ABSTRACT
The contemporary microelectronics package is a very sophisticated composite structure constructed from a large number of various materials with diversified thermomechanical properties, which very often are not well defined. This precludes exact prediction of the residual stresses built into the package during the production process. In many packages inorganic adhesives such as Au–Si eutectic solder [1] and silver-filled glass [2,3] are used to attach the silicon die to the substrate. To use an Au–Si eutectic as the die-attaching adhesive, the die normally needs to be coated with an Au layer on its back side and then bonded onto a lead frame or substrate with Au plating on the die-attaching paddle. The thin layer of eutectic, which can be considered rigid, transmits to the die the stress induced by the mismatch in the coefficient of thermal expansions (CTES) of the die, solder and lead frame. This stress can lead to vertical or horizontal die cracking especially when the die size increases [4,5]. Thus, alternate die-attaching adhesives are needed to improve the reliability of the die attachment.
