Interfacial stresses in a bi-material assembly subjected to external tensile forces and bending moments applied to the ends of one of its components

We examine an elongated bi-material adhesively bonded or soldered assembly with a continuous compliant attachment (bonding layer). The assembly is subjected to external tensile forces and bending moments applied to the ends of one of its components. We develop a simple and physically meaningful predictive analytical (ldquomathematicalrdquo) model for the evaluation of the interfacial shearing and peeling stresses in the bonding material, with consideration of the effect of the compliance of the bonding layer. The developed model can be helpful in the stress-strain analysis and physical design of various assemblies of the type in question, and particularly of printed-circuit-board (PCB)/surface-mounted-device (SMD) assemblies in electronic and photonic packaging. Particularly, these models enable one to evaluate the maximum interfacial stresses in the bonding material from the predicted or measured strains in the PCB in the vicinity of the SMD package. The numerical example carried out for the case of PCB bending in a concave fashion indicated that the interfacial shearing stresses computed with consideration of the assembly bow were lower, and the peeling stresses calculated with taking into account the effect of tension, were higher, than the corresponding stresses predicted for the situation, when the assembly was subjected either to the tensile forces only, or to the bending moments only. We explain the physics of this phenomenon. We show, as an illustration, how the developed stress model can be used for the evaluation of the dynamic response of a PCB/SMD assembly to an impact loading applied to the PCB support contour.