What Are Silkscreens
In general, a Printed Circuit Board (PCB) design has a variety of layers, and the silkscreen is just one of them. Since the silkscreen is printed on the PCB’s surface, there are usually two silkscreen layers, the upper and lower, for each PCB.
Silkscreens store text information on the board for people to read and understand. On the silkscreen on a PCB, it is possible to print any information, including the reference designations for components logos of companies, manufacturer marks, and warning symbols, as well as version numbers, part numbers, date codes and more. However, the space on a PCB’s surface is very limited, so it is recommended to limit your printing to only useful or vital information. Therefore, the silkscreen layer typically is a legend of the component, which shows the locations of different components that will be placed on the board, along with corporate logos and board design numbers.
Today, custom-built digital inkjet printers designed specifically for printing PCBs are commonly used to print silkscreen images on PCB surfaces using the design information on boards. Silkscreens were initially printed using screen printing techniques from which the term silkscreen comes. The reason for this name is the old screen printing technique that required an ointment or fine cloth such as polyester or silk for the screen and a frame constructed from aluminum, wood, and so on. As technology improved, many various faster and simpler techniques for printing silkscreens were created, but the name was the same.
Methods of Silk Screen Printing
Silkscreens are positioned on the PCB in three ways：
Manual Screen Printing
This is performed for PCBs if the registration tolerance of 0.005″ or line widths are greater than 0.007″. The screen printing manual is carried out by using a stencil that contains texts and traces. The traces are created with nylon. The link is directed by the stencil onto the laminate layer. Then, the ink is baked in the baking oven to cure the ink. This is among the most simple methods of making silkscreen layers, and it allows for large font sizes, as well. It could take a while to perfect this technique.
Liquid Photo Imaging (LPI)
This technique is employed to screen lines with a width of more than 4 mil. The process behind LPI is basically the same as that of the solder mask process. In this case, however, it is coated by epoxy and then brought under ultraviolet light. The laminate is then dried and then reshaped. This technique ensures better accuracy than hand-printed screen printing.
LPI employs white color and will require more ink than the other two kinds of print on silk. It takes a long time to set up this kind of printing.
Direct Legend Printing (DLP)
It is among the most costly processes of the three. In this method, inkjet projectors and acrylic inks are employed. The ink is applied to the PCB with the CAD software. And then we use to ink is then exposed to ultraviolet light. The acrylic link isn’t suitable for PCBs that be immersion silver.
A DLP system has advantages in terms of time as well as board spacing. However, it is a costly method. So, it’s important to think about all these factors and choose the best method.
Importance Of Silkscreening For PCB Manufacturer And Its Benefits
In addition to identifying layers and components, the process of silkscreening can be beneficial for the manufacturer in numerous ways. We have also listed the advantages of working with us:
● It is easy to spot mistakes on the PCB, and actually silkscreening can reduce the number of errors.
● The marking of components gets more readable and easy to read, even if the board is filled with components.
● It’s useful for marking active components on the board.
● As a highly experienced manufacturer of silkscreen circuit boards, we make sure that we don’t print epoxies onto soldered pads as the epoxy will melt into the joint.
● We ensure exact labeling and identify damaged components. This can reduce total PCB costs.
● In order to reduce the impact on the environment, we use environmentally-friendly methods, there are no films or sheets used. This is done by spraying ink directly onto the substrate that will absorb the ink.
● We permit you to indicate where you require labels for the board, and you are able to include them in your sketch.
● By using specific silkscreening in areas that are not critical, the board could be used as a faceplate for your device that is backlit with your company’s logo on it.
In the field of silk screen circuit boards, JarnisTech is one of the most well-known manufacturers. If you are planning to upgrade your equipment and need marking on PCBs or copies and scan data from existing PCBs, we are able to provide our services. It is important to print information on non-critical areas, and we avoid soldering. In addition, we adhere to the guidelines outlined in IPC-4781 certification and performance specification for permanent, semi-permanent, and temporary inks for marking or legends and/or legends. If you require more information about PCB silkscreening, contact us by phone at (0086-755-23034656) or email us with questions via [email protected].
Screen Printing Is How You Print on PCB
The process of printing screen is the process of stretching fine stainless steel or polyester wires on a rigid frame that acts as a carrier for images. The stencil for the desired image is made using photosensitive glue onto the mesh. The emulsion is typically applied to each side of the mesh, and a specified thickness is constructed on the side that is under (the part that touches the boards).
As illustrated in the figure as shown in the figure, the screen is placed right above the board as well as the medium (ink) is placed behind an elastic squeegee. As the squeegee is moving across the screen and the mesh of the screen gets into proximity to the PCB and allows the medium to flow across the PCB.
The squeegee blade is initially pressed into the openings of the image. Then, it removes excess material when it moves over each of the apertures. The mesh aperture on the screen gets separated from the print surface by the squeegee leaving the ink behind that was within an aperture in the mesh. The medium moves in a slight manner after printing to minimize visible mesh marks that are left on the print. This process is known as leveling.
Since the screen is in contact with the substrate as the squeegee is able to pass across it, this method is often referred to in the field of off-contact printing. For every 100mm of the frame’s width, the snap-off distance typically is 0.5mm. Its thickness ink will be determined by the amount of emulsion, as well as the mesh.
How to Design Silkscreen for PCB
To enhance the quality of the PCB identification as well as assembly and testing, it is important that the silkscreen is in compliance with certain specifications for the design. According to JarnisTech, These include:
Some fonts are not suitable for printing silkscreens on PCBs. Designers must check with their contract manufacturer for fonts that are clear and legible after printing.
The fabricator is able to apply the silkscreen to the solder mask layer that color used for the silkscreen must provide contrast with the mask. Silkscreen colors of white work best on a solder mask layer. However, any color that is contrasting and allows an easy reading should suffice.
Clearance and Dimension
To ensure that the screen is legible and easy to read for proper legibility and readability, the lines and letters on the silkscreen need to be clear and have the proper dimensions. Designers should consult their contract manufacturer regarding this issue. In no way should the ink of the silkscreen printing contaminate the copper pads that can be soldered.
PCB Design Guidelines and DFM
What Information Does a Silkscreen Provide
Silkscreens may not play any effect on the functionality of a PCB. However, it is considered valuable because of the information it offers. For instance, it can aid anyone in the following:
● Know the warning signs.
● Parts that are polarized.
● Identify test areas.
● Find the components using references.
● Find the numbers that are specific to the printed circuit board.
● Identify the manufacturer markings, version numbers, and so on.
A lot of PCB engineers who design PCB believe that silkscreen does not impact its performance. Therefore it doesn’t pay any attention to the silkscreen. But, if you are an experienced hardware engineer, you must be aware of these particulars.
● Area for placement.
● Don’t try to copy Via’s style on the silkscreen.
● Do not place the silkscreen onto high-speed signals(e.g., clock lines, etc. ).
● The direction of reading on the silkscreen should coincide with the direction of the use.
● The pin’s number should be engraved in the silkscreen.
● Silkscreen printing on special electronic components.
● Silkscreen of the hole in the mount.
Provide PCB Silk Screen Printing for Your PCB Manufacturing
With more than 20 years of experience as a market-leading company, JarnisTech is one of the most professional PCB companies in China. Highly specialized not just in the development of prototype PCBs and PCB assembly but also in small and medium-sized quantity PCB fabrication. We can silkscreen your PCBs, and we’ll do our best to meet the requirements of silkscreen.
Should you need to ask about any concerns you have, feel free to reach us via [email protected]. We’ll be glad to assist you.