Ultrasonic metalMetals welding (USMW) is a solid-state welding technology that is used primarily in electrical and electronic applications, including aluminumAluminum wire connections for modern automobiles. From the manufacturing to the welding process, aluminumAluminum stranded wiresStranded wires are subjected to numerous potential influences that affect their final state and therefore welding quality, such as the time-dependent formation of oxide layers as well as contamination during production, transportation, and storage. Current research is focused on the influence of contaminations and oxide layer properties on the ultrasonic weldingUltrasonic welding quality of aluminumAluminum stranded wiresStranded wires. Wires were systematically stored under different environmental conditions to study the influence of contamination sources (temperature, humidity, insulation materials degradation) on the welding quality. Studies demonstrated that humidity and storage temperature are decisive factors in the properties after welding.