Safety is no small matter: How does conformal coating provide a strong barrier for emergency lights and exit signs?

Spraying conformal coating on the surface of the printed circuit boards (PCBs) of emergency lights and exit signs is a very important and common process. Its core function can be summarized in three words: protection, protection, and preservation.
Conformal coating, as the name suggests, is a special coating applied to the surface of PCBs, forming a thin protective film. This film is primarily designed to withstand three harsh environments, hence the name "conformal coating." Its specific functions are as follows:

Core Functions: Defending Against Three Main Environmental Threats

Moisture and Damp Protection

Function: This is the most important job. Conformal coating effectively blocks moisture and condensation from the air.

Why it matters: Moisture is the number one killer of PCBs. Water can cause:

Circuit corrosion: Accelerates oxidation and rusting of traces and solder joints.

Ion migration: Metal ions move through thin water layers under an electric field, forming dendrites that reduce insulation and may cause short circuits.

Leakage current: Lowers surface insulation resistance, leading to signal distortion or equipment malfunctions.

Mold and Dust Protection

Function: Fills gaps on the PCB surface to form a smooth protective layer, preventing dust, dirt, and particles from building up.

Why it matters: Dust and contamination can create multiple problems:

Moisture absorption: Dust itself can absorb water, worsening humidity issues.

Short circuits: Conductive debris (like metal particles) can create shorts.

Poor heat dissipation: Thick dust layers block heat from escaping components.

Chemical Corrosion Resistance

Function: Protects against acids, bases, salt spray, solvents, fuels, and other chemicals.

Why it matters: In some industrial, automotive, or marine environments, PCBs may be exposed to corrosive gases or liquids. Conformal coating acts like a “protective suit” for the PCB, preventing chemicals from directly contacting components and traces.

2. Extended Benefits

Beyond the “three protections” above, conformal coating offers several other important advantages:

Improved Electrical Insulation

The coating itself is a strong insulator, and applying it significantly increases insulation strength between traces (voltage withstand), preventing arcing or short circuits from closely spaced components. This is crucial for high-voltage applications.

Mechanical Stress Protection

The coating has strength and flexibility, which helps:

Vibration and shock protection: Keeps large components (like big capacitors or inductors) in place, reducing damage such as solder joint cracking during transport or use.

Wear protection: Prevents accidental scratches to the circuit during installation or maintenance.

Slows Aging and Extends Lifespan

By combining all the protections above, conformal coating slows down PCB aging in harsh environments, extending the overall life and reliability of electronic products.

3. Which Products/Scenarios Need Conformal Coating Most?

Outdoor electronics: Streetlight controllers, outdoor security cameras, weather station devices (exposed to sun and rain).

Automotive electronics: Engine control units, body control modules (facing temperature swings, oil, vibration).

Industrial equipment: Factory controllers, motor drivers (dusty, oily, vibrating environments).

Aerospace and marine equipment: High humidity, salt spray, extreme temperature variations.

Medical devices: Require high reliability and safety, resistant to disinfectants and moisture.

Consumer electronics: Control boards in washing machines or air conditioners (high humidity areas).

4. Summary

In simple terms, spraying conformal coating is like putting a light but strong “raincoat” on a precision PCB. This “raincoat” helps it resist wind and rain (moisture and mold), block dirt (dust), stay safe from chemicals, and become more resilient to shocks and scratches. Ultimately, it ensures that electronics can operate stably and last longer even in tough, harsh environments.

For products like emergency lights and exit signs, which might be installed in stairwells, garages, or factories with challenging conditions—and have extremely high reliability requirements—applying conformal coating is a critically important and necessary process.