What Is the Typical Via Size for a 4 Layer PCB?
Typical Via Size for a 4 Layer PCB
A via is a hole drilled into the layers of a PCB and lined with copper to establish an electrical connection between them. Vias are essential in multilayer PCB designs as they allow current to pass between the layers of the board and also help to transfer heat from one layer to the other. Because of the important role they play, it’s vital that they are properly managed and routed to ensure proper performance. The right PCB via size will depend on the specific scenario, but some general guidelines are helpful to follow.
The most common type of via is a through-via, which passes vertically through the board’s structure. They can be etched, laser-drilled, or milled to achieve the correct diameter. Regardless of the method used, all through-vias are subject to some amount of inductance and require careful routing to minimize their impact on signal fidelity, power loss, and other critical design parameters.
Through-vias are most often plated with gold, but they can be nickel or silver as well. While gold is generally preferred for high-speed signals, it’s not always possible due to budget constraints or design requirements. For this reason, it’s best to use copper in most cases when routing through-vias. Make sure that they are located close to the source and destination of the signals, and that the length of the stubs is kept as short as possible.
What Is the Typical Via Size for a 4 Layer PCB?
For through-vias, the size of the finished hole and the annular ring is a major consideration. The copper in the annular ring allows for tolerance against manufacturing errors such as misregistration of the holes in the inner layer stackup and provides conductivity between the pad on the outer layer and the copper in the via. However, the larger the annular ring, the more space it consumes on the inner layer which could be used for components, routing, or internal planes.
Another important consideration is the shape of the via’s component pads. Unlike the round shape of most through-vias, the pads of component pins and SMT ICs are often non-round. To prevent solder from wicking down the via’s barrel, it’s recommended that they be a minimum of 0.5mm wider than the diameter of the through-via. The resulting pad will provide adequate clearance for the plated through-via’s copper while still allowing for proper signal routing and keeping within ampacity limits.
There are several different types of 4 layer pcb board available including blind, buried, and microvia. While these can all be useful for certain situations, they require a greater level of expertise and knowledge to implement effectively. For example, it’s not recommended to use buried vias in high-speed signal applications because they can cause unwanted resonance and reduce the integrity of the PCB’s signal path. When using these technologies, it’s best to consult a professional PCB manufacturer with the proper experience and tools to ensure they are implemented correctly.