The starting position of a screen printerĪs shown in the figure, the screen is positioned just above the board, and the medium (ink) lies in front of a flexible squeegee. The emulsion is usually applied on both sides of the mesh, and a defined thickness is built upon the underside (the side that contacts the board). A stencil of the required image is created by applying a photosensitive emulsion to the mesh. The screen printing process involves a screen formed by stretching a mesh of fine polyester or stainless steel wires over a rigid frame to serve as an image carrier. To reduce the problems occurring due to machine printing errors, tolerance should be presented by a few mils difference.įinally, the best pattern for the silkscreen can be achieved by following these guidelines.For easy readability, marking should be done using standard colors (white color is widely used) and proper shapes.There are some more points to be considered while designing the silkscreen, they are: Testing aids: It includes test point indicators, mode, and jumper indicators. Reference indicators should be used according to the available space. Manufacturer’s identification: It includes markings such as board pad number, serial number, labels, and the logo.Īssembly aids: It involves polarity and pin one indicator. Regulatory requirements: It involves marking and labeling of components to identify lead (Pb), lead-free (Pb-free), and other attributes from IPC. Thus, it is critical to prioritize the marking as given below: However, with the ongoing development toward smaller PCBs, this may not be possible. It may be fascinating to include indicators for all components and other informational imagery that may be useful for assembly, testing, or repair of the board. Suitable fonts used in high tech electronic PCB Proper use of silkscreen markings The most common sizes are 35 mil height and 5 mil line width and also 25 mil height and 5 mil line width. Designers should mention the requirements for silkscreen printing such as size, height, color, and font type. Later, the appropriate font should be incorporated into the design. However, it is best to consult with the fabricator about the kind of font that can be generated on the board. Some circuit board manufacturers allow the designer to create any type of font style for the silkscreen. PCB layout showing the silkscreen marking Appropriate fonts This is done to ensure there is no overlap or covering of the indicators. While designing a PCB layout, markings such as polarity, pins, and reference indicators must be close to the associated components and should be visible after component mounting. These parameters are specified according to manual silkscreen printing, liquid photo imaging, and direct legend printing. The printing method influences many design parameters such as size, clearances, and location of silkscreen markings on different elements, such as component pads, traces, and vias. It is essential to find out the specific method that a board manufacturer implements for silkscreen printing. Top view of PCB digital footprint Silkscreen printing process In the case of a capacitor half-shaded circle for negative and “ +” for positive polarity. It indicates pin no.1 of the IC, “( + or –)” in the case of diodes and LEDs, ( C) for cathode, and ( A) for anode. These are typically represented by a dot(. The orientation marking on the silkscreen gives the direction in which the component is soldered. A few parameters for designing are listed below. Silkscreen layout aids in the assembly of a circuit board by providing reference designators. Silkscreen on a PCB Design considerations for PCB silkscreen The most critical information should be prioritized if you have limited space. Silkscreen information varies according to the size of the circuit boards. PCB silkscreen provides text-based information of different circuit points, components, and other circuitry information as per requirement. RLC Resonant Frequency and Impedance Calculator.Bandwidth Rise Time and Critical Length Calculator.Transmission Line Reflection Calculator.Trace Width and Current Capacity Calculator.
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