PCB Design 3

Question 1

What is the primary reason to avoid 90-degree (right-angle) trace bends at high frequencies?

Accepted Answer

The outer corner of a 90° bend can cause acid traps and slightly increases effective trace width, affecting impedance

Answer

At high frequencies, 90° bends slightly increase the effective trace width at the corner, changing characteristic impedance and potentially causing reflections; 45° chamfers or arcs are preferred.

Question 2

What does 'layer stackup' refer to in multilayer PCB design?

Accepted Answer

The arrangement and thickness of copper and dielectric layers that make up the PCB

Answer

Layer stackup defines how copper signal, ground, and power layers are arranged, along with the dielectric materials and thicknesses between them, directly impacting impedance and EMI.

Question 3

What is 'crosstalk' in PCB design?

Accepted Answer

Unwanted coupling of a signal from one trace onto an adjacent trace

Answer

Crosstalk is electromagnetic coupling between adjacent traces where a changing signal on an aggressor trace induces a voltage or current on a nearby victim trace.

Question 4

What is the purpose of a 'via-in-pad' technique?

Accepted Answer

To place a via directly within a component pad, saving space and improving electrical performance for fine-pitch components

Answer

Via-in-pad places the via directly under an SMD component pad, reducing inductance and saving routing space, commonly used with BGAs and high-frequency components; the via must be filled and capped.

Question 5

What is 'net tie' used for in PCB design?

Accepted Answer

Intentionally connecting two different net names at a single point to allow separate simulation or analysis

Answer

A net tie allows two separately named nets (such as AGND and DGND) to be connected at a single star point on the board while keeping them electrically distinct in simulation.

PCB - Design Practice Test

PCB - Design Practice Test

PCB Design 3