In PCB design, ESD resistance of PCB can be realized through layering, proper layout and installation. During the design process, most design changes can be limited to adding or removing components through prediction. By adjusting PCB layout and wiring, ESD can be well prevented.

Static electricity from the human body, the environment and even inside electronic devices can cause various damage to precision semiconductor chips, such as penetrating the thin insulation layer inside components; Damage to the gates of MOSFET and CMOS components; Trigger lock in CMOS device; Short-circuit reverse bias PN junction; Short-circuit positive bias PN junction; Melt the weld wire or aluminum wire inside the active device. In order to eliminate the interference and damage of electrostatic discharge (ESD) to electronic equipment, it is necessary to take a variety of technical measures to prevent.

How to enhance anti-ESD function in PCB design

In the design of PCB board, anti-ESD design of PCB can be realized through layering, proper layout and installation. During the design process, most design changes can be limited to adding or removing components through prediction. By adjusting PCB layout and wiring, ESD can be well prevented. Here are some common precautions.

Use multilayer PCBS whenever possible. The ground and power planes, as well as the tightly spaced signal line-ground lines, can reduce common-mode impedance and inductive coupling to 1/10 to 1/100 of a double-sided PCB compared to a double-sided PCB. Try to place each signal layer close to a power or ground layer. For high-density PCBS with components on both the top and bottom surfaces, very short connections, and lots of ground filling, consider using inner lines.

For double-sided PCBS, tightly interwoven power supplies and grids are used. The power cord is next to the ground and should be connected as much as possible between the vertical and horizontal lines or fill zones. The grid size of one side shall be less than or equal to 60mm, or less than 13mm if possible.

Make sure each circuit is as compact as possible.

Put all connectors aside as much as possible.

If possible, direct the power cord from the center of the card away from areas that are directly exposed to ESD.

On all PCB layers below the connector leading out of the case (prone to direct ESD hits), place wide chassis or polygon filled floors and connect them together with holes at approximately 13mm intervals.

Mounting holes are placed on the edge of the card, and the top and bottom pads of open flux are connected to the floor of the chassis around the mounting holes.

When assembling PCB, do not apply any solder on top or bottom pad. Use screws with built-in washers to provide tight contact between PCB and metal chassis/shield or support on ground surface.

The same “isolation zone” should be set up between the chassis floor and the circuit floor on each layer; If possible, keep the spacing at 0.64mm.

At the top and bottom of the card near the mounting hole, connect the chassis ground and the circuit ground with 1.27mm wide wires every 100mm along the chassis ground wire. Adjacent to these connection points, a pad or mounting hole for installation is placed between the chassis ground and the circuit ground. These ground connections can be cut with a blade to remain open, or jump with magnetic beads/high frequency capacitors.

If the circuit board will not be placed in a metal chassis or shielding device, the top and bottom chassis ground wire of the circuit board can not be coated with solder resistance, so that they can be used as ESD arc discharge electrode.

A ring is set around the circuit in the following manner:

(1) In addition to the edge connector and chassis, the entire periphery of the ring access.

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

(3) The holes are connected in a ring every 13mm.

(4) Connect the annular ground and the common ground of the multi-layer circuit together.

(5) For double panels installed in metal cases or shielding devices, the ring ground shall be connected to the common ground of the circuit. The unshielded double-sided circuit should be connected to the ring ground, the ring ground should not be coated with flux, so that the ring ground can act as an ESD discharge rod, at least a 0.5mm wide gap on the ring ground (all layers), so that a large loop can be avoided. Signal wiring should not be less than 0.5mm away from the ring ground.