Components Identified on the Silkscreen

Printed circuit boards (PCBs) are the basis of all electronic devices. While they are primarily used as an electrical conduit, they also carry a multitude of other components that are vital to the operation of the device in question. To ensure that the different elements work together smoothly, it is important to mark the various components and their locations on the PCB. This is done through the silkscreen layer, which consists of human-readable text and symbols that identify components and their locations. It is also used to display warning symbols, company logos, date codes and other details. The silkscreen layer is normally white, but other colours can be applied as well.

The silkscreen layer is a key component of the PCB assembly process, and it provides essential information on the component’s location and function. It can contain reference designators, polarity indicators, pin one indicators and jumper settings.

These indicators are useful in guiding pcb assembly and reducing the risk of misinterpretation or error. The orientation markings on the silkscreen are particularly crucial as they indicate the direction in which a specific component should be soldered. The orientation markings are typically represented by a dot(.) for IC pin 1 and a symbol or text that indicates the component’s polarity, such as “(use + or -)” for diodes and LEDs, and the half-shaded circle for capacitors.

How Are Components Identified on the Silkscreen?

In addition to identifying components, the silkscreen can also include reference designators, unique identifiers for each assembly location, component symbols, manufacturer marks and version numbers. Having these labels on the silkscreen can reduce the amount of time it takes to assemble a board, as it is easier for assembly personnel to locate components. Additionally, these labels can make troubleshooting and maintenance easier.

It is important to avoid printing silkscreen characters directly over the component pads, as this can have a negative impact on the solderability of the pad. It is also not recommended to print silkscreen character directly over a via hole, as this could obstruct the opening of the hole and potentially cause an unintended connection between two components.

To print the silkscreen, fabricators use a stencil and epoxy ink. For thinner line widths, they may employ the liquid photo imaging method, which involves coating the surface of the PCB with a light-sensitive epoxy and then exposing it to UV light. Once the light is exposed, the unexposed epoxy will disappear, leaving behind the desired silkscreen image on the PCB. The silkscreen is then fixed with an oven to cure the ink.

Lastly, the silkscreen is normally coated with a solder mask layer. The solder mask insulates the copper from other components and provides the PCB its characteristic green colour. The silkscreen layer is a very critical part of the PCB, and it is important to double-check your designs before sending them to a manufacturing facility. For example, you should not put idents over component pads and you should allow for registration tolerances of up to 5 mil.