Impedance is the combination of the capacitance and inductance of a circuit when operated at high frequency.
Impedance PCB
Impedance is the combination of the capacitance and inductance of a circuit when operated at high frequency. Though also measured in Ohms, it is somewhat different than resistance which is a DC characteristic. Impedance is an AC characteristic, meaning that it is related to frequency, resistance is not.
What is Controlled Impedance?
Unless you have carefully designed the trace and its environment, impedance is typically "uncontrolled", meaning that impedance will vary in value from point to point along the trace.
At high frequencies, PCB traces do not behave like simple connections, controlled impedance helps us ensure that signals are not degraded as they route around a PCB.
Essentially, controlled impedance is the matching of substrate material properties with trace dimensions and locations to ensure the impedance of a trace's signal is within a certain percentage of a specific value. Controlled impedance boards provide repeatable high frequency performance.
1）Impedance PCB with 4 Layer M/L 1.6 mm FR4 1 oz copper service
Controlled ImpedancePCB
Layer: 4L
Material: FR4
Size: 24*16cm
Board Thickness: 1.2mm
Surface finish: Immersion gold
Solder Masker: Green
Copper Thickness: 1Oz
Special: Impedance PCB
CONTROLLED IMPEDANCE DATA
This impedance information is published to assist users of the PCB Train service who are looking for a track impedance calculator to predict track impedance.
These guidelines relate only to PCBs fabricated on the PCB Train 4 Layer M/L 1.6 mm FR4 1 oz copper service. View the multi-layer build here.
Customers use this information at their own risk.
Layer descriptions are defined as follows:
oLayer (1) = top copper
oLayer (2) = inner-layer top
oLayer (3) = inner-layer bottom
oLayer (4) = bottom copper
Our calculations and measurements have established the following:
oA layer (1) single free standing copper track (a micro-strip) of 0.40 mm width will have an impedance of 50 ohms with respect to a solid copper ground plane on layer (2)
oA layer (1) single free standing copper track (a micro-strip) of 0.18 mm width will have an impedance of 75 ohms with respect to a solid copper ground plane on layer (2)
oA layer (2) single free standing copper track (a micro-strip) of 1.64 mm width will have an impedance of 50 ohms with respect to a solid copper ground plane on layer (3)
oA layer (2) single free standing copper track (a micro-strip) of 0.68 mm width will have an impedance of 75 ohms with respect to a solid copper ground plane on layer (3)
oA layer (2) single free standing copper track (a micro-strip) of 0.26 mm width will have an impedance of 100 ohms with respect to a solid copper ground plane on layer (3)
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