Iso Die Package Selection for Compact Surface Mount Assembly
Matching package creepage distance to board pollution degree prevents arc flash failure while maintaining high density surface mount assembly yields.
Partial Discharge
Insulation Defect
Localized electrical breakdown of a small portion of a solid or liquid insulating system under high voltage stress does not bridge the space between the conductors. The partial discharge occurs within voids, cracks, or along the boundaries of different insulating materials. This localized activity gradually degrades the surrounding material over time.
It represents a precursor to complete insulation failure.
Detection Method
High-frequency sensor systems capture the transient electromagnetic emissions produced by the discharge events. These sensors track the rapid charge displacement using inductive, capacitive, or ultrasonic transceivers. Measuring the charge in picocoulombs provides an assessment of the insulation health.
This electrical noise must be distinguished from external radio-frequency interference.
Deterioration Phase
Persistent micro-discharges generate heat, chemical products, and ultraviolet radiation that attack the polymer chains of the insulator. This attack enlarges the void and increases the intensity of subsequent discharge events. As the void expands, the breakdown risk accelerates, eventually leading to a complete dielectric puncture.
This phase of damage cannot be reversed by lowering the voltage.
Calibration Procedure
Injection of a reference charge pulse into the test circuit simulates the response of the discharge sensor under operational conditions. This calibrator pulse must have a rise time below ten nanoseconds to match the rapid rise of an actual discharge event. The calibration process compensates for the attenuation and dispersion of the signal within the test cables and high-voltage connections.
Regular calibration allows engineers to establish a reliable baseline measurement, which is required to detect early insulating defects before they cause costly hardware failures.