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.
Optodic bonding of optoelectronic components in transparent polymer substrates-based flexible circuit systems
In the field of modern information technology, optoelectronics are being widely used, and play an increasingly important role. Meanwhile, the demand for more flexible circuit carriers is rapidly growing, since flexibility facilitates the realization of diverse functions and applications. As a potential candidate, transparent polymer substrates with a thickness of about a hundred micrometers by virtue of their low cost and sufficient flexibility are getting more attention. Thus, accomplishing an integration of optoelectronic components into polymer based flexible circuit systems increasingly is becoming an attractive research topic, which is of great significance for future information transmission and processing. We are committed to developing a new microchip bonding process to realize it. Taking into account the fact that most economical transparent polymer substrates can only be processed with restricted thermal loading, we designed a so-called optode instead of a widely adopted thermode. We employ UV-curing adhesives as bonding materials; accordingly, the optode is equipped with a UV irradiation source. An investigation of commercial optoelectronic components is conducted, in which their dimensions and structures are studied. While selecting appropriate transparent polymer substrates, we take their characteristics such as UV transmission degree, glass transition temperature, etc. as key criterions, and choose polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA) as carrier materials. Besides bonding achieved through the use of adhesives cured by the optode, underfill is accordingly employed to enhance the reliability of the integration. We deposit electrical interconnects onto the polymeric substrate to be able to bring the optoelectronic components into electrical operation. In order to enlarge the optical coupling zone from component to substrate within the proximity of the adhesive or underfill, we employ transparent interconnects made of indium-tin-oxide. We present the results of the performance tests, including the contact resistances, mechanical tests and environmental tests.
Properties of a monopivot centrifugal blood pump manufactured by 3D printing
An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model. Although the surface roughness of the 3D-printed model was significantly larger than that of the commercially available model, the hydraulic performance of the two models almost coincided. The hemolysis level of the 3D-printed model roughly coincided with that of the commercially available model under low-pressure head conditions, but increased greatly under high-pressure head conditions, as a result of the narrow gap between the rotating impeller and the pump casing. The gap became narrow under high-pressure head conditions, because the axial thrust applied to the impeller increased with increasing impeller rotational speed. Moreover, the axial displacement of the rotating impeller was twice that of the commercially available model, confirming that the elastic deformation of the 3D-printed impeller was larger than that of the commercially available impeller. These results suggest that trial models manufactured by 3D printing can reproduce the hydraulic performance of the commercial product. However, both the surface roughness and the deformation of the trial models must be considered to precisely evaluate the hemolytic properties of the model.