The demands on PCB design rise along with the level of automation. The efficiency and standard of the production procedure may be impacted, and automatic SMT may even malfunction if the PCB design fails to conform to the specifications of the SMT device. Ineffective pad design or inability to wrap up the manufacturing process might result from poor PCB shape, clamping edge, and panel design.

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PCB Design Factors That Affect SMT

In a state-of-the-art type of electronic manufacturing known as surface mount technology, components are placed and soldered on a specific location on the PCB. SMT is more suited for large-scale automated manufacturing owing to its higher level of automation than conventional through-hole technology (THT).
One of the most important components of SMT and a significant factor in the caliber of SMT production is printed circuit board design. In the sections that follow, we’ll look at the PCB design components that have an effect on quality from the standpoint of SMT equipment production.

The following are the primary necessities for PCB design from SMT devices:

Board Size

The maximum and minimum size specifications of the printer and chip mounter, which generally fall in the range of 50mm x 50mm to 330mm x 250mm (or 410mm x 360mm), must be met by the PCB design. If the PCB is too thin, the planned size shouldn’t be overly big because the reflow temperature could cause it to distort. 4:3 or 3:2 is the best length-to-width ratio.

The PCB must be organized into panels if its size is less than the bare minimum needed for the device. The dimensions and thickness of the PCB are used to calculate the total quantity of panels.

Pattern

The PCB must be made with the transmission path between devices considered because it will be transported along that path throughout the making. The best PCB for transmission is a regular rectangular PCB with a flat route clamping edge. An edge may occasionally have a right angle added to it to create a chamfer.

However, problems with PCB positioning and transmission in the device may arise if the route clamping edge is not straight. You can either fill the empty space to make the clamping edge parallel or modify the PCB by adding a crack edge in order to fix this.

Clamping Edge

Parts shouldn’t be positioned along the clamping edge’s path while the printed circuit board is transported through the device since doing so could cause the device to compress them, which would impact chip attachment. For instance, some components might be placed close to the PCB’s bottom side. The top and lower ends shouldn’t be employed as clamping edges in this situation. The two short edges, on the other hand, can be utilized as clamping edges if there are no components close to the two side edges.

Trace Width

The standard of the SMT process in PCB design can be affected by a number of significant factors, including trace width. The term “trace width” describes how wide the conductive tracks or lines are on a printed circuit board. It is crucial to properly design the trace width since it affects the quantity of current that can pass through it.

The current flow, the thickness of the trace, the material used to make the trace, and the required temperature must all be taken into account when determining the proper trace width. Generally speaking, a greater trace width is needed for increased current flow. To account for the thermal expansion and contraction that take place during the soldering process, the trace width should also be modified.

The distance from the trace and other PCB components is an essential variable as well. The distance between the trace and other components should be sufficient to avert short circuits while also allowing for effective PCB area utilization.

Via Design

An additional essential aspect of PCB design that might affect how well surface mount technology works is via design. A multi-layer PCB’s vias are conductive connections made between the layers. To guarantee that the electrical signals are effectively passed via the circuit board, good design is crucial.

The diameter, aspect ratio, and positioning of vias are parameters to take into consideration while designing vias. The aspect ratio should be tuned to guarantee the proper connection between layers, and the diameter should be sufficient for sufficient current flow. To avoid short circuits and ensure effective use of space on the circuit board, place vias close to the components they link and space them apart from one another.

You can make sure that electrical impulses are transferred correctly and effectively during the SMT process by taking these elements into account.

Mark

For automatic devices, the PCB Mark acts as a crucial identifier and aids in the correction of any manufacturing mistakes. Designing the mark requires taking into account its size (ideally 0.5mm to 3mm, with an even circle of 1mm diameter being the best option), form (ideally a perfect circle), and surface (even and reflective, like the soldering plane of the PCB pad).

It must have a clear backdrop region without any solder mask or silkscreen around the mark and other pads. Ineffective designs with silkscreen letters or lines close to the mark can frequently result in device identification mistakes and have a detrimental effect on production effectiveness.

Careful consideration must be given to a number of factors when designing SMT printed circuit boards, including trace width, via design, and PCB mark.

6 Considerations for SMT PCB Designs