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Failure Analysis of Hall-effect Position Sensors in Brushless Direct Current Motor

Brushless direct current motor is wildly used in accuracy-control system which needs strictly control of motor speed. It is used to start the aircraft engine on the ground. Hall-effect position sensor is one of the most important components without which a brushless direct current motor cannot operate properly. However, failure of hall-effect position sensor can be found either in working or in test conditions. Here, a failure analysis was conducted on a hall-effect position sensor in brushless direct current motor. To find out the reason of the sensor's breakdown, some methods were conducted during failure analysis. External appearance inspection and internal microscope inspection was carried out to observe the obvious damage. Function and resistance test were used for confirming the status of hall-effect position sensor. The X-ray analysis and Scanning Electron Microscope (SEM)/Energy Dispersive Spectrometer (EDS) analysis were used to describe the failure mechanism. A referential sample was also put into SEM/EDS analysis and resistance test to make the result more persuasive. Investigations showed that the failure of Hall-effect position sensor was fully responsible for the residual solder that causing a short circuit between the two pins of the sensor.