Detailed Guide to Cleaning Printed Circuit Board
If the PCB is exposed to external contaminants, it will lead to overheating or corrosion to degrade the performance.
Printed circuit boards are an essential part of the electronic ecosystem that runs a lot of different processors and processes that contribute to the speed and performance of the system. If the printed circuit board gets dirty, that can cause overheating and other issues in the electronic system. Most electronic devices today have printed circuit boards as the underlying hardware that integrates all the passive components and circuits to make complex circuitry. Each printed circuit board integrated inside an electronic hardware product has an ideal operating condition and a standard manufacturing process. Several of these can cause the printed circuit board to get dirty and create problems in the entire performance of the hardware platform.
Printed circuit boards are an integral part of any electronic system components placed on a green printed circuit board that provides mechanical strength to the components enabling the PCB to be mounted onto a bigger electronic system. When it comes to keeping the printed circuit board clean, they are prone to accumulate dust and sometimes can come into contact with liquids by splashing or soaking. When printed circuit boards are exposed to these elements, they gradually corrode the solder joints, further damaging the circuit's efficiency and performance.
Cleaning printed circuit boards is the most crucial part of any electronic appliance maintenance. The board contains components that control the entire electronic system operation by maintaining performance. This is one of the reasons why printed circuit boards need to be kept away from external contamination so that the operator can achieve ideal output from the hardware platform. However, even if the operator wishes to keep the printed circuit board in complete isolation for ideal high performance, it is nearly impossible to keep the printed circuit board dust-free. These devices are likely to go through containment, which increases the possibility of the printed circuit board malfunctioning.
It is important to clean the printed circuit board regularly so that the board can function in its ideal operating condition. Cleaning printed circuit boards can also extend the lifetime of the hardware device platform. The process will ensure that the printed circuit boards have a high-quality, durable nature in the longer run. To understand the process of cleaning, the operator must have a proper knowledge of how to clean a printed circuit board to upgrade and maintain the hardware device's performance.
When the printed circuit board gets contaminated, they can isolate the onboard component preventing heat loss and overheating the entire electronic system. In a basic printed circuit board, there are several functionalities in a compact form factor; hence, they are more susceptible to contamination and damage in the form of corrosion. If the operator fails to clean a printed circuit board properly, that can harm the device's durability, effectiveness, and reliability. The lifespan and longevity of the printed circuit board will also be negatively affected.
How do Circuit Boards Get Dirty?
Printed circuit boards get dirty over time with dust, water, and other contaminations that may lead to ineffective operation of the device. Some of these contaminants can cause temporary damage, while some can cause permanent damage to the equipment. If the electronic device has a fan onboard, that can draw in debris found in the air to build up unwanted materials for overheating and component failure. The liquid is one of the common ways in which electronic devices are affected. Once the liquid comes in contact with other electrical components of the printed circuit board, it can cause short-circuiting. This harms the circuit and damages the device's working.
Residues Resulting from Manufacturing
With the spacing between adjacent conductors having reduced, the problems of residue and contaminants on the printed circuit boards are becoming an increasing problem in terms of the reliability of PCB. Electrochemical migration refers to ion migration through a medium, such as flux residue, under the influence of an electromagnetic field. When these printed circuit boards are working under stress voltage, there can be an intermittent fault that decreases the reliability.
Creep corrosion is the phenomenon where the sulfide crystal of copper or silver is generated on the surface of the printed circuit board. When this sulfur in the air combines with copper or silver, copper sulfide or silver sulfide is formed. These compounds will grow in a director that makes fine leads open or shortcuts between spacing leads, resulting in poor-quality printed circuit board manufacturing.
Impact of the Working Environment
If the printed circuit boards are packed in a sealed box or a bag to keep contamination out, they will affect the durability of the solder joints. Some of the operating conditions that affect the working of the printed circuit board are the exposure of electrical components to air which can cause corrosion. Even if the operator is required to do extra soldering on the electronic components, it is very important for the user to ensure no additional flux residue. The printed circuit board gets heated for high-performance application devices if there is no proper cooling technology. This also affects the printed circuit board's working and requires regular cleaning.
Improper Use
Sometimes, the user does not use the electronic device recommended by the manufacturer. The manufacturer always gives out a user manual for the operator to use the electronic device at its optimum environment for high performance. However, this is not possible for everyone as the usage can vary from person to person. When the operator uses the electronic devices at a higher power supply or in a damp and wet environment, it is very likely that the printed circuit board will get spoiled.
Why Clean a Printed Circuit Board (PCB)?
When the printed circuit board degrades over time, it’s worthwhile to protect or clean them every few years if the user needs it to operate for more years. Overheating and corrosion are two main reasons why the user should regularly clean the printed circuit board because overheating will cause more power consumption. Overheating has become a major issue in small-form factor integrated circuits as they are more vulnerable and susceptible to external contaminants. A clean operating environment for the printed circuit board keeps it away from dirt and dust to increase reliability for a long time.
Improve the Reliability of Circuit Boards
As previously explained, to increase the reliability of any printed circuit board, the hardware has to be protected against contaminants. Printed circuit boards get dirty to affect their performance for three reasons– printed circuit boards are soldered or assembled in an unclean environment, flux residues are left on the board even after the assembly, and the finished printed circuit board are insufficient to protect from the environment during its operation. To ensure the long-term reliability and durability of the integrated circuits, the user must clean flux residues thoroughly from the printed circuit board without any leftover residues.
Prevent PCB Component Corrosion
If the printed circuit board is exposed to external contaminants, they can act as insulation on the components and block the airflow. Also, if they are exposed to liquids or aerosolized liquids, they can cause corrosion on solder joints and circuit traces. These corrosive parts on the printed circuit board can cause impedance issues or open circuits. Preventing printed circuit board corrosion can be simple as placing a conformal coating over the exposed copper areas. Epoxy coating, aerosol spray coating, and solder masks are commonly used and effective barriers to oxidation and corrosion.
Prevent Adhesion Issues with Conformal Coating
Even though the conformal coating is recommended for corrosion issues, they have several drawbacks which are important to understand. Conformal coating failures are divided into three main categories–
Failures due to incorrect selection of the material
Failures in the conformal coating masking process during production
Failure in the conformal coating production process itself.
However, to prevent these issues, the printed circuit board can be kept clean to improve the adhesion of the coating and remove contamination, such as mold release agents on components. It is important to check the compatibility of the conformal coating to the solder resist and laminate so that good adhesion is achieved. The fabricator must choose a less permeable conformal coating to limit moisture penetration to the surface of the laminate. Reducing the coating thickness also reduces the problems associated with the coefficient of thermal expansion. Applying primer to treat the printed circuit board surface will increase the bonding of the conformal coating to the substrate.
Avoid Dendritic Growth from Ionic Residues
Researchers have found that a circuit board with a high level of ionic contamination will result in deteriorated insulation resistance and dielectric strength. The major source of ionic contamination is the printed circuit board itself. This environment causes dendrite growth on the surface of the printed circuit board, which reduces the lifetime of the electronic product. IPC defines dendritic growth as the growth of conductive metal filament on the printed circuit board through an electrolytic solution under the influence of a direct current voltage bias. To prevent this, the fabricator must adhere to IPC-5704 to minimize the risk of latent field failures due to ionic contamination-related dendrite growth.
Contamination types
The printed circuit board can get contaminated in various ways, and these are typically divided into four types– organics, inorganics, water, and particulate. The organic contaminants include rosin solder pastes and fluxes that come in grades of activation and create strong solder joints. This organic contamination is dissolved and removed with cleaning fluids or flux removers. The inorganic contaminants are usually flux and solder paste activators, such as acids, bases, and halogens. They come from polar residues left from lead-free and no clean fluxes and solder pastes.
They usually require more aggressive cleaning fluids to remove contaminants– specifically white residue. The water comes under inorganic contamination. If the water is trapped inside small areas on the printed circuit boards, they can cause corrosion. Particulate is a polar contaminant commonly found on PCBA and is insoluble, and cannot be dissolved in water or cleaning fluid.
Ionic Contamination
Ionic contamination is also common and arises when ionic residues remain on the printed circuit boards, affecting reliability and functionality. These ionic contaminants become conductive when in solution, and exposure to moisture makes ionic residues disassociate into positively or negatively charged elements. Performing printed circuit board ionic contamination analytics is very important as it reduces the risk of defects caused by contaminants. This testing is performed to detect ionic residues resulting from the fabrication and soldering process.
How to Clean a Wet Circuit Board
Printed circuit boards are used inside electronic devices that are part of our daily lives. These electronic devices can get wet through water spills which can cause these products to affect their operation. This happens because the printed circuit board gets wet, and the liquid gets inside the device and causes the device to stop working. Cleaning the printed circuit board could possibly restore functionality once the board is dried.
Cleaning these printed circuit boards is very important, and if the water is left inside the hardware, that can later cause corrosion. The longer electronic components are exposed to these contaminants; they can cause overheating as well. Often wet printed circuit boards are visible to the naked eye, and the board can eventually look rusty.
Tools needed
Many tools can be used to clean a printed circuit board after it gets wet. But the most common choice is a brush that has soft bristles and is small enough to reach places inside the printed circuit board. The user may also require lint-free towels like microfiber cloths that should be handy to run down and dry off the circuit boards. Household appliances are also used to accelerate the process of drying printed circuit board– an oven is an ideal choice.
Steps of cleaning a Wet Circuit Board
The first thing the fabricator or the operator has to do is unplug the electronic device immediately after the water spill or liquid injection.
Disassemble the electronic device and explore the product’s internal circuitry.
Soak up any remaining liquid with a lint-free cloth, and do not use paper products as it may leave lint or scratch on the board.
Remove the dirt and liquid by brushing with a toothbrush. This includes any globs or dried liquid.
Clean any residue off the printed circuit board using a cotton swab.
Remove and replace any damaged electronic component that may have been in contact with the liquid.
Reassemble the device and test its operation.
How to Clean Solder Flux from a Circuit Board
In layman’s term, flux is a chemical agent that is used for soldering electronic components on the printed circuit board. The purpose of these chemical agents is to remove oxides and impurities from the printed circuit boards. However, using the flux, the operator can also achieve improvement in the solidity of the soldering joints.
However, there are several disadvantages while using flux, that is, it leaves residues on the boards. Flux is acidic in nature– which means it can corrode the components and also damage the printed circuit board subsequently. There are many ways to remove the flux on printed circuit boards– with isopropyl alcohol. Flux residues can be cleaned using an isopropyl alcohol solution.
There are also ways to remove flux residues without using alcohol. There are specific products in the market which are sold as flux cleaners and these products are slower drying and more powerful than isopropyl alcohol. They are safe as well to use on the surfaces of printed circuit boards. These can be applied by spraying, and then removing the flux residues with a brush.
Another way to clean solder flux from a printed circuit board is using an aggressive cleaner. This is done for water-solution flux residues, wherein a saponifier can be added to help the removal process.
Factors that make it Difficulty to Clean Flux Residues
Fabricators and operators have claimed that cleaning flux residues on the printed circuit boards is one of the most complex and complicated processes when cleaning. There are two reasons why cleaning flux residues can be a difficult task– saponification factor and compatibility of the cleaning chemical agent. While cleaning if the no-clean residue on a printed circuit board is partly cleaned away– this can be worse for the reliability of the board than leaving flux residues untouched from a corrosion view point. When flux residues are not cleaned, the harmful components of the flux residue like flux activators are locked up in the carrier resin matrix. Hence, these flux residues should not allow any leaching out of harmful chemicals that could cause corrosion of the printed circuit boards.
Circuit Board Corrosion
Printed circuit boards usually use metal for the connection between each onboard component. As we all know, metal parts are susceptible to corrosion. Similarly, the onboard metal used in printed circuit boards, when used daily, can be affected due to corrosion. This corrosion can further damage the printed circuit board, reducing the hardware device's operating performance.
In simple words, corrosion is the process of oxidation that happens when oxygen bonds with metal, producing rust and causing the metal to lose its chemical properties. When printed circuit boards are in use, they eventually face the issue of corrosion and need treatment for their longevity. Some metals have high resistance towards corrosion, such as graphite, gold, silver, and copper-nickel alloy.
Causes of Circuit Board Corrosion
There are several reasons why printed circuit boards can undergo corrosion– atmospheric, galvanic, electrolytic, and fretting. Atmospheric corrosion is the most common cause for metals in the circuit boards to corrode. When metal is exposed to moisture, such as oxygen, there is a reaction wherein the metal ions bond with oxygen atoms and create an oxide. Second is galvanic corrosion which occurs when different types of metals come in the presence of an electrolyte. The more resistant metal will actually corrode at a faster pace than baser metal that’s in contact with it.
In electrolytic corrosion, the adjacent traces experience dendrite growth when ionic-contaminated moisture infects the electrical voltage between them. The last one is the fretting corrosion when the action of closing solder-plated switches creates a wiping action that removes the surface oxide layer. Eventually, the excessive rust builds and prevents the switch from working.
How to Prevent Corrosion in Circuit Boards
There are several ways to prevent corrosion– let’s put this in the correct way. There are several ways to delay the corrosion process so that the longevity of the printed circuit board increases. The corrosion process cannot be avoided forever, and the first way to prevent is by avoiding ionic contamination. When the printed circuit board is exposed to moisture, ionic contamination becomes the cause of corrosion.
Even at the time of manufacturing these printed circuit boards, the operator should avoid getting fingerprints or liquids on the printed circuit boards to keep it clean and dry. Designers should also take care of the printed circuit boards by not letting moisture come in contact with the conductors onboard.
Safety and Prevention Practices When Handling Circuit Boards
Precautions that can be taken in the development phase of the printed circuit boards– avoiding exposing copper traces to air, avoiding leftover debris, avoiding excessive pressure and strain, and wear protection.
In the testing phase of the printed circuit board, the fabricator can avoid condensation if the temperature difference between the board surface and the surrounding becomes more. The fabricator can also use tools to avoid potential damage.
Some precautions once the printed circuit board is manufactured are– maintaining a controlled environment and also ensuring the boards are properly packaged.
When these printed circuit boards are stored, the operator must avoid moisture and electrical static discharge and also remove the batteries for long-term storage.
Key Takeaways
Cleaning printed circuit boards are the most crucial part of any electronic appliance maintenance.
Printed circuit boards get dirty over time with dust, water, and other contaminations that may lead to ineffective operation of the device.
When the printed circuit board degrades over time, it’s worthwhile to protect or clean them every few years if the user needs it to operate for more years.
Overheating and corrosion are two main reasons why the user should regularly clean the printed circuit board because overheating will cause more power consumption.
The printed circuit board can get contaminated in various ways, and these are typically divided into four types– organics, inorganics, water, and particulate.
Cleaning these printed circuit boards is very important, and if the water is left inside the hardware, that can later cause corrosion.
Flux is acidic in nature– which means it can corrode the components and also damage the printed circuit board over time.
When printed circuit boards are in use, they eventually face the issue of corrosion and need treatment for their longevity.
The corrosion process cannot be avoided forever, and the first way to prevent it is by avoiding ionic contamination.
References
[1] https://gesrepair.com/clean-circuit-board/
[2] https://www.candorind.com/how-to-clean-a-circuit-board/
[3] https://worldsway.com/cleaning-pcb-assemblies/
[4] https://www.circuits-central.com/blog/why-pcb-cleaning-is-so-important/
[6] https://www.mclpcb.com/blog/pcb-ionic-contamination/
[8] https://www.pcbbuy.com/news/How-to-clean-PCB-after-water-damage.html
[9] https://www.conro.com/how-do-i-remove-flux-after-soldering-the-pcb-board
[10] https://www.pcbway.com/blog/Engineering_Technical/How_to_Clean_Flux_From_PCBs.html
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