Stub line and via stub

The stub line is commonly known as a thread or a crooked line (especially in router), or a path that the signal does not intend to pass through:

However, the following two scenarios can be ignored:

1. When adding test points, in order to ensure the spacing of test points, you have to pull a line out.

In this case, it is completely forbidden for high speed signal. Because of the large number of simulation and cabling experience, the stub will seriously affect the high-speed line signal quality.

The signal has a limit on the length of the stub, which is determined by the speed of the signal. The signal Integrity engineer can be either simulated or directly consulted.

2. Via stub for press fit component, a via stub is generated when the board is thicker than 2.1mm and the signal is entering the press fit component′s pin at the upper part level.

For example, a 16-layer board, where the signal enters the press fit component′s pin at Layer3, the red path is the path through which the signal passes. The blue path is the extra stub.

This situation is generally 3.125GHz below is not considered, but when the frequency is higher than 3.125GHz, it is necessary to consider the impact of via stub, mainly using back drill technology (rear drill) to solve.

This blog section references: Jimmy originated in the EDA365 high-speed PCB design forum, "How to check the stub line in pads" article.

★ Single-Ze Boat blog Article ★ Original article reproduced please specify: http://www.cnblogs.com/duzezhou/

★ Single-Ze Boat blog Article ★ Original article reproduced please specify: http://www.cnblogs.com/duzezhou/

Stub line and via stub