@article{MohanSteinbergerWaechteretal.2025, author = {Mohan, Nihesh and Steinberger, Fabian and W{\"a}chter, Sonja and Erdogan, H{\"u}seyin and Elger, Gordon}, title = {Additive Manufacturing for Automotive Radar Sensors Using Copper Inks and Pastes}, volume = {15}, pages = {2676}, journal = {Applied Sciences}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2076-3417}, doi = {https://doi.org/10.3390/app15052676}, year = {2025}, abstract = {Radar sensors are critical for obstacle detection and navigation, especially for automated driving. Using the use-case "printing of heating coils on the inside of the front housing (primary radome)" needed for de-icing in winter, it is demonstrated that additive manufacturing (AM) can provide economic and functional benefits for manufacturing of the sensors. AM will allow significant cost reduction by eliminating parts and simplifying the manufacturing process. Different AM technologies for the coils were investigated, first, by applying the conductive traces by fused deposition modeling (FDM), and, second, by printing copper particle-free inks and pastes. The metal layers were electrically and mechanically characterized using a profilometer to measure the trace dimension and a four-point probe to measure the resistance. It was revealed that low-cost conductive filaments with low resistivity and current carrying capacity are commercially still not available. The best option sourced was a copper-polyester-based filament with 6000 µΩcm after printing. Therefore, low-cost particle-free copper inks and commercial copper flake paste were selected to print the heating coil. The Cu particle-free inks were amine-based Cu (II) formate complexes, where the Cu exists in an ionic form. Using contactless printing processes such as ink-jet printing or pneumatic dispensing, the traces could be deposited onto the low-melting temperature (225 °C) polymeric radome structure. After printing, the material needed to be sintered to form the conductive copper traces. To avoid damaging the polymer radome during sintering, two different processes were investigated: low-temperature (<150 °C) sintering in an oven for 30 min or fast laser sintering. The sintered Cu layers achieved the following specific electric resistivities when slowly sintered in the oven: paste 4 µΩcm and ink 8.8 µΩcm. Using laser sintering, the ink achieved 3.2 µΩcm because the locally high temperature provides better sintering. Also, the adhesion was significantly increased to (5 B). Therefore, laser sintering is the preferred technology. In addition, it allows fast processing directly after printing. Commercial equipment is available where printing and laser sintering is integrated. The potential of low-cost copper material and the integration in additive manufacturing of electronic systems using radar sensors as an example are demonstrated in this paper.}, language = {en} } @inproceedings{SteinbergerBhogarajuElger2023, author = {Steinberger, Fabian and Bhogaraju, Sri Krishna and Elger, Gordon}, title = {Correlation between the characteristics of printed sinter paste and the quality of sintered interconnects through non-destructive analysis techniques}, booktitle = {NordPac 2023 Annual Microelectronics and Packaging Conference and Exhibition: Reviewed Papers}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-91-89821-06-4}, doi = {https://doi.org/10.23919/NordPac58023.2023.10186250}, year = {2023}, language = {en} } @inproceedings{BhogarajuMohanSteinbergeretal.2024, author = {Bhogaraju, Sri Krishna and Mohan, Nihesh and Steinberger, Fabian and Erdogan, H{\"u}seyin and Hadrava, Philipp and Elger, Gordon}, title = {Novel Low Temperature and Low Pressure Sintering of ADAS Radar Sensor Antenna Stack}, booktitle = {2023 24th European Microelectronics and Packaging Conference \& Exhibition (EMPC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-0-9568086-9-1}, doi = {https://doi.org/10.23919/EMPC55870.2023.10418277}, year = {2024}, language = {en} } @inproceedings{SteinbergerMohanRaemeretal.2024, author = {Steinberger, Fabian and Mohan, Nihesh and R{\"a}mer, Olaf and Elger, Gordon}, title = {Low temperature die-attach bonding using copper particle free inks}, booktitle = {2024 IEEE 10th Electronics System-Integration Technology Conference (ESTC), Proceedings}, publisher = {IEEE}, address = {Piscataway}, isbn = {979-8-3503-9036-0}, doi = {https://doi.org/10.1109/ESTC60143.2024.10712150}, year = {2024}, language = {en} } @inproceedings{LiuMohdSteinbergeretal.2024, author = {Liu, E and Mohd, Zubair Akhtar and Steinberger, Fabian and Wunderle, Bernhard and Elger, Gordon}, title = {Using µ-RAMAN Spectroscopy to Inspect Sintered Interconnects}, booktitle = {2024 IEEE 10th Electronics System-Integration Technology Conference (ESTC), Proceedings}, publisher = {IEEE}, address = {Piscataway}, isbn = {979-8-3503-9036-0}, doi = {https://doi.org10.1109/ESTC60143.2024.10712149}, year = {2024}, language = {en} }