Silkscreen PCB Assembly

Silkscreen: Why it is the most important final touch on a PCB Assembly?

Oct 31,2022

A printed circuit board comprises components such as resistors, transistors, capacitors, diodes, sensors, and more. With so many fine components on the PCB, it becomes a little complex to identify and understand each of these if you are not familiar with them. Thus, to ease PCB use, it is crucial to add the details and directions on a printed circuit board. This is done by silkscreen printing. Once the PCB assembly is finalized, it undergoes a graphic printing process where essential details are added to the board’s surface. This printed surface is termed as the silkscreen. You may have several questions about silkscreen and its importance.  Read the post below to get the answers to all questions.
An Overview of Silkscreen PCB Assembly
Silkscreen is a layer comprising white ink traces used to indicate graphics and legible letters, which help in determining the components and solder joints. The ink used for silk screening is a non-conductive epoxy and is also available in other colors such as black, yellow, blue, and red. It is drawn on the component and solder sides using standard fonts. The silkscreen graphics include symbols, logos, numbers, codes, and so on.
What Information Does Silkscreen Use in Printed Circuit Board Assembly Convey?
The silkscreen used in printed circuit board assembly can convey the following information:

  • Data codes
  • Warning symbols
  • Directions
  • Locations
  • Component numbers
  • Part polarity
  • Manufacturer marks
  • RoHS compliance
  • Board name
  • Registration numbers
  • Warning signals
How is Silkscreen Applied to the PCB?
A silkscreen is basically applied using three standard techniques. These methods include manual screen printing, liquid photo imaging, and direct legend printing. A brief description of these methods is as follows:
  • Manual Screen Printing: Manual screen printing is the easiest and most cost-effective method. However, it is only used when the PCB line width is greater than 7 mil., and registration tolerance is up to 5 mil. The process includes a stencil that possesses codes and traces made up of nylon resin. The stencil is kept on the laminate or layer of PCB, and the ink is directed through it. This board is then cured in a baking oven to dry the ink.
  • Liquid Photo Imaging: This method provides accurate printing results and cannot be applied on a PCB with a width of less than 4 mil. As the name suggests, in this process, the laminated board is coated with liquid photo epoxy and then treated with UV light.
  • Direct Legend Printing: This is the most expensive and accurate process for silk screening. Direct legend printing utilizes acrylic ink with an inkjet projector, and the ink is applied on the board screen using computer-aided design (CAD) software. Later, the circuit board is exposed to UV light. Additionally, as the method uses acrylic ink, it is not suitable for the printed circuit boards with silver finishing.
Why is Silkscreen Important for Printed Circuit Board Assembly?
Silkscreen marking is helpful in many ways. It is referred to by various people at different phases. For instance, it:
  • Helps the PCB assemblers to identify components, their orientation, their type from BOM, part numbers, and so on during the revision.
  • Allows maintenance personnel to identify proper key components, board name, and hazard marking as well as markings like function, high or low voltage, and so on.
  •  Helps authorities to recognize the registration number, company name, or brand of a printed circuit board.
You can realize several more benefits of silkscreen by getting it done by experts. Sierra Assembly offers printed circuit boards assembly for commercial and industrial applications. All printed circuit boards are thoroughly inspected and tested by experts to ensure their performance in real environments. You can get in touch with the company executives today to know more about silkscreen PCB assembly capabilities.