How to enhance the anti-static ESD function of PCB boards

Steps/Methods

Try to use multi-layer PCBs as much as possible. Compared to double-sided PCBs, the ground plane and power plane, as well as the tightly arranged signal line ground distance, can reduce common mode impedance and inductive coupling, reaching 1/10 to 1/100 of that of double-sided PCBs. Try to place each signal layer as close as possible to a power or ground layer. For high-density PCBs with components on both the top and bottom surfaces, short connecting wires, and many filling grounds, inner layer wires can be considered. For double-sided PCBs, a tightly intertwined power and ground grid should be used. The power cord should be connected as much as possible between the vertical and horizontal lines or fill areas, adjacent to the ground wire. The grid size on one side should be less than or equal to 60mm, and if possible, the grid size should be less than 13mm.

Ensure that each circuit is as compact as possible. Try to put all connectors aside as much as possible.

Introduce the power cord from the center of the card and away from areas susceptible to direct ESD impact. On all PCB layers below the connectors that lead to the outside of the chassis (easily hit by ESD), place a wide chassis ground or polygonal fill ground, and connect them together with through holes every approximately 13mm.

Place installation holes on the edge of the card, and connect the top and bottom solder pads with unobstructed flux around the installation holes to the chassis ground.

When assembling a PCB, do not apply any solder to the top or bottom solder pads. Use screws with embedded washers to achieve close contact between the PCB and the bracket on the metal chassis/shielding layer or ground plane. Set up the same "isolation zone" between the chassis ground and circuit ground on each layer; If possible, maintain a spacing of 0.64mm.

Connect the chassis ground and circuit ground with 1.27mm wide wires every 100mm along the chassis ground wire near the installation holes on the top and bottom layers of the card. Place solder pads or mounting holes for installation between the chassis ground and circuit ground adjacent to these connection points. These ground wire connections can be cut open with a blade to maintain an open circuit, or jumpered with magnetic beads/high-frequency capacitors. If the circuit board will not be placed in a metal chassis or shielding device, solder blocking agents cannot be applied to the ground wires of the top and bottom chassis of the circuit board, so they can serve as discharge electrodes for ESD arcs.

Set a circular ground around the circuit in the following ways:

(1) Place a circular ground path around the entire periphery, except for the edge connectors and chassis ground.

(2) Ensure that the circular width of all layers is greater than 2.5mm.

(3) Annually connect with through holes every 13mm.

(4) Connect the circular ground to the common ground of the multi-layer PCB board reading circuit.

(5) For double-sided devices installed in metal cases or shielding devices, the circular ground should be connected to the circuit common ground. Unshielded double-sided circuits should be connected to the chassis ground in a circular manner, and solder resist should not be applied to the circular ground so that it can serve as a discharge rod for ESD. At least a 0.5mm wide gap should be placed at a certain position on the circular ground (all layers) to avoid forming a large loop. The distance between signal wiring and the circular ground should not be less than 0.5mm.