Air leakage tester for electronic component encapsulations - has electrode on either side of component wall establishing 20 KHz AC at voltage above ionisation but below breakdown levels

摘要

In an automated production line a wheel with arms picks units from a conveyor belt and rotates them to a test head under the control of a stepping motor. A high voltage generator (9) connects a 20kHz signal at voltage between 10 and 30 Kilovolts to the test head. The end of the arm carrying the housing is at earth potential. The voltage is sufficient to cause ionisation of the air but does not cause breakdown of the insulation material. Any small hole in the housing, which would give rise to leakage of insulation filter material, allows a current to pass between the electrodes. When a current flows, it is detected by a transformer secondary connected across the electrodes and a signal is sent to a comparator circuit.