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Why Is the Printed Circuit Board Black?

Jun. 15, 2021
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You may have seen a black PCB. the true color of the PCB is the solder resist layer, not the PCB itself.

 

In most cases, the PCB is green. There are several cases where a different color is used, and for this particular case we will focus on the black PCB.

One of the main reasons for keeping the solder resist layer black is because there is no need for light reflection in this circuit.

Read on to learn more.

Definition of Black Printed Circuit Boards

Printed circuit boards come in different colors. The most common color is green, which is found in most PCBs on the market. Other colors that may suffice include red, blue, and black PCBs, among others.

 

In this particular article, we will focus on black PCBs. black PCBs have a black solder resist layer, which may be due to some reason shared earlier. The main reason is that reflected light may affect the way the circuit works; therefore black ensures that this does not happen.

 

Compared to other colored PCBs, the black PCB is considered prestigious by those who use it. In fact, even Apple uses black PCBs in its devices, and although green PCBs are still the most commonly used color, it has become popular.

 

Black PCBs consist of a black solder resist layer. The black solder resist layer facilitates heat absorption during the reflow process. This depends on whether the user needs to scale up or down the temperature to safely manufacture the sensor used in the circuit.

 

The black PCB silkscreen also tends to turn light to other colors, such as brown, to absorb heat. PCB Manufacturers decide on the color to be used for printed circuit boards as early as the melting stage. That is when it is most convenient and easy to apply the correct color for the PCB. Compared to green, black is mainly used for high-end devices.

Black Printed Circuit Board

 Black Printed Circuit Board

Black PCB Solder Resist

The solder resist is the most important component or material required for the production of printed circuit boards. Also known as solder resist, its main purpose is to coat or varnish the entire surface of the top and bottom of the PCB to form a permanent protective layer on which copper traces are printed.

 

The main reagent that prevents the solder from entering between the conductors is also responsible for creating short circuits in the circuit. This layer is also responsible for providing protection against the environment.

 

Therefore, the solder resist layer of a black PCB is black, which is done during the melting phase. The black solder resist layer is applied when light reflection is not required. Therefore, the solder resist layer is one of the most critical parts of a printed circuit board.

Without a solder resist layer, as mentioned above, the circuit will short out, which will lead to inefficient operation. The soldermask layer helps prevent this from happening. The black solder resist layer is used for display systems where light is not supposed to be transparent.

 

Some circuits do not require light reflection.

In such circuits, the application of a black solder resist layer becomes very important. Masks absorb heat during reflow. This means that you have to reduce the profile or make sure that the temperature sensor has been placed on the board.

 

Another thing that is needed when presenting a black soldermask is enough light. Since it is not easy to see the circuitry, the black soldermask needs enough light that can be angled well enough for the manufacturer to see the board.

 

The inspection process for black printed circuit boards requires powerful magnification so that the circuit can be seen properly without pressure. A green soldermask layer may be easy to inspect and manufacture because the circuitry remains visible during its construction or even inspection.

 

 

 

 


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