It is often said that a chain is only as strong as it weakest link, the same can be true for a series of solder joints on a component. When one is bad, the rest are useless. Quite often, voiding is the failure mechanism.
In many cases voiding can be traced back to residual flux left in the joint. Optimizing the flux content and strength, coupled with reflow profile adjustments, can reduce voiding drastically. Other causes of voiding can be oxidation of the solder and or surface metallizations. Usually a stronger flux or improved storage conditions can help alleviate this issue. Alloy choice can also be a factor.
The variables can be many. Defining the root cause and developing an approach to reduce voiding can be daunting. This paper might offer some guidance: Voiding Mechanisms in SMT
IF your application is more specific, and further assistance is needed, feel free to contact your regional application engineer.
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Seth