What is Legend
In the PCB industry, legend refers to the printed letters or symbols on a circuit board that provide important information for various purposes. This format of printing, also known as silkscreen, includes details such as part numbers, product numbers, reference designators, logos, manufacturer marks, company ID numbers, and warning labels. The legend printing process is crucial for error-free manual assembly and other tasks.
Two main methods are used for legend printing: screen printing (silkscreen) and Direct Legend Printing (DLP). Screen printing involves transferring ink onto the circuit board through a fine mesh screen, allowing for precise and detailed printing of the required information. On the other hand, DLP utilizes inkjet printing technology to directly print the information onto the board directly, offering higher printing accuracy and suitability for small batches.
The absence of legend information does not affect the electrical performance of the circuit, but it plays a vital role in the assembly and maintenance of the board. The colors of ink used for legend printing are typically black or white, although other colors, like yellow can be used based on design requirements. It is important to ensure the legibility of the legend, with recommended minimum width and height dimensions of 0.15mm and 0.8mm, respectively.