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Design Requirement of SMT PCBs Part Four: Mark

Last Updated: Mar 29, 2017

In order to correct the errors generated in the process of PCB fabrication, Mark refers to a set of patterns used for optical localization. Mark can be classified into PCB Mark and local Mark.

Mark Patterns

The shape and size of Mark should be designed according to the specific requirement of mounters with different models. Figure 1 is a sample of Mark, and the following table shows general requirements of Mark.

Mark Patterns on PCB | PCBCart

General Requirements on PCB Marks | PCBCart

Layout Position of Mark

The layout position of Mark is determined by PCB transmission way of mounter. When lead rail is used to transmit PCB, Mark shouldn't be placed near clamping side or position holes and the specific size is different according to mounters. The general requirement is displayed in Figure 2 below.

PCB Mark Design Tips | PCBCart

• In the process of needle location, Mark can't be positioned.


• In the process of edge location, Mark can't be positioned within the area of 4mm from clamping side to edge.

PCB Mark

PCB Mark is a set of patterns for optical localization of the whole PCB.

Mark Patterns on PCB | PCBCart

• PCB Mark position should be placed along diagonal line and the distance between them should be as large as possible.


• For PCB whose length is less than 200mm, at least 2 Marks should be placed like Figure 3a. For PCB whose length is more than 200mm, 4 Marks are required to be placed on PCB like Figure 3b and 1 or 2 Marks should be placed along or near the center line across the long side of PCB.


• Mark of panel should be placed along the diagonal line of each small board, which is shown in Figure 3c.

Local Mark

Local Mark refers to a set of patterns for optical localization of each component with many pins and small spacing between pins (distance between pins and center is no more than 0.65mm).

Local Mark on PCB | PCBCart

The position of local Mark should meet the following requirements:


For QFP components with more than 100 pins, 2 Marks should be placed along diagonal line, which is shown in Figure 4a. For QFP components with more than 160 pins, 4 Marks should be placed at the four corners, which is displayed in Figure 4b.

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