How to do PCB Legend Print

What is PCB Legend Print?

PCB (Printed Circuit Board) legend print, also known as silk screen printing, is the process of applying text, symbols, and logos onto the surface of a PCB. The legend print serves several purposes, including:

• Identifying components and their locations
• Providing assembly instructions
• Displaying company logos and product information
• Enhancing the overall aesthetics of the PCB

The legend print is typically applied using a silkscreen printing process, which involves transferring ink through a fine mesh screen onto the PCB surface. The ink used for legend printing is usually white, but other colors like black, yellow, or red can also be used depending on the PCB’s color and design requirements.

Why is PCB Legend Print Important?

PCB legend print plays a crucial role in the manufacturing, assembly, and maintenance of electronic devices. Here are some reasons why PCB legend print is important:

1. Facilitates PCB Assembly: Legend print provides clear instructions and identification of components, making it easier for technicians to assemble the PCB correctly. This reduces the chances of errors and improves the overall efficiency of the assembly process.

2. Aids in Troubleshooting: When a PCB malfunctions, the legend print helps technicians quickly identify components and trace connections, making it easier to diagnose and fix issues.

3. Enhances Branding: Legend print can include company logos, product names, and other branding elements, which can help establish brand recognition and create a professional appearance for the product.

4. Complies with Industry Standards: Many industries have specific standards and regulations that require certain information to be included on the PCB, such as component values, ratings, and certifications. Legend print ensures that this information is clearly visible and complies with the relevant standards.

Types of PCB Legend Print

There are two main types of PCB legend print:

1. Silkscreen Printing: This is the most common method of applying legend print to PCBs. It involves using a fine mesh screen to transfer ink onto the PCB surface. Silkscreen printing is cost-effective, durable, and suitable for high-volume production.

2. Direct Legend Printing: This method uses a special printer to directly apply the legend print onto the PCB surface. Direct legend printing offers higher resolution and accuracy compared to silkscreen printing, making it suitable for intricate designs and smaller text sizes. However, it is more expensive and slower than silkscreen printing.

PCB Legend Print Design Considerations

When designing the legend print for a PCB, there are several factors to consider:

1. Font Size and Style: The font size should be large enough to be easily readable, typically at least 0.8mm in height. The font style should be simple and clear, such as Arial or Helvetica.

2. Line Width: The line width of the legend print should be at least 0.15mm to ensure good visibility and durability.

3. Spacing: There should be sufficient spacing between text and components to avoid confusion and ensure clear readability. A minimum spacing of 0.5mm is recommended.

4. Placement: Legend print should be placed in a way that does not interfere with components or solder pads. It should also be oriented correctly to be easily readable when the PCB is installed in the final product.

5. Color: The color of the legend print should contrast well with the PCB surface color to ensure good visibility. White is the most common color used for legend print, but other colors can be used depending on the design requirements.

PCB Legend Print Process

The PCB legend print process typically involves the following steps:

1. Design: The legend print design is created using PCB design software, such as Altium Designer or Eagle. The design includes all the necessary text, symbols, and logos.

2. Film Preparation: The legend print design is printed onto a transparent film, which will be used to create the screen for silkscreen printing or the stencil for direct legend printing.

3. Screen or Stencil Preparation: For silkscreen printing, the film is used to create a fine mesh screen with the legend print design. For direct legend printing, the film is used to create a stencil with the legend print design.

4. Ink Preparation: The ink used for legend printing is mixed and prepared according to the manufacturer’s instructions. The ink should have the right viscosity and color to ensure good print quality.

5. Printing: The prepared screen or stencil is placed onto the PCB surface, and the ink is applied using a squeegee or printer. The ink is then cured using heat or UV light to ensure good adhesion and durability.

6. Inspection: The printed PCBs are inspected for any defects or errors in the legend print. This can be done visually or using automated inspection systems.

Best Practices for PCB Legend Print

To ensure high-quality and durable PCB legend print, follow these best practices:

1. Use Vector Graphics: When designing the legend print, use vector graphics instead of raster images. Vector graphics can be scaled without losing quality and ensure sharp and clear print results.

2. Keep It Simple: Avoid using too many different font sizes, styles, or colors in the legend print. Keep the design simple and consistent to ensure easy readability and a professional appearance.

3. Check for Clearance: Ensure that there is sufficient clearance between the legend print and components, solder pads, and other features on the PCB. This will prevent interference and ensure good print quality.

4. Test the Design: Before finalizing the legend print design, test it on a sample PCB to check for any issues with readability, alignment, or durability. Make any necessary adjustments based on the test results.

5. Use Quality Materials: Use high-quality ink and materials for the legend print to ensure good adhesion, durability, and resistance to fading or peeling.

6. Follow Industry Standards: Ensure that the legend print complies with any relevant industry standards or regulations, such as the IPC-A-600 standard for PCB acceptability.

FAQ

1. What is the minimum font size for PCB legend print?

2. The minimum recommended font size for PCB legend print is 0.8mm in height to ensure good readability.

3. Can PCB legend print be applied to both sides of the PCB?

4. Yes, legend print can be applied to both sides of the PCB, depending on the design requirements and manufacturing process.

5. What is the difference between silkscreen printing and direct legend printing?

6. Silkscreen printing uses a fine mesh screen to transfer ink onto the PCB surface, while direct legend printing uses a special printer to directly apply the ink. Direct legend printing offers higher resolution and accuracy but is more expensive and slower than silkscreen printing.

7. How durable is PCB legend print?

8. PCB legend print is generally very durable and can withstand normal handling and environmental conditions. However, the durability depends on factors such as the quality of the ink and materials used, as well as the manufacturing process.

9. Can PCB legend print be customized with different colors and logos?

10. Yes, PCB legend print can be customized with different colors and logos, depending on the design requirements and manufacturing capabilities of the PCB supplier. However, custom colors and logos may require additional setup and production costs.

In conclusion, PCB legend print is a crucial aspect of PCB design and manufacturing, serving important functions such as component identification, assembly instructions, and branding. By following best practices and considering factors such as font size, spacing, and placement, designers can ensure high-quality and durable legend print that enhances the functionality and aesthetics of the PCB.

By adhering to these recommendations and best practices, PCB designers and manufacturers can produce high-quality legend print that enhances the functionality, reliability, and aesthetics of their PCBs.