The Reliability Study of Red Phosphorus Containing Insulation of a DC plug

This Bachelor’s Thesis is a report on the preparation for and practical implementation of the reliability study of red phosphorus containing DC plug’s insulation. KaVo Kerr had received some seven-year-old DC plugs containing red phosphorus as a flame retardant, according to the manufacturer, and the reliability of DC plug’s insulation had to be assessed due to red phosphorus reliability issues known in electronics industry. Red phosphorus failure behaviour includes formation of conductive paths in the insulation under elevated temperature and humidity conditions and voltage bias, therefore DC plugs were subjected to the temperature-humidity-bias test, throughout which the leakage current flowing through the insulation was being measured. The setup for current measurement of 50uA – 100mA range was designed, built and verified over the course of the work in preparation for the study. Results of the study indicate that red phosphorus containing insulation of a DC plug developed leakage current up to 100mA under 80ºC/80%RH/24V conditions in under 13 hours. Leakage current showed intermittent character and the traces of corrosion were observed on some of the plugs after the test. Used red phosphorus manufacturing process is unknown, therefore results are of limited value. Experiment outcomes nevertheless encourage careful consideration and testing of red phosphorus containing materials prior to their long-term use in electronics applications. Further study of the physical and chemical processes that led to the leakage current formation in DC plugs’ insulation is recommended