What is PCB Silkscreen?

A printed circuit board comprises components such as transistors, resistors, capacitors, diodes, and so on. With so many components, it becomes a bit difficult for an operator to understand the board’s design. Hence, directions and important information is printed on a circuit board to help an operator. This is done with the help of silkscreen printing.

A silkscreen is the top layer of a printed circuit board which includes the directions for identifying PCB components. These directions are made using white non-conductive epoxy ink with standard fonts and provides information about the printed circuit board like component names, reference designators etc. Silkscreen printing is applied to both – PCB components and PCB soldering. During the pcb manufacturing process silkscreen layer is applied which is printed directly on the board’s surface.

What Information Does a PCB Silkscreen Convey?

A PCB silkscreen is used to display the following information on a printed circuit board:

  • Electronic symbols
  • Pin numbers
  • Manufacturing details, including version numbers, manufacturer’s name, and so on
  • Switch settings
  • Polarity of parts
  • Reference designators
  • Test points

What Factors should be Considered for PCB Silkscreen Layout?

Although PCB silkscreen printing is an automated process, the following are a few factors to be addressed during the process.  

  • Font Type: Earlier, only a few standard fonts were allowed by CAD software, but now various fonts are used for silkscreen printing. The silkscreen contains important information on which engineers rely. Ensure to choose a font that is clearly readable by everyone.
  • Font Color: PCB silkscreen printing is done in different colors such as white, yellow, red, blue, and so on. Choose a silkscreen color that clearly gets highlighted on your printed circuit boards. For instance, if a PCB is green, white silkscreen printing can be a good option.
  • Designation: The location of the components and connections should be printed as close as possible to avoid any miscommunication. If the component density is high, silkscreen could be printed inside the elements with precise arrows and directions.
  • Reading Directions: The reading directions should be clear and simple, starting from left to right and bottom to top. This will make the circuit board more comprehensive for the engineers.

What are the Different Methods Used for Silkscreen Printing?

There are three main methods used for PCBA silkscreen printing. They are as follows:

  1. Manual Screen Printing: As the name suggests, manual silk screen printing is done by hand. The task is performed with the help of a stencil comprising traces and texts made up of nylon. The non-conductive ink is evenly spread on the upper PCB layer through the stencil. After lamination, the ink is dried in a baking oven. The Manual screen printing method is the most cost-effective and simple. It is specially used for PCBs whose registration tolerance is 0.005.
  2. Direct Legend Printing: This is one of the most expensive and accurate methods of printing silkscreen. Direct legend printing, or DLP, is done using inkjet projectors and acrylic ink. The ink is applied on a printed circuit board using CAD software. This process can be used for PCBs that do not contain a silver finish because acrylic ink is not suitable for the same.
  3. Liquid Photo Imaging of Silkscreen: This printing method is used on a PCB with a width of fewer than four millimeters. Firstly, the lamination is done using light-sensitive epoxy. Once the silkscreen image is printed, it is then exposed to UV light.

PCB silkscreen prints help new operators to make accurate connections. However, it is crucial to get the right information printed through silkscreen. To achieve this, you must partner with a trusted and reliable manufacturer like Suntronic Inc. The company provides excellent PCB assembly services from new product introduction (NPI) to silkscreen printing and PCB plating. You can get in touch with the company today to learn more about their PCB assembly services and PCB silkscreen printing capabilities.