{"id":2635,"date":"2026-10-19T15:00:00","date_gmt":"2026-10-19T07:00:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=2635"},"modified":"2026-10-08T20:14:54","modified_gmt":"2026-10-08T12:14:54","slug":"mobile-pcb-layout-risks","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/mobile-pcb-layout-risks\/","title":{"rendered":"What Should You Keep in Mind When Routing Mobile Phone PCBs? Layer Planning and RF Ribbon Trace Requirements"},"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<h2>1. Why Is PCB Routing for Cell Phones Unique?<\/h2>\n<p>Mobile phone motherboards are among the most challenging types of PCB designs, as they are subject to four constraints simultaneously:<\/p>\n<ul>\n<li><strong>Very cramped<\/strong>: The device is 7\u20138 mm thick, and the motherboard typically measures only 60\u2013100 cm\u00b2, yet it must accommodate over a hundred components.<\/li>\n<li><strong>Coexistence of RF and Digital Technologies<\/strong>: On the same board, there is both a \u2212100 dBm received signal and 1 W of transmit power, resulting in a dynamic range exceeding 130 dB.<\/li>\n<li><strong>Power-sensitive<\/strong>: Battery capacity is limited, so any additional link loss directly translates into a reduction in battery life.<\/li>\n<li><strong>EMC requirements are strict<\/strong>: It must pass electromagnetic compatibility testing conducted by carriers and in accordance with national regulations, and the user's body will alter the antenna characteristics when the device is held.<\/li>\n<\/ul>\n<p>These four points mean that mobile phone cabling cannot be installed according to general rules; instead, it must be categorized and handled based on signal type.<\/p>\n<p>The layout of a mobile phone PCB (Printed Circuit Board) is one of the key factors in ensuring the proper operation of the device\u2019s internal components. In this article, we will take an in-depth look at the issues to consider when routing mobile phone PCBs, as well as whether the display section requires special routing. The effectiveness of mobile phone PCB routing directly impacts the device\u2019s performance and stability, so special care must be taken during the design and manufacturing phases.<\/p>\n<h2>2. Part 1: Key Considerations for Mobile Phone PCB Layout<\/h2>\n<h3>2.1 Hierarchical Planning<\/h3>\n<p>In mobile phone PCB layout, multilayer board designs are commonly used. Each layer has specific functions and signal transmission requirements. The following is a general hierarchical structure for mobile phone PCB layout:<\/p>\n<ul>\n<li><strong>Layer 1: Device Layer<\/strong>: To hold various electronic components.<\/li>\n<li><strong>Layer 2: Signal Layer<\/strong>: It is primarily used to process signals, including address and data signals, as well as some analog circuits.<\/li>\n<li><strong>Layer 3: Stratum<\/strong>: A ground wire used to connect the various components.<\/li>\n<li><strong>Layer 4: Striped Line Layer<\/strong>: Including RF control cables, audio cables, analog interface cables, etc.<\/li>\n<li><strong>Layer 5: Stratum<\/strong>: Reconnect the ground wire.<\/li>\n<li><strong>Layer 6: Power Supply Layer<\/strong>: Includes various power supply lines, such as VBAT, LDO, VMEM, VEXT, VCORE, etc.<\/li>\n<li><strong>Layer 7: Signal Layer<\/strong>: For routing on the keyboard side.<\/li>\n<li><strong>Layer 8: Device Layer<\/strong>: Place the electronic components again.<\/li>\n<\/ul>\n<p>It\u2019s worth taking a closer look at the underlying logic of this eight-layer allocation, as it embodies two core principles of mobile phone board stacking design:<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Floor Number<\/th>\n<th>Features<\/th>\n<th>Why was it arranged this way?<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>L1 \/ L8<\/td>\n<td>Component Layer (Double-Sided Layout)<\/td>\n<td>Maximize component density and improve area utilization<\/td>\n<\/tr>\n<tr>\n<td>L2 \/ L7<\/td>\n<td>Signal Layer<\/td>\n<td>Adjacent to the ground\/power plane, with a complete return path<\/td>\n<\/tr>\n<tr>\n<td>L3 \/ L5<\/td>\n<td>Stratum<\/td>\n<td>Provides a reference plane and shielding for the upper and lower signal layers<\/td>\n<\/tr>\n<tr>\n<td>L4<\/td>\n<td>Strip-line layers (RF, audio, analog)<\/td>\n<td>Sandwiched between two layers of soil, naturally shielded\u2014the cleanest layer<\/td>\n<\/tr>\n<tr>\n<td>L6<\/td>\n<td>Power Layer<\/td>\n<td>Power lines are laid across the entire floor, resulting in low impedance and facilitating multi-point power distribution.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>Note the location of L4\u2014<strong>Place the most sensitive RF and analog lines between two ground planes<\/strong>...is a classic approach in mobile phone layered designs, providing shielding on both the top and bottom so that external interference cannot enter and internal radiation cannot escape. For system selection options for layered designs, see<a href=\"\/en\/blog\/pcb-layout-dieceng\/\">How to Choose the Right PCB Design Stack-Up Scheme<\/a>\u3002<\/p>\n<h3>2.2 Wiring Sequence<\/h3>\n<p>In mobile phone PCB layout, the order of routing is critical. Generally, routing should follow these principles:<\/p>\n<ul>\n<li><strong>RF Ribbon Cables and Control Cables<\/strong>: These lines should be installed first, especially near the antenna, to ensure signal quality.<\/li>\n<li><strong>Baseband RF Analog Interface Cable<\/strong>: Such as txramp_rf and afc_rf; these lines should follow immediately afterward.<\/li>\n<li><strong>Baseband Analog Line<\/strong>: This includes audio and clock lines, which must be routed carefully to ensure the quality of the audio and clock signals.<\/li>\n<li><strong>Analog and Digital Baseband Interface Cables<\/strong>: These lines are used to connect the analog baseband and digital baseband sections.<\/li>\n<li><strong>Power Cord<\/strong>: Power cables should be run last to avoid interfering with other signal cables.<\/li>\n<\/ul>\n<p>\"Start with the difficult tasks and move on to the easy ones\" is a general principle for wiring sequences:<strong>Place the items with the strictest constraints first; work around those with looser constraints.<\/strong>. RF cables have specific requirements for impedance, length, and ground connections, leaving almost no flexibility; power cables just need to be connected and wide enough, and they can be routed around obstacles at any time. Doing it the other way around will inevitably require rework.<\/p>\n<h2>3. Part Two: Specific Wiring Requirements<\/h2>\n<h3>3.1 RF Ribbon Cables and Control Cables<\/h3>\n<p>RF striplines and control lines on mobile phone PCBs require special care. Here are some key requirements:<\/p>\n<ul>\n<li>The line width of an RF stripline is typically 3 mil, and both the top and bottom layers must be surrounded by ground.<\/li>\n<li>The line widths for RF receive signal lines such as RX_GSM, RX_DCS, and RX_PCS are typically 8 mil.<\/li>\n<li>The line width of the antenna switch output lines should also be appropriate; it is generally 12 mil.<\/li>\n<\/ul>\n<p>3 mil (about 0.076 mm)\u2014this figure seems counterintuitive. Why is the most critical RF trace the thinnest? Because it runs through<strong>Stripline<\/strong>In this configuration, the structure is sandwiched between two layers, and the dielectric thickness is small; therefore, even at an impedance of 50 \u03a9, only a very narrow trace width is required. In contrast, microstrip lines that run on the surface, farther from the reference plane, require a wider trace width to achieve 50 \u03a9.<\/p>\n<p>Engineering Values for Common Impedance Targets:<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Signal Type<\/th>\n<th>Impedance Target<\/th>\n<th>Tolerance<\/th>\n<th>Structure<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>RF Main Line (TX\/RX)<\/td>\n<td>50 \u03a9 single-ended<\/td>\n<td>\u00b110% (some \u00b15%)<\/td>\n<td>Strip Line or Surface Microstrip<\/td>\n<\/tr>\n<tr>\n<td>IQ Differential Baseband<\/td>\n<td>100 \u03a9 differential<\/td>\n<td>\u00b110%<\/td>\n<td>Inner layer: must be of equal length<\/td>\n<\/tr>\n<tr>\n<td>USB \/ MIPI Differential<\/td>\n<td>90 \u03a9 differential<\/td>\n<td>\u00b110%<\/td>\n<td>Inner layer or outer layer<\/td>\n<\/tr>\n<tr>\n<td>Clock Line (13\/26 MHz)<\/td>\n<td>50 \u03a9<\/td>\n<td>\u00b115%<\/td>\n<td>Inner layer, land lease<\/td>\n<\/tr>\n<tr>\n<td>Audio Cable<\/td>\n<td>Impedance control is generally not performed.<\/td>\n<td>\u2014<\/td>\n<td>Just reserve the land<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1092\" height=\"615\" class=\"alignnone size-large wp-image-8803\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/practical-guide-for-high-speed-pcb-wiring.jpg\" alt=\"A Practical Guide to High-Speed PCB Routing\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/practical-guide-for-high-speed-pcb-wiring.jpg 1092w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/practical-guide-for-high-speed-pcb-wiring-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/practical-guide-for-high-speed-pcb-wiring-1024x577.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/practical-guide-for-high-speed-pcb-wiring-768x433.jpg 768w\" sizes=\"auto, (max-width: 1092px) 100vw, 1092px\" \/><\/p>\n<h3>3.2 Analog Cables for the RF Interface<\/h3>\n<p>Special attention should be paid to analog lines related to the RF interface, such as TXRAMP_RF and AFC_RF:<\/p>\n<ul>\n<li>These lines should be made as wide as possible and surrounded by ground lines on both sides; the line width is typically 6 mil.<\/li>\n<li>Differential signal lines such as QN_RF, QP_RF, IN_RF, and IP_RF also require precise routing, with a typical line width of 6 mil.<\/li>\n<\/ul>\n<p>TXRAMP_RF (Transmit Power Ramp Control) and AFC_RF (Automatic Frequency Control) are both<strong>Analog Control Voltage<\/strong>...The noise on these lines directly modulates the output power and frequency, so they must be isolated using a guard trace. The I\/Q differential pairs must be of equal length, with the length difference generally kept within 5 mil; otherwise, I\/Q phase imbalance will degrade the EVM.<\/p>\n<h3>3.3 Important Clock Lines<\/h3>\n<p>Clock lines in mobile phone PCBs are critical to the stability of the device. Here are some key requirements for clock lines:<\/p>\n<ul>\n<li>The wires connected to 13 MHz crystals and quartz crystals should be as short as possible and surrounded by ground wires on both sides.<\/li>\n<li>The line width of the clock line is typically 8 mil.<\/li>\n<li>Take special care when routing clock lines to minimize signal interference.<\/li>\n<\/ul>\n<p>The clock line is the signal in a cell phone most likely to cause interference: it is a periodic square wave containing a wealth of higher-order harmonics, with harmonics at 13 MHz extending all the way into the GHz band\u2014which falls precisely within the GSM reception band. Therefore, the rule is clear:<strong>Keep the slot as short as possible, ground it, locate it away from the receiving link, and do not let it cross the ground plane.<\/strong>. The ground plane beneath the clock circuit must remain intact and must not be interrupted by other traces. For general rules on high-speed routing, see<a href=\"\/en\/blog\/nine-high-speed-pcb-signal-routing-rules\/\">Nine Rules for High-Speed PCB Signal Tracing<\/a>\u3002<\/p>\n<h2>4. Part III: Other Wiring Requirements<\/h2>\n<p>In addition to RF and clock lines, there are many other important signal lines on a cell phone PCB that require attention:<\/p>\n<ul>\n<li>High-speed data lines, such as VSDI, VSDO, VSFS, BSIFS, BSDI, BSDO, BSOFS, ASDI, ASFS, and ASDO, should have an appropriate line width, typically 6 mil or greater.<\/li>\n<li>Reset and interrupt signal lines, such as LCD_RESET, SIM_RST, CAMERA_RESET, MIDI_RST, NFLIP_DET, MIDI_IRQ, IRQ_CAMERA_IO, IRQ_CAMERA_IO_X, and PENIRQ, with a line width of at least 6 mil.<\/li>\n<li>Power traces, especially those carrying high-current signals such as VBAT, LDO, VMEM, VEXT, and VCORE, must be sufficiently wide\u2014typically 40 mil or more.<\/li>\n<\/ul>\n<p>Summary of the logic behind selecting line widths for various signal types:<\/p>\n<div class=\"jp-tw\">\n<table>\n<thead>\n<tr>\n<th>Signal Categories<\/th>\n<th>Typical Line Width<\/th>\n<th>Basis for Determining Values<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>RF Stripline<\/td>\n<td>3 mil<\/td>\n<td>Determined by the 50 \u03a9 impedance and the thickness of the laminated dielectric<\/td>\n<\/tr>\n<tr>\n<td>RF Receiver Cable<\/td>\n<td>8 mil<\/td>\n<td>Impedance Control + Loss Reduction<\/td>\n<\/tr>\n<tr>\n<td>Antenna Switch Output<\/td>\n<td>12 mil<\/td>\n<td>Carry higher currents and reduce losses<\/td>\n<\/tr>\n<tr>\n<td>RF Analog Control Line<\/td>\n<td>6 mil<\/td>\n<td>Balancing Impedance and Manufacturability<\/td>\n<\/tr>\n<tr>\n<td>Clock Line<\/td>\n<td>8 mil<\/td>\n<td>Reduce impedance and minimize radiation<\/td>\n<\/tr>\n<tr>\n<td>High-Speed Data Cable<\/td>\n<td>\u22656 mil<\/td>\n<td>Impedance Control + Process Feasibility<\/td>\n<\/tr>\n<tr>\n<td>Reset\/Interrupt<\/td>\n<td>\u22656 mil<\/td>\n<td>Resist interference and prevent false triggers<\/td>\n<\/tr>\n<tr>\n<td>Power Supply (VBAT, etc.)<\/td>\n<td>\u226540 mil<\/td>\n<td>Calculate based on current-carrying capacity; control voltage drop<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The relationship between trace width and current-carrying capacity warrants separate verification: A 1-ounce copper trace with a width of 40 mil (approximately 1 mm) can carry approximately 2\u20133 A under a temperature rise of 10 \u00b0C. When VBAT supplies power to the PA, the peak current can reach 1\u20132 A; therefore, the trace should not only be 40 mil wide but also as short as possible, with additional vias used when changing layers.<\/p>\n<h2>5. Does the display section require special wiring?<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" class=\"alignnone size-large wp-image-8865\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/basic-rules-for-pcb-layout-and-wiring.jpg\" alt=\"Basic Rules for PCB Layout and Routing\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/basic-rules-for-pcb-layout-and-wiring.jpg 1280w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/basic-rules-for-pcb-layout-and-wiring-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/basic-rules-for-pcb-layout-and-wiring-1024x576.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/basic-rules-for-pcb-layout-and-wiring-768x432.jpg 768w\" sizes=\"auto, (max-width: 1280px) 100vw, 1280px\" \/><\/p>\n<p>This is the question posed in the title, and the answer is<strong>\u8981<\/strong>. The display interface (MIPI DSI) is a high-speed differential signal with three mandatory requirements:<\/p>\n<ul>\n<li><strong>Differential impedance: 100 \u03a9 (90 \u03a9 for some specifications)<\/strong>: Use the values specified in the display interface specifications, with a tolerance of \u00b110%.<\/li>\n<li><strong>Differential pairs are of equal length internally<\/strong>: Keep the length difference within 5 mil; the length difference between groups is generally \u226450 mil.<\/li>\n<li><strong>Complete Floor Plan<\/strong>: The reference plane beneath the differential pair must be continuous and must not cross a partition; otherwise, the sudden change in impedance will cause signal reflection.<\/li>\n<\/ul>\n<p>Two other points that are often overlooked: First, MIPI traces should be routed away from antennas and RF links (since the display is one of the largest sources of radiation in a cell phone); second, ESD protection components should be placed close to the connectors, and the ground path should be kept short.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"1280\" height=\"720\" class=\"alignnone size-large wp-image-8568\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/dfm-reliability-design-for-pcb-wiring.jpg\" alt=\"DFM Reliability Design for PCB Routing\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/dfm-reliability-design-for-pcb-wiring.jpg 1280w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/dfm-reliability-design-for-pcb-wiring-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/dfm-reliability-design-for-pcb-wiring-1024x576.jpg 1024w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/dfm-reliability-design-for-pcb-wiring-768x432.jpg 768w\" sizes=\"auto, (max-width: 1280px) 100vw, 1280px\" \/><\/p>\n<h2>6. After threading the needle: Five-Point Self-Check<\/h2>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"842\" height=\"474\" class=\"alignnone size-large wp-image-8807\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/accurate-line-resistance-control-for-established-wiring-methods.jpg\" alt=\"PCB\u65e2\u5b9a\u5e03\u7ebf\u65b9\u5f0f\u7684\u7cbe\u51c6\u7ebf\u7535\u963b\u63a7\u5236\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/accurate-line-resistance-control-for-established-wiring-methods.jpg 842w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/accurate-line-resistance-control-for-established-wiring-methods-300x169.jpg 300w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2023\/08\/accurate-line-resistance-control-for-established-wiring-methods-768x432.jpg 768w\" sizes=\"auto, (max-width: 842px) 100vw, 842px\" \/><\/p>\n<ol>\n<li><strong>DRC Full Inspection<\/strong>: Check whether the line width, spacing, and hole diameter are all within the board manufacturer\u2019s capabilities; compare against<a href=\"\/en\/capabilities\/\">PCB Manufacturing Capabilities<\/a>Verify.<\/li>\n<li><strong>Impedance Verification<\/strong>: Substitute the actual laminate parameters (including tolerances for copper thickness and dielectric thickness) into the calculation to verify that the impedance falls within the tolerance range.<\/li>\n<li><strong>Backflow Path Inspection<\/strong>: Is there a continuous ground plane beneath each high-speed\/RF signal, and are there any cross-sections?<\/li>\n<li><strong>Power Integrity<\/strong>: Does the power supply network have sufficient bandwidth and decoupling capacitors, and is the voltage drop within the allowable range?<\/li>\n<li><strong>DFM Check<\/strong>: Whether the distance from the component to the board edge, the pad spacing, the stencil apertures, and the shielding enclosure wall positions meet manufacturability requirements.<\/li>\n<\/ol>\n<h2>Conclusion<\/h2>\n<p>Mobile phone PCB routing is a critical part of mobile phone design. A well-designed layout and routing ensure unimpeded communication between the various internal components of the phone, thereby improving its performance and stability. When designing a mobile phone PCB, it is essential to follow the principles and requirements outlined above to ensure smooth manufacturing and outstanding performance.<\/p>\n<p><em>Want to learn more about mobile phone PCB routing?<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"600\" height=\"338\" class=\"alignnone size-large wp-image-8936\" src=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2024\/01\/pcb-high-frequency-circuit-board-wiring-precautions.jpg\" alt=\"Precautions for Routing High-Frequency PCBs\" srcset=\"https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2024\/01\/pcb-high-frequency-circuit-board-wiring-precautions.jpg 600w, https:\/\/www.jingpengpcb.com\/wp-content\/uploads\/2024\/01\/pcb-high-frequency-circuit-board-wiring-precautions-300x169.jpg 300w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<h2>7. Troubleshooting: Steps for Identifying the Cause of a Problem<\/h2>\n<p>If you encounter issues while debugging the mobile version, follow the steps below to troubleshoot as quickly as possible:<\/p>\n<ul>\n<li><strong>Test the passive components first<\/strong>: Use a vector network analyzer to measure the insertion loss and standing wave ratio of the RF link to confirm that the routing and matching are correct.<\/li>\n<li><strong>Test the active component again<\/strong>: Measure the output power, EVM, and receiver sensitivity to determine which part of the link is malfunctioning.<\/li>\n<li><strong>Check the power supply<\/strong>: Use an oscilloscope to examine the ripple in the PA's power supply; many spurious issues originate from the power supply.<\/li>\n<li><strong>Check the clock<\/strong>: Verify that the clock line is fully grounded and does not cross any partitions.<\/li>\n<li><strong>Check Blocked Items<\/strong>: Verify that the shielding enclosure is continuously grounded and that the gap size is significantly smaller than the wavelength.<\/li>\n<\/ul>\n<h2>Frequently Asked Questions<\/h2>\n<h3>1. Does the solder mask play a key role in the Javani effect?<\/h3>\n<p>Yes,<a href=\"\/en\/pcb-factory\/\">Solder Mask<\/a>Film peeling or side etching is one of the main causes of the Giavanni effect and is typically associated with the exposure and development processes.<\/p>\n<h3>2. How can the Javani effect be prevented?<\/h3>\n<p>Methods for preventing the Javani effect include maintaining film negatives, preventing solder mask issues, ensuring proper silver plating placement, and optimizing the design.<\/p>\n<h3>3. How can we improve the quality of the silver plating process?<\/h3>\n<p>Improving the quality of the immersion silver plating process requires chemical suppliers to select the appropriate chemicals, control the corrosion rate, and take appropriate measures regarding storage and handling.<\/p>\n<h3>4. What are the storage conditions for electroplated silver PCBs?<\/h3>\n<p>Electroplated silver PCBs should be stored in an environment with a temperature of 30\u00b0C and a relative humidity of 40%, and their storage period should be managed according to the first-in, first-out principle.<\/p>\n<h3>5. Why do RF cables need to be 50 \u03a9 instead of just any impedance?<\/h3>\n<p>This is because the inputs and outputs of each module (PA, filter, switch, antenna) in the RF link are designed for 50 \u03a9. Impedance mismatch causes reflections; the reflected power not only reduces transmission efficiency but also returns to the PA, leading to worsened VSWR or even damage. Engineering specifications generally require return loss to be \u2264\u221210 dB (VSWR \u22642:1) within the operating frequency band.<\/p>\n<h3>6. Why must differential pairs be of equal length?<\/h3>\n<p>Differential signals are transmitted via the voltage difference between two wires; unequal wire lengths can cause the signals to arrive at different times (skew). The greater the time difference, the greater the proportion of differential-to-common-mode components, resulting in reduced common-mode rejection and increased EMI. For high-speed differential pairs, the internal length difference is generally required to be \u22645 mil.<\/p>\n<h3>7. Why is the spacing between holes drilled in the ground so important?<\/h3>\n<p>If the two ground traces on the board are not connected to the main ground at multiple points, they will become floating conductors, which at high frequencies may actually act as radiating antennas or resonant cavities. Generally, ground vias are routed at a distance of \u03bb\/20 of the highest frequency of concern; at 2 GHz, this is approximately 3.75 mm, though in practice, a safer margin of 1\u20132 mm is often used.<\/p>\n<h3>8. Why should the power cord be run last?<\/h3>\n<p>Since power lines have the fewest constraints (they just need to be connected, wide enough, and have an acceptable voltage drop), they can be routed around other signals at any time. If power lines are routed first, the RF and high-speed lines routed later will be blocked by the channels occupied by the power lines, forcing you to either reroute the power lines or make critical signals take a longer path\u2014neither of which is ideal.<\/p>\n<h3>9. Why is HDI so widely used in mobile phone circuit boards?<\/h3>\n<p>This is because the component density is too high. Once the BGA pitch falls below 0.4 mm, through-holes cannot pass between the pads (there is no space between the pads to accommodate the holes), so blind vias and microvias must be used to route the signals directly to the inner layers. The number of layers in an HDI board (first-order, second-order, third-order, or arbitrary-layer) represents the degree of freedom in this routing; the higher the layer count, the higher the density\u2014and the higher the cost.<\/p>\n<h3>10. How can you verify during the design phase that the PCB manufacturer is capable of producing the board?<\/h3>\n<p>Four items that must be verified in advance: minimum line width and spacing, minimum via diameter (separately for mechanical drilling and laser drilling), impedance control capability (whether \u00b110% or \u00b15% can be achieved), and interlayer alignment capability. Compare these requirements with the PCB manufacturer\u2019s published capability chart, and clarify any ambiguities before placing an order. For the relationship between impedance and loss, see<a href=\"\/en\/blog\/impedance-and-loss-of-pcb\/\">The Effects of PCB Impedance and Loss on Signals<\/a>\u3002<\/p>\n<p><strong>Related Reading<\/strong>\uff1a<a href=\"\/en\/blog\/prototype-of-automotive-soft-rigid-flexible-composite-panels\/\">Points to Consider When Prototyping Automotive Rigid-Flex Boards<\/a> \u00b7 <a href=\"\/en\/blog\/pcb-multilayer-board-tg\/\">Stability and Reliability of Multilayer PCBs<\/a> \u00b7 <a href=\"\/en\/blog\/pcb-layout-routing-design-rules\/\">Basic Rules for PCB Routing<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>1. \u624b\u673a PCB \u5e03\u7ebf\u4e3a\u4ec0\u4e48\u7279\u6b8a \u624b\u673a\u4e3b\u677f\u662f PCB \u8bbe\u8ba1\u91cc\u96be\u5ea6\u6700\u9ad8\u7684\u4e00\u7c7b\uff0c\u56db\u4e2a\u7ea6\u675f\u540c\u65f6\u6536\u7d27\uff1a \u7a7a\u95f4\u6781\u7d27\uff1a\u6574 [&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 Should You Keep in Mind When Routing Mobile Phone PCBs? Layer Planning and RF Ribbon Trace Requirements","description":"What are the risks involved in mobile phone PCB routing? This article explains layer planning, routing sequence, and the specific requirements for RF ribbon cables, control lines, and analog lines. It provides ready-to-use parameter values and key operational guidelines."},"_slim_seo_primary_term_category":0,"_slim_seo_primary_term_post_tag":0,"footnotes":""},"categories":[405,26],"tags":[],"class_list":["post-2635","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\/2635","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=2635"}],"version-history":[{"count":5,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/2635\/revisions"}],"predecessor-version":[{"id":19896,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/posts\/2635\/revisions\/19896"}],"wp:attachment":[{"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/media?parent=2635"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/categories?post=2635"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jingpengpcb.com\/en\/wp-json\/wp\/v2\/tags?post=2635"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}