Simulative Investigations of the Mechanical Reliability of the Flexible Optoelectronic Packaging Using Optodic Bonding
With the constant innovation and development of the advanced materials and technologies in the field of optoelectronics, a variety of applications adopting the benefits of optoelectronics is increasingly penetrating into our daily routines. The way of packaging has a huge impact on the performance of optoelectronics in mechanical, electrical as well as optical properties. Particularly, flexible packaging is becoming a trend thanks to its compatibility to any irregular surfaces in diverse applications. By employing transparent polymer foils, such as polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET), as carrier substrates for optoelectronic packaging, a greater mechanical flexibility can be achieved. Their transparency expands the range of application, for instance in optical sensing areas. In addition, they are mostly cost-effective, which enables an economical roll-to-roll manufacturing process. However, the challenge of using them is their low glass transition temperatures. In previous works, a novel optodic bonding process employing UV curable adhesives for processing these thermally sensitive polymer foils was introduced and verified as a promising technology for flexible optoelectronic packaging. In this work, we conduct further investigations of its mechanical reliability with the focus on the aspect of flexibility. FEM-based simulations for emulating various mechanical loadings including shear, bending and tensile stresses are implemented. We perform analyses of the influencing factors, particularly their degree of efficiency on the mechanical stability, e.g. the material properties of the optoelectronic components, the employed polymers as well as the bonding adhesives. These comprehensive investigations establish a constructive guideline for choosing materials for flexible optoelectronic packaging. In addition to this, we attain a convincing statement for the reliable feasibility of the optodic bonded packages with respect to a sufficient mechanical flexibility and stability.
Advanced flexible electronics: challenges and opportunities
Thin, lightweight and flexible electronics are being regarded as an important evolutionary step in the development of novel technological products. Interestingly, this trend has emerged in a wide range of industries; from microelectronics to photovoltaics and even solid state lighting. Historically, most attempts to enable flexibility have focused on the introduction of new material systems that, so far, severely compromise the performance compared to state-of-the-art products. The few approaches that do attempt to render contemporary high-performance materials flexible rely on layer transfer techniques that are complicated, expensive and material-specific. In this paper, we review a method of removing surface layers from brittle substrates called Controlled Spalling Technology that allows one to simple peel material or device layers from their host substrate after they have been fabricated. This allows one to fabricate high-performance electronic products in a manner of their choosing, and make them flexible afterwards. This technique is simple, inexpensive and largely independent of substrate material or size. We demonstrate the power and generality of Controlled Spalling by application to a number of disparate applications including high-performance integrated circuits, high-efficiency photovoltaics and GaN-based solid state lighting.
Transparent and flexible force sensor array based on optical waveguide.
This paper suggests a force sensor array measuring contact force based on intensity change of light transmitted throughout optical waveguide. For transparency and flexibility of the sensor, two soft prepolymers with different refractive index have been developed. The optical waveguide consists of two cladding layers and a core layer. The top cladding layer is designed to allow light scattering at the specific area in response to finger contact. The force sensor shows a distinct tendency that output intensity decreases with input force and measurement range is from 0 to -13.2 dB.