Large area electronics is becoming an embedded part of structural elements such as automotive and architectural glasses. In this study, the effect of glass lamination based fabrication process on the electrical performance and production throughput yield (TPY) of printed conductive wires and surface mounted (SMD) connectors on polyethylene terephthalate (PET) carrier film were investigated by measuring their electrical conductivity after lamination. Based on the experiments, lamination decreases the production yield of conductive wires and connectors due broken wires or dislocated connectors, especially if they are located close to the corners of laminate. On the other hand, lamination was observed to improve the electrical conductivity of wires. In addition, some potential failure mechanisms are discussed.

By integrating electronics inside the laminated glass, the windows and structural glass elements can be transformed to be functional and interactive. Once the electronics is embedded into the glass in lamination process, the electronics is exposed to different type of stresses, having an influence on performance and reliability. In order to understand the consequences of lamination and to explain the reason for failures, non-destructive optical coherence tomography (OCT) based method was used in this study. In addition, thermo-mechanical simulations were done to find possible causes for observed failures in light emitting device (LED) chips and wirings. Combining the analyzed OCT data with simulations, was shown to be very effective tool to select right materials and optimize the lamination process for glass embedded electronics.

Capability of high speed and low-cost manufacturing makes the printing techniques very promising approach for largearea flexible electronics mass manufacturing. Due to fast and intensive technology development, the lack of knowledge about the reliability and lifetime of printed electronics is obvious, requiring further investigation. Especially, the effect of torsional bending on lifetime is mostly unexplored field of reliability testing. In this study, a torsional bending test of parallel printed silver conductors (0.3 mm, 0.5 mm pitch) on polymer substrate (Polyethylene terephthalate, 125 m thickness) were conducted and analyzed. According to the experimental results, torsional bending causes wear-out type failures in conductors and the length-to-width (LTW) ratio of the sample's substrate was observed to have a significant impact on reliability. If the LTW ratio is smaller than 3, the lifetime of printed conductor seems to collapse, and samples lasted for approximately only 17 bending cycles on average. Lifetime was improved by increasing the LTW ratio and samples withstood over hundreds of cycles with LTW ratio of higher than 15. However, the distance of a conductor from the edge of the substrate was not observed to have any significant influence on the reliability under torsional bending.

Structural electronics consists of printed electronics and silicon-based rigid electronics and load-bearing supporting parts of a device (plastic, glass etc.). One interesting example of structural electronics is large area elements in which light emitting diodes (LEDs) are embedded into the glass laminate. LEDs are used as light sources to create i.e. smart surfaces for the architectural and automotive industry. Once the LEDs are embedded into the structure, they undergo the high temperature conditions and stresses, which are known to have an impact on their lifetime. Many of these aspects are not known for structural electronics. In this study, a thermal simulation model for surface mounted LED on polymer substrate was designed in Comsol Multiphysics -simulation software and the validity of it was evaluated with T3ster measurements.According to measurements, the simulation model is accurate and temperature variations between the simulation and the measurement results was less than 1.0 %. Developed model could be used as a basis for designing the structural LED elements and evaluating their performance characteristics in different user cases.

Hybrid structural electronics (HSE) consists of printed electronics, conventional rigid electronics and load bearing supporting parts of a device (plastic, glass etc.). Extra-large area and flexible lighting elements with embedded light emitting diodes (LEDs) are an example of such applications. LEDs can be used e.g. as light sources to create smart surfaces for the architectural or automotive industry. Once the LEDs are embedded into the structure, they cannot be replaced. In order to make sustainable HSE products with long lifetime, the new type of designs is needed. The elements of HSE undergoes conditions with elevated thermal stresses while in operation. That is known to have an impact on their performance and lifetime, thus making a proper heat management of the LED crucial. Due to the novel additive manufacturing methods, structures, and unconventional material combinations, many thermal management related aspects are not known. In this study, a two-step hybrid method, including thermal modelling and measurements, is utilized to estimate thermal behavior of a surface mounted LED on polymer substrate used in HSE. The model is created and simulated in COMSOL Multiphysics. The validity and accuracy of the model's thermal behavior is verified through measurements with thermal transient measurements. Based on the experimental verification, the proposed simulation model only has small (less than 2 %) temperature variations when compared with measurements. Hence, the developed model can be used as a basis for designing structural LED elements and predicting their performance characteristics in different user cases.