Static electricity from inside the human body, the environment, and even electronic equipment can cause various damage to delicate semiconductor chips, such as penetrating a thin insulating layer inside the component; damaging the gates of MOSFETs and CMOS components; and flip-flops in CMOS devices Short-circuited, reverse-biased PN junction; short-circuited forward-biased PN junction; melted weld line or aluminum wire inside the active device. In order to eliminate the interference and destruction of electronic devices by electrostatic discharge (ESD), various technical means are needed to prevent them. In the design of the PCB board, the anti-ESD design of the PCB can be realized by layering, proper layout and installation. In the design process, most of the design modifications can be limited to increasing or decreasing components through prediction. ESD can be well protected by adjusting the PCB layout. Here are some common precautions. * Use multi-layer PCB as much as possible. Compared to Double-sided PCB, the ground plane and power plane, as well as the tightly arranged signal line-ground spacing, can reduce the common mode impedance and inductive coupling to achieve a double-sided PCB. /10 to 1/100. Try to keep each signal layer close to a power or ground plane. For high-density PCBs with components on the top and bottom surfaces, short traces, and many fill locations, consider using inner traces. * For double-sided PCBs, use a tightly interwoven power and ground grid. The power cord is close to the ground, and should be connected as much as possible between the vertical and horizontal lines or the fill area. The grid size on one side is less than or equal to 60 mm, and if possible, the grid size should be less than 13 mm. * Make sure every circuit is as compact as possible. * Put all connectors aside as much as possible. * Set the same "Isolation Area" between the chassis ground and circuit ground of each layer; if possible, keep the separation distance 0.64mm. * When soldering the PCB, do not apply any solder to the top or bottom pads. Use a screw with an inset washer to make the PCB in close contact with the metal chassis/shield or ground plane bracket. * If possible, introduce the power cord from the center of the card and away from areas that are susceptible to direct ESD. * On all PCB layers below the connector that leads to the outside of the chassis (easy to be directly hit by ESD), place a wide chassis or polygon fill and connect them with vias every 13mm apart. . * Place a mounting hole on the edge of the card, and connect the top and bottom pads with no solder resist around the mounting hole to the chassis ground. * At the top and bottom of the card near the mounting hole, the chassis ground and circuit ground are connected together by a 1.27 mm wide line every 100 mm along the chassis ground. Adjacent to these connection points, pads or mounting holes for mounting are placed between the chassis ground and the circuit ground. These ground connections can be made with a blade to keep open or jump with magnetic beads/high frequency capacitors. * If the board is not placed in a metal chassis or shield, solder resists should not be applied to the top and bottom chassis grounds of the board so they can act as discharge electrodes for ESD arcs. * Set a circular ground around the circuit in the following way: (1) In addition to the edge connector and the chassis ground, a circular path is placed around the entire periphery. (2) Ensure that the annular width of all layers is greater than 2.5 mm. (3) Connect the ring shape with a via hole every 13mm. (4) Connect the ring ground to the common ground of the multilayer circuit. (5) For double panels installed in metal chassis or shielding devices, the ring ground should be connected to the circuit publicly. The unshielded double-sided circuit should be connected annularly to the chassis ground, and no solder resist should be applied to the annular ground so that the annular discharge can act as a discharge rod for the ESD, and at least one position on the annular ground (all layers) A 0.5mm wide gap prevents the formation of a large loop. The distance of the signal wiring from the annular ground cannot be less than 0.5 mm. * In the area that can be directly hit by ESD, a ground wire should be placed near each signal line. * The I/O circuit should be as close as possible to the corresponding connector. * For circuits susceptible to ESD, they should be placed close to the center of the circuit so that other circuits can provide some shielding. * A transient protector is usually placed at the receiving end. Connect to the chassis ground with short, thick wires (less than 5 times the width, preferably less than 3 times the width). The signal and ground wires coming out of the connector should be connected directly to the transient protector before they can be connected to other parts of the circuit. * Usually placed in series with resistors and beads on the receiving end, and for those cable drivers that are easily hit by ESD, consider placing resistors or beads in series on the drive end. * Place a filter capacitor at the connector or within 25 mm of the receiving circuit. (1) The thick and thin wires are connected to the chassis ground or the receiving circuit ground (the length is less than 5 times the width, preferably less than 3 times the width). (2) The signal line and the ground line are first connected to the capacitor and then connected to the receiving circuit. * Make sure the signal line is as short as possible. *When the length of the signal line is greater than 300mm, be sure to lay a ground wire in parallel. * Make sure that the loop area between the signal line and the corresponding loop is as small as possible. For every few centimeters of the long signal line, the position of the signal line and the ground line should be changed to reduce the loop area. * Drive signals from a central location of the network into multiple receiving circuits. * When possible, fill the unused areas with land and connect the fill areas of all layers every 60mm. * Make sure that the loop area between the power supply and ground is as small as possible, placing a high frequency capacitor close to each power supply pin of the integrated circuit chip. * Place a high frequency bypass capacitor within 80mm of each connector. * The reset line, interrupt signal line, or edge trigger signal line cannot be placed near the edge of the PCB. * Make sure to connect to ground at two opposite end positions of any large ground fill area (approximately greater than 25mm & TImes; 6mm). * When the length of the opening on the power supply or ground plane exceeds 8 mm, connect the sides of the opening with a narrow line. *Connect the mounting holes to the circuit ground or isolate them. (1) When the metal bracket must be used with a metal shielding device or a chassis, a zero ohm resistor is used for the connection. (2) Determine the mounting hole size to achieve reliable mounting of metal or plastic brackets. Large pads should be used on the top and bottom layers of the mounting holes. Solder resists should not be used on the bottom pads, and the underlying pads are not wave soldered. welding. * 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) High frequency filtering is used. (2) Keep away from the input and output circuits. (3) Keep away from the edge of the board. *The PCB should be inserted into the chassis, not at the open position or at the internal seam. * Pay attention to the wiring under the magnetic beads, between the pads, and the signal lines that may come into contact with the beads. Some beads have very good electrical conductivity and may create unexpected conductive paths. * If a chassis or motherboard has several boards installed, the board that is most sensitive to static electricity should be placed in the middle. microwave PCB Microwave PCB,Microwave Frequency PCB,Bare Copper Microwave PCB,High Frequency PCB Storm Circuit Technology Ltd , https://www.stormpcb.com
microwave PCB`s is a type of PCB designed to operate on signals in the megahertz to gigahertz frequency ranges (medium frequency to extremely high frequency). These frequency ranges are used for communication signals in everything from cellphones to military radars. The materials used to construct these PCB`s are advanced composites with very specific characteristics for dielectric constant (Er), loss tangent, and CTE (co-efficient of thermal expansion).
High frequency circuit materials with a low stable Er and loss tangent allow for high speed signals to travel through the PCB with less impedance than standard FR-4 PCB materials. These materials can be mixed in the same Stack-Up for optimal performance and economics.
The advantages of using materials with a low X, Y and Z CTE is a resulting PCB structure that will remain extremely stable in high temperature environments while operating at up to 40 GHz in analog applications. This allows for the effective placement of very fine pitch components including, in some cases, bare die-attach. Additionally, the low CTE materials will facilitate the alignment of multiple layers and the features they represent in a complex PCB Layout.
Features
.CTEr = +40/+50 ppm per °C (low); Tg (glass transition temperature) is 280°C
.ER = 3.38/3.48 at 10.0 GHz
.ER is constant to 40.0 GHz
.ED (electro-deposited) copper only
.Layer-to-layer thickness control = +/- 0.001
.Fabrication costs are typical to slightly increased
How to solve the ESD problem in PCB design?
In the design of the PCB board, the anti-ESD design of the PCB can be realized by layering, proper layout and installation. In the design process, most of the design modifications can be limited to increasing or decreasing components through prediction. ESD can be well protected by adjusting the PCB layout. Here are some common precautions.