3. A Study of the Reliability of Electronic Telecommunication Systems Working at Subsea Level

Reliability is of increasing importance for electronics systems operating at harsh environments, such as the electronic telecommunication systems used at subsea level. The aim of this research was to investigate the reliability of such electronic systems through a simulated accelerated thermal cycle test. The paper presents a step-by-step process of designing accelerated thermal cycle test using field operating conditions. The Coffin-Mansion equation was used to calculate the accelerated factor for the thermal cycle test. In order to simulate the expected life time of 25 years, the solder assembly samples were subjected to 400 temperature cycles, with every cycle lasting for 40 min. Reliability was determined by measuring shear strengths of solder joints of different electronic components at set intervals. Although some of the components showed an initial decrease in shear strength, it was generally concluded that the electronic assemblies are able to maintain their shear strength for up to 25 years. The fracture surfaces of the solder joints, after shear testing, were also analyzed for brittle and ductile fractures, with the use of scanning electron microscopy (SEM).