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A non-destructive visual failure analysis technique for cracked BGA interconnects

Quickly determining the cause of open failures in assembled BGAs is critical to the success of electronics manufacturing. The use of larger, stiffer components with more flexible printed circuit boards only increases the chance of mechanically fracturing interconnects during assembly and test. The use of BGA endoscopes during visual inspection has expanded over the last several years to evaluate the quality of assembled BGAs. Visual inspection alone, however. does not reveal all open defects. This paper describes a new technique that enables the non-destructive localization of opens that are not typically visible due to shadowing, flux residue, or soldermask. The technique involves applying a small, controlled, upward force to the BGA substrate to separate and ‘see’ the displacement of the pre-existing fractured surfaces. It has been shown through experimental results for several package styles that this controlled force technique can be used to localize the cracked interface without causing damage to previously good interconnects.