PCB with different solder mask colors

Solder mask is the main protective layer of the circuit board against corrosion and oxidation. Solder mask affects the quality of PCB. Without protection from the welding layer, the performance of PCB will decrease and shorten the normal working life of the device. More importantly, a solder mask provides a barrier between the weld point and other conductive elements of the printed circuit board during PCB assembly, which helps prevent the formation of a welding bridge.

The role of solder mask

1. In the welding process, the gap between the pad and the pad is very small. A solder mask can prevent a short circuit between the pad and the pad.

2. Let the PCB weld only where it must be welded.

3. Solder mask prevents deterioration and corrosion of insulation caused by environmental factors such as dust and moisture. A solder mask can protect the line for a long time.

4. Solder mask has high insulation, which makes it possible to densify the circuit.

What are the color options for the PCB solder mask?

PCB manufacturers use liquid optical imaging to make solder masks, such as LPI or LPISM. This is essentially a special ink that can be printed, sprayed or screened on PCB and other items in PCB production.

PCB manufacturers can use a mixture of polymer and coated solder masks to achieve a thin coating that can be applied to almost all PCB surfaces, making it an effective alternative to conventional PCB coatings. After cleaning and scrubbing the panel, it is cured with ultraviolet light.

A common disadvantage is that LPISM cannot always be used on PCBs if they require special electroplating surface treatment.

Divide by solder mask color

1. Green solder mask

The green standard is still a common PCB resistance option because it makes everything visible. White text on a green background has high contrast and the finishes are not bright enough to reflect too much light, reducing glare. A green solder mask is a common choice for circuit board manufacturers, and some may find it an effective way to highlight high-quality processes because the color does not interfere with the display wiring.

2. White solder mask

Solder mask applications for white printed circuit boards are becoming more common because they can make PCBs look particularly beautiful in a clean environment. However, practical application in PCB factories may be more difficult because the white solder mask hides the traces well. And the risk that white solder masks might slowly turn yellow.

3. Black solder mask

The black solder mask produces slightly fewer visibility problems than the white option. The contrast is small, but the labels and large components are easy to see. The disadvantage is that light may catch components and cast small shadows, making the marks harder to see. The black PCB solder mask option is also not generally recommended because the heat increases, which may discolor the screen prints and make the circuit board harder to clean. Like white, it is a very beautiful PCB board, and the black solder mask has a unique visual effect.

4. Red solder mask

Red PCB boards are becoming a popular choice. Their contrast is not as good as green boards, but they give PCBs a fresh look when compared to old industry standards. Screen printing stands out against a red background.

5. Blue solder mask

Heavy-labeled circuit boards should consider using blue liquid light to image solder masks, as it is in sharp contrast to screen printing. Without proper lighting and enlargement, the marks will become more difficult to see, so this is the balance of the blue option. Blue is usually chosen because of its appearance. It's not as dramatic as white or black, but it does offer a compelling aesthetic choice, suggesting complexity and craftsmanship, especially when you install it on an LCD. It shows dirt more easily than some other colors.

6. Yellow solder mask

Many new colors are emerging, but they may be difficult to manage. Yellow is a pleasant color, but it has poor contrast with screen printing and tracing, making it difficult to use in any practical application. Different colors will balance different needs, such as cleanliness, visibility and style. Always try a PCB sample before running with the new color selection.

Although the color of the Solder Mask has no effect on the plate, the thickness of the Solder Mask has a great effect on the impedance. According to the experience of IPCB, the red Solder Mask is easy to control the bubbles and thickness. First, the price of the Solder Mask is more expensive, and the quality is indeed desirable. The second is that this color can cover some defects on the circuit, and the green solder mask will be more obvious. The third is imaging. It seems that the exposure of red and yellow solders is relatively stable. The exposure of green solders is not certain, while white solders are not easy to control.

The viscosity of solder masks varies with different colors. The green Solder Mask is small, the red, yellow and white Solder Mask is slightly larger, and the black Solder Mask is large. On high-density PCB, the distance between pads is small, and the width of the solder mask is small. When screen printing solder mask is used, solder resists with low viscosity and is easier to be printed on PCB. Therefore, sometimes the PCB that can be made in green cannot guarantee the quality of solder resistance after changing the color. In addition, the blue solder masks and black solder masks are respectively doped with cobalt and carbon, which have certain conductivity, so there is a risk of short circuits. The PCB of the green solder mask is environmentally friendly, and it will not release toxic gas when used in a high-temperature environment.