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Do you know the function of PCB solder mask?  What are the options for PCB solder mask?

2020-05-08

IPC has established a solder mask testing standard as an industry guide for material manufacturers, OEMs, and PCB manufacturers. IPC SM-840D classifies solder mask layers, Class T and Class H, summarized as follows:
T-Telecommunications: including computers, telecommunications equipment, complex commercial machines, instruments and certain non critical military applications. The solder mask layer on this type of circuit board is suitable for high-performance commercial and industrial products that require extended service life but do not endanger life if service is interrupted.
H - High reliability/military: including critical continuous performance, intolerable equipment downtime, and/or equipment that is a life support project. The solder mask layer on this type of circuit board is suitable for applications that require high-level assurance and uninterrupted service.

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Do you know the function of PCB solder mask?
1. Delaying the aging process: Prevent damage to PCBs caused by ultraviolet radiation, slow down the aging rate of materials, especially for circuit boards exposed to outdoor or strong light environments for a long time. Solder mask can form a protective film on the PCB, protecting the circuit from external physical damage, dust, moisture, and chemical substances, and extending the service life of the circuit board.
2. Insulation protection: The solder mask layer has good insulation performance. By accurately coating it on non welding areas, solder mask can effectively isolate various circuits on the circuit board, avoid short circuits and electrical faults during the soldering process, avoid potential circuit damage, and improve the electrical performance and safety of the product.
3. Improve soldering quality: Solder mask can prevent solder from splashing onto areas that do not require soldering, ensuring the cleanliness and accuracy of the soldering area. This helps to improve soldering quality and reduce manufacturing defects.
4. Improve appearance: Solder mask forms a smooth and uniform surface on the PCB, which is not only aesthetically pleasing but also convenient for subsequent labeling, printing and other processes, improving the overall appearance quality of the product.
5. Enhanced insulation performance: The solder mask layer has good insulation performance, which can enhance the electrical insulation of the PCB, reduce the possibility of leakage and electrical interference, and ensure the normal operation of the circuit.
6. Facilitating testing: During the PCB manufacturing process, the solder mask layer can protect the circuit from mechanical equipment such as test pins, while facilitating pin insertion testing and visual inspection, improving testing efficiency and accuracy.
7. Environmental Protection and Compliance with Standards: Modern solder masks typically comply with ROHS (Restriction of the Use of Certain Hazardous Substances Directive) and other environmental standards, helping to reduce the impact of electronic waste on the environment and meeting the requirements of the international market.
8. Optimize heat dissipation performance: Although this is not a direct function of solder mask, through reasonable design, such as avoiding or reducing solder mask layers in critical heat dissipation areas, the heat dissipation performance of PCBs can be optimized.

Therefore, suitable and high-quality solder mask can significantly improve the reliability and service life of PCBs. Careful selection and application of solder mask in the design and production process of circuit boards is one of the key measures to ensure long-term stable operation of circuit boards.

Do you know what are the options for PCB solder mask?
Green solder mask layer
Green solder mask has always been a popular PCB solder mask option because it allows everything to be clearly visible. The green solder mask layer has good contrast between areas with and without copper below the solder mask layer. You can easily see the marks with your eyes, but for the black solder mask layer - you don't know.
White solder mask layer
The application of white solder mask layer is becoming increasingly popular because white can make PCBs look very beautiful in a clean environment. However, the white solder mask layer effectively hides the traces. In some cases, visual inspection is almost impossible, especially if you are in a room with only overhead light.
Black solder mask layer
Compared to the white option, the black solder mask layer gives PCBs a high-end and professional appearance, which visually provides stronger technical and aesthetic value for products, especially suitable for consumer electronics products with high visual appearance requirements.
It is worth noting that the black solder mask layer also poses certain challenges. Due to its high light absorption, black PCBs may be more prone to absorbing heat during the manufacturing process, which may lead to thermal stress in certain situations and require control during the design and manufacturing process. In addition, the black solder mask layer has a stronger ability to conceal internal defects in PCBs, so higher standards and strict quality control measures need to be adopted in production and inspection processes.
Red solder mask layer
Choosing a red solder mask layer also requires consideration of some factors. The red solder mask layer can relatively reflect the details of welding points and circuits, making it easy to identify problems in production inspection and later maintenance. Its bright colors also help improve the error detection rate in optical inspection (AOI) processes. For example, compared to dark solder mask layers (such as black and green), red may have a slightly weaker ability to conceal internal defects in some cases, which may have a certain impact on the visual aesthetics of circuit boards. At the same time, in specific application environments, users also need to consider factors such as the physical and chemical stability of solder mask.
Blue solder mask layer
A circuit board with heavy labels should consider using a blue solder mask layer, as it forms a clear contrast with screen printing. If there is no appropriate lighting and magnification, the marks under the blue solder mask layer will become more difficult to see. Compared to other colors, it is more prone to dirt.
Purple solder mask layer
Many new colors are emerging, but they may be difficult to manage. Sometimes, different production batches may show subtle differences. Yellow and orange are pleasant colors, but their contrast in screen printing and traces is like a pool. The gray solder mask layer is commonly considered for LED printed circuit boards/aluminum PCB projects.

Crystal clear color solder mask layer
Different colors will balance different requirements, such as cleanliness, visibility, and style. Before starting mass production of new colors, you can always try samples with us.
Before attempting the next PCB design, we warmly welcome you to contact our sales personnel to obtain free samples - you can use them as a reference. Our main suppliers of solder mask ink include Taiyo Japan, Taiyo USA, and Taiyo Suzhou.