“Stretchable” electronics: Does one really need a good thermal expansion (contraction) match between the silicon die and the plastic carrier?

Simple analytical (ldquomathematicalrdquo) stress models are developed for a silicon die embedded into, or surface mounted onto, a thin ldquostretchablerdquo plastic carrier. We consider a situation when the die/carrier assembly is manufactured at an elevated temperature, then cooled down to a low (say, room) temperature and then subjected to an external tensile load applied to the carrier. The induced stresses are due therefore to the combined action of the thermal and the mechanical loading. We evaluate the stress in the die and the interfacial stresses. The developed models can be used in the stress/strain analyses and physical design of the assemblies of the type in question in large area (dasiastretchablepsila) electronics. The models indicate particularly that appreciable stress relief could be expected if regular (high expansion) carrier materials are employed. In such a situation the compressive thermal stresses in the die will be compensated, to a greater or lesser extent, by the tensile external loading. Our models can be used also in the design of the experimental setups (e.g., when deciding on the appropriate location of the strain gages), and in the analysis (interpretation) of the test data.