Interfacial Shear and Peel Stresses in Multilayered Thin Stacks Subjected to Uniform Thermal Loading

Abstract

An analytical approach has been developed to evaluate the interfacial shear and peel stresses in multilayered thin stacks subjected to uniform temperature variation. The approach, which is based on an extension of Suhir's bimetal thermostat model, provides a system of coupled linear second order differential equations used in solving for the interfacial stresses. Once these stresses have been determined, the normal stress in each layer and the deflection of the stack can be readily obtained.Two numerical examples are used to demonstrate the capability of the approach. The first example deals with a five-layered symmetric double-shear solder joint. The results are compared to a nonsymmetric three-layered solder joint to study the effect of bending and the interactions of material properties. One of the interesting features observed is that the maximum interfacial shear stress does not necessarily occur at the edge. The other numerical example is a four-layered transistor stack mounted on a substrate. The structural behavior is analyzed, and the effect of geometric dimension is examined. The present approach is shown to provide more accurate results than those of others based on the same assumptions. In addition, applications of the approach to more general stack configurations are also discussed.

Interfacial thermal stresses in solder joints of leadless chip resistors

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Advanced HiCTE flip chip packaging of 90-nm Cu/Low-K chips: Underfill, novel terminal pad structures, and processing optimization

“…The fatique and creep behaviors within the package and between critical interfaces are thus likely to have a more adamant coupling effect with the dynamic temperature exposures. 24 This is a phenomenon that will need future characterization study as the level of stress and strain impact on the packaged module tends to be more prominent in 90-nm node with a higher number of metallization layers. Failing units in previous technology nodes can still be observed through non-TC type of stressings.…”

Thermomechanical peeling in multilayer beams and plates—a solution from first principles

“…Pan and Pao (1990) presented a set of first order equations based on conventional thin plate theory to determine displacement and strain in multilayer plates; shear and peeling were not included. Pao and Eisele (1991) extended the approach of Suhir (1986) to multiple layers to generate a coupled series of linear second order differential equations; the solution did not deliver the expected change of sign of the peeling stress near the free ends. An exact solution for bending and axial stress in multilayer beams was developed where a relatively thick substrate bore thin film layers, also bonded at a common temperature (Hsueh, 2002); again peeling and shear were not addressed.…”