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TY - THES AU - Walch, Emmanuel TI - Investigation of the mechanical properties of a connector - silver - enamel - float glass composite PB - Rheinisch-Westfälische Technische Hochschule Aachen VL - Dissertation CY - Aachen M1 - RWTH-2020-08013 SP - 1 Online-Ressource (XIV, 145 Seiten) : Illustrationen, Diagramme PY - 2020 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University N1 - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2020 AB - Heated automotive backlights are composed of the soda-lime-silicates glass substrate, the enamel and silver thick films, and several lead-free soldered connectors. The challenges faced with this composite stack are significant cumulated degradations of the initial glass strengths by the subsequent addition of layers and connectors. SEM fractographic analyses undertaken on the composite stack have revealed that fracture originates in the enamel layer and more precisely the region near the interface with sintered silver. The soda-lime silicate glass and enamel glass frit were found to have comparable values while the fracture toughness of sintered silver has been found to be one order of magnitude higher. The most critical defects of the stack are located in the enamel, due to their relatively large size, and the fragile nature of this layer. Additionally, the amount of compressive residual stress in the enamel film is lower compared to the surface of the tempered glass substrate. Finally, the soldering of the connector transfers tensile stresses in the brittle part of the stack. Therefore, tensile stresses are applied to the porosities present in the enamel. Theses porosities act as stress concentrators, facilitating the propagation of cracks which in turn decreases drastically the mechanical strength of the composite stack. In the case of high tensile soldering stresses, several cracks can propagate in the enamel from pre-existing critical defects and propagates to the glass, leading to the formation of glass chipping in the glass substrate. The formation and growth of large glass chips can lead to spontaneous breakage of the backlights. The soldering process has the highest influences, among the process parameter, onto the mechanical strength of the composite stack. The robustness of the automotive backlight can be increased by reducing the amount and size of porosities in the enamel layer and by optimizing the residual stresses in the stack. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2020-08013 UR - https://publications.rwth-aachen.de/record/794983 ER -