How to Clean a Circuit Board

Everyone desires a clean and tidy environment, and while we often focus on surface cleanliness, such as spotless monitors and clutter-free desks, it’s not enough. The dirt on the surface of electronic devices can affect the user’s mood, and internal contaminants can have negative impacts on performance. For instance, dust inside a computer can slow down its operation. Addressing this issue, TechSparks provides a comprehensive PCB cleaning guide in this article, beneficial for both commercial production and end-users.

Dirty PCB to be cleaned

Why Should You Clean Circuit Board

Circuit board requires cleaning at three stages: Manufacturing, Assembly, and Post-Use.

  • Manufacturing: This involves the formation of the PCB main body. Cleaning opportunities include after lithography, after etching, after drilling, and before final inspection.
  • Assembly: This process involves assembling and soldering, especially when SMT and THT are separated. Cleaning is necessary after each soldering operation.
  • Post-Use: After the PCBA board is used in a device, if there is a perceived delay, it is advisable to check for dust on the PCBA board.

So, why do we have to clean the circuit board?

Firstly, the entire bare board production process involves the use of various chemicals. If residues are left on the board surface without timely cleaning, it may lead to corrosion.

PCB etching residual liquid that needs to be cleaned

Additionally, during CNC machining, some debris may remain on the PCB surface or in holes. If not cleaned promptly, these residues can attach to solder joints with the solder paste during assembly, ultimately negatively impacting component adhesion and soldering.

Debris generated by CNC PCB processing

When using the device, taking a computer as an example, despite the presence of heat dissipation systems and filters, tiny dust particles and dirt in the air can still adhere to the PCBA board during use. The end result is impaired circuit cooling and compromised electrical connections.

dusty computer circuit board

Contaminants Requiring Cleaning

Unexpected substances on the PCB surface are almost universally considered contaminants, and these substances can originate from the environment or the manufacturing process. They can be broadly categorized into four types: organic compounds, inorganic compounds, water, and particulate matter.

Organic Contaminants

Grease that needs to be cleaned on PCB

Include rosin solder paste used during soldering and flux to improve welding quality; unintended contact with the board during handling or the accumulation of grease during transportation; inks, paints, or other pigments used for component markings.

When removing such residues, it is recommended to use dedicated cleaning solutions with mild and appropriately strong solvents to avoid secondary damage.

Inorganic Contaminants

Flux residue that needs cleaning

Including polar substances formed during the high-temperature decomposition of lead-free solder and no-clean flux, such as chlorides and electroplating salts; undissolved or excessive substances during the soldering process; some residual chemical substances in solder mask ink.

In contrast, inorganic contaminants on PCB typically manifest as white residues, making their removal relatively challenging. The use of robust cleaning solutions with corrosive properties is advised, and thorough rinsing with water after cleaning is essential to prevent residual cleaning agents from becoming new contaminants.

Water or Water Stains

Water stains on PCB that need to be cleaned

For PCB, water on the surface is also considered a contaminant. Therefore, necessary PCB moisture protection measures should be implemented during manufacturing, transportation, and usage to prevent interference from humidity that could lead to short circuits or damage.

Additionally, a mistake is to try to spin it dry! PCBA boards form strong connections with components through soldering, and excessive force during drying may cause damage. Secondly, for densely packed circuits with numerous components, water droplets may be confined beneath the components, making it challenging to remove. The correct approach involves using a heater for effective drying.

Particulates

Particulate that needs to be cleaned on PCB

Including dust, dirt, fabric fibers, and metal debris, is the most common type of contaminant. Due to the presence of static electricity, these pollutants tightly adhere to the PCB surface.

For such contaminants, an antistatic cleaning solution proves effective in breaking static electricity bonds. Additionally, fine brushes or compressed air can be used to directly remove particulate matter from the PCB surface.

What Is Needed to Clean PCB

Cleaner

Cleaners for PCBs

When it comes to cleaning PCB, choosing the right cleaner can significantly enhance the effectiveness of the cleaning process. Here’s a brief overview of some commonly used cleaner and their key features:

  • Baking Soda: An effective cleaner with good stain-removing properties. However, its alkaline nature requires careful usage to avoid negative impacts on sensitive materials or components.
  • Isopropyl Alcohol: The most commonly used choice, effective against organic contaminants but may have limited impact on adhesive or grease-type pollutants. Apply with caution, using a cotton swab dipped in a small amount of solution.
  • Distilled Water: Used for secondary rinsing after using chemical cleaning agents. Due to its lower cleaning efficacy, it’s typically employed for less adherent contaminants.
  • Household Cleaners: Offer stronger cleaning effects but pose the highest threat to PCB. Opt for cleaners without phosphates to prevent corrosive effects.

Tools

PCB cleaning tools

Merely using cleaners is insufficient when cleaning circuit boards. To achieve more effective results, a combination of various tools and cleanup methods is essential:

  • Compressed Air: A non-contact cleaning method generating high-speed airflow through a specialized nozzle, swiftly eliminating dust, fibers, and particles. This is a safe method as it doesn’t involve any chemical solvents or liquids.
  • Brushes: To efficiently clean impurities in component crevices,  brushes are recommended. Remember, the brushes must be soft-bristled to prevent damage to the circuit and components.
  • Towels: Apply an appropriate amount of cleaner to the towel and gently wipe the surface. The towel should be soft and lint-free to avoid static and fiber residue.
  • Oven: After cleaning, PCB surfaces often retain some moisture. To prevent prolonged moisture exposure, using an oven for rapid drying is advisable. Ensure proper temperature and time settings to prevent overheating damage.

Machines

PCB cleaning machine

In commercial settings, the demand for efficiently and consistently cleaning PCB often requires advanced equipment to meet both customer and manufacturer acceptance standards. Here are some applications of advanced machines:

  • Ultrasonic Cleaning Machine: Utilizes the power of ultrasonic vibrations and microbubble implosions to remove small particles, grease, and other challenging contaminants from the PCB surface.
  • Gas Atomization Cleaning System: Forms micrometer-level aerosol particles through atomizing the cleaning agent, allowing the cleaning fluid to easily penetrate PCB structures, leaving no gaps untouched for comprehensive cleaning.
  • CO2 Cryogenic Cleaning System: Utilizes the freezing effect of liquid carbon dioxide during phase transition to make contaminants brittle, followed by gas impact to remove them. This PCB cleaning technique boasts no residues, eliminating the need for secondary cleaning, but its application is limited.
  • Ion Cleaning System: Uses ion migration and movement in an electric field to remove static electricity and ionic contaminants from the PCB surface. Suitable for cleaning highly precise electronic components and sensitive circuit boards.

PCB Cleaning Process Steps

  1. Disassembly

Power off! Power off! Power off! It’s essential to ensure the device is powered off before disassembling electronics; this is common sense. Remember the disassembly process and keep components like screws well-organized to avoid issues during reassembly. If possible, wear an anti-static wrist strap when handling the circuit board and use gloves throughout the entire workflow.

  1. Overall Cleaning

For heavily soiled PCB, use compressed air and a soft brush for overall cleaning to remove loose dust and debris from the PCB surface. This provides better conditions for subsequent cleaning steps. When using compressed air, hold the board upright and keep the nozzle a few inches away to avoid high-pressure air impacting the pins. The soft brush is primarily used for component gaps.

  1. Apply Cleaner

If your board only has some stains, using a cleaner is sufficient. Pour the cleaner onto a towel and wipe the target area. If using cotton swabs, squeeze the swab head before wiping to prevent cleaner spillage into component gaps.

  1. Eraser

Mainly for copper parts, if you notice dullness in copper wires or gold fingers, use an eraser to rub vigorously to restore their shine. Don’t worry about damage, as erasers are soft and won’t generate static electricity.

  1. Baking Soda

If corrosion has occurred on the board, a powerful cleaner like baking soda is recommended. Mix baking soda with water until it forms a paste, then apply it to the corroded area and let it sit for several hours to allow for a full reaction.

  1. Alcohol Wipe

After the thorough reaction between baking soda and the corroded area, use a towel with a small amount of 90% purity alcohol to gently wipe off the paste. It’s recommended to wipe in a clockwise or counterclockwise direction.

  1. Rinse

Use distilled water to rinse the PCB surface and remove the cleaner, preventing chemical residue that could lead to secondary corrosion.

  1. Component Replacement (Optional)

If there is no corrosion and it’s just routine maintenance, you can skip this step. If corrosion is present, investigate the cause. Most corrosion on PCB is due to battery acid leakage. In this case, you need to desolder the components and address the issue to prevent future occurrences.

Ending

In general, anything unexpected present on the surface of a PCB is considered a contaminant and needs to be removed. The key to success lies in choosing the appropriate PCB cleanup method and cleaner based on the type of contaminant.

Hmm, unfortunately, my computer malfunctioned for some reason. I wasn’t sure what caused it, so I decided to remove and clean the memory modules. To my surprise, the inside of the computer was quite dirty, prompting me to write this article. There might be more content on cleaning in the future, so stay tuned!

PS: The images used in the blog are from the internet; please contact for removal if there are copyright concerns.

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