limitations on printed circuit board (PCB)-based assemblies due to the thermomechanical weakness of the FR4 material.Originality/valueThe experiments investigate current density from a novel aspect on more frequently used small-scale components with different track-to-pad configurations – pointing out possible failure sources. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Soldering & Surface Mount Technology Emerald Publishing

Effects of high current density on lead-free solder joints of chip-size passive SMD components

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References (28)

Publisher
Emerald Publishing
Copyright
© Emerald Publishing Limited
ISSN
0954-0911
DOI
10.1108/ssmt-10-2017-0032
Publisher site
See Article on Publisher Site

Abstract

The purpose of this paper is to present a novel approach on investigating critical current densities in the solder joints of chip-size surface mounted device (SMD) components. The investigation involves a numerical approach and a physical validation with selected track-to-pad connections and high current loads (CXs).Design/methodology/approachDuring the investigations, shape of solder fillets was calculated in Surface Evolver, and then the current densities were calculated accordingly in the given geometry. For the verification, CX tests were performed on joints at elevated temperatures. The joints were qualified with X-ray microscopy, cross-section analysis and shear tests.FindingsThis study ascertained that the inhomogeneity in current density depends on the track-to-pad structure of the joint. Also this study found that the heavy CX decreases the mechanical strength, but the degradation does not reach the level of electromigration (EM)-induced voiding.Practical implicationsThe heavy CX significantly affects joint reliability and the results point out to EM-induced failure-limitations on printed circuit board (PCB)-based assemblies due to the thermomechanical weakness of the FR4 material.Originality/valueThe experiments investigate current density from a novel aspect on more frequently used small-scale components with different track-to-pad configurations – pointing out possible failure sources.

Journal

Soldering & Surface Mount Technology – Emerald Publishing

Published: Mar 27, 2018

Keywords: Chip-size components; Current density; Electromigration; Lead-free soldering; Solder shape calculation

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