Study of Interface Strength of Flexible Encapsulation for FHE Applications

In this paper, the effect of cure-time and temperature on the interfacial-strength of flexible encapsulation has been studied for flexible-hybrid electronics (FHE) applications. Viability of FHE in commercialized platforms needs flexible encapsulation which is capable of protection from the environment and mechanical loads in addition to providing the needed flexibility for stresses of daily motion. Flexible electronics have gained a great deal of attention due to a variety of potential applications that could be realized. Flexible electronics encapsulation is particularly challenging owing to the need for durability and high performance in strained states simultaneously with flexibility. With the advent of wearable and implantable electronics on the body, as well as the demands for human-friendly smart soft robots, considerable effort is being made on highly flexible functional materials, particularly stretchable electrodes, by both academic and industrial communities. Stretch, flex and twist functionality are the most demanding of the various deformation types. Flexible electronic devices are affected by mechanical impacts or bending. There are currently no scalable flexible encapsulation processes available for FHE systems to meet their particular performance and reliability requirements. This paper analyzes the effects of different epoxy encapsulation materials in terms of their peel strength. A thorough analysis of the material was carried out for FHE to study the impact of substrate-material, substrate cleaning, curing temperature and time, thickness and ageing on the peel strength. Substrates studied include PET and Polyimide. Cleaning procedures studied include - plasma and isopropyl-alcohol cleaned.