2. It is performed by placing a terminating resistor in between the driver and the receiver. 3. Series Termination. 8 * W + T)]) ohms. In differential pairs, each trace in the pair carries the same magnitude, but opposite polarity. Frequency with Altium Designer. Also Clock lines should be kept away from other signal and Clock lines to a minimum of 5x the trace width or larger if space allows. Traces and their widths should be sized. Therefore, their sum must add to zero. Here’s how length matching in PCB design works. 5 High Speed USB Bias Filter AT85C51SND3Bx high-speed USB design requires a 6. 0uF. Differences Between I2C vs. 1. 16,416. 7 dB to 0. My shortest signal needs 71*3. I2C Routing Guidelines: How to Layout These Common. We only ever have perfect matching at specific frequencies, but there are mid-range frequencies where the return loss spectrum is flat. 254mm. SPI vs. SPI vs. Here’s how length matching in. Dispersion in the PCB substrate causes the signal velocity to vary with frequency. SPI vs. Here’s how length matching in PCB design works. SPI vs. A PCB trace is a thin conductor on a printed circuit board (PCB) that carries electrical signals between components. I have done the impedance calculations to figure out the track geometry needed for 100 ohm differential impedance and confirmed it with the board house. Intra-pair skew is the term used to define the difference between the etch length of the + and - lane of a differential pair. 005 inches wide, but you may have specific high speed nets that need 0. Observation: A 3cm microstrip and a 3cm stripline can get a very different propagation delay! Conclusion: If we would route a bundle of traces, eg. you can use simulations found within your PCB design software to find the amount of source impedance needed to match the trace and the load. Optimization results for example 2. Diorio: Transmission lines 12Track length matching is key when trying to maximise the performance of your PCB. Here’s how length matching in PCB design works. PCB traces must be very short. also your traces might be perfectly matched for a narrow frequency band, but not for other frequencies. More important will be to avoid longer stubs. How to do PCB Trace Length Matching vs. PCB trace length matching vs frequency affects the signal integrity of your circuit designs. Differential pairs are very simple: they are composed of two traces, routed side-by-side, and that carry equal magnitude and opposite polarity signals on each trace. Detangling the hair of a 9-year old doesn’t take as long as routing PCB traces, but the results are just as painful if not done correctly. When a design requires equal-length traces between the source and multiple loads, you can bend some traces to match trace lengths (refer to Figure 24). ε. The extent of this problem will depend on the bus speed, the length of the traces, the trace geometries, the type of fiberglass weave used, and the alignment of the traces to the weave pattern of a PCB. Documentation must somewhere state need of length/impedance matching; Each bus (data, address, control) should preferably be routed on its own layer. Keeping traces short is another way to combat reflections and ringing. I2C Routing Guidelines: How to Layout These Common. This characterstic impedance is independent of length and trace material. The loss increases linearly with the length of the PCB trace. There is another important point to consider, which is trace length matching for parallel buses. Altium DesignerWhat are the differences between subclass 1 and subclass 2? Part 2 delves in timing requirements related to deterministic latency and factors for choosing one subclass over another. PCB trace length matching is exactly as its name suggests: you are matching the lengths of two or more PCB traces as they are routed across a board. With today’s technology, Fast Ethernet (100BASE-TX) and Gigabit Ethernet (1000BASE-T) are. Every board material has a characteristic dielectric loss factor. Here’s how it works. (TMDS) signal traces Ground plane Power plane Low-frequency, single-ended traces Layer 1: Layer 2: Layer 5: Layer 6: High-speed, differential signal traces Ground Vcc2 Low-frequency, single-ended traces Layer 4: Ground Layer 3: Vcc1 5 - 10 mils 20 - 40 mils 5 - 10 mils Fig. These specifications can be found in datasheets, and you should set your high speed design constraints to hold these length specifications. 3) Longer traces will not limit the maximum. significantly reduce low-frequency power supply noise and ripple. 4 Implementing RGMII Internal Delays With DP83867The sections below describe these steps in more detail. The basic idea of this length matching is that the shorter trace follows a detour or meander in order to lengthen it to match the length of the longer trace. The variation in FR4 dielectric constant vs. (5) (6) From the results above we can see that the setup and hold margin are both greater than 0 as desired. The PCB trace to the flex cable 4. It may be convenient to use the same trace width across the entire design, yet it certainly isn’t optimal. This is the ratio of voltage to current as a wave propagates down the line. The same issue applies to routing a clock signal. Use shorter trace lengths to reduce signal attenuation and propagation delay. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. the guard traces could also reduce the return path loop then reducing the unwanted. Let’s dig into this further and get a sense for why you should not route a trace over a gap in a ground plane. The propagation delay is the time taken by a signal to propagate over a unit length of the transmission line: Where: V is the signal speed in the transmission line. Trace lengths need to be precisely matched to avoid creating. Rule 5 – Match the trace length. CSI signals should be routed as 100Ω. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. It suggest (<30cm) for single ended trace length for high speed operation. I2C Routing Guidelines: How to Layout These Common. Set up trace lengths, length matching, differential pairs, and other rules and constraints beforehand to ensure that everything will meet the requirements while you route. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. 2. The frequency of operation is about 10 MHz. In contrast, for an internal trace with the same dielectric material we need the trace to be less than 10. Two of the traces have no reference plane beneath, and their lengths are Trace 1, 35mm, and Trace 2, 120mm. High-speed layout guidelines dictate the most direct trace path isn’t always going to be the ideal routing solution. The narrow spacing and thin layer count will force traces in the pair to be thin as well. Some PHYTER products utilize PCB traces to connect an internal regulator to core supply pins. Route differential signal pairs with the same length and proximity to maintain consistency. Therefore, you should make the 50Ω impedance traces 5. About 11% of the signal will survive one round trip, 1. They are simply the traces on a PCB and depend on the length and the frequency of the signals passing through them. The idea is to ensure that all signals arrive within some constrained timing mismatch. Roh Roh. During the PCB manufacturing process, the trace is typically laminated onto the board’s surface. Many FPGAs do have some feature they call "IO delay calibration" or similar, which allows, within boundaries, to add an adjustable delay to IO lines. The fact that the important quantity determining noise immunity is the signal timing mismatch has motivated the use of delay tuning for differential signals. 5 cm or about 0. 1. Digital information synchronizes to a clock signal. Well, if you manage to get 50 Ohm trace for this LCD on a 2-layer board with meaningful trace widths please find me :) I hope you are aware of the fact that the PCB thickness should be very low. Wavelength of the highest frequency signal, 𝛌 𝐦 = 𝐯/𝐟 𝐦. I believe the mismatch of 3 cm in the examples above is not. Why FR4 Dispersion Matters. High-speed PCBs operate in the range of. The Ethernet protocol was standardized in the 1980s and rapidly evolved from speeds of 10 M to 10 G+ bit/s. Frequency with Altium Designer. ALTIUM DESIGNER. Don’t make one signal go all the way across the Printed Circuit Board while the other one just has to go next door. 00 mm − Ball pad size: 0. • Narrower DDR3 output drive ranges that can be recalibrated to adjust for voltage and temperature variations. Differential Pair Length Matching. 010 inches spacing between them. Because the current crowds up against the edge of a trace, this increases the strength of the interaction between the current and the rough wall of the copper trace. . If your chip pin (we call this the driving pin) turns its. The line must meet the 2W principle to reduce crosstalk between signals. Read Article For example: If you have 1 Amp going on a 6 mil wide trace of 1 oz copper for 1 inch of length, that's . 8 substrates of various thicknesses. The goal is to minimize magnetic flux between traces. Some interesting parameters: set tDelay=tRise/10. However: The Raspberry Pi Computer Module 4 (CM4) datasheet states: 2. Some possible changes include the addition of termination components, careful design of impedance matching networks, or redesigning traces to adjust their impedance. Following the 3W rule can. Today's digital designers often work in the time domain, so they focus on. 5 inch. So for bottom traces there will be massive high-frequency signals underneath them on the motherboard within 1-2mm distance. It starts to matter (as a rule of thumb) when the track (or wire) length becomes about one tenth of the wavelength of the highest frequency signal of importance. FR4 is a standard. Impedance profoundly impacts signal quality in high-speed PCBs. When you are distributing power, DC and low frequency, the trace resistance becomes important. At the receiver, the signal is recovered by taking the difference between the signal levels on. I have a PCB with tracks of no controlled impedance. frequency response. 1. 50 dB of loss per inch. 25mm trace. When adjusting the trace length, ensure you get the correct size for a given group of signals—generally, the higher the interface frequency, the higher the length-matching requirements. Just like a trace on PCB, vias have their own impedance, which is often described using lumped circuit models, similar to a transmission line. Observation: A 3cm microstrip and a 3cm stripline can get a very different propagation delay! Conclusion: If we would route a bundle of traces, eg. Sudden changes in trace direction cause changes in impedance. 7563 mm (~30 mils). Obviously, these two points are related; all PCB vias have (or should have) a landing pad that supports the via and provides a place to route traces into a via pad. In Figure 2, you can see that the transmitter waveform consists of data bits of longer duration (lower. For instance, the topology may call for a daisy-chain route, which will increase the total length of the net. Use the results from #3 to calculate the width profile with the integral shown below. mode voltage noise, and cause EMI issues. Control the trace impedance to be as close as possible to the recommended values in Table 2-1 . Everything You Need To Know About Circuit Board Traces Pcba. A fully unified, heavily rules-driven PCB design platform for impedance controlled routing in high-speed PCB design. The RS-485 protocol standard allows up to 32 drivers in one system, supporting communications over distances of up to 1200 meters, and can keep baud rates from 110 Baud to 115200 Baud. What PCB trace width should I use and can someone give me a guideline on how to select the PCB trace width based on the frequency. Eventually, the impedance of your power delivery network will. 192 mm gap shall be 100Ω ± 10%. Tip #4: Trace Length and Spacing. The golden rule used in electronics is that you begin to have small problems when length mismatches are about one-tenth of the effective wavelength of the highest. You'll have a drop of about 0. The Unified Environment in Altium Designer. Length of the trace; As mentioned earlier, the input parameters are subject to change depending on the chosen impedance structure. Here’s how length matching in PCB design works. 393 mm, the required trace width for this particular inductance value is w = 0. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. Opting for longer traces may be a better choice, but pay attention to a transition to transmission line behavior as the trace length is increased. tions at the load end of the trace. In high-speed digital protocols, data is sent over single-ended traces in a PCB that is impedance controlled; each individual trace is. At a foot length (300 mm), a signal frequency having this wavelength is about 1 GHz. PCB trace antennas at lower frequencies,For my results, I find that the minimum inductance is 292 nH per meter when ( w/h) = 1. – The impedance mismatch between vias and signal traces can cause transmission-line reflections. As the frequency increases, PCB traces behave like transmission lines, with a precise impedance value at each point on the trace. However, while designing the PCB, I am not able to match all the lines from the connector to the controller. The full range of the traces is 18. I2C Routing Guidelines: How to Layout These Common. Loosely vs. 0014″. Read Article UART vs. 1 Answer. The longest track is shorter than 1/5000 of a wavelength. C. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. I'm making a high-speed transceiver design and want some direction regarding layout of trace length from P to N. If there are high-speed transition edges in the design, you must consider the problem of transmission line effects on the PCB. This will be specified as either a length or time. Well, even 45' turns will have some reflection. 0 reaching 32 Gb/s, and PAM4 pushing signal integrity and speeds to the limit. This characterstic impedance is independent of length and trace material, depends on substrate thickness and trace width, and is usually in the 50 to 100 ohm range. The need for multiple lines between the microcontroller and peripheral makes component mounting more of an issue and they should be placed as close together as possible to minimize trace lengths. While every trace has an impedance, we don't care about the trace reactance if the trace is only carrying DC current. If. 223 mil for differential) as this would give the single-ended trace lower skin. Frequency Keeping high speed signals properly. At a foot length (300 mm), a signal frequency having this wavelength is about 1 GHz. SPI vs. Cite. ImpedanceOne of these design aspects is the match between PCB via size and pad size. 25GHz §Manage trace lengths to minimize loss üExample: 12” board, 3. Impedance Matching and Large Trace Widths. Recommended 4- or 6- layer stack for a receiver PCB design Rule of thumb says 10° – how much trace length difference that is depends on your trace design, PCB substrate thickness and material. The traces must be routed with tight length matching (skew) within the differential traces. For the other points, the reflections are a result of impedance mismatching. Strictly control the length of the trace of the critical network cable. Inter-pair skew is used toImpedance matching of lower frequency analog signals is required when the impedance mismatch at the ends of an interconnect is large. In contrast, for an internal trace with the same dielectric material we need the trace to be less than 10. Length Matching. On a high-speed PCB (> 100MHz) where wavelengths are shorter, any critical net (see figure 4a) is electrically long enough to make it an efficient radiator, especially when left exposed on the top or bottom layer. Mitering Output Traces to Closely Match Lengths Receiver Inputs •If there is more than 2-cm distance between the connector and the receiver input pins, the PCB must be constructed to maintain a controlled differential impedance near 100 Ω. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. The length and Z o affects path loss and special delays with frequency/length ratios like 1/4 wave impedance reflections (inversion) and all odd harmonics of same. Matching trace lengths at specific frequencies require. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. 3041mm. Here’s how length matching in PCB design works. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. Designing a PCB for PCIe Signals 11 Tsi381 Board Design Guidelines 60E1000_AN001_06 Integrated Device Technology Figure 1: PCIe Board Trace Width and Spacings Example 1. It won't have any noticeable effect on the signal integrity or timing margins. From there, component placement may be adjusted to better set up the high-speed trace routing required. How to do PCB Trace Length Matching vs. If your chip pin (we call this the driving pin) turns its. • Provide impedance matching series terminations to mini mize the ringing, overshoot a nd undershoot on critical sig-nals (address, data & control lines). I2C Routing Guidelines: How to Layout These Common. Here’s how length matching in PCB design works. I then redesigned the board with length matched traces and it worked. PCB trace length matching vs frequency affects the signal integrity of your circuit designs. For the signal trace of width W and thickness T, separated by distance H from a ground (or power) plane by a PCB dielectric with dielectric constant εr, the characteristic impedance is Impedance matching between copper traces is critical for differential routing and between the board materials for high-speed (frequency) signal transmission. If it is low speed stuff, you are probably OK. This 6-layer PCB stackup can enable orthogonal routing on L1/L3 and on L4/L6. To ensu re a robust interface, the designer must address both components. Without traces, a circuit board would not be able to function. These equations show that attenuation occurs in the circuit due to the (RC + GL) term. In summary, we’ve shown that PCB trace length matching vs. In this article, we’ll examine a few tips and tricks for high-speed printed circuit board designs. How to do PCB Trace Length Matching vs. Every trace has a small, nearly indistinguishable series inductance distributed along the trace with an inverse relationship to the cross-section of the trace. However, in some cases, PCB traces may cover multiple layers, particularly in multi-layered printed circuit boards. Trace lengths are also influential, and they should be determined by simulation for each signal group and verified in test. 5cm) and 6in /4 (= 1. The higher the frequency, the shorter the wavelengthbecomes. I2C Routing Guidelines: How to Layout These Common. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. This variance makes Inside the length tuning section, we have something different. However: The Raspberry Pi Computer Module 4 (CM4) datasheet states: 2. A PCB antennarequire s more PCB area, has a lower efficiency than the wire antenna, but is cheaper. Some PHYTER products utilize PCB traces to connect an internal regulator to core supply pins. But for EMC reasons you may very well want to do better than that, in which case you should also take care to maintain the controlled impedance over the portions of the trace that are length matched. 8 mil traces, and that is assuming no space. The PCB trace may introduce 1 ps to 5 ps of jitter and 0. rise time (tRise). I tried to length-match the diffpairs as much as I can: USB (97. Once all the input parameters are entered, click on Calculate Loss. Here’s how length matching in PCB design works. This is the case where the wavelength is much longer than the transmission line. The PCB Impedance Calculator in Altium Designer. 5. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. When you need to evaluate signal integrity and impedance matching, use PCB design and analysis software with an integrated 3D EM field solver and a complete set of CAD tools. The extent of this problem will depend on the bus speed, the length of the traces, the trace geometries, the type of fiberglass weave used, and the alignment of the traces to the weave pattern of a PCB. These traces could be one of the following: Multiple. Design rules that interface with your routing tools also make it extremely. 1 Answer. The allowed deviation in length matching depends on the rise/fall time for digital signals between these two elements, although it is generally recommended that any deviation be less than 10 mm as MII and RMII use TTL logic. The trace impedance or PCB impedance damages the integrity of both analog and digital signals. This impedance is dominated by the physical separation between your power rails, traces, and internal planes in your board. How to do PCB Trace Length Matching vs. ;. Do you guys agree to this? mode voltage noise, and cause EMI issues. 015 meter or 1. CSI-2 (MIPI serial camera): The CM4 supports two camera ports: CAM0 (2 lanes) and CAM1 (4 lanes). Trace Length Matching. 3 can then be used to design a PCB trace to match the impedance required by the circuit. Using this tool, you can calculate 3dB bandwidth (BW), fastest signal rise time (tr), critical length (lc), maximum data transfer rate (DTR), and maximum frequency content (Fmax). SSTL 15 IO Standard (1) FPGA Side on-board termination(2. The typical propagation delay for a signal through a circuit board trace is about 2ns/ft (6. So choose trace width and prepreg thickness to. Figure 3. These traces can be made of materials, typically copper, and are designed to have specific widths and thicknesses to handle different current loads. Jun 21, 2011 at 0:11. Cite. Trace thickness: for a 1oz thick copper PCB, usually 1. That is why tuning the trace length is a critical aspect in a high speed design. Problems from fiber weave alignment vary from board to board. Logged. The world looks different, one end to another. 5 to 17. Also need to be within tolerance range as in USB case it is 15%. For length-matched parallel buses, you'll usually use a mixture of the two. In particular, the transit time of signals often needs to be synchronized by matching the copper length of the traces on the PCB. The typical method for matching timing in a differential pair is to match the lengths of the two lines at the source of the interconnect, also known as phase matching. During that time both traces drive currents into the same direction. frequency can be reduced to a single metric using an Lp norm. 7. The crosstalk issue becomes more severe, especially in HDI PCBs, when traces run at high frequency and high edge rate. The length of a high-frequency trace should be designed so that the critical rise time of the circuit board is shorter than the rise time of the signals. The minimal trace sizes as well as spacing are producer and also. Aside from this simple design choice, you may need to design an impedance matching network for your connector. Read Article UART vs. Other aspects such as stack-up and material selection also play crucial roles. High-speed PCB design requires special considerations to get a functioning design – one being trace length. 5 ns, so a 7-inch or more track carrying this signal should be treated as a transmission line. This document focuses on. 35 dB inherent loss per inch for FR4 microstrip traces at 1. Common impedance values are between 25 and 120. Impedance vs. The switchback routing style (bottom left group of traces) provides a more compact link length compared to the serpentine style. With today's advanced interactive routing features in modern PCB design tools, designers no longer need to manually draw out length tuning structures in a PCB layout. The eleven inch trace length represents a maximum loss host design (PCB plus package). Here’s how length matching in PCB design works. I don’t often like to give answers in absolute terms to PCB design questions, but in this case the answer is clear: Never route a signal over a gap in a ground plane. The cable data sheet provides capacitance, delay, and other properties. Adding a miter for length tuning should be as easy as dragging the mouse across the mismatched trace. Intra-pair skew is the term used to define the difference between the etch length of the + and - lane of a differential pair. Note: The current of the signal travels through the. frequency (no components attached). 3. SPI vs. between buses. Although signals are band-limited when recovered by a high-speed receiver, your interconnect design should account for the entire signal. As discussed previously, the lengths of the two lines in the pair must be the same length. Here’s how length matching in PCB design works. How to do PCB Trace Length Matching vs. Then when it is time to tune the trace, convert those trombone patterns into the tighter serpentine patterns that you need in order to hit your target lengths. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. Max trace-length mismatch between high-speed USB signal pairs should be no greater than 150 mils. To ensure length. 50R is not a bad number to use. SPI vs. Your length matching settings and meander geometry should be easily accessed directly from the layout. For a signal speed in PCB is 15 cm/ns and an allowable skew of a quarter of the period, it gives 2 meters. The typical method for matching timing in a differential pair is to match the lengths of the two lines at the source of the interconnect, also known as phase matching. 1 Ohms of resistance. 1 Answer. 4 mils or 0. 203mm. Technologies DDR3 Routing Topology Page No #5 DQ/DQS/DM:If a transmission line has a 50 ohm impedance, then connecting it abruptly to a 1 V source will cause a 1 V voltage wave and a 20 mA current wave to start travelling along the line. If a short section of a 50 ohm cable has a 75 ohm impedance, then 33% of the voltage signal will be reflected at each end of the 75-ohm section. They recommend 3 times the trace width between trace center and trace center, until here all ok. 5 dBIn low-frequency systems, components are connected by wires or PCB traces. = Most PCB vendors will size traces for you You just tell them Z0 L0 is inductance per unit length C0 is capacitance per unit length. Depending upon the type of components and the signals routed to and from them, trace length, copper weight, and spacing must all be chosen to maximize signal integrity. 2% : 100%):. 3. 66ns. For traces of equal length both signals are equal and opposite. 3. For RF signals at high-speed, the integrity can take a hit (if not designed correctly) at approximately 50 MHz or. How to do PCB Trace Length Matching vs. 2. Cables can be miles long but a PCB trace is likely to be no longer than a foot. If you use the 1/4 rise time/wavelength limit, then you are just guessing at the. For most manufacturers, the minimum trace width should be 6mil or 0. This will help you to route the high-speed traces on your printed circuit board pcb to the correct lengths without having to guess their actual lengths. Read Article UART vs. 3. This is valid up to tens of THz for a typical PCB trace. 152mm. Impedance affects how signals travel through the board, how power is transferred between components, and how signals flow into unwanted areas of the PCB. CBTU02044 has -1. Try running a 10 GHz signal through that path and you will see loss. and the skin effect, we can capture the true impedance vs. If these traces are carrying signals which have a spectral content which includes any frequency greater than (speed of light) / (10 x trace length), then do 45 degree traces. The traces are 0. For example, if the. Some of the common causes of signal loss include: Conductor resistance: The inherent resistance of the conductive traces on a PCB can result in signal loss. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. Search for jobs related to Pcb trace length matching vs frequency or hire on the world's largest freelancing marketplace with 22m+ jobs. There are a few termination techniques that you can use to ensure high-speed signals on your PCB suffer from no reflection or distortion on the trace. $egingroup$ Thanks @KH ! If you will focus on the questions that are in the body and not in the title, I guess the answer will be a bit shorter. Inter-pair skew is used to Routing high-frequency traces close to each other can result in crosstalk and interference. 4 Trace Length Matching PCIe signals have constraint s with respect to trace lengths and matching in order to meet jitter and loss. DKA DKA. Improper trace bends affects signal integrity and propagation delay. Changes in frequency and temperature also cause the dielectric constant to change. How Do Circuit Boards Work Custom Materials Inc. How to do PCB Trace Length Matching vs. 008 Inch to 0. As a thumb rule At what trace lenths should i used differential drivers (LVDS,RS485) etc for SPI interface. 1. Laying out a board with digital and RF sections requires ensuring isolation between different circuit blocks with smart floorplanning. SPI vs. 8 Characteristic Impedance: 50 With my values, with a non-standard thickness board (31 mils thick), I arrived at 55 mils. Inter-pair skew is used toUse a 100 Ω loosely differential routing on the main host PCB if you are using option 1 in Figure 101 at the connector. I2C Routing Guidelines: How to Layout These Common. Frequency Keeping high speed signals properly timed and synchronized requires PCB trace length matching vs frequency. For traces of equal length both signals are equal and op-posite. I'm designing a board which contains an LTE module on it. 1V and around a 60C temperature. Trace length matching and trace length • Avoid running long traces in parallel with grain of the fiber. The exact trace length required also depends on. Trace lengths should be kept to a minimum. Problems from fiber weave alignment vary from board to board. Have i to introduce 0. Their sum must therefore add to zero. So is the PCB trace impedance an impedance or a resistance? It's both (short story). Whether you’re new to PCB design or you’ve made your career out of it, there are many times in RF and high speed design where you need to design microstrip and stripline traces to have a specific impedance. The lines are equal in length to ensure impedance matching of the signals.