Thermal Characterization and Compact Modeling of Stacked Die Packages

In stacked die packages the main risk of the operation is, that any void or delamination in any of the die attach layers results in locally increased thermal resistance consequently may cause overheating and finally might result even in ruining the device. The first part of our paper discusses the methodology recommended to qualify and analyze the integrity of the die attach layers in stacked die packages. The methodology is based on thermal transient characterization and structure function evaluation. The second part of the paper discusses the issues of compact modeling of stacked die packages. Description of the thermal behavior with the Z matrix is suggested and presented on a pyramidal structure. It is demonstrated on a strongly pyramidal stacked die structure that the thermal behavior is strongly asymmetric, suggesting that a 2 resistor description of the thermal behavior would be rather erroneous