Black PCB – An In-Depth Guide About It
Have you ever seen a black PCB and ever wondered about its exoticness? Well, black is actually the color of the solder mask and not of the PCB. What makes the black-colored PCB so different is that most PCBs are green in color. Black PCBs are made to avoid reflection, which helps in the repairing of the PCB.
Black PCB – Definition
Printed circuit boards are available in several colors in the market. Among all of them, green-colored PCB is the most commonly found. Some other colors, although less common than green, are red and blue. They are significantly less reflective; and the black color is the least reflective of all.
Besides, black PCBs are commonly used by firms like Apple, which has given them an additional sense of prestige. The technicians use black color solder masks in making the black PCBs. The black solder mask helps in absorbing heat during the process of reflow. The user can either scale up or down the temperature to make the best use of the sensors without going over the top.
The black PCB’s silkscreen can also turn light into other colors like brown for heat absorption. The PCB or electronics manufacturers decide on the PCB’s color beforehand. Heat absorption is an essential criterion for choosing the black PCB and then comes its aesthetics. The molten stage of the PCB facilitates convenience for applying the solder mask.
This article let us dig a little deeper into attaining detailed insights about black PCB and its potential.
Black PCB Solder Mask
The solder mask, also known as the solder resist, is an essential component or material used in the finalization of the PCBs. Application of the PCB solder mask is the primary step in varnishing or lacquering the whole surface of the PCB. It is done on both sides of the PCB.
It makes a permanent protective layer. It allows copper traces to be printed on itself. The printed circuit board’s solder mask is the primary agent for preventing the solder from spreading through the PCB connectors. It, therefore, avoids a short circuit.
Here are its major characteristics:
- It provides PCB protection from environmental hazards, particularly moisture.
- The black PCB’s solder mask is colored so during the molten stage.
- The black PCB’s solder mask minimizes reflection, allowing technicians to see the circuits, letters, and numbers.
In some circuits, the reflection of light is not required or desired. Using the black solder masks in such circuits is of high importance. The solder masks absorb the heat from the PCB. This means that you have to either reduce your profile or place the temperature sensor on the PCB.
You need to ensure that using while making or repairing a circuit board black-colored is enough lighting conditions. You may need to use a torch with a powerful beam. Besides using a good lighting condition, one may have to tilt the PCB to an angle to see the circuits correctly.
In the quality testing process of the black PCB, they use magnification devices to see the circuit without causing any strain on the eyes.
PCBs with green masks are the clearest to the eyes under normal lighting conditions. This is why most manufacturers still use green-colored PCB masks despite virtually no difference in the PCBs’ cost and the perceived prestige of the black circuit board.
Most electricians and PCB technicians regard the process of applying black solder masks on the PCBs as challenging. It is not achievable under normal conditions of the home. The process is intricate and inefficient in a DIY setting. Nevertheless, if you do venture into such a thing, you may be able to accomplish it, albeit with some imperfections.
When talking about complex circuit boards, applying solder masks to make a black PCB board is not simple. There are several strict rules and regulations concerning the production of such devices. It is very important to stick by the standards to gain commercial success and have fewer repercussions.
There are several stages that one has to follow judiciously. Using technology can help in industrial-grade accuracy and is professionally inevitable. For making complex PCBs, using state-of-the-art software programs is indispensable, as well.
How to prepare a black PCB?
Here is the step-by-step process of making a black PCB.
1- Cleaning
To get started with the black solder mask application process, you have to clean the PCB.
2- Coating with ink
Secondly, you have to do the solder mask ink-coating. In the making of black PCB, needless to say, the black solder mask has to be used before the pre-hardening step.
3- Pre-hardening
After the ink-coating phase comes to the pre-hardening step, then comes the imaging and hardening phases.
4- Development
The development phase follows the pre-hardening step shortly. In this step, the PCB-making technicians use the software before the final step.
5- Hardening
This is the final step in making the black-colored PCB.
Black PCB material
Printed circuit boards are made from several types of materials. The main base is made from silicon. The PCB-making technicians use software programs like Sprint layout to print the design layout of the PCB.
As stated above, the PCB color is derived from that of the solder mask, which is made from resin. Below are the reasons why resin is the best material for making solder masks.
- It is highly resistant to humidity
- It is a perfect insulator for the PCB
- It is resistant to soldering
- It can tolerate heat without compromising on the board’s ability
- It is also aesthetically appealing.
Steps to apply resin to the PCB:
Below are the steps of applying resin to the PCB.
1- Clean up the PCB
This is a significant step in ensuring that the board functions as per its intended ability. A single speck of dust can render it useless. Clean the board with a dry cloth thoroughly.
2- Apply resin
In this step, you can place a piece of blank film and start applying resin onto the board. You can accomplish it with the means of a syringe or plunger.
The amount of resin to be used depends on the area size of the PCB. You will have to make precise measurements to achieve the right balance. Applying too much resin will decrease the resin economy, and too little will do no good.
3- Spread resin evenly
This step is critical; you have to use another piece of blank film such that it lays over the applied resin. This ensures that the applied resin is evenly spread throughout the circuit board. This can be accomplished by using a weighted glass that covers the PCB throughout and ensures spreading the applied resin everywhere.
Using a rubber-edged squeegee can also help make the resin reach difficult areas, especially the corners and edges. You have to ensure not to exert much force in the application process, leading to bad spots and affecting the PCB’s functionality.
Another common problem in making your own black PCBs is leaving air bubbles in the resin. It is important not to hurry to create such a mess, which can even add to the cost.
4- Apply the black solder mask
After applying the resin evenly and removing the glass, you have to apply the solder mask on the PCB. Then, you have to align the film. To give the film a firm grip, you can add a little bit of alcohol to the back of the mask to allow it to stick on the clear film properly.
5- Expose the PCB to UV rays
You can use a torch or any other source of UV light that covers the PCB entirely. Let the source of light be focused on the PCB for nearly 10 minutes.
6- Remove the film
Finally, you can gently remove the film. The PCB is ready.
Black PCB Coating
The black PCB coating has numerous benefits. The safety of the electrical device is its most significant advantage.
The process can be completed with the help of coats made up of the following materials.
1- Acrylic
It gives the PCB protection and adequate elasticity. Application and removal are easy with acrylic coatings, too.
2- Urethane
It offers exquisite protection from chemicals and moisture
3- Silicon
It has a great temperature and chemical resistance
4- Varnish
It is highly insulating and moisture-resistant
Is a black PCB more advanced than other PCBs?
Black PCBs are chosen only by selective manufacturers. Aesthetics is one of the most important purposes of using black PCBs. Besides, thermal regulation, reparability, etc., are other more prevalent reasons for using black PCBs.
Conclusion
Black PCBs have their own set of advantages. Many promising brands use them in their products for a variety of reasons. They make the devices highly repairable by accentuating the circuitry. Making a black color PCB with DIY tips is not so easy; however, it is achievable. You can use some software and tools for accomplishing industry-grade quality in making black PCBs.
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