Printed Circuit Board Design (EED1002) – Practice Flashcards

These flashcards cover essential terminology, processes, and best practices from the EED1002 PCB Design lecture notes, spanning board types, components, layers, schematic and layout workflow, routing guidelines, fabrication methods, and assembly techniques.

What distinguishes a single-sided PCB from other board types?

Copper traces appear only on one side and holes are non-plated through holes (NPTH).

On a double-sided PCB, why are drilled holes copper-plated?

Plating creates plated through holes (PTH) that electrically connect traces on the top and bottom layers.

Why are multi-layer PCBs used?

They increase circuit density and complexity by sandwiching multiple copper and insulating layers.

In PCB terminology, what is a ‘trace’?

A copper track that carries electrical signals on the board.

What is the purpose of a power or ground ‘plane’?

A solid copper layer that distributes power/ground and reduces noise voltage.

Define ‘pad’ in the context of PCB design.

A copper area used for soldering a component’s pin; multiple layers form a padstack.

What is the difference between plated and non-plated through holes?

Plated holes have copper walls for electrical connection; non-plated holes are usually mechanical and non-conductive.

What is a ‘via’?

A small plated through hole used solely to interconnect traces between copper layers.

How does a guide (ratsnest) assist the PCB designer?

It shows straight-line connections between pins to guide manual routing and evaluate part placement.

What unit and spacing are standard for DIP through-hole packages?

100 mils (0.1 inch or 2.54 mm) pin pitch.

What typical pin pitch is used for SOIC and PLCC SMD packages?

50 mils (1.27 mm).

Name two advantages of surface-mount technology (SMT) over through-hole technology.

Smaller component size and ability to mount parts on both sides, increasing board density.

Give the typical size and power rating of a 0603 SMD resistor.

0.063" × 0.031" (1.6 mm × 0.8 mm) and 1/16 W.

What information does a reference designator convey?

A unique identifier (e.g., R1, C3, U2) assigned to each component for easy referencing.

Which PCB layers are counted when describing a ‘4-layer’ board?

Only the copper layers (signal and power planes).

What is the purpose of the solder mask layer?

A polymer coating that prevents solder bridging between adjacent pads during wave or reflow soldering.

Why is silkscreen applied to a PCB?

To print component outlines, reference designators, board revision, dates, and other text.

List the main steps in the PCB design flow.

Part creation, schematic capture, netlist generation, layout, post-processing (CAM, drill, BOM).

What are the two parts created during ‘part creation’?

CAE decal (logical symbol) and PCB decal (physical footprint).

What file is produced by schematic capture and what does it contain?

A netlist (ASCII text) listing every part/package and all electrical connections (nets).

How can two pins be connected in a schematic besides drawing a wire?

By assigning them the same net name.

Why is good component placement critical before routing?

It shortens trace lengths, reduces vias, and speeds up routing.

What is ‘pin swapping’ and why is it useful?

Exchanging similar pins to shorten routes or reduce complexity.

Define ‘design rules’ in routing.

Parameters such as trace width and clearances that govern spacing between pins, traces, and vias.

When might manual routing be required after auto-routing?

If the auto-router cannot complete all connections or violates design constraints.

Give three routing best practices to reduce crosstalk.

Avoid parallel adjacent traces for high-speed signals, route vertical traces on one layer and horizontal on another, and minimize unnecessary trace length.

Why should trace bends be at 45° rather than 90°?

To avoid sharp corners that can cause impedance discontinuities and acid traps during etching.

What is forward annotation?

Updating the PCB layout with changes made in the schematic capture.

What is backward annotation?

Updating the schematic database with changes (part swaps, gate swaps, etc.) made during layout.

Name three outputs generated during post-processing.

Gerber artworks, drill data (Excellon), and bill of materials (BOM).

What format is standard for PCB artwork files?

Gerber format, produced by photo-plotters.

What are the two main methods for removing unwanted copper during PCB fabrication?

Mechanical milling and chemical acid etching.

In photolithography, what does a ‘positive’ photoresist do when exposed to UV light?

Exposed areas become soluble and are removed during developing.

Which chemicals are commonly used as developers for positive and negative resists?

Positive: Sodium Hydroxide (NaOH); Negative: Sodium Carbonate (Na2CO3).

Name two chemicals often used as copper etchants.

Ferric Chloride (FeCl3) and Sodium Persulfate (Na2S2O8).

What is wave soldering?

A mass-production method where the PCB bottom briefly contacts a wave of molten solder to attach through-hole components.

Describe reflow soldering.

Solder paste is applied to pads, SMDs are placed, and the board passes through an oven to melt the solder and form joints.

Why is minimising the number of vias recommended?

Vias add resistance/inductance, increase fabrication cost, and can impact signal integrity.

What is pattern routing mainly used for?

Connecting identical pin numbers across multiple memory devices (e.g., RAM, EPROM) efficiently.

Which substrate material is mentioned for standard FR-4 boards?

Fiberglass composite board, typically 1/8" thick.