The Complete Guide for PCB Cleaning
In today’s world of electronics, you will find printed circuit boards in almost all electrical devices, be it computers or industrial equipment. Once the PCBs get fitted into these electronic devices, they start getting a lot of abuse. Over time, dust, moisture, and grime enter these devices and accumulate to a level that can lead to permanent damage to the device.
Therefore, a service industry responsible for cleaning and repairing PCBs is emerging in the market.
Why need to clean Printed Circuit Boards?
Cleaning a printed circuit board is a vital process in electronic device assembling. There are some reasons why you should clean a PCB:
- To increase the performance: If you do not clean a PCB, it will affect the durability, reliability, and effectiveness of the device. there will be a negative impact on the overall lifespan of the device.
- Enhance the aesthetic appearance of the PCB: Cleaned PCBs look aesthetically more pleasing than dirty ones. The visual appearance of the board makes it attractive to the customers. Oily residues near solder joints or flux residues getting charred appear to be a defect in the PCB.
- Prevent corrosion of PCB: acidic flux residues on the PCB need regular cleaning. If left uncleaned, it will react with the moisture in the air and cause corrosion in different components of the PCB.
- Prevents dendritic growth: the ionic particles in the flux residue react with the moisture in the air, and when you apply the current, they form the branches or chains known as dendrites. As the dendrites are conductive, they lead to current leakage and can cause short circuits over time.
- Makes PCBs suitable for manufacturing: Apart from this, in industries like aerospace, automotive, telecommunications, and military, PCBs should be free of contaminants before they go to the next manufacturing level.
Types of Contaminants You should Know
Different types of contaminants can attack and accumulate in a PCB. They are of two types:
Dry Contaminants:
The accumulation of dirt and dust around PCB is widespread. You can use a small delicate brush like a horsehair paint brush to remove this dirt and dirt. This brush is soft and does not affect the components. However, this brush cannot reach all the areas of the PCB components.
To do a broader and deeper cleaning, you can use compressed air with care as it can damage vital components too. Some specially designed vacuum cleaners for PCB cleaning; however, they also cannot reach every area.
Wet Contaminants:
There are some components in PCB that come with a wax coating. In high-temperature operations, these components can act as a magnet for dust and dirt, leading to sticky grime, which you cannot remove with a brush or vacuum cleaner. Sometimes, the product also accumulates sticky soda, leading to a gooey mess. These contaminants can affect the PCB performance and thus should be removed as soon as possible.
You can remove such grime with a cleaning agent like isopropyl alcohol or IPA and Q-tip, clean cotton cloth, or a small brush. If you are using agents like IPA, you must do it in a well-ventilated area. Apart from IPA, there are several cleaning agents; however, each serves a different purpose. Always remember that complex cleaning agents can cause damage to component markings, plastics, capacitor jackets, or other delicate components like humidity sensors. If unsure of the cleaning agent, you can check that first on an old component or connector and see the effects.
Alternatively, you can use demineralized water. However, make sure to remove any moisture by adequately drying the board.
Different PCB Cleaning Methods
1. Manual Cleaning
Cleaning PCBs with the hand is the most common method of cleaning. In this, you remove various contaminants and other solder substrates with the help of a brush or an alcohol solution. Apart from the brush, you can use different equipment also. This method is very simple and cost-effective as it does not require any special equipment and whatever you need is readily available around you. Another benefit of this method is that it does not cause any harm to humans and the environment.
However, as everything is done physically, the process may take time and not be enough to clean all types of dirt. Another drawback is that you cannot manually reach all the interior parts, and thus not an optimal method for cleaning dense PCBs.
2. Ultrasonic Cleaning
In ultrasonic cleaning, you use a specially designed machine to clean PCBs. First, you must soak the board in ethyl alcohol solution so that dirt, contaminants, and any extra soldering material get loosened. After this, put the board in the ultrasonic cleaner’s cleaning bath. Now the equipment emits high-frequency sound waves into the bath solution, leading to billions of tiny bubbles exploding, which removes any contaminants on the circuit board. This process is known as cavitation.
As these tiny bubbles reach all the exposed surfaces, you can easily clean the dense and complex boards with ultrasonic cleaning. The strong and High-Frequency waves reach the board’s smallest and most difficult areas.
3. Gas Phase Cleaning
You can also call it vapor degreasing or vapor phase cleaning. In this method, you boil a chemical solvent that produces steam, which dissolves all the PCB dirt, dust, and contaminants. The gas phase cleaning method is very effective and environmentally friendly as you can use different chemical solvents for other contaminants. Further, you can filter the contaminants and use the chemical again after cleaning.
Like the ultrasonic cleaning method, this method is very effective as it can reach the deeper sections of the board where a physical brush cannot.
4. Deionized Water Wash
The deionized water wash method effectively and safely removes water soluble flux residue. In this method, you use a water-soluble flux in lead-free pastes or leaded pastes, and the solder gets cleaned by the deionized water. You can also use deionized water jets to wash and rinse the PCBs at high temperatures (144-degree Fahrenheit) and pressures (45 pounds per sq. inch). Following this, you can use air jets to dry the assemblies.
How to clean PCB after soldering?
Soldering means fusing two metals using a metal with a low melting point at high temperatures. This metal binds the metal pieces like glue. You need flux in soldering as it helps in protecting joints from metal oxides which prevent effective soldering. The flux converts the metal oxides into salt and water, which then locks in flux after it hardens.
After soldering, solder flux can accumulate on the board as a tainted yellow crust. This is a common issue in printed circuit boards that you can fix quickly. For this, you need:
- Brush with soft bristles
- 90% rubbing alcohol
- Lint-free cloth or microfiber towel
First, wet your brush with the alcohol and rub the board gently until you see solder flux disappearing. Once you see the board looks clean, dab it with a microfiber towel. After that, you can also use a flux cleaner which you will read in the next section.
How to clean flux from PCB?
For cleaning flux from the PCB, one of the most common methods is to use a cleaning agent like isopropyl alcohol. For this, dip cotton or a foam swab in the alcohol and rub it around the area. This method is enough when you need a visually flux-clean PCB. When applying the solvent, the flux residues do not evaporate. To remove them, you can dissolve the flux so that flux residues soak into the swab.
However, if you want to remove heavily active flux like RA and aqueous, you can rinse the board after swabbing. While the solvent is wet, rinse the board with an aerosol flux cleaner. Now hold the board in such a manner that solvent flows over the board and picks up any residues left and runs off the board.
How to clean PCB corrosion?
It is common for a PCB to corrode due to water or any other source, and cleaning the PCB corrosion can repair it. Cleaning a PCB’s corrosion needs household items that any company can afford. However, it is essential to have fundamental knowledge before attempting the cleaning process. The process involves disassembling the board without damaging the components, and after cleaning, you need to reassemble them.
Here are some materials which you can use for cleaning PCB corrosion:
- Baking Soda: As baking soda is alkaline and has abrasive properties, it is a perfect cleaner. It can clear and neutralize any corroded area without any damage.
- Deionized water: the purpose of using deionized water is that ions in water have conductive properties that can damage the electronics in a PCB. As deionized water has no ions and contaminants, it is best to use it for cleaning.
- Household cleaner: you can use a phosphate-free cleaner to remove corrosion and dirt from a PCB. Phosphates help protect PCBs from corrosion but are a significant source of water pollution.
- Brush: Using a thin and soft brush for cleaning is also an effective method of cleaning corrosion in PCB. However, ensure that you use a soft brush as a soft brush does not cause any scratches to the delicate components.
- Lint-free towel: Clothes made from lint-free fabric or microfiber dries up the PCB fast and do not leave any particles.
- Oven: If you use indirect heat, you can clean a PCB. For this, the household oven is the best. First, heat the oven, turn the flame off, and put the PCB in it.
Summary
When your PCB is clean and clear, it helps you in future troubleshooting and inspection. If the circuit board does not have any contaminants and residual solder, you can easily detect the faults or any potential difficulties in the PCB.
Choose your PCB manufacturer wisely if you want to ensure a clean and high-quality PCB for your electronics. Some manufacturers follow IPC standards and rules for PCB manufacturing, ensuring that you are using the best PCBs optimized for your industrial equipment.
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