Measuring and modelling the thermal behavior of LEDs in structural electronics

Abstract 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 thermal modeling to predict LED thermal behavior in hybrid electronics

Abstract 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, for example, 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. To make sustainable HSE products with long lifetime, the new type of designs is needed. The elements of HSE undergo 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 modeling and measurements, is used to estimate the 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 are 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