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Failures Due to Package Delamination


What failure mechanisms can arise from the presence of internal package delamination?


Delamination, or the separation between two supposedly connected layer interfaces within a package, is generally considered more as a failure attribute rather than as a failure mechanism, i.e., its presence in a package doesn't necessarily mean a failure. Its presence, however, has to be considered a valid package failure if its size, location, shape, or any other characteristic poses a reliability risk in the field, i.e., it can cause the device to fail by a secondary failure mechanism.



Secondary failure mechanisms that arise from the presence of delamination include die corrosion, package cracking, bond lifting, and breaking of the neck or heel of a bond.  Device-related failures such as parametric shifts due to internal contamination can also be induced by package delamination.


Delamination is often addressed in the context of which layer interfaces are involved.  As such, die-to-mold delamination is often treated differently from leadframe-to-mold delamination, since they result in different failure mechanisms and require different corrective actions for elimination.


For instance, a die-to-mold delamination can cause the molding compound to move laterally with respect to the die surface, which can either cause ball bond lifting or neck breaks.  If a moisture path between the die-to-mold delamination and an external feature of the package exists, then moisture and contaminants can reach the die surface from outside, resulting in die corrosion or metal-to-metal leakage.


On the other hand, a die paddle-to-mold delamination is a risk for package cracking, as well as leadframe corrosion. Delamination between the molding compound and lead fingers can exert tremendous shearing stresses on the second bonds of the device, which can lead to heel breaks or wedge bond lifting.



See Also:  SHRT


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