Herndon's (Apple) paper from DesignCon 2003 "Noise Allocation for Near-end Crosstalk and for Uncertainty in Characteristic Impedance". TWL1200 PCB design, the chosen dielectric material is FR-4. It checks a trace layer wise. Step 1: Inner layer core selection. 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 equation for microstrip or stripline impedances. More reliability: The improved signal integrity and power distribution make the 8-layer PCB more reliable than its lower-layer counterpart. It is always a compromise between trace impedance, trace width and prepreg/core thickness and it is best to use a stackup calculator to provide quick ‘what if’ analysis of the possibilities. You have this backwards, the common rule is to use impedance control when the electrical length of the trace is more than 1/10 of a wavelength at the frequency of interest. Controlled Impedance PCB Parameters and Stackup. But every design seeks a different thickness. For an embedded (internal) microstrip, the formulas provided in paragraph 4. Stackups must be kept symmetrical, so there must also be 4 mils of dielectric between layers 7 – 8. There are some advantages to using a microstrip transmission line over other alternatives. Here is my layer stack up image with thickness of dielectric between the copper layers. This tool allows you to create, edit, and simulate your PCB design, and provides. In tab “TransLine” i chose “Coupled Microstrip Line” and i can calculate the impedance of only one track. Here’s a PCB design for assembly checklist you can refer to before you proceed with the assembly process. Next, input the following the parameters: Frequency (f) Resistance (R) Capacitance (C) Inductance (L) The units of these parameters can be changed using the respective drop-downs. Fabrication drawing is one of them. Ensure the positive and negative traces of the differential pairs have matched impedance. These files are utilized for the PCB manufacturing and assembly process. Make sure you use an accurate tool like this before you start building your stackup as this can help you identify the best laminate materials to use for your target impedance and. Coplanar Waveguide Calculator. The stackup you choose certainly plays an important role in the performance of the board in several ways. The ratio of cross-hatch conductor width (HW) to cross-hatch pitch (HP) plays an important role while characterizing the cross-hatch plane. PCB stackups are created by using combinations of the aforementioned four types of transmission lines. PDN impedance is one of those critical concepts in high speed PCBs, but many designers leave it as an afterthought. Detailed analysis in Excel Interface option. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. One: A quick solving calculator lets you seek a target impedance by varying any one parameter, it could be line width, stack height or Er; you choose the variable and set the goal seek. There are many factors that go into calculating the width of an impedance controlled trace. PCBWay's Standard PCB Layer Stack-up. A well-designed PCB stackup can maximize the electrical performance of signal transmissions, power delivery, manufacturability, and long-term reliability of the. Consider DFM guidelines when you design controlled impedance traces. See full list on resources. Adjust the length matching to achieve propagation delay. This allows them to meet the above constraints—controlled impedance, crosstalk, interplane. Assuming the differential pair I am routing is requiring 90 ohm (this is what the hardware guideline say "Route the USB differential pair on the top layer with a trace width and differential spacing tuned to the PCB stack-up for 90Ω differential impedance "). ALTIUM DESIGNER. These are precisely the characteristics of a pair of lines to be designated as a differential pair. controlled impedance structures to the stackup model. As also noted in the picture, the subsequent calculations are on the: [2] top-layer single-end impedance; [3] top-layer differential impedance; [4] inner-layer differential impedance. Impedance is a cornerstone of. altium. The material thickness between layers 1 – 2 should be 4 mils, max. Dielectric constant = 3. Speedstack also supports optional capability for flex-rigid and HDI builds, and connects through rich XML outputs to a variety of CAD and CAM packages including Cadence Allegro (TM), Mentor. Also impedance have often a 10% margin to take into account manufacturing process. To validate the trace width and spacing in your design, use the Better DFM tool. This starts with the layer stackup being configured to support high-speed, RF microstrip, and stripline routing. Controlled Stackup. An ideal 6-layer stack-up is shown in. This decision is based on the type of stack-up used in the PCB design. Step 1 Calculate singled ended impedance for each: Use "impedance + trace space" from top drop down box: Set Z=50R, click single ened, gives a result of track. PCBCart's Standard PCB Layer Stack-up. Best schematic design practices. For PCBs carrying signals above 1GHz, and even frequencies above. Ansys RedHawk. • Ground planes must not be broken in the GND reference layer immediately beneath he transmission line. Impedance: For successful impedance-controlled routing, the circuit board needs to be set up with the correct board layer stackup, trace widths, and spacings. Thickness. The tool also calculates signal losses of any given trace. Speedstack PCB stackup design tool is a packaged combination of the Si8000m field solving impedance calculator and the Speedstack professional layer PCB stackup design system. The screenshot is as shown in the picture q1-pro-pcb. 5(double-sided PCB) 7628 Prepreg 4. 1. A hybrid stackup construction enhances your PCB’s performance and cost-effectiveness by combining different materials or technologies. 010" to get a ratio of 0. It’s library of PCB laminate material reduces material costs without sacrificing performance. The copper thicknesses of the inner and outer layers are 0. . ShareThe number of layers is one of the crucial factors in designing HDI boards. 6-layer rigid-flex stack-up: 6 layers with 3rd and 4th layers as flex. Contents. The characteristics of the high-speed PCB materials impact heat dissipation, signal transmission, and signal. Either the desired impedance at a specific frequency is used to determine the waveguide width, or the width is entered and the impedance is calculated. 7 design rules to reduce crosstalk in your PCB designs. T= Experimental temperature. 0. 4 1 0 4 42. Tips on using your PCB design tools to create the best layer stackup configuration. RLC Resonant Frequency and Impedance Calculator. The design requires controlled impedance traces. Stackup, or buildup of PCBs, has grown in importance over the last decade. 293, 50% of the copper removal can be achieved. A cross-hatch plane is shown in the image below. Being a board designer, you need to know the functionalities of some of the best design tools before you choose the right one. Design the PCB stack-up layers to eliminate impedance buildup and shunt RF energy to the chassis. High speed measurement tools. Since it directly references the stackup information and has a. The relationship between these tools usually goes further than that though with this data also being made available to other portions of the system to configure. 125. PCBWay manufactures multilayer circuit boards with layers in the range from 4 to 14 layers, board thickness from 0. 4mm to 3. Repeat #1 and #2 for each layer. PCB Materials and Stackup Design Guidelines. Step-by-step process of sequential lamination 4-layer PCB stack-up. Therefore via stubs should definitely be reduced in length below 0. A well-designed PCB stackup can maximize the electrical performance of signal transmissions, power delivery, manufacturability, and long-term reliability of the finished product. It is possible to minimize the dependency on discrete decoupling/bypass capacitors by taking advantage of the inherent capacitance in a stack up. The fabrication house can have the. Fax +65 6872 7471Other benefits of using an 8-layer PCB stack-up over lower-layer circuit boards include: Lower radiation: The 8-layer PCB variety has superior signal integrity, which helps to lower radiation emission. Signal integrity is about the quality of the signal passing through a transmission line. The iCD Stackup Planner features a precision 2D Boundary Element Method (BEM) Field Solver providing customers with the accuracy and simulation speed they need for high-speed PCB Design. Atlas Si for Touchstone – PCB Insertion loss processing with Delta-L 4. 4+6+4 HDI stackup Layer buildup/stackup reference. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. Si8000m . AS9100D – Military & Aerospace. TOP - SIGNAL L2. Prepreg. 4-Layer Impedance Control Stackup. For instance, the main IC on this schematic has input impedance at pin8 of 90Ω as defined by the USB standard. Learn more about stackup design in Altium Designer. Hot Network Questions Fixing wrong ideas about coefficients (e. Warning Are you sure to logout ? First Name [ Required ]:. Add a damping resistor near the source. Once you enter the values of all the required. In a traditional PCB design, the designer specifies the width/clearance of the trace to satisfy the current/voltage requirements. Here, the via carrying the signal is placed at the center and is surrounded by 4 ground vias. This dense board with high-speed components will need a multilayer PCB stackup. The dielectric constant of your substrate will affect the geometry required to produce a transmission line with specific impedance and will affect the impedance of. PCB stack-up with controlled impedance requirements. This tool calculates the impedance of a conductor based on various inputs and circuit type. 3. PCB Stack-Up Altium Designer’s impedance calculator takes your board layer stackup information and sends the trace width and thickness results to your design rules. width|space|width. I tried to use the tool “PCB calculator” to determine the size of mi USB tracks. Z-planner Enterprise contains a stackup calculator which ensures signal integrity across a PCB for various controlled impedance models to quickly. 1. Freedom of design. The two impedance controlled lines I have are for USB (90 ohms differential), and a 2. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. The Layer Stack Manager in Altium Designer makes planning your PCB stackup easy. PCB designers typically need to implement impedance control for PCBs used in high-speed digital applications, such as RF communications, telecommunications, computing with frequencies higher than 100MHz, high-speed signal processing, and high-quality analog video (e. Use the Impedance tab to start your PCB impedance calculation for different layers. 6. copper trace on a 4-layer board with 8 mil thick dielectric and Dk = 4. For components running at 5 V or 3. Consider the following points to limit the flexible PCB errors in the bend areas: Avoid 90-degree bends. Speedstack PCB includes Si8000m. This stack-up is constructed using a single lamination. Speedstack is the stackup design tool of choice for professional PCB Designers fabricators and brokers who have a requirement to document and design stackups drill plans and material requirements complete with high speed transmissionline information. Using a power plane as signal reference. I followed some guidelines online and read forums. A PCB's impedance depends on trace geometry, materials, and layer configuration. Planes, in Multilayer PCB’s, provide significant reduction in radiated emission over two layer PCBs. PCB Materials and Stackup Design Guidelines. Arranging stack-up in KiCad. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. The PCB stackup is the substrate upon which all design components are assembled. Layer 4 - Ground/Signal. Contents. Depending on the requirements you can generate a stack-up. Always, ensure symmetry of the build-up. The stackup drawing must contain more information than in the past and the fabrication notes will need to be expanded. Speedstack Si includes Si9000e. A PCB impedance calculation generally refers to the task of calculating trace impedance, or transmission line impedance, based on the stackup and material configuration used in your design. The PCB stack-up has eight layers, with controlled impedance traces on layers 1, 2, 6, and 7. ) to measure the impedance, and both gave roughly 40 ohms. 4mm to 3. A fab drawing specifies all the important information such as board outline, layer stack-up, drill chart, and many more required to manufacture a PCB. This new release builds on the familiar ease of use of the popular In-Circuit Design online Impedance Calculator that has been utilized by tens of thousands of Engineers and PCB Designers world wide since 1996. Different copper profiles in PCB. PCB manufacturing tolerances with respect to material thickness. , FR4), and layer stackup. Adhering to these standards enables your manufacturer to establish a. A lower layer count may increase board size, routing complexity, and the inability to create high-density circuitry. PCB Laminates & Materials Quick Turnaround Program; Why. To meet those requirements I used some online impedance calculators to estimate the required trace properties for a. The first goal in stackup design is to determine the number of signal layers you'll need to support high speed routing for all your interfaces. Panasonic Megatron 6 and Rogers 4350B laminates are more widely used in the industry due to their high-speed reliable characteristics. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. Configuring the PCB for Controlled Impedance Routing. Fortunately, the return path analysis tools in PCB layout CAD systems can easily find and report these problems to the designer. This includes key considerations such as PCB footprint design, component placement, soldering considerations, solder mask checks, BOM assessment, testing, and panelization. s4p files with Delta-L 4. It should include impedance value, trace width, differential pair spacing, and the layer on which the controlled impedance traces are routed. best to use a stackup calculator to provide quick ‘what if’ analysis of the possibilities. Using an impedance control PCB calculator, the engineer determines that 50-ohm single-ended traces require a width of 6 mils and a spacing of 10 mils. Learn more about the integrated field solver from Simberian in Altium Designer. The target impedance value of a design is given by the equation: = ( V x ripple%) / ( 50% x Imax) The formula represents a combination of voltage fluctuation and transient current. Either the desired impedance at a specific frequency is used to determine the waveguide width, or the width is entered and the impedance is calculated. The formula for microstrip trace impedance is: Z = 87 * (W / H) ΩThis means that the actual trace width for a 50 ohm line could vary from design to design. It seems to me I can better use the JL3313 stackup. 2. You can then define each layer as a plane or signal layer. 2. Figure 3. If the PCB stackup is done differently, where the signal layer is closer to the power/gnd plane, then the trace can be thinner while still having the proper impedance. Stack Exchange Network. Link to PCB stackup Speedstack enhanced with Projects Via stub checks Via pad/antipad coaxial calculation. Designers can utilize layer stack management and routing to control board impedance. Notice that there is no impedance information on the stackup drawing. As an example, If I want to meet the 80Ω diff/ 40Ω single impedances, taking the first inner signal layer, and using the Saturn Edge Coupled asymmetric calculator, the input would be: H2= 180um H1= 176um w = 0. 15 mil, and the inductance would be 6. Dimensions. Sample 4 layer flex PCB. I use Saturn PCB Design ToolKit -> Conductor. 6 for 7628) 3313 thinner prepreg between top layer and inner layer (0. By formulas from IPC-2221, PCB Trace Width Calculator can estimate the width of copper PCB boards and the trace required under the given current, and at the same time keep the rise in trace temperature not to exceed the limit. The required inputs are the Dk value for the dielectric constant of the PCB substrate, and the. 2116 Prepreg 4. If you are planning to build an IPC class 3 board, ensure that the. Email: [email protected] is the allowed diversion/variation from a specific dimension. It defines the acceptable variation between the maximum and minimum limits. Their hardware design guideline said the traces between the USB and the termination resistors should have a differential impedance of 90 ohms. The differential one makes sense, but it looks like for single ended 50 ohms, their calculator only suggests a trace width. In a controlled impedance design the designer specifies the impedance rather than the trace width. Connections are formed in the copper layer (s) as conductive traces by etching away (removing) unwanted copper. . It helps you achieve customized electrical, thermal, and mechanical properties for your circuit board design. You should check their website out if your application uses a non-standard stackup for thin or high power applications. ] JLCPCB StackupsTechnically, there is no proper limit to N, though it depends on the layer count and the outer layer thickness. 4mil (1 oz) for plane layers. PCB Layer Calculation and Documentation Tool User Guide . To be successful, they require a thorough understanding of the fabrication process of the PCB and the materials used therein. Gerber files are helpful in both circuit board manufacturing and assembly processes. The stack-up should be symmetrical on either side of the metal core in a multilayer board. For example, in the image above, layer L10 in the stackup is enabled for impedance calculations, with the Top Ref set to 9-L9, which is a Plane layer,. 5 mil as the thickness when the controlled impedance tracks are on top. Formulas from IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Board. This microstrip impedance calculator gives you a good start for estimating the trace width and PCB dielectric thickness that will produce a target impedance value. We recommend the software from Polar Instruments if you want to get exact impedance calculation. Our drone’s PCB should contain at least six layers: four signal layers and two plane layers with a total thickness of 1. Similar to the Saturn tool, this capability allows you to experiment with the stackup and track dimensions to estimate impedances. There are some advantages to using a microstrip transmission line over other alternatives. These can only be determined after the PCB’s controlled impedance is calculated based on the impedance specifications, layout, and layer buildup. Via stitching is implemented for various reasons. The following is the usual FPC stackup information. Start Designing. Select the number of substrate layers. PCB layer count estimation is a vital process in board manufacturing and cost. The thickness of the Kapton stiffeners range from 0. Dielectric material (partially cured) is used to bond copper cores and copper foil in the layer stack-up. . Allegro ® layout editors – Allegro ® PCB Editor and Allegro ® Package Designer Plus – include a spreadsheet-based user interface, Cross-section Editor to help you define an accurate layer stackup with. Watch this Stackup Designer and Impedance Calculator demo in which our design team shows you the best features of our PCB tools. g. The material used is FR-4 with a Dk of 4. ; The laminate should be CAF-resistant and RoHS-compliant to prevent corrosion from hazardous chemicals like lead, mercury, and cadmium. Case 1: 8-layer HDI board design specifications. To open the Layer Stack Manager select Design » Layer Stack. 8. The simplest way for a controlled impedance is to just calculate some track width, (and gap for differential pairs), send the geometry to any PCB manufacturer and hope for the best. For example, good layering can reduce the impedance of the board and limit radiation and crosstalk. 0 for analysis with Si9000e. The surface finish is neglected. Reference layer. It is called ‘turnkey’ as PCBA. (Like Rolf points out in his answer, the "frequency of interest" is more related to the rise and fall times of a digital signal than to the data rate) So when a factory says. Designing for a Specific Impedance [The stackup dielectric will determine what size of trace you need to use in order to conform to the particular impedance. The tool used 0. 6 layer PCB stack up and routing strategy. It enables engineers and designers to understand and control the intricate aspects of PCB layout. 10 layer PCB stack-up . Stackup Editor Zoom: Hybrid Design Shield: Mask: Length unit: Pressed thickness: Impedance/Tpd; Signal Layers Properties. Controlled impedance. 4. Laser drilling creates precise holes on a PCB to establish connections between different layers. Note: The trace on the inner layer need to be much wider than the trace on the outer. Sampson. Place your components, vias, coupling capacitors. 6 layer rigid-flex PCB stack-up with air gap 8 layer rigid-flex stack-up with air gap. Customized Services and Advanced Options (Castellated holes,Edge plating,Impedance control. Sierra Circuits provides stackup design tools and services. Soldermask – Affects on Impedance Since PCB’s are normally covered in Soldermask then the affects of the conformal coating should be considered when calculating impedance. Calculating PCB Stackup. with the following layout parameters (width|space|width): Ohm. Contents. Length of both tracks should be the same. There are in general two approaches to create a PCB stackup, known as controlled stackup and controlled impedance. Contents. they normally use 7. AP166 V2. Just Try "Saturn PCB Design" tool (FreeWare). PCB Layer Calculation and Documentation Tool User Guide Speedstack PCB Stackup Builder Polar Instruments Ltd Polar Instruments Ltd. But in general do these things: Use a Sig/Gnd////Gnd/Sig stackup for more consistent impedance at top and bottom. Ideal board stackup from top to bottom is shown in Table 1. Following images present PCBWay's default layers stack. It is generally accepted to keep the gold thickness to 2-4 μin, as per the IPC-4552 ENIG. The Altium Stackup Manager not only allows you to define the stackup, but you can also create impedance profiles for various SE and DIFF impedances. 2 is an example of the amount of. Ensure that the wire thickness is the same as the trace width. Some fabricators can advise on track. PCB Laminates & Materials Impedance calculators: Using the data created by the layer stackup generator, the impedance calculator will give you the correct width for your controlled impedance lines. Here, = resistivity at copper. mm. On a multilayer PCB this only works when the signal is also on an inner layer-- making it difficult to have the proper impedance AND capacitance on an outer layer. ft. 033 inches. Using. Clear Requirements Keep. The next important part of the electronic circuit design process is to draw the schematic diagram using EDA tools like Altium, KiCAD, and Cadence Allegro. 8-layer HDI stack-up generated using Stackup Designer. when beginning the impedance calculation, the smallest trac e space (4 - 5 mils) is selected. These reflections are referred to as ringing. A PCB impedance calculator is an essential tool for designing stackup structures during the planning stage of layout design. But it lacks the differential impedance (impedance between these two tracks). It is tough to find and fix every single fault in a circuit board. Some fabricators can advise on track geometries if you supply them with your preferred stackup. I am planning to have the PCB (4 layer) manufactured at JLPCB controlled impedance service. By leveraging mathematical precision and providing ease of use, it adds tremendous value to the field, facilitating innovative and efficient designs. High-quality circuit boards as prototype and series at reasonable prices. As you route traces on a real board, they can couple to other traces and conductors capacitively or inductively. Circuits can: Help you with your controlled impedance stack-up. Once these decisions are made, a designer needs to determine the PCB trace width required to hit their required PCB transmission line impedance. You will typically want to include the following information: Trace width you’ve determined for a required single-ended impedance. Review: A new PCB stack-up design and impedance calculator is available for download from Istvan Nagy (see link below). The following is the usual stackup information(4,6,8 layer PCB standard stackup), which also can be used as stackup of impedances. For differential pairs, there is also a spacing value given. /sq. Leave enough space between traces and ask the manufacturer for controlled. Ensure the positive and negative traces of the differential pairs have matched impedance. Consider Figure 2 below: Figure 2Z-Planner Enterprise is a PCB stackup planning calculator which includes a field solver, loss-planning calculator and a dielectric materials library. The microstrip is a very simple yet useful way to create a transmission line with a PCB. Differential Pair Impedance Matching. ENGLAND . PCB Trace Width Calculator. There are many other free calculators available. 2116 Prepreg 4. First, select the desired RLC connection (parallel/series). My problem is to calculate overall impedance (independent of layer stackup topologies). This paper presents a flexible and efficient methodology to optimize stack-up for multi-layer printed circuit boards (PCBs) with enormous search space and various design constraints. Fabricators give trace impedance tables as guides to designers that need to implement controlled impedance in their PCBs. The build-up provides the following information: The copper thickness and weight. An example structure that extends the via structure impedance beyond 5 GHz is shown below: Example via antiap and stitching via arrangement around a signal via with a teardrop on an 8-layer stackup. If you need both impedance calculation and layer stackup/build up documentation the Speedstack PCB offers a considerable saving over purchasing separate licenses. 9 is an example of the amount of information that must be included in the stackup drawing to insure the PCB is correctly fabricated. 4-Layer Impedance Control Stackup. Controlled impedance is the characteristic impedance of a transmission line formed by PCB traces and its associated reference planes. Remember – the tighter the tolerance the more the PCB will cost. 2mm, copper thickness from 18μm to 210μm (0. 4-Layer Stackup. Procedure to use the calculator: 1. PCB stackup design will determine the trace geometry required for controlled impedance, but the impedance calculation needs to consider the entire. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. Controlled impedance: There can be a slight variation in the specified and manufactured impedance values. There are some advantages to using a. The importance of a good layer stackup in your PCB design and understanding the challenges in creating it. Contents. As we know, laser stands for light amplification. For a standard thickness 6-layer PCB, typical values are 0. • When using an impedance calculator, the outer layers of the PCB contain less glass than. 059”. Garenne Park St. This configuration allows for narrower traces to be used for the same. Below terminologies are used for high speed PCB material selection: a. Traces and their stack-up are presented in Figure 7. Field solvers. High-Speed PCB Stackup Design. Sierra Circuits is capable of fabricating circuit boards with a tolerance of ± 5% for controlled impedance. If the ratio is about 0. 1. Many will also be able to include an impedance test coupon on each panel that they fabricate - this can be used to measure the real impedances. Enable the Stack Symmetry option in the Properties panel. Off the top of my head, I can think of Polar and z-calc but I never liked these. For example, if you are using 1 oz of copper for a 1 sq ft area, the thickness of copper is 1 oz. Each power. 8-layer HDI stack-up generated using Stackup Designer. If you’ve created a complete stackup table, then you can include your impedance control spec as a note for your PCB manufacturer. JLCPCB Impedance Calculator. You can load a preset stackup in Altium Designer using the Layer Stack Manager. Apart from the layer. It also has an integrated impedance calculator to get the desired impedance and trace/space values on any signal layer. on layer 3 from the top, between power and ground plane. Here are some of the patent-pending analysis features in Z-zero software: Loss planning, including copper roughness — Layer by layer calculation of loss as a function of geometry, Df, copper roughness on both sides and frequency. Cost increases with the number of layers because of more production steps, more materials, and additional production time. Controlled Impedance PCB Parameters and Stackup. Recommended drill size is 3-6 mils while considering DFM for HDI PCBs. Use a field solver that can account for dispersion and copper roughness. This is assuming that you have a Design Rule in place which links the impedance profile to a. 2313 Prepreg 4. Initial stack-up of the 8-layer board. Advanced PCB transmission line design and stackup. The differential tracks should match this impedance. HDI boards and key considerations 8 layer HDI PCB. Controlling the impedance in your design is dependent on the board layer stackup you choose. Polar Instruments Ltd. It has been correlated many times. It is a full-featured Excel-based tool that helps plan the PCB stack-up so that controlled impedance traces can be effectively implemented. Impedance is a cornerstone of network design, and designers require accurate calculations to. Flex circuit’s polyimide material is lighter than FR4. In the first method, designers have to select materials on their own and calculate impedance, while in the second approach, the manufacturer selects materials and thicknesses to hit an impedance target.