Here is a shorter PCB terminology list for commonly used terms in PCB fabrications, PCB designing, PCB CAM work and PCB Industries.
List of proper PCB Terminology
There are typically two types of holes in PCB.
PTH: Plated thru-hole
PTH holes may be either component holes or vias.
Component holes are for component assembly based on component dimensions.
Via holes carry current from one layer to another layer.
NPTH: Non plated thru-hole
NPTH holes are for PCB mounting purposes. Standard mounting hole sizes are between 3 mm to 5 mm.
PCB holes are made with drill bits, mostly on CNC drilling machines.
Bigger mounting holes( 6 mm or larger ) are made with CNC routing machines.
An annular ring is a copper area around the PTH hole and vias to ensure good connections in circuit boards.
The copper area around the holes is called pads. Pads are in shapes like Round, Square, Rectangle, ovals, Hexagon and octagon etc.
Copper points for SMD component assembly are called SMD pads. There are no holes in SMD pads. Generally, the SMD pad shape is square and rectangular.
In Printed circuit boards, there may be few points where reading has to be taken. These points are called test pads. Generally, the test pads shape is round with silkscreen identification TP.
Test points may be with or without holes.
Trace or Track
A PCB trace or track is a copper conductor line that carries the signal from one pad to another pad or many pads.
A teardrop is an extra copper at a junction of traces and pads ( either with vias or components). Teardrops may be in straight or round shape.
Teardrops are also used for trace transition. For example, when the trace width is reduced to 3 mils from 5 mils, the teardrop is added at the transition point to minimise cracks or stress.
PCB Board Thickness
Generally, Standard PCB thickness is 0.062” ( 62 mils or 1.57mm) for single side circuit boards, double-layered PCB and Multilayer Printed circuit boards.
Other Board thicknesses are 0.3 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2mm, 1.5mm, 2mm, 2.4mm, 3.2 mm
Copper weight confirms the copper thickness on board. Hence copper weight is more important on PCB.
The current-carrying capacity on PCB depends on the thickness of the trace; hence, the higher the copper weight, the higher the current capacity.
1oz of copper is rolled out over an area of 1 square foot is 1oz copper weight, and in this case, copper thickness is 1.4 mils (or 0.035 mm or 35 microns)
Copper weight is measured and discussed in ounces per square foot (oz/ft²) and examples as below.
Copper Weight (oz/ft²)
The copper thickness on board in mils
The copper thickness on board in mm
The copper thickness on board in micron
Most PCBs are made up ofn1 oz copper weight in the industry, and high power PCBs are made up of 2 oz copper weight. Very few PCBs are made up of higher copper weight for special applications.
The printed circuit board’s outer border is called outline. The outline is drawn with lines and arcs in designing software. PCB Outline is also called PCB board Profile.
PCB outline shape may be rectangle, square, round, or any other irregular shape.
Any regular or irregular shape cutting inside a PCB profile is called cutout.
The cutout may be slots, rectangle, square, round hole shape and any other irregular shape.
The cutout may be plated or non plated. ( most of the time non platted)
A cutout is done using a routing bit ( also router bit) on a CNC machine.
A printed circuit board with a cutout on the board profile is a PCB notch.
The Gerber format is an open ASCII vector format for printed circuit board (PCB) designs.
PCB houses need a Gerber to fabricate PCBs.
There are three types of Gerber.
Extended Gerber (Gerber 274X or RS-274X) is a standard format and is common in the industry.
Standard Gerber (Gerber-D or RS-274-D): It is an old data format. The Gerber-D design requires a wheel file( or aperture file) to read the Dcode of all lines, pads, arcs, surfaces and texts.
GerberX2: it is an Extended Gerber file with the metadata. This file format is the latest in industries.
Extension for gerber file is .gbr , .art etc
Following Gerber file layers are necessary to manufacture PCBs:
Top and bottom side solder mask layer files
Top and bottom side silkscreen Layer files (also called Legend layers)
Top and bottom side copper layer files for multilayer PCB inner copper layer files as well.
PCB Border ( outline or profile ) files along with cutout details.
NC drill file ( Excellon-2) file for CNC drilling
Some designers provide PCB production notes, PCB dimensions, drill details, and few more information notes on Gerber files.
One more format for PCB data is ODB++.
PCB Design Files
PCB design software is available for offline and online cloud base.
PCB design software allows designers to design PCB and provides facility for maintaining spacing, Annular ring, track width etc.
The design file is a master file that can export Gerbers. It is easy to make changes in exported Gerber for DFM ( Design for manufacturing) with few limitations, but when there is a change in PCB design ( such as component location change, drill location change, Ground or power plane changes and many more.) Only PCB design files can make changes and allow re-exporting data.
PCB Designing process is known as CAD ( computer-aided drawing or computer-aided design)
Bill of material
BOM is a short form for the bill of material.
BOM is a file that has a list of all the components that will assemble in PCBs.
BOM has a component list and component’s package ( SMD or thru ), component’s part number, Component Qty, Manufacturer of component etc.
BOM files can be exported from design files. Mostly BOM files are in text (.txt) , excel , .csv or .html format.
Single-sided PCB is a fundamental type of PCB. Single-layer PCB has only one side conductive copper material( traces, pads and copper pour) fixed with the substrate.
All the thru-hole components are mounted on one side, and copper traces are on the other side. However, SMD components are assembled on the copper side!
The single side design is best suited for low dense design, low-cost products.
Materials for single-sided are FR4, CEM1, FR1, CEM3, Aluminium.
A Component placement side is called the component side, and a conductive copper side is called the solder side.
Jumpers are used component side to bypass connection from the solder side.
Double-sided PCBs are known as the PTH PCB or two layers PCB or double-sided played thru PCB (DSPT).
Double-sided PCBs are kind of similar to single side PCBs except it has double-sided copper and vias.
Double-sided PCBs are more complex than single side circuitry.
Double side PCBs may be Compaq in design compared to single-sided.
Clearance is the shortest distance between two points on a PCB. Mainly used during DFM and PCBA.
Aspect Ratio :
What is Aspect Ratio in a PCB industry?
The aspect ratio is the thickness of a PCB divided by the diameter size of a drilled hole In PCB fabrication. Aspect ratio is an important parameter for a plating process. Hole sizes that are small compared to board thickness may result in unsatisfactory plating or open holes. Plating must flow through the hole properly to achieve acceptable copper plating.
The bigger the aspect ratio, the more difficult it is to achieve reliable plating.
For the 10:1 Aspect Ratio,
If board thickness is 1.6mm, hole size must be >=0.16mm
If board thickness is 2.0mm, hole size must be >=0.20mm
If board thickness is 3.0mm, hole size must be >=0.30mm