The Ingolstadt University of Applied Sciences carried out the IQLED project from 1 July 2019 to 31 December 2022 under a grant from the German Federal Ministry of Education and Research (BMBF, reference 13FH044PX8). The project was led by Prof. Dr. Gordon Elger and aimed to create reliable, miniaturised interconnects for high‑power optoelectronic devices such as LEDs and lasers that meet automotive reliability standards. Three work packages guided the effort: WP 1 focused on sinter material and process development, WP 2 on the development of a stochastic transient thermal analysis (TTA) technique and the construction of a reliability test rig, and WP 3 on accelerated reliability testing of selected sinter materials and processes.

In WP 1, a range of copper‑based sinter pastes was engineered. Metal‑powder modifications, binder optimisation, and the use of metal salts as atomic‑metal sources were systematically investigated. The paste formulation was iteratively refined through a sinter‑process loop that included paste application, pre‑sintering, and final sintering. The resulting microstructures were characterised by scanning electron microscopy, X‑ray diffraction, and X‑ray photoelectron spectroscopy, revealing a dense, void‑free interconnect network. The sinter pastes exhibited high shear strength; comparative tests showed that pressure‑assisted silver sintering produced superior mechanical integrity compared with conventional SAC 305 solder and pressureless silver sintering. Thermal shock experiments demonstrated that the copper‑based interconnects maintained structural integrity under rapid temperature cycling, a critical requirement for automotive applications.

WP 2 introduced a stochastic pulsed excitation scheme to the TTA method, enhancing time resolution and reducing measurement duration. The improved TTA allowed rapid, non‑destructive assessment of the thermal resistance of individual interconnects, thereby providing a direct indicator of interconnect quality. Validation of the method employed a dedicated test‑sample group, confirming that the measured thermal resistance correlated strongly with mechanical performance metrics. The refined TTA was subsequently integrated into a new in‑situ tester designed for accelerated ageing of optoelectronic modules, enabling high‑throughput data acquisition for life‑time prediction models.

WP 3 applied the developed sinter materials and TTA technique to accelerated reliability tests. The tests confirmed that the copper‑based interconnects could withstand the thermal and mechanical stresses typical of automotive environments, with failure rates below the thresholds set by industry standards. The data generated during this phase fed back into the material optimisation loop, further tightening the performance envelope of the sinter pastes.

Collaboration was central to the project’s success. The university worked closely with Schlenk Metallic Pigments GmbH to gain a comprehensive understanding of the raw materials, and with Osram to align the research with industry needs. The positive outcomes of the project led to the establishment of CuNex GmbH, a spin‑off company that now commercialises the copper‑based sinter pastes and continues to develop copper‑based bonding technologies for high‑performance optoelectronics. The project’s findings were disseminated through high‑impact journal articles and presentations at major conferences such as IEEE Transactions on Device and Materials Reliability and the International Workshop on Thermal Investigations of ICs and Systems.