In PCB design, effective anti-ESD measures can be achieved through careful layering, layout, and installation. By optimizing the PCB layout and routing, ESD risks can be significantly mitigated. *It is advisable to utilize multi-layer PCBs whenever possible. When compared to double-sided PCBs, incorporating ground and power planes, along with closely arranged signal line-ground spacings, can effectively reduce common mode impedance and inductive coupling, thus achieving performance levels comparable to double-sided designs, ranging from 10 to 1/100. Components are placed on both the top and bottom surfaces, connected by very short traces.
Static electricity generated from the human body, the environment, or even electronic devices can inflict various damages on precision semiconductor chips. This includes penetrating the thin insulating layers within components, damaging the gates of MOSFETs and CMOS devices, causing triggers in CMOS devices to become locked, short-circuiting reverse-biased PN junctions, short-circuiting forward-biased PN junctions, and melting solder or aluminum wires within active devices. To eliminate electrostatic discharge (ESD) interference and protect electronic equipment from damage, a variety of technical measures must be implemented.
In PCB design, effective anti-ESD strategies can be achieved through layering, appropriate layout, and installation. Throughout the design process, most modifications can be confined to the addition or removal of components based on predictions. By adjusting the PCB layout and routing, ESD can be effectively mitigated. Below are some common precautions to consider.
*Utilize multi-layer PCBs whenever possible. In comparison to double-sided PCBs, the presence of ground and power planes, along with closely spaced signal line-ground arrangements, can significantly reduce common mode impedance and inductive coupling, achieving levels of 1/10 to 1/100 compared to double-sided designs. Aim to position each signal layer as close as possible to a power or ground layer. For high-density PCBs featuring components on both sides, short connections, and numerous fills, consider utilizing inner layer routing.
*For double-sided PCBs, employ tightly interwoven power and ground grids. Position power lines in proximity to ground lines, maximizing connections between vertical and horizontal lines or filled areas. Ensure the grid size on one side does not exceed 60mm; if feasible, aim for a grid size of less than 13mm.
*Ensure that each circuit is as compact as possible.
*Keep all connectors positioned at the edges whenever feasible.
*If possible, route the power cord from the center of the card, maintaining distance from areas that are particularly vulnerable to ESD.
*On all PCB layers beneath connectors that exit the chassis (areas prone to direct ESD impact), place a wide chassis ground or polygonal fill ground, connecting them with vias approximately every 13mm.
*Position mounting holes at the card’s edge, and connect the top and bottom pads—without solder resist—around these holes to the chassis ground.
*During PCB assembly, refrain from applying solder to the top or bottom pads. Use screws with integrated washers to ensure close contact between the PCB and the metal chassis/shielding layer or the support on the ground plane.
*Establish a consistent “isolation zone” between the chassis ground and circuit ground on each layer; if feasible, maintain a separation distance of 0.64mm.
*On the top and bottom layers of the card near the mounting holes, connect the chassis ground and the circuit ground using a 1.27mm wide wire every 100mm along the chassis ground path. Place pads or mounting holes adjacent to these connection points for mounting between the chassis ground and the circuit ground. These ground connections can be severed with a blade to maintain circuit openness or bridged with magnetic beads or high-frequency capacitors.
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