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Anti static Methods in PCB Design
29Nov
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Anti static Methods in PCB Design

Anti statIC Methods in PCB Design
In the design of PCB board, the system's ESD resistant design PCB board can be realized by layering, reasonable layout, and installation During the design process, most design modifications may be limited to adding or removing components through prediction ESD can be well prevented by adjusting PCB board Here are some common precautions: Use as many multilayer PCB boards as possible Compared with the double-sided PCB board s, the ground plane and the power plane, as well as the closely arranged signal lines and ground wire spacing can reduce the common mode impedance and inductive coupling, making it possible to realize the double-sided PCB board s 1./10 to 1/100. Try to place each signal layer as close to the power layer or ground plane as possible For high-density PCB with components on the top and bottom surfaces, with very short interconnects, and many ground fillers, consider using an inner layer
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Double sided PCB board, using closely intertwined power supply and grounding grid The power cord shall be close to the grounding wire, and the vertical and horizontal conductors or pads shall be connected as much as possible The grid size on one side shall be less than or equal to 60mm, and if possible, the grid size shall be less than 13mm Ensure that each circuit is as compact as possible Lay all connectors aside as far as possible If possible, pass the power cable through the center of the card and away from the area directly affected by ESD Place wide chassis grounds or polygon fills on all PCB layers below the connectors leading out of the chassis (which are prone to be hit directly by ESD) and connect them together with vias about 13mm apart.  Place the mounting hole on the edge of the board. The top and bottom pads around the mounting hole are solderless to connect the main housing to ground During PCB assembly, do not apply any solder to the top or bottom pads Use the screws with included washers to make the mask or bracket on PCB board and metal chassis/ground plane The same "isolation zone" shall be set between chassis grounding and circuit grounding of each layer; If possible, maintain a spacing of 0.64 mm Use 1 to connect chassis grounding and circuit grounding. There are 27mm wide conductors every 100mm along the grounding wire of the main housing at the top and bottom of the board near the mounting hole Adjacent to these connection points, place shims or mounting holes between chassis ground and circuit ground These ground connections can be cut with a blade to keep them open, or jumper/high-frequency capacitors with ferrite beads
If the circuit board is not placed in the metal base or mask, do not apply solder resistance on the top and bottom base grounding of the circuit board, so that they can be used as the discharge electrode of ESD arc.
Set ring grounding around the circuit as follows:
1) In addition to the edge connector and the chassis grounding, a ring grounding path is set around the entire perimeter.
2) Ensure that the annular width of all layers is greater than 2.5mm.
3) Connect rings with through holes every 13mm.
4) Connect the ring ground to the common ground of the multilayer circuit.
5) For double-sided panels instalLED in metal cabinets 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 main housing ground. Welding resistance flux shall not be applied on the ring grounding, so that the ring grounding can be used as the discharge rod of ESD. Place at least one position (all layers) on the circular ground. 0.5mm wide gap to avoid large loop. The distance between signal wire and ring grounding shall not be less than 0.5mm.
In areas that may be directly affected by ESD, ground wires shall be laid near each signal line. The input/output circuit shall be as close to the corresponding connector as possible. Circuits susceptible to ESD shall be placed close to the center of the circuit so that other circuits can provide some masks for them. Generally, series resistors and magnetic beads are placed at the receiving end. For cable drivers that are vulnerable to ESD impact, series resistors or magnetic beads can also be considered at the driving end. The transient protector is usually placed at the receiving end. Use short and thick wires (less than 5 times in width and less than 3 times in width) to connect to the main housing for grounding. The signal wire and ground wire from the connector shall be directly connected to the transient protector before connecting to the rest of the circuit. The filter capacitor shall be placed at the connector or within 25 mm of the receiving circuit.
1) Use short and thick wires to connect the chassis grounding or the receiving circuit grounding (the length is less than 5 times of the width and less than 3 times of the width).
2) The signal line and ground wire are first connected to the capacitor, and then to the receiving circuit.
Make sure the signal line is as short as possible. When the length of signal line is greater than 300mm, the grounding wire must be laid in parallel. Ensure that the loop area between the signal line and the corresponding loop is as SMAll as possible. For long signal lines, the positions of signal lines and ground wires need to be changed every few centimeters to reduce the loop area. The signal is driven from a central location in the network to a plurality of receiving circuits. To ensure that the loop area between the power supply and the grounding is as small as possible, a high-frequency capacitor is placed near each power pin of the IC chip. Place the high-frequency bypass capacitor within 80mm of each connector. Where possible, fill unused areas with ground, joining all layers of filled ground every 60mm. Make sure to connect to the ground at two opposite ends of any large ground fill area (approximately larger than 25mm x 6mm). When the length of the opening in the power or ground plane exceeds 8mm, use narrow wires to connect both sides of the opening. The reset line, interrupt signal line or edge trigger signal line cannot be placed near the edge of PCB. Connect the mounting hole to the circuit common or isolate it.
1) When metal support must be used with metal mask device or chassis, zero ohm resistor shall be used for connection.
2) Determine the size of the mounting hole to achieve reliable installation of metal or plastic support. Use large shims at the top and bottom of the mounting holes. Do not use solder resist on the bottom pad and ensure that the bottom pad does not pass wave soldering.
Protected signal lines and unprotected signal lines cannot be arranged in parallel. Pay special attention to the wiring of reset, interrupt and control signal lines.
1) To use high-frequency filtering.
2) Keep away from input and output circuits.
3) Keep away from the edge of the circuit board.
This PCB should be inserted into the main housing and not installed in the opening or internal seam Pay attention to the wiring under the bead, between the pads, and the signal wires that may contact the beads Some magnetic beads are very conductive and may generate unexpected conductive paths If a main housing or main board will contain multiple PCB boards, the electrostatic sensitive PCB board should be placed in the middle

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