What is Circuit Design

3.7. Silkscreen

The silkscreen layer is used for assembly, identification, and component identification for service/maintenance.

The silkscreen layer sits on the outermost layer of a PCB and provides components reference designators as well as pin 1 or anode/cathode identification for polarized parts.

Plenty of companies still apply the silkscreen layer using silkscreen processes, complete with screen, squeegee and pattern templates.

Image of silkscreen process from http://www.gwent.org/gem_thick_film.html

But silkscreen printers that utilize ink-jet technology are gaining a larger foothold in the industry.  These devices print directly onto PCBs in the same manner inkjet printers print directly onto a piece of paper.

Image of silkscreen printer from http://www.zhengyekeji.com/

Here's an example of the quality from one of these machines:

Image of silkscreen print quality from http://www.shengyekeji.com/

"The Silkscreen layer is not always aligned as it should be on top of a PCB.  And if your silkscreen print ends up on top of a pad, it will disrupt the solder process.  So don't squeeze things in too close to lands."