| Popis: |
Chapter 2 is dedicated to advances in the analysis of mismatched thermal expansion in microelectronic assembly and in printed circuit board (PCB) assembly. Being made of laminated structure and constituted of multiple materials, microelectronic assemblies are susceptible to delamination caused by mismatched thermal expansion between dissimilar materials. The interfacial thermal stresses in a tri-material sandwiched structure has been a subject of active research over the last few decades. While simple analytical solutions are available using the strength of material approach, these analytical solutions have consistently found shearing stress to be the predominant stress and the peeling stress to be of negligible magnitude; this does not agree with numerical analysis that suggests the peeling stress to be the dominant stress. The deviation is attributable to the overly simplified interfacial shear stress function assumed for the beam–adhesive interface and the overly simplified transverse stress function assumed for the adhesive layer. While numerical analysis may be used for robust design analysis, it suffers from stress/strain singularity. This chapter introduces an advanced analytical solution in which the interfacial shearing stress is prescribed with a more sophisticated stress function while the transverse stress in the adhesive layer is prescribed with a stress function that is consistent with the theory of elasticity. This has led to analytical solutions of the interfacial shearing and peeling stresses that are consistent with the numerical solution. Design analysis using the advanced solution has led to many useful insights for robust design of microelectronic assembly against thermal-induced failure. |
