510 mm, or 20 mils, and the minimum inductance is 292 nH/m. PCB manufacturing, if copper foil with a width tolerance of 18μm is selected as the signal transmission to control the impedance, the allowable trace width tolerance is usually ±0. One key thing to consider is the plating thickness is much thinner than a typical 70 microns outer layer (2oz copper) and can go as low as 16 to 25 microns, requiring a relatively large drill diameter to get enough copper to match the cross-section of the trace. Neither of those cover controlled impedance calculations, if you need those look elsewhere. 7E-6 to 2. where Z 0,surf can be computed as specified in Eq. 2. Thank you. Designing trace width for HDI impedance adjustments. 08 mm: 3. 25, but gives me nice trace from the module to the stub then to. Best is 5mils, but 4mils is OK, too. Adequate trace width is necessary to ensure the desired amount of current can be transported without overheating and damaging your board. It seems I could largely do without any impedance matching considerations, given what the trace lengths are. Verify Against Other Design Rules. 24. 1 Answer. of typical printed circuit board trace geometries. Coil Inductance Calculator. What is the width of a trace for 100 ohm impedance? The width of a trace for a specific impedance depends on the dielectric constant, height above the reference plane, and other parameters. The PCB Impedance Calculator in Altium Designer. I will see if I can come up with something for vias similar to my Transmission Line. 3 shall be used. Microstrip Trace: Embedded Microstrip Trace: Stripline Trace: Dual Stripline Trace: Geometric Parameter Definitions. If the Length, l, to diameter, d, ratio is known, you can calculate the Inductance, L, series resistance, Rs and the aspect ratio l/d is related to Q = L/Rs for a given conductor material. Single Ended Impedance Ω. Also, the copper thickness affects the minimum trace. This model was originally developed by analyzing trace impedance measurements using a regression model. Most board manufactures will have a preferred tool that PCB designers can use to calculate the Impedance but there. Note: Units do not matter for this calculation as long as they are consistent. Features: Three-in-one calculator. These calculators mostly ignore the losses. Apr 7, 2008. However, at this time, I don’t know of a good way to do calculations for wagon wheel spokes. TransLine. Typ e, V ref and, if needed, I a d j , select the field you want to calculate (one of the resistors or the output voltage) and enter the other two values. To update trace width, select the traces of interest and use the "Route > Retrace Selected" command. 7E-6 [Ω · cm], L is the trace length [cm], α is the resistivity temperature coefficient, whose value for copper is 3. This tool calculates the matching network necessary to terminate a line of the specified characteristic impedence (Z o) in a specific complex load impedence (R L + jX L) at a specified frequency. trace width and thickness, distance from other copper features, dielectric constant, and dielectric thickness or distance to reference plane of the board material all contribute to the impedance of a. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. trace width for a characteristic impedance of 50 Ohms on Dk = 4. For example, with a thickness of 0. Simpler calculators will use the less-accurate IPC-2141 equations. To use this tool, enter the values for trace thickness, substrate height, trace width. For example, on the left side of Figure 4, a 4-4-4 mil geometry has a differential impedance of 91 Ohms. The width of each track should be as per the requirements. W=trace width. 78 mil. If impedance control is necessary, determine the trace width required to reach your impedance target. Twisted-Pair Impedance Calculator; Stripline Trace Width Calculator;. It displays the impedance of the input and output match in a 50Ω test environment as measured on a network analyzer. $$H$$ = subtrate height $$W$$ = trace width $$T$$ = trace thickness $$epsilon_{r}$$ = substrate. I use FR-4, so H=1. e. Microstrip Trace: Embedded Microstrip Trace: Stripline Trace: Dual Stripline Trace: Geometric Parameter Definitions. 41)] * ln[5. , power and/or GND) constitutes a stripline layout. ) Dramatically decrease the spacing in between differential pairs: I know:As explained in Part 1 of this series ( Circuit Cellar 367, February 2021 [3]), PCB manufacturers can propose different PCB stack-ups, and specifying a low thickness for the so-called “top prepreg” will help to reduce the trace width. When working with a power rail, high-voltage components, and other portions of your board that are sensitive to heat, you can determine the power trace width you need to use in your layout with a PCB trace width vs. PCB Trace Impedance Calculator. For example the width of the trace(W) is 6 mils and the distance between the differential pair(A) is 8 mils. The subsequent dialog that appears - the Impedance Formula Editor dialog - contains impedance calculators for both Microstrip and Stripline impedance. Such a stripline is constructed with two traces referenced to the same reference planes above and below the traces with a dielectric material between them. 72mil. 048, b = 0. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. For example: Yellow Violet Red Gold: 4 7 x100 ±5% = 4700 Ohm, 5% tolerance. 4mm PCB for a trace width of 0. This form of microstrip is composed of two traces. T T = trace thickness. Most formulas calculate impedance from width, because width is a boundary condition and it's easier to calculate forward from a boundary condition, than backwards to reconstruct it. 3-in-1 calculator: temperature rise above ambient, trace width, and maximum trace current capacity; Evaluates trace resistance, voltage drop, and power loss; PCB dielectric requirement. This change in trace. Microstrip Impedance Calculator. The calculator has an input box for the resistivity which defaults to 1. Via impedance Via step response Via DC resistance Via impedance Via resonant frequency Via thermal resistance Via voltage drop Via power dissipation in dBm. ALGEBRAIC EQUATIONS Single Track For the stripline of Figure 2 with a symmetrically centred track of zero thickness, Cohn[3] has shown that the exact value of the characteristic impedance is 4. Differential Impedance Ω. Just as important as determining an appropriate trace width for a single-ended trace is determination of an appropriate spacing between two traces in a differential pair. 5. Identify best matched Rogers' bonding material by sorting according to design attributes. Review: A new PCB stack-up design and impedance calculator is available for download from Istvan Nagy (see link below). The new version includes: Additional dielectric materials. Pad Stack Calculator 4. W. Spacing with copper weightSierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. This free trace width calculator is based on IPC-2152. Z0,air Z 0, a i r = characteristic impedance of air. Calculates the characteristic impedance and per-unit-length parameters. There are several formulas and online calculators that can be used to calculate trace width. This calculator not only provides the number of recommended signal layers but also assists you with PCB area, number of nets, and net density. Electrical Spacing. The trace impedance (Z) of a PCB trace can be calculated using the formula for microstrip transmission lines: Z = (87 * Log10 [ (2 * H) / (0. H: Height. Here, the via carrying the signal is placed at the center and is surrounded by 4 ground vias. At 2 amps I'd worry more about voltage drops. A 20 mil trace will have a much greater tolerance for losing metal than a 3 mil trace would. In the first section of the PCB DFM tool, you need to key in the part number (name of the design), revision (edition of the design), number of layers on the board and board dimensions. This page covers Microstrip Width Calculator. If you need to mass produce PCB's at low cost, the minimum trace width should not be pushed too hard. Coplanar Waveguide Calculator. If you know the values of any of the two parameters (conductor width, max temperature, max current capacity) it determines. So just set the trace width constraint in your PCB router to 13 mils, and your routes will all be precisely 50 Ohms. Other parameters to consider. 393 mm, the required trace width for this particular inductance value is w = 0. Controlled Impedance; PrePreg Chart. Sierra Circuits Impedance Calculator. How to achieve 100ohm impedance for HDMI differential pair on FR4? 4. For example on 0. Microstrip Trace Impedance Calculator;The calculator utilizes the formula for calculating the impedance of a microstrip trace: Impedance (Z) = [87 / √(ε + 1. Board Classes. Altium Designer’s impedance calculator takes your board layer stackup information and sends the trace width and thickness results to your design rules. Figure 2. εr:Controlled impedance traces can minimize signal reflections and thereby reduce propagation delay. For a first design (e. Select a trace impedance profile over the length of the taper. This calculator finds both odd and even transmission line impedance. The application below provides a simple way to calculate the required trace width (in mil) for a given input current and temperature. 725. I used some online calculator to calculate parameters of trace so it has 50 Ohm impedance. Here are the steps to validate your design using Better DFM: 1. Controlling trace width within a tolerance of +/- 10% is necessary for better impedance control. Based on Figure 4, it can be concluded that as trace width changes by 0. β2 = 0. But if you route a pair of traces with close coupling, the odd-mode impedance is less than the SE impedance for the same trace width (unless you adjust the line width). Calculate the pcb trace impedance of. Inputs: Optional Inputs: Results for Internal Layers: Results for External Layers in Air: Notes: The trace width is calculated as follows: First, the Area is calculated: See full list on protoexpress. To calculate the trace width/spacing, I used SaturnPCB. 6. 41)] * ln[5. they normally use 7. 25 mils , t = 1. Some numbers that work: Track width 4 thou, track separation 4 thou, depth to plane 6 thou on 1 oz copper gets you pretty close according to the Saturn PCB toolkit. thermal, and signal integrity aspects of traces on a PCB. The fabrication etching process will have a greater effect on traces that are long and isolated, so it is better to make them wider when possible. 5 mils and spacing of 4. Odd Mode Impedance (Zodd) Ω . Where: H is the height of the PCB above the ground plane. Dielectric material: This is the prepreg and core materials utilized on each side of the controlled impedance trace layer. Layers contain controlled impedance that is why we need to specify these impedances in the fab notes since there can be more than one value of impedance traces per layer. Sierra Circuits’ Via Thermal Resistance Calculator is an advanced PCB design tool that expedites the process of designing thermal vias. Tuning the Width and Gap Settings. 30967mm) is slightly larger the size of the smallest pad (0. You will see the trace width is 5. Trace width is an important design parameter in PCB design. 6mm 2. Thickness. Input Your Specs to Get Started. It uses formulas from IPC-2221 (formerly IPC-D-275). Trace width is one of the most influential elements affecting characteristic impedance and Figure 4 below demonstrates the relationship between characteristic impedance and trace width. 1 to 2. Use the results from #3 to calculate the width profile with. PCB Trace Width Calculator This tool uses formulas from IPC-2221 to calculate the width of a copper printed circuit board conductor or "trace" required to carry a given current while keeping the resulting increase in trace temperature below a specified limit. If you are using very fast rise/fall times (regardless of frequency) and ringing is your problem, you'll need to use a trace impedance calculator, with the trace. The characteristic impedance of the trace can be calculated using the below formula: Formula to calculate characteristic impedance of a PCB trace. Maximum Unambiguous Range Calculator. 50 Ohms and then specifically sets this trace width as a qualifier. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. So, you need to calculate how much resistance a PCB trace can provide. Gaps in signal traces impact the entire test waveform, and its single-point impedance is too high, making the entire waveform uneven. Altium will assume you want to confine the signal to your trace (and ground plane), rather than cause radiation. differential trace impedance for USB (90 Ohms) on 2-layer FR4 board. Figure 3 is the plot of impedance versus trace width for the three most common types of transmission lines in PCBs—surface microstrip (SMS); buried microstrip (BMS) and centered stripline (CSL). 0mm1. This calculator assumes the distance between the two reference planes to be an equal distance. The edge couple differential microstrip transmission line is a common technique for routing differential traces. A calculator designed to calculate the trace width of a stripline based on the maximum current rating Embedded Microstrip Impedance Calculator This calculator helps you compute the characteristic impedance of an embedded. Sierra Circuits’ Trace Width, Current Capacity and Temperature Rise Calculator is an advanced PCB tool that works based on the latest IPC-2152 standard. The designer can normally enter their desired impedance, and the calculator will determine the PCB trace width needed to meet that impedance goal. Height: Height of the substrate. If the calculated routing trace width is a value that cannot be ordered, you can tune the width and gap settings. I'm not sure which calculator to trust. The velocity factor is simply: 1 / sqrt (e_r*mu_r). 2. This is. At 10 MHz, you don't need to worry about trace width/impedance unless you're using long traces and very fast rise/fall times. Advanced Electronics Solutions. 25mm, a trace width of 0. The dielectric constant of a material IS slightly frequency dependent. So, the dielectric at my 5-6GHz frequency range is 3. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. 3mm of the microcontroller), therefore i rounded the width to 0. 0; 1 < ε r < 15 ) Select the units for all dimensions: mm mils. If you reduce this trace width to 19 mils, the characteristic impedance will result in about 52. Stripline Impedance. The width of the conducting layer is important to calculate the radiation intensity since it directly affects the bandwidth of the signal waves. Controlling the impedance in your design is dependent on the board layer stackup you. Scientific Calculator. layout impedance. ] Internal Layer Results: Copper Area: External Layer Results: [Mils] [Square Mils] [Volts] Trace Width Calculator Results: Via Current. The PCB design tools in Allegro include an impedance calculator that will help you size your traces so that they have defined characteristic impedance. Dielectric thickness vs. Figure 2. Note: The results are only for approximation and rough estimation, the. Select a configuration: Microstrip Trace. The Calculator. T-Match Topology. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. This can be calculated in function of current, here you can set up for your specifications Trace width calculator. copper trace on a 4-layer board with 8 mil thick dielectric and Dk = 4. PCB Trace Width Calculator. Next, determine the trace. Share. Using the EEWeb Microscrip Impedance Calculator, I find that with 1oz/ft^2 copper and a substrate height of 0. To use this tool, enter the values for trace thickness, substrate height, trace width, trace spacing and subtrate dielectric in the calculator above and press the "calculate" button. The PCB trace impedance increases as the width decreases. Using the EEWeb Microscrip Impedance Calculator, I find that with 1oz/ft^2 copper and a substrate height of 0. In reality, we don’t need to use that trace width due to the way the traces in differential pairs will couple to each other. JLCPCB Impedance Calculator. Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. Other conductor properties include: ; Conductor skin depth ; Conductor voltage drop ; Conductor. Another advantage of assigning the impedance property is that allegro automatically assigns the width of the track based upon the assigned impedance value. It displays the impedance of the input and output match in a 50-ohm test environment as measured on a network analyzer. EM fields are an important consideration while designing PCBs and require a field solver to predict their effect on the circuit board. Below is the calculation. Having carefully specified the board/prepreg material, I also ask for tolerances and based on that calculate the widths for eg. Copper foil roughness and trace width affect signal propagation and impedance. Below is the schematic Below is my layout. Effective Antenna Aperture Calculator. 048 x dT0. Impedance Calculation. The tool generates odd, even, common, and differential impedance as output values. . View All Tools. Our Impedance Calculator uses a 2D field solver to calculate near-end crosstalk based on the following equation: NEXT = V b /V a = ¼ (C mL / C L + L mL / L L). The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. If the ratio is about 0. The default units for all given values, except the substrate dielectric, is in mil. 5mil clearance on a 63 mil board (1. Via is considered as a cylinder of copper and its circumference is 2 𝝅r or 𝝅d where d is the size of via hole. The application will often drive the trace widths and types in a PCB design and at a certain point, there is. ViaMin. Trace Width (W) ( mils ) Calculate W . While the manufacturer uses Si9000, the result does not match with what the other tools get. At times, you need to lower the copper weight to achieve a specific impedance. Calculates the characteristic impedance and per-unit-length parameters of typical printed circuit board trace geometries. There are many factors that go into calculating the width of an impedance controlled trace. Dielectric Height (H1) ( mils ) Dielectric Constant (ER1) Trace Information . From here, we can see that there are specific stack-ups where a CPW and a microstrip/stripline will have 50 Ohm impedance and the same trace width, even though the ground clearance is quite close clearance to the trace in the CPW. Here is a couple of calculator links:In fact, striplines often make components such as band-pass filter's more accurately, with more symmetric roll-off and no lower cutoff frequency. I had a request for a calculator to find the width of a PCB trace based on its voltage drop or power dissipation. 6mm pcb thickness ) with 8 mil trace width, 8 mil trace spacing , 1. Chemandy on the other hand tells me 14. 4 mil, εr. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a. 7E-6 [Ω · cm], L is the trace length [cm], α is the resistivity temperature coefficient, whose value for copper is 3. With t = 0. This calculator computes the characteristic impedance of a twisted-pair cable based on its dimensions. The calculator below uses Wadell’s. 1< W/H < 3. For a standard FR-4 substrate with a dielectric constant of around 4. So Adjust trace width to match the impedance to 50 Ω Ω. The KiCad PCB Calculator is a set of utilities to help you find the values of components or other parameters of a layout. Line Types and Impedance (Zo))Impedance (L/C)-*Lower Er Materials Net Higher Impedance Traces and Faster Propagation Times per given Trace Width & Trace-to-Ground Separation. This calculator finds both odd and even transmission line impedance. Differential Microstrip Impedance Calculator (Using Zo) Embedded Microstrip Impedance Calculator. The best way to calculate trace impedance is by using a trace impedance calculator. Share. To use these to design for a target impedance, simply cycle through various geometric. The Impedance Formula Editor dialog. Things I noticed in any RF IC. There are a few methods for calculating trace impedance in a circuit board as long as the dielectric constant and trace geometry are known: Use the IPC-2141. Here, =. Most of the microstrip impedance calculators you’ll find online use a similar process: enter your microstrip geometry and Dk value for your PCB substrate materials, and the tool will return the impedance for your. The general rule is separation distance should be equal to 3 times the trace width. Stripline Impedance. ϵr ϵ r = substrate dielectric. Just enter the given values for trace thickness, substrate heights, trace width and substrate dielectric in the calculator above and press the "calculate" button. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. For an embedded (internal) microstrip, the formulas provided in paragraph 4. Layout designers will use a PCB impedance calculator to solve the electromagnetic field and deliver accurate trace variables for fabrication. Voltage regulator circuit board. 66, the trace height is 1. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric. 44, c = 0. The aim of the Impedance Calculator is to support the. trace width:. 2mm1. The microstrip is a very simple yet useful way to create a transmission line with a PCB. The calculator then uses a formula to calculate the width and spacing of the trace or transmission line required to achieve the desired characteristic impedance. ε: Dielectric constant of the PCB material. The circumference will be analogous to the trace. 031. The information should include the impedance value, the trace width, the spacing for. Altium Designer includes a PCB trace impedance calculator, PCB trace width calculator under IPC 2152, and a plethora of other important design tools. You can then check this PCB trace width against. Simons, "Coplanar Waveguide Circuits, Components, and Systems", Wiley. 725. It is important to calculate the impedance of the line. This tool includes an industry-standard field solver that is built into your PCB layer stackup. to select appropriate isolation materials, layer thickness, trace width, distance between traces,. Since impedance does not care about the absolute scale, it is. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. 679 nH. Thickness: Thickness of the stripline conductor. 2mm from the ground plane below. It would be nice to have a mm/mil switch including the board thicknesses. 92445. Length-tuning structures and their effects on impedance. Figure 2. What's Inside. To manufacture controlled impedance printed circuit boards, one must be able to measure impedance. (Fat!) Formulas for calculating this can be found in various. 92445. TransLine. The default units for all given values, except the subtrate. Trace Width (W) Figure 3. You may use this online tool to calculate an estimate of the minimum trace width for a given current and copper weight. ft. 1oz 2oz inner Copper Weight. Use our online tool to calculate the minimum trace width for a given current and copper weight. 1 mm gives roughly 50 ohms impedance. IPC 2141 Trace Impedance Calculator. In the case where there is a plane present, a correction factor is applied to determine the required copper. 3. 22mm. Now also calculates DC resistance with temperature compensation. For a 1 inch trace, this value would have a total inductance of ~7. 44. Enter 9. 024, b = 0. After determining the layer thickness and copper weight, you simply determine the trace width you need to use for a defined characteristic impedance. Impedance captures the real. This dialog allows you to view and (if required) modifythe formulae used to calculate Impedance and Trace Width when using impedance-controlled routing. Impedance depends on many parameters, including but not limited to trace width, trace thickness, and laminate thickness. This calculator can calculate the impedance and propagation delay of the embedded microstrip. Abrupt changes in trace width cause impedance discontinuities. This is the reason why engineers specify the trace width in their designs. However, if you select “impedance control” options when getting a quote from a manufacturer, it’s important to know that this will bring additional engineering costs. Via Current Calci 1. Try This New Tool. Instructions. From the above tables, we can evaluate the current carrying capability of a specific trace width. To learn more about trace impedance calculators, Wadell’s equations, and some drawbacks of impedance calculators, read this article on single-ended microstrip impedance calculators. 6 Band Resistor. The tool generates odd, even, common, and differential impedance as output values. Optimization results for example 2. 3 mils in the Substrate 1 Height text box, re-enter 75Ohms in the Impedance text box and click the Upper Trace Width Calculate button W2, the upper trace width resolves to 5. This is found to be 10mm. The trace width required to deliver a specific impedance can be calculated as part of an impedance profile, in the Impedance tab of the Layer Stack. 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. $$Z_{0}$$ = characteristic impedance of the microstrip in ohms (Ω). 048. This online microstrip impedance calculator calculates the characteristic impedance of the microstrip (Ω), W/H ratio, and effective dielectric constant (εe) by entering the value of dielectric material relative permittivity (εr),. 2E-6 Ohm-cm. Menu. Once you know the characteristic impedance, the differential. Not all calculators will explicitly state this. Asymmetric Stripline. To use this tool, enter the trace width, thickness, ambient temperature, temperature rise, and the microstrip length and click the "calculate" button. Overview. Can PCB traces be too wide? Yes, PCB traces can be too wide, which may lead to inefficient use of board space and increased manufacturing costs. Pulse Repetition Frequency (PRF) Calculator. To use these to design for a target impedance, simply cycle through various geometric values for the trace width until the calculator returns the target impedance. 8W + T)] Where: Z: Characteristic impedance of the microstrip trace. In any case, you do not want to use the Altium estimate for the trace width to achieve a given impedance to design an antenna. where. When in doubt, use 1 for copper, . However, a 5mil stripline trace featuring ground 6 mils below and above will produce about 50. Place critical components, such as microcontrollers or high-speed ICs, close to the power source to avoid trace stubs. W is the width of the trace. Input Your Specs to Get Started. Using this application, you can quickly identify the thermal resistance of a single or a combination of vias. Broadside Trace Inductance Calculator. 0 ohms; even impedance: 38. Deliver -/+ 5% impedance tolerance. 1. Make sure you understand the factors that influence transmission line impedance, and if needed, use a calculator to get an initial estimate of impedance before programming the required trace width as a design rule. One beneficial criterion is to look at the track width calculated for a 50-ohm impedance. Disclaimer: Our trace width calculator tool is exclusively designed to evaluate optimum trace width, maximum trace current, and temperature rise above the ambient required for a feasible PCB design. Microstrip Trace Impedance vs. A trace width calculator is a tool used to calculate the width of a trace on a printed circuit board (PCB). The trace width can then be calculated by re-arranging this formula to determine the cross-sectional area that. There is some relationship with trace width and board cost in mass production. 533 to target 50 Ohms impedance. ) Increasing the trace width crazily: Or. PCBWay is a professional quick-turn PCB prototyping, PCB Assembly and low-volume production manufacturer located in Shenzhen China. I am designing a 4 layers PCB and under the antenna trace I have a keepout, so there is no cooper on the 2 internal layers ( L2 and L3). The second part shows the impedance table which gives the details of impedances on different layers along with the trace widths and trace spacing. It is not uncommon that the calculated trace width will be a value that cannot be ordered, for. Provide values for H, T, W and the relative permittivity of the dielectric and click the button corresponding to unknown parameter Z o to calculate its value. 127mm. Online calculators will generally use Wadell's equations to determine the transmission line impedance numerically. Sierra Circuits’ Trace Width calculator Sierra 3-in-1 trace current calculatorThe stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. As a quick rule of thumb for 50 ohms, you want the ratio of the trace width to the height above the ground plane (probably your board thickness) to be around 1. Calculate the effective dielectric constant. t t is the trace thickness, in oz/ft 2.