{"id":1590,"date":"2026-10-13T09:00:00","date_gmt":"2026-10-13T01:00:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1590"},"modified":"2026-10-08T20:14:33","modified_gmt":"2026-10-08T12:14:33","slug":"pcb-rc-ground-to-chassis","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/pcb-rc-ground-to-chassis\/","title":{"rendered":"What is the purpose of a resistor-capacitor connection used for grounding between a PCB and a metal enclosure at a PCB manufacturing plant?"},"content":{"rendered":"<style>\n.jp-tw{overflow-x:auto;margin:26px 0;-webkit-overflow-scrolling:touch;}\n.jp-tw table{border-collapse:collapse;width:100%;min-width:560px;font-size:15px;line-height:1.65;background:#fff;}\n.jp-tw th,.jp-tw td{border:1px solid #dde3ea;padding:11px 14px;text-align:left;vertical-align:top;}\n.jp-tw thead th{background:#eef2f7;color:#1b2733;font-weight:700;white-space:nowrap;border-bottom:2px solid #c9d3de;}\n.jp-tw tbody tr:nth-child(even){background:#fafbfc;}\n.jp-tw tbody tr:hover{background:#f1f5fa;}\n.jp-tw tbody td:first-child{font-weight:600;color:#1b2733;}\n@media(max-width:767px){.jp-tw table{font-size:14px;min-width:520px;}.jp-tw th,.jp-tw td{padding:9px 11px;}}\n<\/style>\n<p>Grounding issues in electronic products have long been a topic of great interest. In this article, we will focus on grounding issues related to metal enclosures and circuit boards, as well as why high-voltage capacitors and resistors are used in some system designs to address this problem.<\/p>\n<h2>1. First, distinguish between the three meanings of \u201d\u5730\u201d<\/h2>\n<p>Before discussing chassis grounding, it is essential to distinguish between three concepts that are often confused; otherwise, the entire line of reasoning that follows will be flawed:<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Symbol<\/th>\n<th>Name<\/th>\n<th>Physical Meaning<\/th>\n<th>Are they at the same potential?<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>GND \/ SGND<\/td>\n<td>Signal Ground, Circuit Ground<\/td>\n<td>Reference potential points for all signals on the PCB<\/td>\n<td>It doesn't need to be grounded; it can operate while suspended in the air.<\/td>\n<\/tr>\n<tr>\n<td>EGND \/ Chassis<\/td>\n<td>Chassis Grounding, Protective Grounding<\/td>\n<td>The potential of a metal enclosure is typically connected to PE.<\/td>\n<td>It depends on whether the power distribution system complies with standards.<\/td>\n<\/tr>\n<tr>\n<td>PE<\/td>\n<td>Protected Areas (Land)<\/td>\n<td>A conductor that is truly grounded<\/td>\n<td>Defined as the zero-potential reference<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Ideally, these three should be at the same potential, but in reality this is often not possible:<strong>The enclosure may become loose due to improper electrical wiring.<\/strong>\uff0c<strong>There may be a power-frequency common-mode voltage on the PE.<\/strong>\uff0c<strong>Depending on the rectifier topology, the PCB's GND may not be directly connected to PE.<\/strong>(For example, directly connecting GND to PE after a 220 V rectifier bridge would cause a short circuit.) It is precisely because GND and EGND require the contradictory characteristics of \u201dlow-frequency isolation and high-frequency coupling\u201d that the parallel RC circuit solution was developed.<\/p>\n<h2>2. The Function of a Capacitor<\/h2>\n<p>Typically, in electronic devices, a high-voltage capacitor C1 (1\u2013100 nF\/2 kV) is connected in parallel between the ground (GND) of the PCB and the metal enclosure (EGND), along with a high-value resistor R1 (1 M). What is the rationale behind this design?<\/p>\n<h3>2.1 Electromagnetic Immunity (EMS) Perspective<\/h3>\n<p>The purpose of this capacitor is to reduce the impact of potential high-frequency interference on the circuit, assuming that PE (Protective Earth) is connected to ground. It suppresses the transient common-mode voltage difference between the circuit and the interference source, using ground potential as a reference. Although a direct connection between GND and PE is the most ideal scenario, such a connection may sometimes be impractical or unsafe. For example, when 220V AC passes through a rectifier bridge, the resulting GND cannot be connected to PE. Therefore, a path that allows low-frequency signals to pass while blocking high-frequency signals is required\u2014and this is the role of the capacitor.<\/p>\n<h3>2.2 Electromagnetic Interference (EMI) Perspective<\/h3>\n<p>\u4ece<a href=\"\/en\/capabilities\/\">EMI<\/a>From this perspective, if the metal chassis is connected to the PE, a high-frequency path is established that prevents high-frequency signals from radiating outward. A capacitor can block DC while allowing AC to pass through. This capacitor forms a high-frequency path that allows high-frequency interference within the circuit board to flow into the chassis and then into ground via the chassis, thereby preventing antenna radiation caused by high-frequency interference.<\/p>\n<h3>2.3 Electrostatic Protection<\/h3>\n<p>In some cases, the enclosure may lack a reliable ground connection, or the potential on the enclosure may be unstable, leading to electrostatic issues. If the circuit board is directly connected to the enclosure, this could result in damage to the chips on the board. By adding a capacitor, low-frequency high voltage and electrostatic discharge can be isolated, thereby protecting the circuit board. Typically, Y-capacitors or high-voltage film capacitors with capacitance values ranging from 1 nF to 100 nF should be selected.<\/p>\n<h2>3. How to Determine Capacitor Values: Don\u2019t Just Pick 1 nF at Random<\/h2>\n<p>The capacitance value determines \u201dthe frequency at which GND and the chassis are considered to be connected.\u201d The calculation is simple: it is the capacitive reactance:<\/p>\n<ul>\n<li><strong>Capacitive Reaction Formula<\/strong>: Xc = 1 \/ (2\u03c0\u00b7f\u00b7C). 1 nF is approximately 159 \u03a9 at 1 MHz and approximately 1.6 \u03a9 at 100 MHz.<\/li>\n<li><strong>Frequency of change<\/strong>: Use the frequency at which Xc equals the target impedance (typically 10\u2013100 \u03a9) as the starting point for \u201deffective connectivity.\u201d<\/li>\n<li><strong>Upper Bound Constraint<\/strong>: The higher the capacitance, the greater the power-frequency leakage current. Safety regulations impose strict limits on contact current, which is the fundamental reason why capacitance cannot be increased arbitrarily.<\/li>\n<\/ul>\n<p>The voltage rating should not be reduced arbitrarily either. This capacitor is connected between two \u201dgrounds\u201d where kV-level transients may occur,<strong>You must use a Y capacitor (safety-certified capacitor) or a high-voltage film capacitor.<\/strong>...Standard MLCCs will break down and short circuit under surge conditions, actually directing the dangerous voltage directly to the circuit board. Y capacitors are classified as Y1 (8 kV peak voltage rating) and Y2 (5 kV); Y2 or Y1 are commonly used in applications where the case is grounded.<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Capacitance<\/th>\n<th>1 MHz capacitive reactance<\/th>\n<th>10 MHz capacitive reactance<\/th>\n<th>50 Hz Capacitive Reactance<\/th>\n<th>Power-frequency leakage current (220 V)<\/th>\n<th>Applicable<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1 nF<\/td>\n<td>159 \u03a9<\/td>\n<td>15.9 \u03a9<\/td>\n<td>3.2 M\u03a9<\/td>\n<td>\u22480.07 mA<\/td>\n<td>Medical Devices with Stringent Leakage Current Requirements<\/td>\n<\/tr>\n<tr>\n<td>2.2 nF<\/td>\n<td>72 \u03a9<\/td>\n<td>7.2 \u03a9<\/td>\n<td>1.45 M\u03a9<\/td>\n<td>\u22480.15 mA<\/td>\n<td>Common Values for General IT Equipment<\/td>\n<\/tr>\n<tr>\n<td>4.7 nF<\/td>\n<td>34 \u03a9<\/td>\n<td>3.4 \u03a9<\/td>\n<td>0.68 M\u03a9<\/td>\n<td>\u22480.32 mA<\/td>\n<td>Optimizing When EMC Margin Is Insufficient<\/td>\n<\/tr>\n<tr>\n<td>10 nF<\/td>\n<td>15.9 \u03a9<\/td>\n<td>1.6 \u03a9<\/td>\n<td>0.32 M\u03a9<\/td>\n<td>\u22480.69 mA<\/td>\n<td>Industrial equipment must comply with safety regulations.<\/td>\n<\/tr>\n<tr>\n<td>100 nF<\/td>\n<td>1.6 \u03a9<\/td>\n<td>0.16 \u03a9<\/td>\n<td>32 k\u03a9<\/td>\n<td>\u22486.9 mA<\/td>\n<td>Typically exceeds the limit; limited to scenarios without a residual current limit<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1064\" height=\"878\" class=\"alignnone size-large wp-image-10099\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-single-point-grounding-and-multi-point-grounding.png\" alt=\"The Difference Between Single-Point and Multi-Point Grounding on PCBs\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-single-point-grounding-and-multi-point-grounding.png 1064w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-single-point-grounding-and-multi-point-grounding-300x248.png 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-single-point-grounding-and-multi-point-grounding-1024x845.png 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-single-point-grounding-and-multi-point-grounding-768x634.png 768w\" sizes=\"auto, (max-width: 1064px) 100vw, 1064px\" \/><\/p>\n<h2>4. The Function of Resistors<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" class=\"alignnone size-large wp-image-8712\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/high-speed-pcb-design-eliminates-crosstalk.jpg\" alt=\"Eliminating Crosstalk in High-Speed PCB Design\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/high-speed-pcb-design-eliminates-crosstalk.jpg 1280w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/high-speed-pcb-design-eliminates-crosstalk-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/high-speed-pcb-design-eliminates-crosstalk-1024x576.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/high-speed-pcb-design-eliminates-crosstalk-768x432.jpg 768w\" sizes=\"auto, (max-width: 1280px) 100vw, 1280px\" \/><\/p>\n<p>In addition to the capacitor, a large resistor R1 (1M) is usually connected in parallel. This resistor prevents damage to the circuit board caused by electrostatic discharge (ESD).<\/p>\n<h3>4.1 Preventing ESD<\/h3>\n<p>If only a capacitor is used to connect the PCB ground to the chassis ground, the PCB will become a floating ground system. During ESD testing or when used in complex electric field environments, charges entering the PCB will have nowhere to dissipate and will gradually accumulate. When the charge accumulates to a certain level\u2014exceeding the minimum voltage rating of the insulation between the circuit board and the chassis\u2014a discharge will occur. This discharge can generate currents ranging from tens to hundreds of amperes within a few nanoseconds, potentially causing circuit failure or damaging components connected near the discharge point. By connecting a resistor in parallel, the charge can be gradually dissipated, thereby eliminating the high voltage.<\/p>\n<h2>5. How Did We Arrive at 1 M\u03a9: Time Constants and Trade-offs<\/h2>\n<p>1 M\u03a9 is not a fixed answer; it is the intersection of two constraints:<\/p>\n<ol>\n<li><strong>Discharge rate constraint (requires a small value of R)<\/strong>: The discharge time constant is \u03c4 = R\u00b7C. Taking R = 1 M\u03a9 and C = 2.2 nF, \u03c4 \u2248 2.2 ms; the static charge is completely discharged within tens of milliseconds, which meets the test cycle requirement of 10 repeated ESD discharges. If R is increased to 10 M\u03a9, \u03c4 becomes 22 ms, and the charge will accumulate during continuous discharge.<\/li>\n<li><strong>Safety and Immunity Requirements (High R Required)<\/strong>: If R is too small, it will directly couple the power-frequency common-mode voltage from the enclosure into the circuit, while also reducing the system\u2019s insulation resistance to ground, which may result in failure of the withstand voltage test. R = 1 M\u03a9 typically strikes a balance between the two.<\/li>\n<\/ol>\n<p>Engineering Adjustment Rules:<strong>If ESD issues are severe, reduce R to 470 k\u03a9\u20131 M\u03a9; if power-frequency interference or withstand voltage tests fail, increase R to 2\u201310 M\u03a9.<\/strong>. In addition, the resistor must be selected<strong>Models with sufficient voltage rating and surge protection<\/strong>\u2014Standard 0805 surface-mount resistors have a voltage rating of only 150\u2013200 V; if connected across a point that may be subjected to kV-level transients, they will break down. High-voltage thick-film resistors or multiple resistors connected in series should be selected instead.<\/p>\n<h2>6. Complete Behavior of a Parallel RC Circuit: Three Frequency Bands<\/h2>\n<p>If we analyze the overall behavior of C and R connected in parallel in terms of frequency, it becomes clear why this combination can simultaneously satisfy these conflicting requirements:<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Frequency Band<\/th>\n<th>Key Component<\/th>\n<th>GND\u2013EGND Equivalent<\/th>\n<th>Design Objectives<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>DC \/ Mains (50\u201360 Hz)<\/td>\n<td>Resistance R<\/td>\n<td>High resistance (M\u03a9 range), effectively open-circuit but with a discharge path<\/td>\n<td>Isolates the power-frequency ground loop while slowly dissipating static electricity<\/td>\n<\/tr>\n<tr>\n<td>Medium frequency (kHz\u2013several MHz)<\/td>\n<td>R and C together<\/td>\n<td>Impedance as a Function of Frequency<\/td>\n<td>Transition zone: The impedance is determined by the two components in parallel.<\/td>\n<\/tr>\n<tr>\n<td>High frequency (several MHz and above)<\/td>\n<td>Capacitor C<\/td>\n<td>Low resistance (a few \u03a9 to tens of \u03a9), approximately a short circuit<\/td>\n<td>Provide a return path for common-mode noise to suppress radiated noise<\/td>\n<\/tr>\n<tr>\n<td>ESD \/ Surge Transients<\/td>\n<td>Capacitor C (in conjunction with R)<\/td>\n<td>Instantaneous low resistance; energy is clamped<\/td>\n<td>Divert transient energy to the housing rather than through the chip<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2>7. Comparison of Four Chassis Grounding Schemes<\/h2>\n<p>A RC parallel circuit is just one of four options; in actual projects, you must first determine which one to use:<\/p>\n<ul>\n<li><strong>Directly short-circuit<\/strong>: The chassis is directly connected to GND via copper posts or conductive springs. This provides the best EMC performance, but requires that the chassis be reliably connected to PE and that there be no topologies within the equipment that cannot be grounded (such as direct rectification). It is suitable for equipment with fixed installations and standardized grounding practices, such as industrial control systems and communication base stations.<\/li>\n<li><strong>RC Parallel Circuit<\/strong>: The solution discussed in this article, which balances EMC and floating ground safety, is the mainstream choice for consumer, medical, and portable devices.<\/li>\n<li><strong>Capacitance Only<\/strong>: Low-frequency signals are completely isolated, but there is a risk of charge buildup, so this method is generally not used on its own.<\/li>\n<li><strong>Fully Floating Ground<\/strong>: There is no electrical connection between the PCB and the enclosure. In fact, it is safer if the enclosure is poorly grounded (since the impedance of the power-frequency circuit is extremely high), at the cost of having to rely entirely on other measures for EMC.<\/li>\n<\/ul>\n<p>For information on choosing between single-point and multipoint grounding, please refer to<a href=\"\/en\/blog\/pcb-single-point-grounding-and-multi-point-grounding\/\">The Difference Between Single-Point and Multi-Point Grounding on PCBs<\/a>; For ground handling in digital\/analog hybrid systems, see<a href=\"\/en\/blog\/digital-analog-grounding-pcb-layout\/\">The Role of Digital, Analog, and Ground in PCB Layout<\/a>\u3002<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" class=\"alignnone size-large wp-image-10381\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-electrostatic-protection-design.jpg\" alt=\"Electrostatic Protection Design for PCBs\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-electrostatic-protection-design.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-electrostatic-protection-design-300x225.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcb-electrostatic-protection-design-768x576.jpg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<h2>8. Important Notes<\/h2>\n<p>When addressing grounding issues in electronic products, there are some important considerations:<\/p>\n<ul>\n<li>If the device enclosure is properly grounded, the PCB should be connected to ground at a single point on the enclosure. This helps eliminate power-frequency interference without causing interference to the PCB.<\/li>\n<li>If there are safety concerns regarding the equipment in its operating environment, it is essential to ensure that the equipment housing is securely fastened.<\/li>\n<li>To achieve better results, it is recommended that the device enclosure be connected as securely as possible, while the PCB should be connected to the enclosure at a single point. If the enclosure does not have a good ground connection, set the PCB to floating ground\u2014that is, do not connect it to the enclosure\u2014because in this case, the PCB is isolated from ground, and the loop impedance of power-frequency interference is extremely high, so it will not cause interference to the PCB.<\/li>\n<li>When multiple devices need to be connected to each other, it is best to ensure that each device\u2019s enclosure is connected to ground and that each device\u2019s PCB is connected to its respective enclosure at a single point.<\/li>\n<li>The enclosure may not be reliably grounded. This can occur when the power distribution network does not comply with safety standards, there is no ground wire, the soil around the grounding rod is too dry, or the grounding bolt is rusted or loose.<\/li>\n<li>In environments with electromagnetic interference\u2014such as those containing high-power transformers, high-power motors, induction cookers, and harmonics in high-voltage power grids\u2014the effects of grounding must also be taken into account.<\/li>\n<li>High-frequency noise may be generated within a PCB, such as from high-frequency switching transistors, diodes, storage inductors, and high-frequency transformers. These sources of interference can cause potential fluctuations between the PCB\u2019s signal ground and the chassis, or generate static electricity between them; therefore, ensuring proper and reliable grounding is essential and is a requirement of product safety standards.<\/li>\n<\/ul>\n<p>When addressing grounding issues in electronic products, taking into account both EMS and EMI considerations, as well as electrostatic protection requirements, can ensure the product\u2019s performance and reliability. Therefore, it is crucial to carefully consider grounding solutions when designing electronic products.<\/p>\n<h2>9. Six Key Points for Board-Level Implementation<\/h2>\n<p>Even if the schematic is correct, it still needs to be properly implemented on the PCB; otherwise, the results will be significantly compromised:<\/p>\n<ol>\n<li><strong>Connection Point Locations<\/strong>: The RC network must be placed<strong>Single-point grounding<\/strong>Do not connect too many points, or else a ground loop will form.<\/li>\n<li><strong>Trace Length<\/strong>: The longer the leads on this capacitor, the greater the parasitic inductance, and the poorer the high-frequency performance. An ESL of 1 nH results in a resistance of 0.6 \u03a9 at 100 MHz, which is enough to cause a low-impedance path to fail.<\/li>\n<li><strong>Reliability of Enclosure Connections<\/strong>: The chassis connection points must be made<strong>Conductive oxidation treatment or protective coating<\/strong>, use a star-shaped washer (toothed washer) to pierce the oxide layer; otherwise, the contact resistance will increase over time.<\/li>\n<li><strong>Creepage Distance<\/strong>: The creepage distance and clearance on the PCB between the two terminals of the Y capacitor must comply with safety regulations; slots should be cut where necessary.<\/li>\n<li><strong>Avoid cross-segmentation<\/strong>: There should be no ground-level expansion joints beneath the area where the grounding point is located; otherwise, the detour in the return path will create a new source of radiation.<\/li>\n<li><strong>Testing Reserved<\/strong>: Leave a jumper or a 0\u03a9 position that allows the RC network to be disconnected, to facilitate comparison of the \u201dconnected\/disconnected\u201d effects during EMC debugging. For information on the role of a 0\u03a9 resistor in this type of debugging, see<a href=\"\/en\/blog\/impedance-matching-and-0-ohm-resistance\/\">Impedance Matching and 0-Ohm Resistors in PCB Design<\/a>\u3002<\/li>\n<\/ol>\n<h2>10. Common Failures and Countermeasures<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"767\" height=\"431\" class=\"alignnone size-large wp-image-10092\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/application-of-0-ohm-resistor-in-circuit-design.jpg\" alt=\"Applications of 0-Ohm Resistors in Circuit Design\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/application-of-0-ohm-resistor-in-circuit-design.jpg 767w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/application-of-0-ohm-resistor-in-circuit-design-300x169.jpg 300w\" sizes=\"auto, (max-width: 767px) 100vw, 767px\" \/><\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Phenomenon<\/th>\n<th>Root Cause<\/th>\n<th>Verification Methods<\/th>\n<th>Countermeasures<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>How many ESD test cycles cause failure?<\/td>\n<td>The resistance is too high, causing the charge to discharge slowly.<\/td>\n<td>Shorten the discharge interval and retest<\/td>\n<td>R drops to 470 k\u03a9\u20131 M\u03a9<\/td>\n<\/tr>\n<tr>\n<td>Dielectric Strength Test\u2014Breakdown<\/td>\n<td>Insufficient voltage rating of the capacitor or inadequate creepage distance<\/td>\n<td>Verify Capacitor Specifications and PCB Spacing<\/td>\n<td>Replace the Y1 capacitor and add a slot to increase the creepage distance<\/td>\n<\/tr>\n<tr>\n<td>Conduction Emissions Exceed Limits<\/td>\n<td>The capacitance is too low, and the high-frequency circuit impedance is high.<\/td>\n<td>Comparison Test of Increased Capacitance<\/td>\n<td>C: 4.7\u201310 nF (leakage current must be accounted for)<\/td>\n<\/tr>\n<tr>\n<td>Excessive contact current<\/td>\n<td>The capacitance is too high<\/td>\n<td>Measured using a contact current tester<\/td>\n<td>C drops to 1\u20132.2 nF<\/td>\n<\/tr>\n<tr>\n<td>Grounding failure after a period of use<\/td>\n<td>Oxidation at the housing connection points; loose bolts<\/td>\n<td>Measuring Ground Resistance<\/td>\n<td>Star washers, conductive plating, periodic tightening<\/td>\n<\/tr>\n<tr>\n<td>Power-line hum in the input signal<\/td>\n<td>Multiple grounding points create a ground loop<\/td>\n<td>Comparison of Partial Ground Break Points<\/td>\n<td>Change to single-point grounding<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" class=\"alignnone size-large wp-image-8632\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcba-electrical-reliability.jpg\" alt=\"Ensuring Electrical Reliability in PCBA Product Design\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcba-electrical-reliability.jpg 1280w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcba-electrical-reliability-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcba-electrical-reliability-1024x576.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/pcba-electrical-reliability-768x432.jpg 768w\" sizes=\"auto, (max-width: 1280px) 100vw, 1280px\" \/><\/p>\n<p>When performing on-site grounding corrections, follow these three steps; the issue is usually resolved in a single round:<\/p>\n<ul>\n<li><strong>Step 1: Check whether the chassis is actually grounded<\/strong>. Use an earth resistance tester to measure the impedance between the chassis and the PE conductor; if it exceeds 0.1 \u03a9, first address the mechanical connection (remove oxidation, add star washers, and tighten the bolts). This step can resolve half of the \u201dgrounding issues.\u201d<\/li>\n<li><strong>Step 2: Compare the three states: \u201dDirect Connection \/ RC Circuit \/ Floating Ground\u201d<\/strong>. Reserve a jumper or a 0\u03a9 position at the test point; measure radiated emissions and ESD once for each of the three states, and select the optimal one.<\/li>\n<li><strong>Step 3: Fine-tune the parameters of the selected solution<\/strong>. First, adjust the capacitance (which affects EMC and leakage current), then adjust the resistance (which affects ESD and power-frequency immunity), changing only one variable at a time.<\/li>\n<\/ul>\n<h2>Frequently Asked Questions<\/h2>\n<h3>1. Why do electronic devices need to be grounded?<\/h3>\n<p>Electronic devices require grounding to ensure circuit stability and safety. Grounding prevents the discharge of static electricity, reduces electromagnetic interference, and protects users.<\/p>\n<h3>2. Why use capacitors and resistors for grounding?<\/h3>\n<p>Capacitors and resistors play an important role in grounding. Capacitors can reduce high-frequency interference while maintaining circuit stability, while resistors help prevent damage to the circuit caused by electrostatic discharge.<\/p>\n<h3>3. Why is it necessary to connect the circuit board to the enclosure?<\/h3>\n<p>Connecting the circuit board to the enclosure effectively reduces electromagnetic interference while providing greater safety. This connection ensures that the circuit board and the enclosure share the same ground potential, thereby reducing interference and protecting the circuitry.<\/p>\n<h3>4. What is electrostatic discharge (ESD)?<\/h3>\n<p>Electrostatic discharge refers to the process by which electrical charges transfer from one object to another under certain conditions, typically generating high voltages and currents. This can cause damage to electronic devices and circuits.<\/p>\n<h3>5. Why is it important to consider grounding solutions?<\/h3>\n<p>The choice of grounding scheme affects the performance and reliability of electronic products. Different application scenarios require different grounding schemes, so careful consideration is necessary to ensure the product functions properly.<\/p>\n<h3>6. Can I keep only one of the capacitor and resistor?<\/h3>\n<p>This is not recommended. Leaving only the capacitor will cause the circuit board to become a floating ground system, where electrostatic charges have nowhere to dissipate and gradually accumulate, eventually leading to breakdown and discharge. Leaving only the resistor, on the other hand, means that high-frequency common-mode noise lacks a low-impedance return path, resulting in radiated emissions that exceed standards. The two components address issues in different frequency bands and are both essential.<\/p>\n<h3>7. Why does this capacitor have to be a Y capacitor?<\/h3>\n<p>Because it is connected across two ground points that may be subjected to kV-level transients (surge, ESD), a standard MLCC would break down and short-circuit under such transients, thereby directing the dangerous voltage directly to the circuit board. Y capacitors are safety-certified; their failure mode is an open circuit rather than a short circuit, and their voltage ratings are clearly specified (Y1 is 8 kV peak, Y2 is 5 kV).<\/p>\n<h3>8. Can the 1 M\u03a9 resistor be replaced with one of a different resistance value?<\/h3>\n<p>Yes, but adjustments must be made to meet two constraints: ESD discharge requires a low resistance value (the time constant \u03c4 = R\u00b7C must be much smaller than the discharge interval), while power-frequency immunity and insulation requirements call for a high resistance value. When ESD issues are severe, the resistance should be reduced to 470 k\u03a9\u20131 M\u03a9; when power-frequency interference or withstand voltage requirements are not met, it should be increased to 2\u201310 M\u03a9. At the same time, the resistor itself must have sufficient withstand voltage; standard surface-mount resistors typically have a withstand voltage of only 150\u2013200 V.<\/p>\n<h3>9. What should you do if the enclosure isn't properly grounded?<\/h3>\n<p>It is best to configure the PCB as a floating ground, meaning it has no electrical connection to the chassis. In this configuration, the PCB is isolated from ground, and the loop impedance for power-frequency interference is extremely high, so it will not cause interference on the PCB. The trade-off is that EMC issues must be addressed through other means (filtering, shielding, layout). In this scenario, installing a RC network may actually introduce interference.<\/p>\n<h3>10. \u963b\u5bb9\u7f51\u7edc\u653e\u5728 PCB \u7684\u54ea\u4e2a\u4f4d\u7f6e\u6700\u597d\uff1f<\/h3>\n<p>\u653e\u5728\u552f\u4e00\u90a3\u4e2a\u5355\u70b9\u63a5\u5730\u70b9\u4e0a\uff0c\u4e14\u5c3d\u91cf\u9760\u8fd1\u673a\u58f3\u8fde\u63a5\u67f1\uff08\u87ba\u9489\u5b54\uff09\u3002\u5f15\u7ebf\u8d8a\u77ed\u8d8a\u597d\uff0c\u56e0\u4e3a\u5f15\u7ebf\u7535\u611f\u4f1a\u76f4\u63a5\u62b5\u6d88\u7535\u5bb9\u7684\u9ad8\u9891\u6548\u679c\u3002\u63a5\u5730\u70b9\u6240\u5728\u533a\u57df\u4e0b\u65b9\u4e0d\u8981\u6709\u5730\u5e73\u9762\u5206\u5272\u7f1d\u9699\uff0c\u5426\u5219\u56de\u6d41\u8def\u5f84\u7ed5\u884c\u4f1a\u4ea7\u751f\u65b0\u7684\u8f90\u5c04\u6e90\u3002<\/p>\n<p><strong>Related Reading<\/strong>\uff1a<a href=\"\/en\/blog\/how-to-correctly-connect-the-ground-wire\/\">How to Properly Connect a Ground Wire and Choose the Right Grounding Method<\/a> \u00b7 <a href=\"\/en\/blog\/pcb-english-part-1\/\">Chinese-English Glossary of Common Technical Terms Used in Printed Circuit Board Manufacturing<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>\u7535\u5b50\u4ea7\u54c1\u7684\u63a5\u5730\u95ee\u9898\u4e00\u76f4\u662f\u4e00\u4e2a\u5907\u53d7\u5173\u6ce8\u7684\u8bdd\u9898\u3002\u5728\u672c\u6587\u4e2d\uff0c\u6211\u4eec\u5c06\u91cd\u70b9\u8ba8\u8bba\u91d1\u5c5e\u5916\u58f3\u4e0e\u7535\u8def\u677f\u7684\u63a5\u5730\u95ee\u9898\uff0c\u4ee5\u53ca\u4e3a\u4ec0\u4e48\u5728\u4e00 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"What is the purpose of a resistor-capacitor connection for grounding between a PCB and a metal enclosure at a PCB factory? - Jingpeng Electronics","description":"Why is a resistor-capacitor combination connected between the PCB ground and the metal chassis? This article explains the respective roles of capacitors and resistors from the perspectives of EMI, EMS, and electrostatic protection. It also highlights common misconceptions to help you avoid easily overlooked details."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[405,26],"tags":[],"class_list":["post-1590","post","type-post","status-publish","format-standard","hentry","category-pcb-design","category-blog"],"_links":{"self":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1590","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/comments?post=1590"}],"version-history":[{"count":3,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1590\/revisions"}],"predecessor-version":[{"id":19878,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/1590\/revisions\/19878"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=1590"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=1590"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=1590"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}