Definition of Stitching Vias
Unlike regular vias used for signal routing and electrical continuity between different layers of a PCB, stitching vias form an array strategically placed within larger copper areas on the board. They serve as connectors for essential zones like ground planes, power nets, and signal paths.
Figure 1: Stitching Vias
Purposes of Stitching Vias
Ground plane continuity
In a multilayer PCB, ground planes may exist on different layers due to the complexity of the circuit. These ground planes are typically interconnected to provide a consistent ground reference. However, due to factors like signal traces, components, or other design considerations, gaps can occur in the ground plane. These gaps interrupt the continuous ground path, potentially leading to undesirable effects like signal interference and EMI. So in this case, stitching vias are used to bridge these gaps in the ground plane continuity. They create a conductive pathway that effectively joins the ground planes on different layers, even though they might be physically separate.
When applying stitching vias for current management purposes, they can play roles in the following two ways:
Reduce Heat dissipation
When current flows through a conductor, such as a trace or via, a certain amount of heat is generated due to the resistance of the material. In high-current applications, this heat generation can be substantial. By strategically placing stitching vias, designers can create a pathway for heat to flow from areas of high heat generation to areas where it can be dissipated more efficiently. This helps in spreading out the heat, preventing localized hotspots, and maintaining more uniform temperatures across the PCB.
Reduce Inductance
When high-frequency currents flow through a PCB's conductive paths, they can experience increased inductance due to the physical layout and properties of the conductors. This inductance can lead to voltage drops and signal integrity issues. Stitching vias provide short, direct routes for the currents to travel between different ground or power planes, bypassing the longer and more inductive routes.
Layout tips
Placement at Corners and Edges: Corners and edges of a PCB are prone to heightened inductance. Stitching vias are most effective when strategically placed in these areas to mitigate inductive effects.
Surround with Copper Fill: Enhance grounding by enveloping stitching vias with copper fill on both top and bottom layers. This practice solidifies the connection to the ground plane.
Uniform Distribution: Distribute stitching vias as uniformly as possible throughout the PCB to create a consistent low-inductance path for currents.
