A Creep Model For Pressure Sensitive Adhesives Under Shear Load

Nowadays, pressure sensitive adhesives (PSAs) are widely used in consumer electronics applications due to their small form factor, easy assembly, ability to accommodate misalignment and flatness variation. It's important to understand the creep behavior of PSAs, because the PSA assembly is expected to survive sustained environmental as well as operational loads without failures. Also, prior knowledge of creep behavior will aid in the selection of appropriate PSA, depending upon the application requirements. However, the literature regarding the creep behavior and models of the PSA assembly under consideration was limited.Therefore, in this work, shear mode creep behavior of a commercially available thin foam tape with pressure sensitive adhesives (PSA) on both sides was investigated. In order to understand the creep behavior of a specific thin foam tape with double-sided PSA, constant load creep tests were conducted at different load levels, temperature and humidity conditions. Creep deformation of the PSA layer was recorded at different intervals during the test. The accelerated test data was used to develop a novel time-stress-temperature-humidity dependent empirical creep deformation model for the PSA, which is the main contribution of this paper. The lumped model is able to predict primary and steady state creep behavior of the PSA. The insights from this work regarding the creep behavior of similar PSA systems and the creep prediction model will be of value to engineers for virtual testing and selection of PSAs for future consumer electronics products.