# 4-Layer Stackup Info

I have a design with a short RF microstrip on a 4-layer board, and would like to do some basic impedance calculations. Is there a stackup of the DKRed 4-layer board for reference?

To calculate the impedance of an RF microstrip, you’ll need the following information:

1. Dielectric Constant (Dk): The dielectric constant represents the relative permittivity of the material used in the PCB stackup. Different layers may have different dielectric constants. Typical materials used in PCBs include FR-4 (Dk ≈ 4.2 to 4.6) and specialized high-frequency laminates with higher Dk values.
2. Trace Dimensions: You’ll need the width (W) and height (H) of the microstrip trace. The width is typically the outer dimension of the trace, and the height is the distance from the trace to the reference plane below it.
3. Trace-to-Reference Plane Spacing: The microstrip trace is typically referenced to a ground plane or a power plane below it. The spacing (S) between the trace and the reference plane is also an important parameter for impedance calculations.

Once you have this information, you can use various online calculators or simulation tools to estimate the impedance of your microstrip. Here is a general approach:

1. Determine Effective Dielectric Constant: The effective dielectric constant (Dkeff) accounts for the effect of the dielectric materials above and below the trace. It can be calculated using empirical formulas such as the IPC-2141 standard or by using specialized field solvers.
2. Calculate Characteristic Impedance: Once you have the effective dielectric constant, you can use a microstrip impedance calculator or formulas like the semi-empirical Wheeler’s formula or numerical methods such as the Method of Moments to calculate the characteristic impedance (Z0) of the microstrip.
3. Consider Tolerances and Manufacturing Variations: It’s important to keep in mind that the actual impedance of the microstrip may vary due to tolerances in trace dimensions, dielectric constant, and manufacturing variations. It’s a good practice to consider these factors and perform a sensitivity analysis to understand the impact on your design.

You can also post your question to PCBway here: Electrical Engineering about PCB - PCBWay
You may get some more useful guidelines.

Hi bidrohini, I appreciate the response, lots of valid and relevant information.

My original inquiry was to request the layer thicknesses for the 4-layer PCB from DKRed, but have since found it here.