Effects Of Moisture On Delamination Failure Of Microelectronics Package During Solder Reflow

The polymer material which is commonly used in microelectronics packaging is easy toabsorb moisture when exposed to humid ambient conditions. The presence of moisture in thepackages induces hygroscopic stress through swelling and vapor pressure in solder reflowthat is the cause for the eventual popcorn cracking. Therefore, moisture plays an importantrole in the integrity and reliability of electronic packaging. More and more researchers arefocused on the study of moisture absorption, diffusion and moisture induced failure.In this paper, role of moisture played on electronic package’s delamination failure duringsolder reflow has been investigated. Inspired by the idea of general self-consistent method,this paper proposed a micromechanical model which can also be called consideration of theevolution of meso-phase structure model, in which the effective elastic modulus is estimatedby Mori-Tanaka method. A deformation equation of polymer materials under thermalexpansion and vapor pressure is derived through this model, which can determine the vaporpressure and porosity of polymer during solder reflow. The deformation, vapor pressure andporosity of die attach film in chip scale package (CSP) panel during solder reflow has beencalculated.Interfacial pores which deformed so large during solder reflow caused by vapor pressurethat they might bond together, eventually came to be an interfacial crack. Thus the secondpart of this paper considered a flat elliptical interfacial crack between die attach film andsubstrate. The energy release rate of different virtual cracks has been calculated andcompared. Also, the stability of extended crack is discussed.In the last part of this paper, an interfacial crack between die attach film and substrate isanalyzed by finite element software. The components of interfacial crack tip strain energyrelease rate are calculated by virtual crack closure technique and the crack mode is alsodiscussed.