CAD Specialist Electrical and Electronics Design Flashcards

What is the purpose of a 'Design Rule Check' (DRC) in PCB CAD software?

Answer: Checks that physical layout constraints such as clearances and trace widths are satisfied

A DRC automatically verifies that the PCB layout meets specified manufacturing and electrical constraints — such as minimum clearances, trace widths, and annular ring sizes — before fabrication.

In PCB design, what is a 'via'?

Answer: A plated hole that electrically connects copper traces on different PCB layers

A via is a plated-through (or blind/buried) hole whose barrel wall is copper-plated, creating an electrical connection between traces on different PCB layers.

Why is 'controlled impedance' important in high-speed PCB design?

Answer: It matches trace impedance to source and load impedance to preserve signal integrity

Controlled impedance ensures that trace characteristic impedance matches the source and load, preventing signal reflections, ringing, and degradation at high frequencies.

What does a 'copper pour' (flood fill) accomplish on a PCB layer?

Answer: Fills unused board areas with copper connected to a net — typically ground

A copper pour fills unused PCB real estate with copper tied to a specified net (usually ground) to lower impedance, improve EMI shielding, and assist heat dissipation.

In Gerber-based PCB fabrication output, what information does the NC drill file contain?

Answer: X,Y coordinates and diameters of all holes to be drilled

The NC drill file (Excellon format) contains the x,y coordinates and tool-size codes for every hole — vias and component through-holes — that the CNC drill must produce.

What is the primary purpose of a 'keepout zone' in PCB layout?

Answer: Restricts component placement, copper routing, or both within a defined area

A keepout zone enforces design restrictions — preventing copper traces, component placement, or both — within an area to satisfy mechanical clearance, RF isolation, or regulatory requirements.

Which PCB layer prevents solder from adhering to areas between pads during reflow soldering?

Answer: Solder mask layer

The solder mask is a polymer coating applied over the PCB surface that covers all copper except the exposed pads, preventing solder bridges between adjacent pads.