PCB Corrosion: What Causes It and How to Clean and Prevent It?

Jun 20,2024

Corrosion on PCB can cause metal surfaces to discolorate, pitting or tarnishing, as well as electrical shorts, open circuits, or lower conductivity, variety of reasons can be the cause for corrosion such as moisture exposure, impurities, or chemical reactions.

What is PCB Corrosion?

The term PCB corrosion means the degradation or deterioration of printed circuit boards (PCB) due to various factors such as exposure to moisture, contaminants, or chemical reactions. Printed circuit boards are largely made of metal and, if exposed to oxygen, it causes oxidation that happens when oxygen bonds with metal, which leads to corrosion on PCB.

Types of Corrosion Affecting PCB:

  • Galvanic Corrosion
  • Crevice Corrosion
  • Pitting Corrosion
  • Filiform Corrosion
  • Electrochemical Migration
  • Environmental Corrosion
  • Solder Corrosion

How these corrosion types cause circuit board corrosion?

  • Galvanic Corrosion: When different metal components on the printed circuit board come into contact with one another in the presence of an electrolyte (such moisture), a chemical reaction happens that results in PCB corrosion is known as galvanic corrosion. For E.g. (This may occur when copper traces come into contact with tin or aluminum.)
  • Crevice Corrosion: Crevice corrosion known as localized corrosion is caused by moisture and impurities building up in small gaps or crevices on the PCB. Where components are closely connected or there is very little ventilation on the circuit board, it can cause crevice corrosion.
  • Pitting Corrosion: Due to exposure to the humid or polluted areas of the environment, a concentrated chemical reaction occurs and later causes tiny holes or pits to emerge on the PCB surface known as Pitting Corrosion. Exposure to corrosive substances or pollutants can be a cause of corrosion on PCB.
  • Filiform Corrosion: When oxygen and moisture find space to enter between material layers, under coatings or underlying metal on PCB, filamentous corrosion occurs and is visible as worm- or thread-like filaments, causing PCB corrosion.
  • Electrochemical Migration: When moisture and electrical potential are present, ions from metallic PCB components migrate electrochemically, creating conductive pathways between adjacent traces or components. Electrical failures and short circuits may result from this.
  • Environmental Corrosion: Environmental corrosion occurs due to the PCB parts being exposed or coming in contact with environmental factors like high humidity, temperature fluctuations, exposure to seawater, or corrosive gasses. One can prevent it by applying protective materials and coatings. It is important to have management of moisture and environmental factors during PCB assembly.
  • Solder Corrosion: When the solder joints on the circuit board are exposed to corrosive substances or contaminants, leading to the degradation of the joint integrity over time, causing solder corrosion. Which can further result in poor electrical connections or mechanical failure of components.

How to Clean off a Circuit Board Corrosion? 

If there is corrosion on PCB caused from water damage or from another source, cleaning it may repair it. There are some circuit board corrosion cleaner tools and materials available on the market which will help you with cleaning a printed circuit board, but it is recommended that someone with a fundamental knowledge of electronics should attempt to clean a PCB. Before you start cleaning the corrosion on PCB, one should first disassemble the board and avoid damaging the components. When you separate the PCB from an electronic, stay away from water and disconnect the device.

Here's a step-by-step guide on how to clean circuit board corrosion:

Materials Needed - 

  • Isopropyl alcohol (highest concentration available, typically 90% or higher).
  • Soft-bristled brush (e.g., toothbrush).
  • Cotton swabs.
  • Distilled water (If required).
  • Clean, lint-free cloth.
  • Safety goggles and gloves (optional but recommended).

Steps to Follow - 

  • Safety Precautions:
Make sure you are in a well-ventilated place before beginning to prevent clean chemical fumes from entering your lungs. Wear protective goggles and gloves when working with older electronics to shield yourself from potentially dangerous materials.
  • Disconnect Power:
Make sure that the circuit board is turned off and that the power is disconnected if the circuit board is a part of an electrical device.

  • Assessment:
Look for corrosion on PCB. Examine any obvious indications of damage, such as discoloration or rust.

  • Remove Loose Debris:
Use a soft-bristled brush (such as a toothbrush) to gently brush away any loose debris or particles from the surface of the circuit board. Take care not to exert excessive pressure, as this may harm delicate parts.

  • Cleaning Solution Preparation:
Pour a small sum of isopropyl alcohol into a container. To ensure optimal cleaning efficiency, make sure the alcohol content is at least 90%.

  • PCB Corrosion Cleaning Steps:
Dip a clean cotton swab into isopropyl alcohol and carefully rub the corroded sections of the circuit board. Make a circular motion that will loosen and dissolve the corrosion.

  • Rinsing (Optional):
  1. If needed, rinse the circuit board with distilled water to get rid of any remaining alcohol residue.
  2. Dip a clean cotton swab or cloth into distilled water and carefully wipe the board's surface.
  3. Allow the board to dry the air thoroughly before moving on to the next step.

  • Drying:
Let the circuit board air dry completely or use a lint-free cloth to gently pat it dry. To avoid any short circuits, ensure that no moisture remains on the board.

  • Inspect Again:
Check to ensure all corrosion on PCB has been removed. If you find any, repeat the cleaning process (mentioned above).

  • Reassembly and Testing:
Once the board is dry and clean, reassemble the device. Plug it in and turn it on to check if it functions correctly.

There is another advanced circuit board corrosion cleaning process called ultrasonic PCB cleaning. 

What Is Ultrasonic PCB Cleaning for corrosion removal? 

Ultrasonic PCB cleaning is a process that uses high-frequency sound waves to clean printed circuit boards (PCB). This method is highly effective for removing contaminants, such as flux residues, dust, dirt, and even corrosion on PCB, from the surface and crevices of the PCB.
An ultrasonic cleaner consists of a tank filled with a cleaning solution, typically a mixture of water and a mild detergent or specialized PCB cleaning solvent.
The cleaner is equipped with ultrasonic transducers that generate high-frequency sound waves (typically 20-40 kHz).

How to Prevent Corrosion on PCB?

To ensure the longevity and reliability of electronic devices, one should overview the PCB to prevent it from corrosion.

Here are several effective ways to prevent PCB from corrosion:

  • Use Conformal Coatings.
  • Use Corrosion-Resistant Materials.
  • Control the Environment.
  • Proper PCB Design.
  • Seal Connectors and Components.
  • Regular Cleaning and Maintenance
  • Avoid Exposure to Corrosive Chemicals.
  • Quality Control and Testing.

Regularly inspect your PCB for early signs of corrosion, which is a common issue caused by factors such as moisture, contaminants, and chemical exposure. Address the corrosion on PCB promptly and follow the step of circuit board corrosion cleaning methods, like using isopropyl alcohol and ultrasonic cleaning, can help restore functionality to corroded boards.  Early detection allows for easier cleaning and can prevent more significant damage. Establish a routine maintenance schedule that includes cleaning, applying protective coatings, and ensuring that the storage environment is controlled for humidity and contaminants.