@article{LiuContiBhogarajuetal.2020, author = {Liu, E and Conti, Fosca and Bhogaraju, Sri Krishna and Signorini, Raffaella and Pedron, Danilo and Wunderle, Bernhard and Elger, Gordon}, title = {Thermomechanical stress in GaN-LEDs soldered onto Cu substrates studied using finite element method and Raman spectroscopy}, volume = {51}, journal = {Journal of Raman Spectroscopy}, number = {10}, publisher = {Wiley}, address = {Chichester}, issn = {1097-4555}, doi = {https://doi.org/10.1002/jrs.5947}, pages = {2083 -- 2094}, year = {2020}, abstract = {Local thermomechanical stress can cause failures in semiconductor packages during long-time operation under harsh environmental conditions. This study helps to explain the packaging-induced stress in blue GaN-LEDs soldered onto copper substrates using AuSn alloy as lead-free interconnect material. Based on the finite element method, a virtual prototype is developed to simulate the thermomechanical behavior and stress in the LED and in the complete LED/AuSn/Cu assembly considering plastic and viscoplastic strain. The investigations were performed by varying the temperature between -50°C and 180°C. To validate the model, the simulation results are compared to experimental data collected with Raman spectroscopy. Studies of the urn:x-wiley:03770486:media:jrs5947:jrs5947-math-0003 phonon mode of GaN semiconductor are elaborated to understand the induced thermomechanical stress. The model enables evaluation of the stress in the interfaces of the assembly, which otherwise cannot be accessed by measurements. It serves to predict how assemblies would perform, before committing resources to build a physical prototype.}, language = {en} } @inproceedings{LiuContiBhogarajuetal.2021, author = {Liu, E and Conti, Fosca and Bhogaraju, Sri Krishna and Elger, Gordon}, title = {Simulations and experiments to analyze stress phenomena in soldered and sintered interconnections between silicon nitride chips and copper substrates}, booktitle = {2021 22nd International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-6654-1373-2}, doi = {https://doi.org/10.1109/EuroSimE52062.2021.9410869}, year = {2021}, language = {en} } @article{SchmidBhogarajuLiuetal.2020, author = {Schmid, Maximilian and Bhogaraju, Sri Krishna and Liu, E and Elger, Gordon}, title = {Comparison of Nondestructive Testing Methods for Solder, Sinter, and Adhesive Interconnects in Power and Opto-Electronics}, volume = {10}, pages = {8516}, journal = {Applied Sciences}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {2076-3417}, doi = {https://doi.org/10.3390/app10238516}, year = {2020}, abstract = {Reliability is one of the major requirements for power and opto-electronic devices across all segments. High operation temperature and/or high thermomechanical stress cause defects and degradation of materials and interconnects, which may lead to malfunctions with costly or even life-threatening consequences. To avoid or at least reduce failures, nondestructive testing (NDT) methods are common within development and production of power and opto-electronics. Currently, the dominating NDT methods are X-ray, scanning acoustic microscopy (SAM), and transient thermal analysis (TTA). However, they have different strengths and weaknesses with respect to materials and mechanical designs. This paper compares these NDT methods for different interconnect technologies, i.e., reflow soldering, adhesive, and sintered interconnection. While X-ray provided adequate results for soldered interfaces, inspection of adhesives and sintered interconnects was not possible. With SAM, evaluation of adhesives and sintered interconnects was also feasible, but quality depended strongly on the sample under test. TTA enabled sufficiently detailed results for all the interconnect applications. Automated TTA equipment, as the in-house developed tester used within this investigation, enabled measurement times compatible with SAM and X-ray. In the investigations, all methods revealed their pros and cons, and their selection has to depend on the sample under tests and the required analysis depth and data details. In the paper, guidelines are formulated for an appropriate decision on the NDT method depending on sample and requirements.}, language = {en} } @inproceedings{PascucciContiBhogarajuetal.2021, author = {Pascucci, Jacopo and Conti, Fosca and Bhogaraju, Sri Krishna and Signorini, Raffaella and Liu, E and Pedron, Danilo and Elger, Gordon}, title = {Micro-Raman to detect stress phenomena in Si-chips bonded onto Cu substrates}, booktitle = {Integrated Optics: Design, Devices, Systems and Applications VI}, editor = {Cheben, Pavel and Čtyrok{\´y}, Jiř{\´i} and Molina-Fern{\´a}ndez, I{\~n}igo}, publisher = {SPIE}, address = {Bellingham}, isbn = {978-1-5106-4385-7}, doi = {https://doi.org/10.1117/12.2576414}, year = {2021}, language = {en} } @inproceedings{ContiLiuBhogarajuetal.2020, author = {Conti, Fosca and Liu, E and Bhogaraju, Sri Krishna and Wunderle, Bernhard and Elger, Gordon}, title = {Finite Element simulations and Raman measurements to investigate thermomechanical stress in GaN-LEDs}, booktitle = {2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-6293-5}, doi = {https://doi.org/10.1109/ESTC48849.2020.9229843}, year = {2020}, language = {en} } @inproceedings{ContiLiuBhogarajuetal.2021, author = {Conti, Fosca and Liu, E and Bhogaraju, Sri Krishna and Lenz, Christoph and Seitz, Roland and Elger, Gordon}, title = {Stress evaluations of silicon nitride chips bonded onto copper substrates via SAC soldering, AuSn soldering, and copper sintering}, booktitle = {2020 26th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-7643-7}, doi = {https://doi.org/10.1109/THERMINIC49743.2020.9420523}, pages = {204 -- 208}, year = {2021}, language = {en} } @inproceedings{LiuSchmidBhogarajuetal.2021, author = {Liu, E and Schmid, Maximilian and Bhogaraju, Sri Krishna and Elger, Gordon}, title = {Advanced location resolved transient thermal analysis}, booktitle = {2020 26th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-7643-7}, doi = {https://doi.org/10.1109/THERMINIC49743.2020.9420538}, pages = {191 -- 196}, year = {2021}, language = {en} } @inproceedings{ZippeliusHanssLiuetal.2020, author = {Zippelius, Andreas and Hanss, Alexander and Liu, E and Schmid, Maximilian and P{\´e}rez-Vel{\´a}zquez, Judith and Elger, Gordon}, title = {Comparing prediction methods for LED failure measured with Transient Thermal Analysis}, booktitle = {2020 21st International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-6049-8}, doi = {https://doi.org/10.1109/EuroSimE48426.2020.9152657}, year = {2020}, language = {en} } @inproceedings{HanssLiuAbdullahetal.2019, author = {Hanss, Alexander and Liu, E and Abdullah, Muhammad Rizwan and Elger, Gordon}, title = {Failure Identification in LED packages by Transient Thermal Analysis and Calibrated FE Models}, booktitle = {2019 20th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-5386-8040-7}, doi = {https://doi.org/10.1109/EuroSimE.2019.8724558}, year = {2019}, language = {en} } @inproceedings{ElgerLiuContietal.2019, author = {Elger, Gordon and Liu, E and Conti, Fosca and Signorini, Raffaella and Brugnolotto, Enrico and Bhogaraju, Sri Krishna}, title = {Modelling Thermo-Mechanical Stress in GaN-LEDs Soldered on Copper Substrate with Simulations Validated by Raman Experiments}, booktitle = {2019 20th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-5386-8040-7}, doi = {https://doi.org/10.1109/EuroSimE.2019.8724533}, year = {2019}, language = {en} } @inproceedings{SignoriniContiBrugnolottoetal.2019, author = {Signorini, Raffaella and Conti, Fosca and Brugnolotto, Enrico and Pedron, Danilo and Liu, E and Bhogaraju, Sri Krishna and Elger, Gordon}, title = {Thermomechanical local stress in assembled GaN LEDs investigated by Raman optical spectroscopy}, booktitle = {Integrated Optics: Design, Devices, Systems, and Applications V}, editor = {Cheben, Pavel and Čtyrok{\´y}, Jiř{\´i} and Molina-Fern{\´a}ndez, I{\~n}igo}, publisher = {SPIE}, address = {Bellingham}, isbn = {978-1-5106-2729-1}, doi = {https://doi.org/10.1117/12.2520992}, year = {2019}, language = {en} } @inproceedings{BrugnolottoBhogarajuLiuetal.2019, author = {Brugnolotto, Enrico and Bhogaraju, Sri Krishna and Liu, E and Conti, Fosca and Pedron, Danilo and Signorini, Raffaella and Elger, Gordon}, title = {Investigation of thermomechanical local stress induced in assembled GaN LEDs}, booktitle = {2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-2078-2}, doi = {https://doi.org/10.1109/THERMINIC.2019.8923629}, year = {2019}, language = {en} } @inproceedings{SchmidHermannLiuetal.2022, author = {Schmid, Maximilian and Hermann, Joseph and Liu, E and Elger, Gordon}, title = {Correlation of Scanning Acoustic Microscopy and Transient Thermal Analysis to Identify Crack Growth in Solder Joints}, booktitle = {Proceedings of the Twenty First InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems: ITherm 2022}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-6654-8503-6}, doi = {https://doi.org/10.1109/iTherm54085.2022.9899664}, year = {2022}, language = {en} } @inproceedings{LiuBhogarajuLuxetal.2022, author = {Liu, E and Bhogaraju, Sri Krishna and Lux, Kerstin and Elger, Gordon and Mou, Rokeya Mumtahana}, title = {Investigation Of Stress Generated By Interconnection Processes With Micro-Raman Spectroscopy (μRS)}, booktitle = {Proceedings IEEE 72nd Electronic Components and Technology Conference: ECTC 2022}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-6654-7943-1}, doi = {https://doi.org/10.1109/ECTC51906.2022.00123}, pages = {739 -- 745}, year = {2022}, language = {en} } @article{HanssSchmidLiuetal.2015, author = {Hanss, Alexander and Schmid, Maximilian and Liu, E and Elger, Gordon}, title = {Transient thermal analysis as measurement method for IC package structural integrity}, volume = {24}, pages = {068105}, journal = {Chinese Physics B}, number = {6}, publisher = {IOP Publishing}, address = {Bristol}, issn = {2058-3834}, doi = {https://doi.org/10.1088/1674-1056/24/6/068105}, year = {2015}, language = {en} } @inproceedings{BhogarajuSchmidLiuetal.2022, author = {Bhogaraju, Sri Krishna and Schmid, Maximilian and Liu, E and Saccon, Rodolfo and Elger, Gordon and Klassen, Holger and M{\"u}ller, Klaus and Pirzer, Georg}, title = {Low cost copper based sintered interconnect material for optoelectronics packaging}, booktitle = {2022 IEEE 72nd Electronic Components and Technology Conference (ECTC)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-6654-7943-1}, doi = {https://doi.org/10.1109/ECTC51906.2022.00270}, pages = {1720 -- 1725}, year = {2022}, language = {en} } @article{LiuBhogarajuWunderleetal.2022, author = {Liu, E and Bhogaraju, Sri Krishna and Wunderle, Bernhard and Elger, Gordon}, title = {Investigation of stress relaxation in SAC305 with micro-Raman spectroscopy}, volume = {2022}, pages = {114664}, journal = {Microelectronics Reliability}, number = {138}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0026-2714}, doi = {https://doi.org/10.1016/j.microrel.2022.114664}, year = {2022}, language = {en} } @inproceedings{ContiLuxBhogarajuetal.2021, author = {Conti, Fosca and Lux, Kerstin and Bhogaraju, Sri Krishna and Liu, E and Lenz, Christoph and Seitz, Roland and Elger, Gordon}, title = {Raman spectroscopy to investigate gallium nitride light emitting diodes after assembling onto copper substrates}, booktitle = {Optical Sensors 2021}, editor = {Baldini, Francesco and Homola, Jiri and Lieberman, Robert A.}, publisher = {SPIE}, address = {Bellingham}, isbn = {978-1-5106-4379-6}, doi = {https://doi.org/10.1117/12.2591947}, year = {2021}, 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} }