Conference Agenda

While demand is growing for electronics, the amount of generated E-waste is a considerable concern [1] regarding sustainability and the environment. Transient electronics [1] and, more generally, biodegradable electronics are the pathways [2] where the current research trends are headed. Transient technology enables electronics to be zero-waste. while being capable of disappearing with minimal or non-traceable remains over stable operation time. Biodegradables are more used as substitutes for rigid alternatives [2].

In this paper, a novel substrate is presented for sustainable microelectronics applications, more specifically, printed circuits. DAT1 is a biodegradable, water-soluble insulating material that can alternatively replace current PCB insulating materials in selected applications. It does not contain metal, microplastic or petroleum derivates. (Certificates are available at [3]). In the paper, we present the process of preparing conductor tracks on the boards with thick-film technology and subtractive laser processing of copper. We investigate the surface roughness, present peel-testing, and basic assembling approaches (based on surface mounting) with low-temperature reflow soldering (LTS with SnBiAg-based alloy, Alpha OM520). We present water adsorption tests with water solubility analysis in ESPEC EHS-211M climatic chamber (25°C, saturated RH).

It was found that conductive patterns can be created on the surface using conventional copper materials and thick-film printing technologies. Components can be joined by conductive adhesive or low-temperature (SnBi) alloys, maximizing profiles at 150-160 °C. DAT1 and Cu foil structures with aqueous surfaces can be pressed together, forming a pre-preg basis. Laser etching of the substrate is achievable. The obtained peel force is currently 0.6-0.7 N/mm, below the accepted value of 1.4 N/mm. Surface roughness was recorded between 0.84 and 1,2 µm. The composition of the substrate surface did not change after the heating of the reflow. Moisture absorption resulted in ~15% after 75 hours. Water degradability was presented qualitatively after 48 hours of degradation in water.

The resulting circuits could be used in low-humidity environments or when the advantage of solubility is required.

[1] Kun Kelvin Fu, Zhengyang Wang, Jiaqi Dai, Marcus Carter, and Liangbing Hu, Transient Electronics: Materials and Devices, Chem. Mater. 2016, 28, 11, 3527–3539 Publication Date: April 28, 2016 https://doi.org/10.1021/acs.chemmater.5b04931

[2] A. Géczy, C. Farkas, R. Kovács, D. Froš, P. Veselý and A. Bonyár, "Biodegradable and Nanocomposite Materials as Printed Circuit Substrates: A Mini-Review," in IEEE Open Journal of Nanotechnology, vol. 3, pp. 182-190, 2022, doi: 10.1109/OJNANO.2022.3221273

[3] Degraway, Certificates, accesed at 2024. 02. 05. https://degraway.com/

Highly crosslinked polymers play a crucial role in protecting sensitive electronics in harsh environments. Therefore, having adequate knowledge of the underlying swelling mechanism is necessary to optimize encapsulation thickness for prolonging the lifespan of highly sensitive electronic devices, such as medical equipment.

The goal of this work is to model the superimposed heat and mass transfer in the encapsulation. The model is based on the PC-SAFT equation of state accounting for the interactions between solvent and polymer [1]. The elastic forces of the polymer chain due to the cross-linking are considered by the elastic contribution [2]. The thermodynamic model is parameterized by gravimetrical measurement of the polymer network swelling. Diffusion is described by the application of the Maxwell-Stefan equation, where the chemical potential serves as the driving force for mass transfer and is calculated using the thermodynamic model. To account for abnormal diffusion behavior, we enhance the Maxwell-Stefan model with the viscoelastic Kelvin-Voigt model consisting of a parallel viscous damper and an elastic spring. The encapsulated electronics are considered as a heat source in the simulation, which is accounted for by introduction of an energy balance. Further, the influence of the non-isothermal temperature field on the diffusion behavior is considered.

Here an approach for the modelling of the diffusion in an electronic device during utilization will be shown and discussed. This approach is capable of accounting for changes in diffusion speed in relation to temperature profiles within the polymer matrix.

• [1] P. Krenn, P. Zimmermann, M. Fischlschweiger & T. Zeiner, J. Chem. Eng. Data 2020, 65, 5677.
• [2] B. Miao, T. A. Vilgis, S. Poggendorf & G. Sadowski, Macromol. Theory Simulations 2010, 414.
• [3] P. Krenn, P. Zimmermann, M. Fischlschweiger & T. Zeiner, J. Mol. Liq. 2021, 116809.

PurPest is an EU funded project (Horizon Europe, grant ID 101060634) that will develop and demonstrate an innovative sensor system prototype (SSP) that can rapidly detect five different pests during import of plant material and in farmer fields to stop establishment of these pests and to reduce pesticide inputs by at least 50%. This approach is based on detecting specific volatile organic compounds (VOCs) that are released by the pests or infested plants at low concentrations (< ppm). Specific detection of low VOC amounts required the development and combination of several miniaturized technologies into a sensor system prototype (SSP), such as pre-concentrators, micro gas chromatograms (µ-GC), electronic nose arrays and surface enhanced Raman spectroscopy (SERS) chips. The project is currently conducting controlled plant experiments to collect and identify the VOCs of interest. Machine learning (ML) and artificial intelligence (AI) will be used to identify any particular VOC patterns that indicate the presence of the target pests. This generated data will then inform the development of the different SSP components, such as pre-concentrators, µ-GC retention layers and sensor coatings. The SSP will require innovative packaging solutions to include several types of sensors. Moreover, the project targets collaborating with other sensor projects, like newly granted EU project, COMPAS. In order to facilitate this interaction, a certain level of standardization for connection of the sensors and electronics will be necessary. The current paper presents a short update on application of coatings and the overall packaging and integration concepts of the SSP. The PurPest project is conducted by a consortium of 18 partners from 10 European countries, with eight universities, six research institutes and four highly innovative SMEs. The project started in January 2023 and will last for 48 months. The website is www.purpest.eu .