Guidelines for diode polarity mark silk-screening — the diode symbol, “K” for cathode or “A” for anode. To ensure the best accuracy, we recommend extra care in marking diodes to remove any ambiguity. The preferred method is to place the diode schematic symbol in the. To ensure proper installation by your circuit assembler, it is important to include a mark on the silkscreen layer to identify which terminal is the anode and which terminal is the cathode. The diode's footprint will show a line on one side of the outline, and that line corresponds to the cathode. In this comprehensive guide, we'll walk you through everything you need to know about the PCB design silkscreen layer, from. The red and green LED cathodes are indicated with silkscreen bars on bottom. Cathode indications of several dual LEDs (D113, D114, D115) annotated again with silkscreen bars.