PCB Blog - How to enhance the anti-static ESD function of PCB board

In the design of the PCB board, the anti-ESD design of the PCB can be realized by layering, proper layout and installation. During the design process, most design modifications can be limited to adding or removing components through prediction. By adjusting the PCB layout, ESD can be well protected. The static PCB copying power from the human body, the environment and even the internal PCB copying sub-equipment will cause various damages to the precision semiconductor chips, such as penetrating the thin insulating layer inside the components; destroying the gates of MOSFET and CMOS components; CMOS The trigger in the PCB copy board of the device is locked; the PN junction of the reverse bias is short-circuited; the PN junction of the positive PCB copy board is short-circuited to the bias; the PCB copy board melts the welding wire or aluminum wire of the PCB copy board in the active device. In order to eliminate the interference and damage to electronic equipment caused by electrostatic discharge (ESD), various technical measures need to be taken to prevent it. In the design of the PCB board, the anti-ESD design of the PCB can be realized through the layered and proper layout of the PCB copy board and the PCB copy board wiring and installation. During the design process, most design modifications can be limited to adding or removing components through prediction. By adjusting the PCB layout and wiring, the PCB copy board can be well prevented from ESD. Here are some common precautions.

Use multi-layer PCB as much as possible. Compared with double-sided PCB, ground plane and power plane, and closely arranged signal line-ground line spacing can reduce common-mode impedance and inductive coupling to 1/1 of double-sided PCB. 10 to 1/100. Try to place each signal layer as close to a power or ground layer as possible. For high-density PCBs with components on both top and bottom surfaces, with very short interconnects, and many ground fills, consider using inner layers. For double-sided PCBs, use tightly interwoven power and ground grids. The power wires are placed close to the ground wire, with as many connections as possible between vertical and horizontal wires or padding. The size of the grid PCB copy board on one side is less than or equal to 60mm. If possible, the grid size should be less than 13mm. Make sure that each circuit PCB copy board is as compact as possible. Keep all connectors aside as much as possible, and if possible, route the power PCB traces through the center of the card and away from areas that are directly affected by ESD. Place wide chassis grounds or polygon-filled grounds on all PCB layers below the connectors leading out of the chassis (easy PCB copy boards are directly hit by ESD) and connect them with vias at intervals of about 13mm together. Place the PCB copy board mounting holes on the edge of the card, and use the top and bottom pads of the PCB copy board without solder resist to connect to the chassis ground around the mounting holes. During PCB assembly, do not apply any solder to the top or bottom PCB pads. Use screws with embedded PCB washers to achieve close contact between the PCB and metal chassis PCB copy/shield or ground plane brackets. Between the chassis ground and the circuit ground of each layer, set the same "isolation area"; if possible, keep the separation distance of 0.64mm. On the top and bottom layers of the card near the mounting holes of the PCB copy board, connect the chassis ground and the circuit ground with a 1.27mm wide line along the chassis ground line every 100mm. Adjacent to these connection points, place pads or mounting holes for mounting between the chassis ground and the circuit ground PCB. These ground connections can be diced with a blade to keep them open, or jumpered with ferrite beads/high frequency capacitors. If the circuit board will not be placed in a metal chassis or a PCB copy board shielding device, solder resist should not be applied to the ground wires of the top and bottom chassis of the circuit board, so that they can be used as discharge electrodes for ESD arcs.

To set a ring ground around the circuit in the following PCB layout:
(1) Except that the edge is connected to the PCB copying device and the chassis ground, a ring ground path is placed around the entire periphery.
(2) Make sure that the annular width of all layers is greater than 2.5mm.
(3) Connect the rings with via holes every 13mm.
(4) Connect the ring ground to the common ground of the multi-layer PCB copy board circuit.
(5) For double-sided PCB copy boards installed in metal chassis or shielding devices, the ring ground should be connected to the circuit common ground. For unshielded double-sided circuits, the ring ground should be connected to the chassis ground. Solder resist should not be applied to the ring ground, so that the ring ground can act as a discharge bar for ESD. Place at least one place on the ring ground (all layers). 0.5mm wide gap, so as to avoid the PCB board to form a large loop. The distance between the signal wiring and the ring ground should not be less than 0.5mm.