In radio frequency applications, the phenomenon of micro-discharge often occurs in high-power components, such as high-power cable assemblies, high-power board-to-board connectors, and high-power devices. It can create micro-discharge channels, leading to phenomena such as partial discharge, arc discharge, breakdown discharge, which may result in decreased insulation performance or damage to products, affecting the normal operation of the system, hence effective avoidance measures need to be taken in the early design phase.

Basic Concepts of Micro-Discharge Effect:

Micro-discharge effect is a vacuum resonance discharge phenomenon that occurs between two metal surfaces or on a single dielectric surface.

It is typically excited by the radio frequency electric field transmitted in the component, where electrons accelerated in the radio frequency electric field gain energy and collide with the surface, producing secondary electrons.

a.        Micro-discharge between metal surfaces requires the electron mean free path to be greater than the gap distance between the two metal surfaces, and the electron mean transit time between the two surfaces must be odd multiples of the half cycle of the radio frequency electric field.

b.        Micro-discharge on a dielectric surface requires the DC electric field generated by the surface charge to accelerate electrons back to the dielectric surface, thereby producing secondary electrons.

This phenomenon has a special electric field enhancement effect at the microstructure level. When the electric field strength reaches a certain value, a discharge phenomenon occurs in the local region of the dielectric material, forming a small arc.

Schematic Diagram of Micro-discharge Effect Process

Conditions for Micro-Discharge Effect Occurrence:

1.        High Voltage: Micro-discharge effect requires high voltage conditions to occur. Generally, the higher the voltage, the easier the micro-discharge effect occurs.

2.        High Resistance: Charge flow in high-resistance dielectrics is restricted, leading to local charge accumulation. Examples include PTFE, PEI dielectrics.

3.        Non-uniform Electric Field: When the electric field intensity reaches a certain level, electrons in the local region gain sufficient energy to induce charge flow.

Hazards of Micro-Discharge Effect:

1.        Increased noise and harmonic distortion, decreased output power;

2.        Damage to inner cavity surfaces, shortened lifespan;

3.        Increased system voltage standing wave ratio, signal distortion;

4.        Permanent component failure;

Connector center pin burnt

Methods to Suppress Micro-Discharge Breakdown:

1.        Increase clearances and creepage distances;

2.        Use hybrid dielectric structures;

3.        Adopt stepped transition structures;

4.        Use weather-resistant and stable coatings;

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