PCB Layout Tips and Tricks

Avoid ground loops.

 The term “ground loop” can, in my opinion, refer to any situation in which a difference in ground potential impacts a system. Consider the following scenario: two modules are linked through a lengthy cable. The return current in the connection causes one module’s ground voltage to be significantly larger than the ground voltage of the other module. However, in this discussion, I’m referring clearly to a loop of ground connections; for instance, the following:

If you need to create many ground connections on a china PCB using individual traces, a loop similar to the one shown above would not be difficult to make. Knowing that this form of conductive loop is an effective receiver of magnetic interference should come as no surprise if you’ve read my essay on mutual inductance.

The presence of a ground plane does not preclude the possibility of establishing a ground loop. Because the CAD application will not prevent you from creating traces between ground points while a ground plane is present. However, suppose you consistently use vias or through-holes for ground connections. In that case, this issue should be mitigated significantly: by dropping vias to the plane, you create a direct connection from the component to a ground point that is connected to all other ground points in the circuit via a low impedance path.

 A System of Integrated Protection

A solid ground plane provides some, but not total, protection from electromagnetic interference (both radiated and received). Using a ground plane alone will not resolve all of your EMI difficulties, particularly if you have components on both sides of the board; a well-constructed conductive enclosure would be more advantageous. Nonetheless, any amount helps, and if you’re concerned about EMI, you now have an additional reason to incorporate a ground plane into your design plan.

The Capacitor on the Plane of the PCB

This is a tiny benefit that applies only to ground planes next to a power plane. Nonetheless, I feel it is necessary to state. A ground plane separated from a power plane by a thin dielectric sound is a lot like a parallel-plate capacitor, and it is. This structure provides a small amount of distributed power supply capacitance to your whole circuit board but is not designed to replace your board’s decoupling capacitors fully.

Real-World Obstacles

In my opinion, a four-layer printed circuit board (china PCB) cannot work correctly without a ground plane. While a highly dense architecture might need the usage of both internal layers for conventional signal routing, this appears unlikely: while the plane does take up routing space, the amount of routing space required by the board is decreased by reducing ground connections.

A considerably more frequent occurrence is that a ground plane is omitted due to time or financial restrictions that make a two-layer board more practicable. The ground plane now occupies one of the two available PCB prototype layers. Is it genuinely desirable to include a ground plane if it requires putting virtually all traces and components onto a single layer? Yes, in my opinion, a ground plane is still preferred unless the circuit is so simple that the ground connections may be made using well-organized, low-impedance traces. However, if your space constraints prevent you from creating a board large enough to incorporate a ground layer on the bottom and a clean pattern on the top, you may want to consider upgrading to a four-layer board.

Summary Including a ground plane on your printed circuit board (PCB prototype) is a simple, low-cost, and highly effective way of creating electrical devices with improved signal integrity, accuracy, and resistance to interference. Consider these benefits when building your following board layout if you are not accustomed to employing a ground plane.

ChinaPCBOne Technology LTD. is the author of this article on China PCB. Find more information, about PCB prototype.

Clare Louise