Mechanism analysis of plastic encapsulated DC/DC converters with unweldable pins

The plastic encapsulated DC/DC converters have been widely used in data communication, oa equipment, industrial instruments etc. in these years. One of the fundamental problem which obstacle to its further application is the unreliability of the pins. In light of a batch of plastic encapsulated DC/DC converters with unweldable pins, four group contrast experiments are designed to analyze the failure mechanism. The four group components have the same type, the same manufacturer and different batches. The experiment consists of external inspection, SEM, energy spectrum analysis, solderability test and burn-in test. The results show that the inadequate storage during the past 6 years causes the pins´ corrosion of the plastic encapsulated components. Then the corrosion becomes serious in the follow-up series of experiments, and leads to a decrease of the components´ solderability. Eventually the batch of plastic encapsulated DC/DC converters fail. From the comparison, the direct cause of the failure is wet storage environment.