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Silkscreen PCB Labeling: Standards, Symbols, and Significance

What is Silkscreen PCB?

Table of Contents

What is SilkScreen on PCB?

Silkscreen on PCB is the layers of printing on board that contain labels, markings, and symbols. It helps users, assemblies, and technicians identify the circuit board’s components and also the reference points on the boards. 

The silkscreen on a Printed Circuit Board (PCB) is crucial in the assembly, testing, and maintenance. It’s not involved in making the circuit work but is essential for identifying components and helping with various tasks.

Usually, PCB silkscreen is printed in white or a different color over the solder mask

The silkscreen on PCB contains the following information:

  • Component outlines
  • Warning symbols 
  • Test Points
  • Reference designators
  • Logos
  • Polarity markings, and other helpful information. 

This information is valuable during both the assembly and troubleshooting stages.

It’s important to note that the silkscreen is a visual guide and shouldn’t interfere with the electrical functioning of the PCB. The ink that is used for silkscreen is epoxy ink, a non-conductive multicolored ink. 

Careful attention is needed during printing to ensure the silkscreen doesn’t cover or obscure important circuit details. 

The details on the silkscreen are often taken from the PCB design files and are a crucial part of the overall documentation for the PCB.

Why is Silkscreen Used in PCB?

PCB Silkscreen

PCB Silkscreen is used for various reasons. Let’s look into why silkscreen is used for PCB:

Component Identification: The markings on the PCB, known as the silkscreen layer, help us spot and place different parts. This includes showing outlines of components, reference codes, logos, and how things should be. This is handy when putting the circuit together and figuring out what’s wrong with it later.

Assembly Help: When building a PCB, the silkscreen marks guide technicians and assemblers in putting components in the right spots. This is super important in complicated circuits with many parts, where getting things in the correct place is key for everything to work properly.

Troubleshooting: If something’s not right with the circuit, the markings on the silkscreen can be a big help in finding out which part is causing the trouble and how it should be positioned. It makes it easier for technicians to figure out and fix problems.

Documentation: The info on the silkscreen often comes from the original design plans for the PCB. It’s like a visual record of how everything was supposed to be laid out. This becomes part of the documentation for the PCB, making it easier to refer to, repair, or modify in the future.

Polarity and Orientation: The silkscreen often includes markings to show which way components should be put in. This helps prevent damage or issues caused by putting things incorrectly.

User-Friendly Interface: For people who might use or interact with the PCB, like in everyday electronics, the silkscreen can show helpful details about connectors, buttons, or other features.

Visual Aid without Electrical Impact: The silkscreen is a visual layer that doesn’t mess with how the circuit works. It’s printed on top of the solder mask, which shields the conductive traces. This ensures that the visuals don’t mess with the actual electrical stuff, keeping the circuit working as it should.

Silkscreen PCB Printing Process

The common process of applying the silkscreen on PCB includes:

Preparation of PCB Silkscreen

Designing the silkscreen for a PCB involves utilizing appropriate design software to place components add clear text, and symbols strategically. Designers must consider component placement, select appropriate colors, and manage layers effectively. 

A thorough review ensures accuracy, and once the design is complete, it is exported for production. It guides the manufacturing process to ensure the printed silkscreen precisely reflects the design intentions, serving as a valuable visual guide for PCB assembly and maintenance.

Creating a Stencil

Think of a stencil as a guide for placing labels and markings. This stencil, often made from thin materials like metal or polyester, has openings that determine the areas where the ink will be applied to the PCB.

Applying and Curing the Ink

This step spreads white ink over the PCB through the stencil openings. Once the ink is applied, the PCB undergoes a curing process. It involves exposing the PCB to heat, which aids in drying and hardening the ink. It ensures that the markings become firmly attached to the PCB surface.

Adding Component Information

The silkscreen layer is not just for aesthetics; it contains crucial information. Component names, reference designators, and symbols are added during this step. This information helps technicians and engineers correctly identify and place components during assembly.

Final Inspection

After the ink is cured, a thorough inspection ensures that the silkscreen printing is accurate and aligns with the design specifications. This final check guarantees that the markings serve their purpose in guiding the assembly and maintenance of electronic circuits.

SilkScreen PCB Printing Techniques

There are three most common techniques for applying silkscreen on PCB:

Manual PCB Screen Printing

Manual Silkscreen PCB Process

Manual PCB silkscreen printing involves applying the silkscreen layer by hand. It can be done using various techniques, including stencils or templates. While automated methods offer precision and efficiency, manual printing is suitable for prototyping or low-volume production. It allows for more flexibility in adjusting designs on the fly, while on the other hand, it may lack the consistency and speed of automated processes.

Liquid Photo Imaging (LPI)

Liquid Photo Imaging (LPI)

Liquid Photo Imaging is a silkscreen PCB printing technique where a photosensitive liquid ink is applied to the PCB surface. The board is then exposed to ultraviolet light through a film stencil with the desired markings. 

The exposed areas then harden, creating a durable silkscreen. Excess ink is washed away, leaving behind clear and precise labels, making it a precise and high-quality method for PCB marking.

Direct Legend Printing (DLP)

Direct Legend Printing (DLP)

It is a silkscreen PCB technique where a printer directly applies ink onto the board. This method skips the need for a separate stencil. The printer follows a digital design, directly creating component names and symbols on the PCB surface. 

DLP is faster than LPI, but the resolution may not be as high. It’s a more straightforward process but may be less detailed compared to the precision of liquid photo imaging.

PCB SilkScreen Guidelines

Before applying PCB, make sure you follow the below guidelines:

  1. Clear Markings: Make sure the labels and symbols on the silkscreen are easy to read. Use fonts and symbols that are clear and straightforward. It helps in identifying components during assembly.
  2. Enough Space: Keep much space between the markings and the actual components. It prevents things from getting too compact, reducing confusion during assembly.
  3. Color Contrast: Choose a color for the silkscreen that stands out well against the various types of PCB. It ensures that the markings are visible and easy to read. 
  4. No Overlapping: Avoid text or symbols overlapping with other elements like pads or traces. It prevents confusion, especially during the soldering process.
  5. Consistent Orientation: Keep all the text and symbols facing the same way for a neat and easy-to-follow visual guide.
  6. Consider Component Height: Consider the components’ height and width when placing markings. 
  7. Layer Clarification: Clearly distinguish the silkscreen layer from other layers on the PCB. 
  8. Production Awareness: Be mindful of the manufacturing process understanding the limits for font sizes and line widths. Ensures that your design is produce accurately.
  9. Regular Reviews: Check and double-check your silkscreen design regularly. It helps catch any mistakes or areas for improvement, ensuring a more effective visual guide.
  10. Clear Export: When sending your design for production, make sure the files clearly and accurately represent what you want.

 

Conclusion

Silkscreen Printing is an important step in PCB manufacturing. It provides necessary information for PCB assembly and helps to increase the overall efficiency of the process. It also helps in quality control. The various printing techniques can be used based on the application and design requirements. 

If you want to enhance your PCB designs with professional silkscreen printing, then ElePCB offers reliable PCB manufacturing services. 

Whether you need clear component identification, assembly assistance, or troubleshooting support, our advanced silkscreen printing techniques ensure precision and clarity. 

Contact ElePCB today for quality silkscreen printing. Elevate your PCBs with ElePCB.

FAQs

What color is PCB Silkscreen?

The most common color for silkscreen PCB printing is white. This is due to its high contrast against the typically green solder mask, enhancing readability. While other colors are technically possible, they might increase costs and affect the markings' clarity. White remains the standard choice for its practicality and cost-effectiveness.

What is the standard cost of PCB silkscreen?

The cost of silkscreen on a PCB is relatively low. Silkscreen printing is a standard step in PCB manufacturing, and the expense is typically included in the overall fabrication cost. Besides, custom colors or additional features might add extra charges, but basic silkscreen labeling is generally an affordable component of the PCB production process.

What is the role of silkscreen in PCB documentation?

Silkscreen details are an integral part of PCB documentation. It serves as a visual record of the intended layout, making it easier to refer to, repair, or modify the PCB in the future. This documentation aspect enhances the overall maintenance and lifecycle management of the PCB.

Can silkscreen markings be customized for specific user needs or industry standards?

Yes, silkscreen markings can be customized to meet specific user requirements or align with industry standards. Designers can include component names, logos, and other details based on the application. Adhering to standards ensures consistency and clarity in the markings for universal understanding.

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About Michael

Michael is the general manager of ELEPCB, a leading PCB design and manufacturing company based in China. He has over 10 years of experience in the PCB industry, and has been involved in various projects.

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