PCB Technical - In what way do duplex PCBs use power and grounding nets?

Here are some common preventive measures. Use multi-layer PCBs as much as possible, ground planes and power planes, and tightly arranged signal lines-ground spacing can reduce common mode impedance and perceive coupling to double-sided PCBs from 1/10 to 1/100 to double-sided PCBs. Each signal layer is as close as possible to the power layer or ground layer.

For high-density PCBs with components on the top and bottom surfaces, with very short connectors and many fill positions, consider using internal wires. For duplex PCBs, please use tightly interwoven power and ground nets. The power line is close to the ground line, and connect it between the vertical and horizontal lines or the filled area as much as possible.

By adjusting the PCB layout and routing, ESD can be well protected. Static electricity from the human body, the environment and even electronic equipment can cause various damages to complex semiconductor chips, such as penetrating the thin insulating layer inside the component; damaging the gate of MOSFET and CMOS components; the trigger in the locked CMOS device; the short-circuited pn Junction; and short-circuit forward-biased PN junction; solder or aluminum wire to melt the inside of the active device.

In order to eliminate electrostatic discharge (ESD) interference and damage to electronic equipment, it is necessary to take various technical measures to prevent it. In the design of PCB board, PCB anti-ESD design can be realized by layering, proper layout and installation. During the design process, the vast majority of design modifications can be limited to the addition or reduction of components through prediction. By adjusting the PCB layout and routing, ESD can be well protected.

One side of the grating size is less than or equal to 60mm. If possible, the grating size should be less than 13mm.

Make sure that each circuit is as compact as possible.

Put all the connectors aside as much as possible.

If possible, bring in the power cord from the center of the card and keep it away from areas susceptible to ESD.

Place a wide chassis or polygonal filler on all PCB layers under the connectors that lead to the outside of the chassis (directly hit by ESD), and connect them together at about 13mm intervals.

Place the mounting holes on the edge of the card and connect the mounting holes around the top and bottom pads of non-blocking flux to the chassis bottom panel. When assembling the PCB, do not apply any solder on the top or bottom pads.

Use screws with embedded washers to achieve close contact between the PCB and the metal chassis/shield or ground support.

Set the same "isolation" between the chassis and the circuit on each floor, and if possible, the separation distance is 0.64mm. At the top and bottom of the card near the mounting hole, the chassis and circuit are connected to 1.27mm wide lines every 100mm along the chassis ground. Near these connection points, place the pads or mounting holes for mounting between the chassis and the circuit.

These ground connections can cross the blades to keep the road clear, or use beads/high frequency capacitors to jump.

If the circuit board is not placed in a metal chassis or shielding device, it cannot be coated on the top layer of the circuit board and the bottom layer of the bottom frame, so that they can be used as discharge electrodes for ESD arcs.

Set up a ring ground around the circuit in the following ways:

(1) In addition to the edge connector and chassis area, place a circular path around the entire perimeter.

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

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

(4) Connect the ring ground to the common ground of the multilayer circuit.

(5) PCB copy board For double-sided boards installed in metal chassis or shielding devices, the ring ground should be connected to the circuit in a common way. The unshielded double-sided circuit should be connected to the chassis, and the ring floor should not be coated so that the ring ground can be used as an ESD discharge rod. Place at least one 0.5mm wide gap (all layers) in a certain position of the ring to avoid large ring. The signal wiring distance of the ring ground cannot be less than 0.5mm.