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Delamination is the disbonding between two surfaces that are supposed to be attached. Its important effects on the semiconductor package have emerged with improvements in its detection. The adhesion of the molding compound to the die surface and leadframe/die paddle surfaces is both chemical and mechanical in nature.
Chemical bonding is a function of the coupling agent contained in the molding compound. Mechanical bonding is achieved by the differential contraction of materials. Delamination can occur between the molding compound and any of the following: the die surface, the die paddle surface, the leadframe surface, and the die attach material. Delamination between the molding compound and any of these can lead to failure. Failure mechanisms that can result from die surface delamination include 'first bond' lifting, wire necking, cratering, and intermetallic failures. Die paddle/leadframe delamination, on the other hand, can cause 'second bond' lifting, heel cracking, and even broken wires. Leadframe delamination can also lead to internal package cracking that can allow conductive paths to form, which can result in current leakages. Corrosion is also possible if the delamination reaches the package external, creating a path for contaminants and moisture to enter
the package. Cracks in the die passivation can also result from die surface delamination after temperature cycling. Delamination can also lead to package cracking during solder reflow. Plastic package delamination is generally caused by: 1) non-optimized molding parameters; 2) excessive temperature gradient across the mold die; and 3) inferior encapsulation material properties.
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