Rogers RT/duroid 5870 and 5880 glass microfiber reinforced PTFE composites are designed for exacting stripline and microstrip circuit applications.

Today we’re learning what stripline and microstrip line are.

Stripline: a banded line that walks in the inner layer and is buried inside the PCB, as shown below

The brown part is the conductor, the green part is the PCB insulating dielectric, stripline is the ribbon wire embedded between the two layers of conductors.

Because stripline is embedded between two layers of conductors, its electric field distribution is between two conductors (planes) that wrap it, and does not radiate energy or be disturbed by external radiation. but because it is all surrounded by dielectric (dielectric constant is larger than 1), the signal is transmitted slower in stripline than in microstrip line!

Microstrip line: a strip line attached to the surface of a PCB layer, as shown below

The brown part is the conductor, the green part is the PCB insulating dielectric, and the brown block above is the microstrip line.

The light green part is epoxy organic material.

Since one side of the microstrip line is exposed to the air (which can form radiation around or be disturbed by radiation around it), and the other side is attached to the PCB insulating dielectric, the electric field formed by it is distributed in the air. The other part is distributed in PCB insulating medium. Its outstanding advantage is that the signal transmission speed in the microstrip line is faster than that in the stripline.

Conclusion

1. Microstrip line is a banded wire (signal line) separated from the ground plane with a dielectric. If the thickness, width, and distance between the line and the ground plane are controllable, its characteristic impedance is also controllable.

2. Stripline is a copper strip line placed in the middle of the dielectric between two layers of conductive plane. If the thickness and width of the line, the dielectric constant of the medium and the distance between the two conductive planes are controllable, then the characteristic impedance of the line is also controllable.

Impedance calculation of microstrip and Striplines:

a. microstrip line Z ={87/[ sqrt (Er+ 1.41)]} ln [5.98 H/(0.8 W+T)]

Among them, the W is the line width, the T is the copper thickness of the line, the H is the distance from the line to the reference plane, and the Er is the dielectric constant of the PCB plate material. This formula must be applied at 0.1<(W/H)<2.0 and 1<(Er) to 15.

b. stripline Z =[60/ sqrt (Er)] ln {4H/[0.67π(T +0.8W)]}

Among them, the H is the distance between the two reference planes, and the line is located in the middle of the two reference planes. This formula must be applied in W/H<0.35 and T/H<0.25.