Rethinking PCB manufacturing: A digital and sustainable approach

khashayar Ghaffarzadeh
2 days ago
5 min read

Contact: Max Scherf, Maximilian.Scherf@profactor.at

Reimagining the entire life-cycle of electronics—from raw material sourcing to end-of-life management—is essential for building a sustainable economy and society.

The EU-funded HyPELignum project addresses this challenge by exploring a holistic approach for manufacturing electronics with net zero carbon emissions, centred around additive manufacturing and wood-derived materials.

Methodology

Materials

By creating novel materials derived from wood feedstock, such as lignocellulosic composite boards, bio-derived resins, and functional compounds incorporating abundant, low-impact metals, a transition towards green electronics can be realized. These new materials expand the technological possibilities for electronics while maintaining a strong focus on environmental responsibility.

A key material in this development is Cellulose Nano Fibrils (CNF), known for its excellent mechanical performance, ease of application, biodegradability, and eco-friendly nature. CNF has emerged as a promising material for eco-electronics due to its unique properties. Initial research at Empa demonstrated the feasibility of using CNF from delignified pulp (ECF) for eco-electronics applications. The prepared CNF samples exhibited robust mechanical strength and stability in indoor environments, providing a strong foundation for further development. While CNF-based ecoPCBs show strong mechanical properties comparable to FR4 PCBs, they face challenges regarding water vapor absorption and dimensional stability under extreme conditions (i.e. Temperatures above 170°C).

The conductive traces on the l-CNF boards were fabricated by inkjet printing a highly conductive, low-viscosity nanoparticle ink (NanoDimension) using the DragonFly™ IV printer (see Figure 1a)). Assembly of electronic components on l-CNF boards was done using curable glue from LOCTITE® AA 3491 from Henkel (mechanical fixation), and conductive paste from LOCTITE EDAG PF 050 E&C from Henkel (conductive bonding).

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High-resolution inkjet printing of electronic circuits

To understand the behavior of the ink on the substrate, surface contact angle measurements and calculation of the surface energy were performed on the l-CNF board. A good match between surface energies of the surface and ink was observed, which was subsequently confirmed by printing results that exhibit good quality (sufficient resolution, no significant de-wetting or spreading of the ink on the l-CNF substrate).

l-CNF boards were wiped with ethanol to remove grease and dust particles before loading to the printer. The printing pattern was adapted from an open-source project, “Fair Mouse,” from NAGER IT. Next to the printed board for the sustainable mouse, other test structures were printed on l-CNF boards to estimate the adhesion and resistance of printed layers. The printing process includes inkjet deposition of conductive ink layer by layer followed by inline NIR drying of the ink to evaporate the carrying solvent and sintering to achieve good conductivity. The l-CNF board was kept at 120°C (tray temperature) during printing.

Figure 1: Test l-CNF board loaded in the DragonFly printer a); Test structure printed on the board to estimate quality of printing and resistance of printed interconnections b).

Characterization of printed lines

Before printing the mouse electronic design, conductive traces on l-CNF were characterized to confirm that a good resistance of the printed track can be achieved. Layers up to the thickness of 40µm were printed and 3D profiles were measured. Figure 1b) depicts the typical shape of layers of 7µm and 40µm, respectively. 3D profiles were measured by Keyence VK-X3000 laser scanning microscope (see Figure 2a)). Resistance of printed tracks was characterized using a custom-made four-probe point station with source-meter Keithley 2400 and 4-wire measurement using Keysight 34465A (see Figure 2b). Printed interconnections with the thickness of 40 µm exhibit sheet resistance as low as 6,3mΩ/sq. For printing of the demonstrator board, the interconnection pattern with 20 µm in thickness was printed as a compromise between printing time and sufficient conductivity. Line resistances for different line lengths are depicted in Figure 2c) (measured on a line with 150 µm in width).

Figure 2:Profiles of conductive layers printed on l-CNF substrate, the 3D profile view was taken in the printing direction a); Test station for resistance measurements b); line resistance vs line length c)

Assembly of SMDs

The assembly of passive components on the inkjet-printed circuit, built on a lignin-based PCB, was carried out manually. To ensure the mechanical stability of the electronic components, a commercially available UV-curable adhesive was applied to fix the electronic components on the top of the substrate. Electrical connections were made by glueing the components on the bottom (interconnections) side using a low temperature cured conductive paste. Curing to establish good electrical contact was done in convection oven at 120°C for 30 minutes. The functionality test of the whole assembly was done simply by attaching a USB cable and connection to a USB port in a PC. The inkjet-printed antenna was integrated onto the textile band via heat-seal bonding, utilizing the C-Base bonding system to attach the corresponding chip. The fabricated sustainable printed circuit board was tested and found fully functional after placing it in a 3D printed housing out of wood-filled PLA filament, as it is demonstrated in the video in the supplement information.

Demonstrators

Mouse demonstrator (conventional, fully printed, ecoPCB)

The development of this first working demonstrator, which is 97% based on ecofiendly material (by weight), represents a significant advancement in the creation of eco-friendly devices. This demonstrator not only showcases the feasibility of using biodegradable substrates in electronics but also sets a precedent for future innovations in sustainable technology.

Figure 3: l-CNF PCB with assembled components in mouse housing a); Bottom view of the l-CNF PCB with inkjet printed conductive traces

Smart furniture

A key demonstration of HyPELignum’s approach is the smart furniture demonstrator, which integrates wood-based electronics, energy-efficient µchips, and sensors into a functional furniture design (see Figure 4). This render illustrates how wood-derived materials can host electronic components in a practical, aesthetically pleasing application, highlighting the synergy of sustainability, design, and functionality.