Pcb circuit board is widely used in electronics, computers, electrical appliances, mechanical equipment and other industries. It is the main support body of electronic components. Here, let’s learn the basic knowledge of pcb circuit board and the process of pcb board corrosion.
What is corrosion?
Corrosion is one of the most common phenomena that we observe in our daily lives. For example, particular objects made of iron are sometimes covered with some orange or reddish-brown layer. The formation of this layer results from a chemical process called rusting, which is a form of corrosion. Corrosion is the process of decay caused by a chemical reaction between a material and its environment. The reaction usually takes place in the form of oxidation. Corrosion occurs when an exposed surface of metal comes into contact with a gas or liquid. And the process is related to the temperature of the exposed environment, acids, and salts, etc. Most metals are susceptible to corrosion, but all materials will degrade.
Which materials on the pcb are prone to corrosion
Fiberglass board is the core material of pcb. It is a flexible plastic, so it should not corrode no matter what environment it is in. And it helps to prevent damage such as accidental breakage.
The next layer after the substrate is a layer of copper foil bonded with an adhesive and then thermally fixed to the substrate. The most common printed circuit boards have two layers of copper foil, which is a material prone to corrosion. During the bonding process, heat and pressure are applied to sandwich the prepreg in the middle and activate the epoxy, causing it to bond the core to the copper or copper to copper. This effectively reduces the copper foil’s contact with air and reduces the chance of corrosion.
And copper foil is considered to be a highly corrosion-resistant material because it forms a thin, protective, highly adhesive oxide film on the surface.
After the copper foil/copper sheet is a solder resist layer. Again this is not prone to corrosion. Usually, the PCB solder resists layer is green, but some manufacturers use a different color, such as red. Manufacturers use solder resistors to keep copper traces and pads insulated from other metals, solder, or other conductive material sheets.
The solder mask layer also uses to help guide users by showing them which areas of the board can solder and marking the areas that cannot solder with green or other colors.
After applying the solder resist layer, the last layer is the screen printing layer, which is usually white ink. It is also free from corrosion.
Process of PCB corrosion
It is challenging for corrosion to occur in pcb under a normal environment. This is because the pcb manufacturer will add some compartments during the production of the pcb. This will greatly reduce the chance of metal components on the pcb in contact with air. If the scrap pcb, we usually use a corrosion solution to pcb corrosion.
Corrosion solution is usually configured with ferric chloride and water. Ferric chloride is an earthy yellow solid, which also quickly absorbs water in the air, so it should store it in a sealed place. Configuration of ferric chloride solution is generally used 40% ferric chloride and 60% water. In the configuration process, the ferric chloride should be more, or use warm water (not hot water, prevent the paint off) and make the reaction faster Note that ferric chloride is corrosive. Be careful not to touch your skin and clothes, and use a cheap plastic tub for the reaction container.
Starting from the edge of the corrosion of the PCB circuit board, when the unpainted copper foil is corroded after the corrosion should be promptly removed from the circuit board. This will prevent the paint from peeling off and corroding the useful lines. At this point, rinse with water. By the way, use bamboo and other objects to scrape off the paint (this time, the color from the liquid, is easier to remove). If it is not easy to scrape, rinse with hot water. Then wipe dry and sandpaper clean, it reveals the shiny copper foil, a printed circuit board is ready. To preserve the results, we usually use rosin solution to paint over the polished PCB circuit board to help solder and prevent oxidation.
How to prevent corrosion on pcb
PCBs contain bare copper and are susceptible to oxidation and other contaminants that can disrupt functionality and shorten the life of the board. While this is not a common topic in circuit board development, several anti-corrosion techniques can protect against it.
This is a crucial production step for pcb. This process should use desiccant in order to reduce the contact between pcb and air during the production process. And choose the suitable solder resist. Because the solder resists, a layer is a protective element in the board. According to the design of the pcb to select the right solder resist layer can effectively protect the board.
The production of mesh copper plate choice can prevent moisture in the pcb between the board layers from moving. The final show can complete in order to remove the water in the pcb. You can choose to bake the pcb board.
pcb fabrication is completed
After the pcb production is completed, you can choose to apply a special coating on its surface and choose to encapsulate it. This way, the finished pcb can exist in a more acidic environment and ideal for high-temperature environments.
The pcb can then be microencapsulated, which is the most common protection method for components or assemblies prone to corrosion. Finally, note that although the finished pcb is protected against corrosion in many ways. However, should take care not to place the pcb in a hot and acidic environment.
How to remove corrosion on pcb
If your PCB is corroded from water damage or other sources, cleaning it may fix it. Cleaning a circuit board requires everyday household items that even a small company can afford. However, only someone with basic knowledge of electronics should attempt to clean a PCB. the process involves disassembling the board and avoiding damage to components. When you separate the PCB from the electronics, please keep it away from water and disconnect the device.
You can use a variety of tools to clean PCBs, but some tools are best suited to eliminate corrosion. Cleaning a corroded circuit board involves the following materials.
The alkaline and abrasive properties of baking soda make it the perfect cleaner for corroding PCBs. It will remove and neutralize any corroded areas without causing damage.
When you use water to clean your circuit boards, you must make sure it is free of contaminants. The ions in ordinary water have conductive properties that can degrade the performance of electronics. Meanwhile, deionized water has no impurities or ions that can cause damage.
Phosphate-free household cleaners can help you effectively remove dirt and corrosion. Phosphates protect PCBs from erosion, but they are also a significant source of water contamination.
Soft bristle brushes:
If you don’t have a special PCB cleaning tool, you can use a toothbrush or paintbrush. Brushes with soft bristles will not scratch the delicate parts of the board.
Towels made of microfiber and other lint-free fabrics speed up the drying process without leaving particles behind.
A simple home oven will thoroughly dry PCBs when you use indirect heat, but never put a board in the oven without first making sure the stove is turned off.
In short, keeping PCBs clean and dry enough to prevent corrosion is not tricky with little care and attention. Taking these precautions does not guarantee that any of your PCBs will not corrode, but it can significantly reduce the likelihood of corrosion. It is always worthwhile to take as many steps as possible to reduce the possibility of decline.