What is Mark
Mark refers to a specific element or feature on a PCB that serves as a reference point or indication for mounters during the assembly process. It is a shape or symbol strategically designed and placed on the PCB to assist in the accurate placement of components.
The mark can take various shapes, including a solid circle (●), triangle (▲), rhombus (◆), square (■), cross (＋), or hollow circle (○). While the solid circle is considered the optimal choice, other shapes can also be used.
The size of the mark is an important consideration. Typically, the diameter of the Mark ranges from 1.5-2mm. However, for mini-versions or layouts with high density, the diameter can be adjusted, provided it remains at least 0.5mm and does not exceed 5mm.
The surface finish of the Mark can vary, with options such as bare copper, tin plating, or gold plating. It is crucial for the plating layer to be flat and not excessively thick.
To aid in identification during the assembly process, the Mark should have an area without soldermask around it. This area should have a width of 1-2mm, creating contrast between the soldermask material color and the Mark.