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BGA reliability.

"Corrosion Study on BGA Assemblies"

Authors: Alexandrine Guedon-Gracia, et ah,

Abstract: This paper presents aging tests on BGA assemblies in a salt spray chamber. The test vehicle is composed of BGA components with SAC balls mounted on FR-4. The BGA is a daisy-chained component. Electrical continuity of the assembly can be tested thanks to electrical resistance measurement of the solder joint chain. The assemblies are put in a salt spray chamber at 35[degrees]C with 5% NaCl water according to ASTM B117-09, which is an accelerated test to stimulate the effects of a severe marine atmosphere on exposed surfaces. Assemblies are removed at 24, 48, 72 and 96 hr. Electrical resistance and weight are measured during the test. Solder joints and copper pads are observed and analyzed with an optical microscope. Samples are cross-sectioned and polished to reveal the solder microstructure, which is examined by SEM equipped with an EDX system. Corrosion of some Cu pads was observed, in particular for pads without solder alloy. Solder joint deterioration was visible but no electrical failure detected. The microstructure was observed in order to determine the corroded residues found on the surface solder balls after salt spray test. The Ag3Sn contained in SAC solder joints seems to accelerate tin corrosion because of the galvanic corrosion mechanism. (SMTA Pan Pac Symposium, January 2016)

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Title Annotation:In Case You Missed It
Publication:Printed Circuit Design & Fab Circuits Assembly
Date:Feb 1, 2016
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