Access to critical die and package structures for failure analysis purposes is complicated in stacked die devices in small packages, such as thin plastic Lead Frame Chips Scale Packages also known as Quad Flat No Leads Packages. This paper discusses the failure analysis solutions developed to effectively access the areas of interest. It illustrates two different ways of analyzing the bottom die: a repackaging technique and a technique for accessing from the backside of the bottom die. One of the major concerns during the evaluations that had been addressed was the difficulty of removing the nonconductive die attach material in between the top and bottom die. This was resolved by a novel method of thermal decomposition of the material. Observations suggested that the die extraction process did not introduce surface oxidation or contamination that may have led to a bonding failure.

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