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IPC Standards for Annular Rings
The IPC standards define three product classifications (Class 1, Class 2 and Class 3) based on the required level of device reliability. Each of these classes defines guidelines for fabrication, cleaning, and inspection of PCBs for different applications. Issues such as component placement, via hole plating, residual contaminants, trace sizes, and other design aspects are all addressed in the standards for each of these classes.
Devices that meet class three requirements require continuous uptime with high performance. Devices meeting this class should be designed for use in harsh environments and the devices must function when required. Class 3 products are often found in a number of important applications, including in the medical and aerospace fields.
Specification on annular rings are designed to assure a large connection area between a via pad, the drill hole, and any component that may be mounted on it. When designing a multi-layer PCB with the goal of complying with IPC 6012, the important dimension is pad diameter. Meeting the minimum IPC Class 3 annular ring requirements requires that the pad size be large enough to accommodate the diameter of the via.
Designing for Manufacturing with Class 3
The ideal hole placement in a pad is dead center according to Class 3 specifications. However, off-center hole placement is also acceptable. Placing the hole close to the trace connection does not meet Class 3 requirements as this weakens the connection between the trace and the pad. Placing the hole so that it touches the edge of the pad is also unacceptable under Class 3 specifications. The via hole must be no closer that 0.05 mm from the edge of the via pad.
Manufacturing tolerances should be able to meet these hole placement requirements for devices that are designed according to Class 3 specifications. The size of annular rings used in via pads must be enlarged compared to other specifications in order to meet the drill hole requirements of the Class 3 specifications.
There are a number of other specifications on vias defined under the IPC 6012 Class 3 specifications. These specifications include requirements on board thickness, copper plating in various via structures, and the presence of any copper voids in filled vias. A PCB design software package with the best CAD tools can ensure that your device meets many of these requirements. Working with the right manufacturer can help you meet the other requirements.
Devices that meet class three requirements require continuous uptime with high performance. Devices meeting this class should be designed for use in harsh environments and the devices must function when required. Class 3 products are often found in a number of important applications, including in the medical and aerospace fields.
Specification on annular rings are designed to assure a large connection area between a via pad, the drill hole, and any component that may be mounted on it. When designing a multi-layer PCB with the goal of complying with IPC 6012, the important dimension is pad diameter. Meeting the minimum IPC Class 3 annular ring requirements requires that the pad size be large enough to accommodate the diameter of the via.
Designing for Manufacturing with Class 3
The ideal hole placement in a pad is dead center according to Class 3 specifications. However, off-center hole placement is also acceptable. Placing the hole close to the trace connection does not meet Class 3 requirements as this weakens the connection between the trace and the pad. Placing the hole so that it touches the edge of the pad is also unacceptable under Class 3 specifications. The via hole must be no closer that 0.05 mm from the edge of the via pad.
Manufacturing tolerances should be able to meet these hole placement requirements for devices that are designed according to Class 3 specifications. The size of annular rings used in via pads must be enlarged compared to other specifications in order to meet the drill hole requirements of the Class 3 specifications.
There are a number of other specifications on vias defined under the IPC 6012 Class 3 specifications. These specifications include requirements on board thickness, copper plating in various via structures, and the presence of any copper voids in filled vias. A PCB design software package with the best CAD tools can ensure that your device meets many of these requirements. Working with the right manufacturer can help you meet the other requirements.
