PCB screen printing for long has been a very important part of PCB manufacturing. It is utilized in a variety of procedures, including plating and putting resists to its copper surface as well as adding peelable and solder resists.
It’s definitely accurate to state that the use of screen printing has decreased as technology developed over time. This is most likely because the PCB screen printing capabilities are limited by PCB design’s technological requirements. As an illustration, it will be very challenging to apply the solder resist picture with a similar level of precision and definition to the modern Circuit board with several surface-mounted pads.
What Does PCB Screen Printing Mean?
A tool, such as a stencil or mesh, is used in the printing technique known as PCB screen printing for transferring solder paste and ink onto the circuit board surface or in the PCB microvias and vias. A reversing stroke allows the screen briefly touch its substrate across a contact line after a squeeze or blade is used to move throughout the screen and fill the apertures of this tool with ink.
Even as screen bounces back after its blade has crossed, the ink wets the substrates, then it is drawn away from the tools apertures due to this. PCB assembly and PCB manufacturing both use PCB screen printing.
What does a PCB’s Silkscreen Offer?
The last step in the circuit board manufacturing operation is to add a silkscreen layer. A layer known as silkscreen employs ink traces for identifying all of the Circuit board components, the test points, PCB parts, warning symbols, marks, as well as logos, among other things. These letters, numbers, and shapes aren’t really a new language. Moreover, they can convey the purpose of each pin. Although it’s possible that silkscreen is sometimes used on a solder side, which raises the cost, this silkscreen gets applied onto its component side. In order to discover and identify the components, a thorough PCB silkscreen would be helpful to both the engineer and manufacturer.
Epoxy ink that is non-conductive is what is used. These markings are made with carefully formulated ink. Although silkscreens could be of any color, the three common colors which are typically utilized are white, black, and yellow. You will undoubtedly come across Boards with red, gray, and blue silkscreens if you disassemble enough devices.
Why would someone use the silkscreen layer?
In PCB boards, the silkscreen isn’t really typically used. Customers must request this, and adding a silkscreen onto the circuit board typically entails an extra fee. The following are some significant advantages of selecting a silkscreen layer:
- This aids in locating test spots on the Circuit board for the benefit of engineers and personnel. They can take measurements after this point and it helps with troubleshooting.
- Also, it may be utilized to indicate the locations on the circuit board where components should go so that users don’t forget to do so.
- These warning symbols that are typically used to signify the greater parameter values, including voltage, power, and current, benefit from silkscreen coating as well.
- It serves as the reference indicator for identifying the type of component as well as polarity orientation, which could be used to indicate values of resistors, inductors, as well as other components, decreasing the likelihood of inserting a component using the incorrect value present on the circuit board.
What Information Is Provided by a Silkscreen?
A silkscreen might not be necessary for a Circuit board to function, but it is nevertheless valuable for the info it conveys.
For example, it will assist anyone in:
- Recognizing any warning symbols
- Parts’ polarity;
- Test-point identification
- Identify the components using reference designators.
- Recognize the circuit board-specific numbers.
- Recognize manufacturer markings, version numbers, etc.
Silkscreen Printing Techniques
Three methods are used to apply the silkscreen to the PCB:
Manual PCB Screen Printing
Whenever line widths were larger than 0.007 or the registering tolerance is at 0.005, this is performed for PCBs. Utilizing a stencil with traces and text, manual pcb screen printing can be done. Nylon is used to create the traces. And through stencil, the ink gets applied to the laminate or layer. The ink then is dried in a baking oven after that.
Among the simplest methods for making the silkscreen layer, it also allows huge font size. Years may be needed to master this art.
LPI – Liquid Photo Imaging
When its screen printing lines is thicker than 4 mil, the technique is utilized. The LPI procedure is quite similar to the application of the solder mask procedure. The laminate is covered with epoxy in this procedure, though, and then exposed to UV light after that. After that, the board gets created and cured. Compared to manual PCB screen printing, this method guarantees more precision.
Compared to the two PCB screen printing types, LPI employs white color and uses more ink. For this kind of printing, the time required is lengthy.
DLP: Direct Legend Printing
Among the remaining three procedures, DLP is among the costliest. Acrylic inks as well as the inkjet projector are both employed in this procedure. Using CAD software, the ink gets applied onto the PCB. The Ultraviolet light is then shone on the ink. This acrylic link would be inappropriate for Boards that might be finished in silver.
Conclusion
On a Circuit board, you ought to desire a PCB screen printing. It makes it simple for users to comprehend your Circuit board as well as how it was put together because it informs you where each component is located. Add a silkscreen when ordering PCBs. Your Circuit board will receive a silkscreen from the manufacturer. The quality of this would be much better than any DIY PCB screen printing.
If you desire a printed circuit board that best meets your needs and tastes, communicate openly and frequently with a contract manufacturer. Inform them you desire a silkscreen right away and go over the details.
