In Situ Characterization and Modeling of Strains near Embedded Electronic Components During Processing and Break-in for Multifunctional Polymer Structures
Emerging molding concepts, such as in-mold assembly, are enabling electronic structures to be directly embedded in thermoplastic polymers to provide integrated packaging for better protection and a more multifunctional structure in “in-mold assembly processes”. During the molding process, stress can develop at the interface of the polymer and embedded electronic component due to shrinkage of the polymer that precipitates fracture or fatigue during the life cycle of the product. Additionally, the interaction between a mold and the polymer melt is altered in a multi-stage molding process where a polymer for superior impact protection can be molded over another polymer that is more compatible with the embedded electronic component. Currently, we do not fully understand the impact of various parameters governing the in-mold assembly process on the residual strains that develop in polymers around embedded electronic components in order to develop process models. Therefore, in this chapter experiments are presented that are designed and executed to measure the strains involved and the manner in which they develop. An in situ open mold experiment is employed using the full-field deformation technique of Digital Image Correlation (DIC) to characterize the displacement and corresponding strain fields that evolve near embedded electronic elements as the polymer shrinks from the molten to the solid state during processes and during break-in of the electronic component. It was determined that the use of multi-stage molding may reduce the residual stresses in addition to providing superior impact protection. However, there was a higher concentration of strain near the polymer-component interface during break-due to lower thermal conductivity. Experimental data was consistent with a thermomechanical model up until the point of failure.
KeywordsAxial Strain Digital Image Correlation Electronic Component Residual Strain Acrylonitrile Butadiene Styrene
This work was supported by NSF grants EEC0315425 and DMI0457058, and by ONR award number N000140710391. Opinions in this paper are those of the authors and do not necessarily reflect those of the sponsors.
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