Electronic device failure is one of the major concerns of everyone around the globe. However, corrosion is one of the main reasons for this failure. Corrosion enhances the track resistance of copper over the circuit board surface. Moreover, progressive corrosion affects the efficiency of the board or sometimes damages it completely. Therefore, let’s dive into the basic details of board corrosion. This also helps you in taking proper care of the PCB, which allows the PCB to operate well throughout its life.
What is Corrosion?
Corrosion refers to the process of metal oxidation. This occurs when metal bonds with oxygen. In Printed circuits with traces of copper, corrosion creates the oxidation of copper, which acts as an electric non-conductor. As the oxide of copper splinters off, the track of copper reduces the volume and increases the resistance, which may cause efficiency issues.
PCB surface comprises lead, copper, nickel, and tin thin layers that become more sensitive to corrosion. At the same time, some metal substrates like gold, silver, graphite, and copper have the ability to resist corrosion. Thus, many PCB fabricators mostly cover the substrate metal, such as copper, on the circuit with metals, such as gold, to avoid corrosion. PCBs contain copper traces in high amounts which makes them sensitive to corrosion.
Corrosion has various types with distinct natures and understanding, which helps in the prevention of corrosion.
Forms of Corroded PCB
1. General Corrosion
General corrosion refers to the most typical type of corrosion, which is also termed atmospheric corrosion or attack corrosion. A type of chemical reaction occurs between the environment oxygen and the PCB copper, which results in corrosion. This reaction turns the copper into an oxide of copper with low conductance of electricity. The resistance rise may cause issues in the PCB as it stops the free movement of current in the board. It changes the color of the PCB, but the traces of copper’s mechanical properties stay intact. This process makes it comfortable to detect and avoid it.
Sulfur and moisture in the air can cause corrosion. It creates a reaction with the PCB copper and makes a bond of copper sulfate. Copper sulfate comprises a powdery substance corrosive in green color. It’s a non-conductive material that erodes the boards and copper gradually until it creates a discontinuity in the tracks of copper.
This type of corrosion can also occur with the moisture and salt available in the air, particularly in sea areas. It reacts with tracked copper and forms a compound of lead-tin/iron and trace copper of electrical components. Therefore, this process erodes the copper and causes discontinuity in electrical conductance.
2. Localized Corrosion
Localized corrosion refers to a form of corrosion that limits the level of corrosion on a very small and specific area of the circuit. Therefore, localized corrosion has three types which include
· Pitting Corrosion
It is mainly noticed as cavities and holes in the surface of copper, a type of galvanic corrosion localization that leads to damaging the conducting area. As the depth and diameter of the pit increase, it automatically directs to board failure, like discontinuity. Those compounds that create pitting corrosion usually hide these failures and make it hard to find them.
· Crevice Corrosion
Crevices under elements or other apparatus can gather left-over problems like motion or different impurities like cleaning suspension. Close by, copper responds with these substances, and the decomposition begins in the crevices.
· Filiform Corrosion
Despite the fact that surface enamel generally preserves copper cushions, dampness can get in under similar surface enamel. Responding to copper, the dampness begins the decomposition cycle, which then can spread through the same track to different fragments of the panel.
3. Galvanic Corrosion
It also has other terms like bi-metallic corrosion. It is usually because of the availability of two distinct metals. Galvanic corrosion mostly occurs between the components of metal like tin or gold plating and board copper in the presence of electrolyte corrosion. However, galvanic corrosion has various similarities in behavior with pitting corrosion. But they also have a main difference. Galvanic corrosion arises when two distinct electrochemical metals come in contact electrically as they both make a connection with the Circuit electrolyte.
4. Dendrite Formation
The traces of copper produce dendrites because of the ionic contamination between moisture and the PCB surface. However, the growth of these dendrites results in a short circuit which leads to the malfunctioning of a PCB.
5. Intergranular Corrosion
The presence of chemicals on the granular edges of PCB copper trace creates intergranular corrosion. This happens because the grain edges mostly contain high levels of impurities. Thus, this makes them sensitive to this form of corrosion.
Effective Methods to Remove Corroded PCB
Corroded PCB has two ways of cleaning. This includes a special cleaning spray for PCBs and a solution of baking soda, alcohol, and water.
- First of all, remove the power source and batteries of the device. This not only helps in preventing the short circuit but also keeps you safe from getting injured. Also, remember that this process may expose PCB electronic components to the available corrosion. Therefore, do the process keenly and carefully.
- Corrosion comes in the form of a greenish or white substance that feels and looks like crust. Some general areas to look for corrosion includes battery connectors, charging ports, SIM card ports, and such other wired material that allows connection between them and the device.
- Clean with Q-tips or cotton swabs. In addition to this, you may use water, baking soda, and isopropyl alcohol to scrub corrosion. Vinegar also acts helpful. Apply the solution over the affected surface and wipe it off in a backward and forward manner until it removes all corrosion. Furthermore, you may use the solution over the corroded surface and leave it for a long time and then wipe it off.
- Utilize a dryer for drying the circuit with a soft fabric and cool set. Always remember not to use a dryer on the heat-up setting to dry the circuit. Ensure that the circuit dries completely before turning on the device or replacing the battery.
- Make sure to replace the failed batteries with fresh batteries. Put old batteries for recycling. Also, make sure not to throw them with common trash as this can cause severe environmental damage.
Tools Used to Remove the Corroded PCB.
· Baking Soda
Baking Soda helps in removing the corrosion from the PCB. Acidic leaks and salty water exposure result in these types of corrosions. Because soda acts only mildly abrasive, it removes erosion without having any negative effects.
· Isopropyl Alcohol
Because it is readily evaporative and inexpensive, isopropyl alcohol makes a great circuit cleaner. However, unlike other Circuit cleaners, the beverage has fewer chemicals in it. Always use gloves when handling isopropyl alcohol because its concentration might harm your skin.
· Deionized or Distilled Water
The majority of people give priority to deionized or distilled water. This happens because it does not contain ions for conducting electricity. Hence, it does not degrade the PCB. Make sure that water bottles must remain closed when they are not in use. This prevents the water from contaminating dust and dirt particles from the atmosphere.
· Compressed Air
Compressed air acts as a calming method of space dirt that assembles on top and within photoelectric leverages crack to blow surrounding air inside the tool across the open areas of the device. The openings seem small, which helps in opening the apparatus and cleaning the board carefully alongside compressed air.
Baking Soda for Corroded PCB
The materials recorded above can reestablish consumed regions on a PCB. Follow these moves in order to clean a leading circuit body of consumption:
- Record the Printed Circuit Boards’ design and arrangement. Make sure to catch everything and make notes or an image so you can rebuild the board after cleaning it.
- Dismantle the PCB’s links and chips. This step permits you to get to each decomposing piece of the board.
- Scrub with baking soda and refined water. Join one section of baking soda with 2 to 4 sections of water and mix well to make a paste. Then, at that point, utilize your brush to wash the paste into every single eroded region. Permit the board to get it free from moisture for 20 to 30 minutes, then wash it with more refined water.
- Utilize the cleaner that is present in your home to make one more pass. Splash the cleaner on all contaminated parts, then, at that point, utilize a new brush to wash once more. Wipe the board off with the build-up-free towel.
- Remove the dampness from the PCB in the broiler. Set the broiler to 170°C, then switch it off totally once it completes the process of preheating. Place the board into the broiler to allow the waiting heat to dry any excess dampness.
- Rebuild and try out the board. Set up all parts back and check whether the PCB works once more. Utilize a remover to dispose of any extra erosion on the off chance that the board is not working once again.
Preventing Corroded PCB
The conversation above clarifies that erosion happens essentially within sight of dampness and foreign electrolytic substances present on the outer layer of the PCB. This is particularly valid for circuit sheets in outrageous barometrical circumstances, like in marine regions or aviation. In such conditions, Printed Circuit Boards become exceptionally powerless to various kinds of consumption.
Taking A Few Steps To Ensure Prevention Of Corrosion
Manufacturers, OEMs, and Consumers can easily clean the assembly of PCB while ensuring the removal of all residue or chemical contaminants like flux residue.
- Make sure to keep the PCB assembly always dry.
- Second, electrolytes must not be present during the assembly of PCB.
- Last but important, try to use a conformal finish on the surface of the PCB assembly as it removes the electrolyte or moisture.
However, the main goal of avoiding circuit corrosion is to keep the board away from liquids or moisture to contact with the PCB surface. For this, one practical method illustrates arranging the assembly of PCB inside a closed space with an appropriate IP Rating.
Therefore, this does not always work. Thus, you must try another approach to keeping the circuit safe from liquid or moisture contact and use a protective coating to surround the PCB. This process is termed conformal coating. The conformal coating comes in various forms. This includes a solder mask, epoxy coating, or aerosol coating. Therefore, use conformal coating appropriately to avoid concerns like taboutrmal management.
Repairing Corroded PCB Boards
The amount of damage of corrosion depicts the success of the repair of a PCB. However, it makes the damage visual after wiping off the sulfate or oxide formation. Therefore, it’s important to extract these chemical residues completely from the surface of the board to prevent repetition. Hence, engineers advise utilizing lint-free fabric completely submerged with isopropyl alcohol. Or one can also use vinegar, water, or baking soda for this very purpose.
To prevent the PCB from corrosion, many designers are advised to build a PCB and keep the environment in mind in which a PCB will work. RayPCB possesses great years of experience in assembling and manufacturing almost all forms of circuit boards for distinct applications in almost all sorts of environments.