1.Improving the beauty and visual appearance of the electronic board

After assembly of the electronic board, if the flux residue spreads over the solder joints and creates spots, it may look like a real defect such as a solder joint void. If the flux residue is from a rework process, it acts as an error label in the rework area and draws attention to the work, even if there is no concern.

2.Prevent corrosion on parts and PCB

Flux residues left on electronic circuits are acidic. If they are not removed by the cleaning process, the residues can absorb the humidity of the environment from the air and lead to the corrosion of the bases of the parts and PCB pads, and finally cause the disruption of information transmission as well as the decrease in the speed and quality of the system.

3.Removing dust on the electronic board

The effect of dust on electrical and electronic equipment is unfavorable and reduces the useful life of the equipment. And dust may cause you to send your board to an electrical repair center for repairs. Most of the people are indifferent to the maintenance of electronic equipment against dust and this causes their electronic devices to have a shorter life.

Normally, dust is not a conductor of electric current, but when its amount is high, it causes current leakage, which often happens in computer systems. The percentage of air humidity has an effect on current leakage, more humidity helps dust and dirt to be better conductors.Dust has a negative effect on motorized systems, cooling fans attract dust due to the magnetic field they have and cause them to lose their initial efficiency little by little or cause a lot of noise.

4.Eliminate possible contamination in the manufacturing process

Printed circuit boards may also be contaminated during the manufacturing stage. Particles and ionic residues left from soldering, adhesives left from connecting parts and other things, including contamination during board manufacturing. These pollutants weaken connections and can lead to short circuits in parts. Another reason for the contamination of the electronic board can be mentioned is the cool pad and the cooling of the device. In many electronic devices such as laptops, a fan is used to reduce the temperature of the parts. These fans absorb suspended particles of dust and by sticking to the circuit, they increase the friction on the contact surface. This issue causes the temperature of the board to increase and damage its parts.

At what stages do we need to clean the printed circuit boards?

First, the raw board is cut to the required size, and after the drilling operation, the surface of the board is brushed to remove the surface oxide and eliminate excesses. Then the boards are immersed in the preparation solution for 5 minutes and at a temperature of 55 degrees Celsius, so that the surface of the epoxy resin inside the holes swells and ensures that the action of chemical deposition of copper on the surface of the holes in the next steps is ideal. will be done The next step is to put the boards in the cleaning solution with a temperature of 80 degrees Celsius for 5-10 minutes.

This solution, the main ingredient of which is permanganate, is able to erase all the pollution, stains and resin appendages inside the holes and create a uniform surface inside the holes and cause the copper to stick inside the holes. After washing, in order to remove any permanganate agents on the surface and inside the holes, put them into the neutralizer and wait for 5 minutes at a temperature of 55 degrees Celsius until the neutralization reaction is complete. Now the boards are placed in an alkaline cleaning solution with a temperature of 60-70 degrees Celsius and after 4-6 minutes, the holes are receptive to copper in the chemical deposit copper stage. After the board is completely washed by the MICRO ETCH solution at a temperature of 40-50 degrees Celsius and for 2-0.5 minutes, the copper is removed. At this stage, the copper is prepared so that the adhesion of the chemical copper on the surface of the board is completely ideal.

After washing, the board enters the preliminary activator solution and after 2 minutes, it directly enters the ACTIVATOR solution with a temperature of 20-30 degrees Celsius and a time of 3-5 minutes, and again after washing the boards with the CONDITIONER solution which has The temperature is equal to 20-30 degrees Celsius. During the time of 8-10 minutes, the catalyst covers the holes, which enables the copper particles inside the holes to be accepted by the chemical copper solution. After washing, the boards, which are kept by special hangers for immersion in the solutions, are put into the chemical copper solution at a temperature of 20-30 degrees Celsius, and in 15-20 minutes, a thickness equivalent to 0.4 microns of copper is covered on all board surfaces. covers. After leaving the chemical copper bath, the boards are put into a solution of 5-10% by volume of sulfuric acid for neutralization, then with an acidic copper electrolyte solution, a thickness equivalent to 20-30 microns of copper covers all the surfaces and inside the holes of the board for 40 minutes.

After this stage, the boards are washed and in order to protect the surface, to prevent any pollution and oxidation, they enter the anti-stain solution with a temperature of 20-30 degrees Celsius and for 2-5 minutes. In the next step, the layer sensitive to ultraviolet light (laminate) covers all the lines and surfaces of the holes that make up the main circuit, and only the parts that must be removed in the copper removal stage remain. This process is called surface coating (TENTING). After the coating process, the excess copper parts of the board surface are removed by the copper removal solution and only lines and holes remain. In the next step, the laminate layer is also removed by STRIPPER solution, then the board is dried and enters the silk printing stage.

At this stage, all board surfaces except the holes and the outer surface of the holes (pads) are covered by resistant paint or a layer sensitive to ultraviolet light (SOLDERMASK). Then the boards enter the lubricating solution. And after that, by immersing the boards in molten tin and lead alloy, the above alloy covers the pads and inside the holes, and after leaving this tank, the surface of the board is covered by a stream of hot air with high pressure and a temperature of 300 degrees Celsius. It completely opens the board holes that are covered with tin and lead alloy and causes this alloy to spread uniformly on the wall and outer surface of the holes. Of course, it should be noted that all the mentioned items in the alloy stage are done by a device called HOT AIR LEVELING. At the end of this stage, the board is ready for delivery after final cutting and quality control.

Types of pollution in electric boards

• Flux residue and excess material left on the board surface during assembly
• Dust and its deposition on the electrical board
• Oxides formed by the reaction of metal conductors with various gases
• Floating particles and ionic residues from soldering
• Adhesives remaining from connecting parts and other materials left on the surface of printed circuits during the assembly process

Examining the best methods of cleaning the electronic board

There are several methods for cleaning printed circuit boards, and here we will review the most important of them.

1.Compressed air spray to clean the electronic board

One of the simplest and most effective ways to clean the electronic board is to use a compressed air spray. These sprays can easily remove any dust as well as surface and dry pollution from the surface of the board. For this, compressed air spray should be sprayed from a distance of a few centimeters in a standing position on the surface of the board so that dust and pollution are directed outside. Remember that spraying compressed air inside the device can cause damage to the board or the board itself. Also, long-term spraying can lead to freezing of parts.

In relation to dry spray, we should mention that these sprays are a type of electronic parts cleaner and are widely used for washing the board. But greasy or oily sprays are used to clean and lubricate moving parts on some electronic devices. Therefore, when buying a cleaning spray, pay attention to its type.

Isopropyl alcohol to clean the board

Isopropyl alcohol is a type of disinfectant solvent that is also a very good option for cleaning printed circuits. These alcohols are able to remove any traces of grease, fingerprints and surface stains from the electronic board. On the other hand, these alcohols dry and evaporate quickly due to their low boiling point, and they contain less chemicals than other cleaners.

To clean the electronic board with isopropyl alcohol, first cut the board and then use a soft-bristled brush to dip the surface of the board in alcohol. You can also use a toothbrush instead of a pen. Note that rough brushing can cause damage to components such as capacitors and cause problems with the board.

Vacuum cleaner for electronic parts to clean the board

There are equipment called vacuum cleaners or vacuum cleaners for electronic components on the market, which are suitable for cleaning the board from dry dirt and dust. It should be noted that using a household vacuum cleaner to clean the board is not recommended at all. Because these devices produce thousands of volts of static electricity that can damage electronic components. However, this method of cleaning the board has a series of disadvantages, the most important of which is the lack of access to all points of the board and the quality of cleaning is not the same on all levels of the board. Therefore, this issue should be taken into account.

Sodium bicarbonate (baking soda)

Another way to clean the electronic board is to use sodium bicarbonate or baking soda. This material has the quality of gentle wear and is very effective in removing corrosion and deposits on the surface of the board. To use this substance, you need to mix a quarter cup of baking soda with three tablespoons of water to make a paste. After disconnecting the board from the cable, start cleaning the corrosion areas with a soft, lint-free cloth. Give some time for the material to dry and finally wash it with distilled water.

Thinner to wipe the electronic board

Thinner is a type of cleaning solvent that many people use to clean the electronic board. This material has a high evaporation rate and can work well in eliminating excess fluxes on the board. To use thinner to clean the board, first disconnect the board and then smear its surface with thinner. Before drying, brush or brush the required parts to clean the surface well. Finally, clean it with a lint-free cotton cloth.

Ultrasonic device to clean the board

One of the best ways to clean the surface of the electronic board is to use an ultrasonic bath device. This device cleans the board in the shortest time and removes all the parts from any extra material. For this, just put the board in the machine to clean it well. The average time required to clean normal boards with an ultrasonic device is around 10-20 minutes.

Cleaning the board with an ultrasonic device is done through ultrasonic waves and a suitable solution. These waves are emitted by the piezoelectric ceramics inside the transducer located in the bath, and by passing through the special solutions, they form small bubbles in the liquid solution. The bubbles increase in volume and finally explode. Bursting of bubbles causes high energy and pressure, which separates the contamination from the surface of the board and cleans it.

Using dry ice or CO2 gas to wash electronic boards

The last and most important way to clean electronic boards is to use CO2 gas or dry ice.

In short, dry ice has many uses in the industry, including its uses, the following can be mentioned:

Applications of dry ice in electronic industries:

Cooling of electronic components:

Dry ice is used as a cooling agent due to its very low temperature. Because it can help assemble electronic components and control their temperature during testing and repairs so that they are not damaged. Also, this work can help maintain the useful life and quality of parts.

Parts dryer:

Due to its drying properties, dry ice can remove moisture from parts by performing the drying process and maintain their quality and performance. Because electrical and electronic communications are very sensitive and cannot be in contact with moisture.

Overheating of electronic components:

In some cases, dry ice can be applied temporarily by preventing electronic components from heating up to excessive temperatures, before necessary repairs.

Thermal test:

When electronic components are repeatedly exposed to temperature changes, they can fail or become unstable. The use of dry ice in thermal testing can help regulate the temperature of stress and its intensification in electronic components and improve their performance.

Checking and testing parts:

Dry ice is also used in the electronic industry to check and test the correctness of the components. With its extremely low temperature, dry ice can identify hot spots and thermal problems in parts, allowing potential problems in the manufacturing process to be identified and fixed.

Cleaning parts:

Dry ice is also used to clean electronic components due to its low temperature and drying properties. Dry ice is able to re-combine dirty, stuck and contaminated items with electronic components and clean and purify the components.

Why is the best washing method using dry ice?

Using dry ice in electronic industries can help maintain the quality, performance and durability of electronic components. Therefore, this technique is considered as an effective and interesting method in the electronics industry and is very useful for improving the quality and stability of electronic systems. Also, the use of dry ice makes the humidity to its lowest level compared to other methods. and this will improve the quality of system performance. Due to the softness and transient nature of dry ice, there is very little risk of collateral damage to surfaces during the cleaning process. In addition, no secondary waste will be produced in this process.Because the process is so much faster than traditional cleaning methods, machine downtime can be reduced by up to 80%, getting you back up and running faster without compromising your bottom line. The speed and concentration of the dry ice coming out of the hose can be controlled so that it affects only the dirt, grease or oil you are cleaning. This prevents any unwanted and possible damage to other parts. Most of the dirt and dry debris ends up on the floor, where it can be swept or vacuumed. In the process of cleaning with dry ice, even the most stubborn dirts are quickly and easily removed. According to the mentioned issues, HighPCB company, by using this method in washing printed circuit boards, increases the quality of this circuit. and increases efficiency to a significant extent.

Benefits of washing with dry ice

1. No need for water
2. More effective than other washing methods
3. No need for chemicals
4. Failure to create an electrical connection due to non-conductivity of dry ice
5. Reduction of maintenance time for electronic boards and machines
6. Cleaning with minimal disassembly and moving of parts
7. Compatibility with the environment
8. Saving money, time, labor and detergents
9. Not exposing parts to corrosive solvents
10. No damage and scratches on the surfaces
11. No need for drying time

Finally, according to all the mentioned cases, the most effective and efficient washing method is the use of dry ice or washing with CO2 gas. By using this washing method, HighPCB Company has increased the quality and efficiency of the products and increased the performance of the products. Optimizes printed circuit boards to a great extent.