Legend printing, also known as silkscreen printing, is the process of applying informational texts or patterns onto the surface of a circuit board. This information may include component reference designators, switch settings, test points, part numbers, version numbers, company logos, or other decorative patterns that enhance the board’s appearance. Two main methods are used in legend printing: screen printing and Direct Legend Printing (DLP).

 

Screen printing works based on the principle that the graphic areas of a mesh screen allow ink to pass through, while the non-graphic areas block the ink. During the legend printing process, a screen is first created using a legend film. Ink is then forced through the screen mesh under pressure, transferring the design onto the circuit board. Finally, the board is baked in an oven at a high temperature to ensure the ink is securely adhered to the surface.

 

Another method for printing legends is Direct Legend Printing (DLP), which utilizes electronic inkjet technology. DLP prints information directly from CAD/CAM files onto the circuit board using special ink. The ink is then cured using ultraviolet lamps to complete the printing process. Compared to traditional screen printing, DLP offers higher printing accuracy and eliminates the need for films, but it is typically preferred for small batches or sample runs. In contrast, screen printing is better suited for large-scale production due to its cost-effectiveness and ease of use.

 

While the absence of legend information does not affect the electrical functionality of a circuit board, it plays a crucial role in the assembly and maintenance processes. The most common ink colors used for legends are black and white, but Wellcircuits also offers yellow or other colors based on customer design specifications. To ensure optimal readability, Wellcircuits’ manufacturing standards require that the width and height of legend characters be at least 0.15mm and 0.8mm, respectively.

If you have any questions about PCBs or PCBA, please feel free to contact us at info@wellcircuits.com.