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NPL Report MATC(A) 164
Cracked area
Figurę 6. Crack in a SnAgCu soldcr joint after thcrmal cycling.
The crack area growth in terms of the number of cycles was evaluated by measuring the number of pixels in the appropriate part of the image, and the results are presented in Figurę 7. Since this method gives morę quantitative results than does micro-sectioning, it can be used for assessment of non-cracked area i.e. to study the stress acting on a solder joint, and to analyze the whole area of a crack. It is not dependent on the positioning of the cross-sectional piane, as is the case with micro-sectioning.
Figurę 7. Percentage of cracked area under 2512-type resistors as a function of the number of thcrmal cycles, for SnAgCu soldcr
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