What is PCB design screen printing? Why are they included in the design plan? Does your PCB need to be a readable silk screen?
What is screen printing?
Generally, a printed circuit board (PCB) design has many different layers, and the screen layer is one of these layers. Since the silk screen must be printed on the surface of the PCB, each PCB has at most two silk screen layers, namely the top and the bottom. Silk screen can print text information on cardboard for humans to read and interpret. On the silk screen of the PCB, you can print various information such as component reference indicators, company logos, manufacturer logos, warning symbols, part numbers, version numbers, and date codes. But the space on the PCB surface is limited, so it is best to limit it to useful or important information. Therefore, the silk screen layer usually only saves a component legend, showing the position of various components on the company logo and circuit board design number.
Currently, custom digital inkjet printers dedicated to printing PCBs are most commonly used to print screen-printed images from circuit board design data onto the PCB surface. The first screen printing was to use the screen printing method to get the name screen printing from it. The name is due to the traditional screen printing technology that requires fine cloth like silk or polyester as a screen and a frame made of wood, aluminum, etc. Now with the advancement of technology, many different simpler or faster screen printing methods are developed, but the name remains the same.
How to design the screen?
It is worth noting that editing the silk screen layout in the printed circuit board design is a small step in the printed circuit board design, because the silk screen is not required to assemble the printed circuit board. However, although this is not an absolutely necessary step, it is still an important step to assist circuit board assembly by providing references during construction and troubleshooting. There are various computer programs for PCB design on the market, such as the well-known Mentorgraphic PAD layout and router. For Mentorgraphic PAD when designing the PCB layout when placing components in the layout of the design file, a component reference indicator will be automatically assigned to each component on the component layout.
When designing the PCB layout, we move and rotate the components on the layout. The component reference indicator codes move and rotate as they are attached to the component. Therefore, editing the screen becomes necessary in this case. There are also programs where you can design silk screens and write component reference indicator codes yourself so that they can be used with the corresponding component locations. In these procedures, you only need to pay attention to the following points, and pay attention to assigning different reference codes to each component.
Direction/overlap
Whether you are editing the automatically generated screen printing or designing the screen printing layer from scratch, if you want to design a screen printing layer design with good readability, you need to pay attention to some key points. In order to design a good screen, you need to: edit the text direction of the component reference indicator, part type, etc. so that all of them have the same direction, if possible, set the top and bottom, which means the screen is easier to read .
Before rotating the text and adjusting the component reference indicator marks, check for common problems with overlapping text. As an example, as shown in Figure 1, the markers have different directions and overlap. In the picture, you can see how to use the mark as a reference when assembling, and how confusing and difficult it will be if it is not corrected. Therefore, you need to rotate and move the component reference mark to the correct direction and position of the corresponding component.
