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What is PCB fiducial mark and considerations in PCB design?


What is fiducial mark and why it is required in PCB?

What-is-fiducial-mark-and-why-it-is-required-in-PCBThe orientation and the positioning of the circuit pattern on the printed circuit board are recognized with the help of the fiducial marks. Most of the boards use 3 fiducial marks and all of them have their own purpose. They are usually located at the lower left-hand corner, upper right-hand corner and the lower right-hand corner of the circuit board.

PCB Fiducial mark is a round shape mark which is used as a reference point for the pick and place of the assembly lines. A fiducial mark/marker is a circuit pattern recognition mark or marker.

What kind of PCB fiducial mark is it?

PCB fiducial mark is designed to correct the errors generated in the PCB production process, for optical positioning of a set of graphics. The type of PCB fiducial mark is divided into Local fiducial markers and Global fiducial markers.

1.Local fiducial markers
The local fiducial mark is the copper marks that outside of the corner of a quad packed surface mount component, which consists of two markers placed diagonally on the component’s outside border. A bigger circuit board will have a less angular misalignment. By placing markers close to the fine pitch components, they aid in machine placement.

2.Global fiducial markers
There are two copper references on the edges of the diagonal of printed circuit board. These fiducial markers are used to establish the board’s orientation in relation to the X and Y axes.kind-of-PCB-fiducial-mark

What is PCB fiducial mark made of?

Copper is used to create PCB fiducial marks. Each material which is used in the manufacturing of PCB is supported by Surface Mount Technology or SMT components. Gold, silver and polymer are also used to make fiducial marks. The fiducial pad must be completed using the same metal as the board’s other metal components.

How to place PCB fiducial mark?

A copper layer is positioned in a circle without being pierced. Absolutely no solder mask must be present. The ideal PCB fiducial mark sizes are 1 and 3 mm. It is vital to keep a clearing area that is about the same diameter as the marker. Each PCB has three fiducials placed in a “L” pattern. Three more fiducials are put in a “L” pattern on the panel edge for a multiple circuit board in a panel.

In order to create maximum distance, the fiducials are placed as far on the outside of the circuit board. The recommended reference for the designation is FD1 to FD3 for TOP side, FD4 to FD6 for BOTTOM side. Additionally, fiducials must to be mentioned in the solder paste data.

Considerations about PCB fiducial mark production and PCB design

For accurate part positioning and clearance in large volume assembly, fiducial marks are typically required. You might get such from a restricted or schematic expert. There are several suggestions and things to keep in mind with PCB fiducial marks.

● A copper layer that is not drilled is placed in a circle to create the fiducial marker. This time, do not need to put solder mask on the PCB fiducial marker.

● Optimum size should be in between 1 and 3mm.

● For placing components more precisely, 3 global fiducials should be positioned on the edge of the printed circuit board.

● A minimum of two fiducial markers are positioned diagonally along the outside edge of the surface-mounted component in local fiducial.

● The fiducial marker must stay 0.3 inches away from the edge of the board.

● No silk-screening, wiring, etc. within 3 mm of the overall diameter of the Mark point.

● It’s shape generally is a solid circle with a diameter of 1mm (±0.2mm), and the color is much different from the surrounding background color.

What is maximum amount of fiducial mark in PCB?

PCB surface should have at least three reference points, the location and distance between the three points should be as far away as possible.3 fiducials ensure that the circuit board is not loaded incorrectly in the pick and place machine. The fiducial should have a maximum diameter of 3mm (0.120 in). If you are working on the same PCB the size difference must not be the same.
maximum-amount-of-fiducial-mark-in-PCBWhen preparing to place two fiducial marks on the PCB diagonally, do not symmetrical with the shape of the printed circuit board (do not put on the radial direction), otherwise it is easy to cause the wrong placement direction.

In the length of the printed circuit board less than 200mm, set at least 2 difucial mark. when the length of the printed circuit board is greater than or equal to 200mm, set 4 marks, and in the length of the printed circuit board on or near the center line set 1 ~ 2 marks.

Where is the PCB fiducial mark generally added?

The fiducial marks should be added at the corners of the printed circuit board. The edge shouldn’t cross all the way of the board. As a result, the fiducials may become enclosed by the machine jaws. They should be placed 5mm apart from each other. The quantity of fiducial markings is not subject to any rigorous regulations.

The layout of PCB fiducial mark should be distributed in all four corners, and the componentfiducial mark are distributed along the diagonal of the components.Therefore, It is best to place two fiducial markers on the PCB’s opposing corners.Large BGA, large precision ICs, and components below 0.6mm pitch should have local reference points.

How far is it from the edge of the board?

The fiducial marker must remain 0.3 inches from the board’s edge (Including the fiducial marker’s clearance space,). A fiducial marker’s ideal size should fall between 1.5mm and 3mm.

It is necessary to maintain a clearing space whose diameter is comparable to the marker’s. It’s crucial to have enough space around the fiducial pad. Set up a clear space all around the pad (no copper, solder mask, silkscreen, etc.) Having that area helps the camera to focus on the target without being

Can you still produce if you forget to add PCB fiducial mark in PCB design?

Can-you-still-produce-if-you-forget-to-add-PCB-fiducial-mark-in-PCB-designThese markers, regardless of size or shape, are crucial for the production of PCBA nowadays. Without PCB fiducials, automation, which is used in varied degrees by CMs who manufacture electronic circuit boards, would not be conceivable. They are very important for the production of PCB.


We hope that this article has answered all of your questions about PCB fiducial marks and perhaps even taught you something new. On the IBE website, you may find more articles about PCB and PCBA, and find a good choice of PCBA service provider.,



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