PCB Design Glossary


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0

0201

0201 refers to a part size common to resistors, capacitors, diodes, and other passive components.  An 0201 part is 20 mils (0.020 inches) long and 10 mils (0.010 inches) wide.  These parts are difficult to see without magnification equipment and hand soldering of these parts is all but impossible.  


0402

0402 refers to a part size common to resistors, capacitors, diodes, and other passive components.  An 0402 part is 40 mils (0.040 inches) long and 20 mils (0.020 inches) wide.

These parts are very difficult to solder by hand without the aid of magnification equipment and a very small tipped soldering iron.


0603

0603 refers to a part size common to resistors, capacitors, diodes, and other passive components.  An 0603 part is 60 mils (0.060 inches) long and 30 mils (0.030 inches) wide.  These parts can be seen without magnification and can be soldered by hand with some difficulty.


0805

0805 refers to a part size common to resistors, capacitors, diodes, and other passive components.  An 0805 part is 80 mils (0.080 inches) long and 50 mils (0.050 inches) wide.  These parts can be hand-soldered without too much difficulty.


A

Active Components

Active components can control the power gain in a circuit, usually with a controlling input.  Examples include transistors, vacuum tubes, thyristors.


Advanced Assembly

Advanced Assembly is a PCB Assembly shop in Aurora, Colorado.  Advanced Assembly is a sponsor of this course.

Advanced Assembly Logo

Visit this website here:

https://aapcb.com

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Annular Ring

One of the steps in fabricating a via is to drill holes through a series of parallel circular pads on adjacent layers.  Mathematicians call the copper ring that remains an annulus.  Engineers colloquially call it an annular ring.
From left to right - a buried via, a blind via, a through via, stacked microvia and staggered microvia.


Antipad

Surrounding every pad is an area with no copper that acts as an insulator.  This is called the anti-pad.


AOI

AOI is an initialism that stands for Automated Optical Inspection.  A camera moves rapidly over all areas of the board looking for issue that would affect the quality of the PCB.  If an issue is found, the board is either crossed out or flagged for follow up by a human operator.  

AOI does not detect internal flaws in a PCB.


B

BGA

Ball Grid Arrays are components that connect to a PCB via a rectangular series of pads and solder-balls.

Ball Grid Array


Bill of Materials

The bill of materials (B.O.M.) is an itemized list of parts and components that will be used in a design.  Each component will have a designator, a part number, supplier, etc....

Each BOM should be saved as a CSV, XLS, or XLSX file with no merged cells, no formulas, or other unusual formatting.  It is a good idea to have alternate part numbers on hand in case they are needed.


Blind Via

A blind via extends from an external layer of a PCB to an internal layer.  They are initially formed as through-holes vias that undergo an additional lamination cycle.

Three Types of Vias

From left-to-right, a through-hole via, a blind via, a buried via.


Block

Circuits can be divided into blocks that have a particular function.  One benefit of this approach is that a functional block can be easily reused in future designs


C

Calf Path

One day through the primeval wood
A calf walked home as good calves should;
But made a trail all bent askew,
A crooked trail as all calves do.

Since then three hundred years have fled,
And I infer the calf is dead.
But still, he left behind his trail,
And thereby hangs my moral tale.
The trail was taken up the next day
By a lone dog that passed that way;
And then a wise bellwether sheep
Pursued the trail o’er hill and glade
Through those old woods, a path was made.

And many men wound in and out
And dodged and turned and bent about
And uttered words of righteous wrath
Because ’twas such a crooked path;
But still, they followed — do not laugh —
The first migration of that calf,
And through this winding woody-way stalked
Because he wobbled when he walked.

This forest path became a lane
That bent and turned and turned again;
This crooked lane became a road,
Where many a poor horse with his load
toiled on beneath the burning sun,
And traveled some three miles in one.
And thus a century and a half
They trod the footsteps of that calf.

The years passed on in swiftness fleet,
The road became a village street;
And thus, before we were aware,
A city’s crowded thoroughfare.
And soon the central street was this
Of a renowned metropolis;
And men two centuries and a half
Trod in the footsteps of that calf.

Each day a hundred thousand rout
Followed this zigzag calf about
And o’er his crooked journey went
The traffic of a continent.

A hundred thousand men were led
By one calf near three centuries dead.
They followed still his crooked way,
And lost one hundred years a day;
For thus such reverence is lent
To well-established precedent.

-- Sam Walter Foss

Capacitor

Capacitors connect two nets of different electric potentials with an electric field.  They can temporarily store energy in a small portion of a circuit.  While there is no direct electrical connection between the two nets, changes in one net will affect the other.


Consignment

Parts that are shipped directly from a customer to an assembly house are said to be "consigned."  This method is often used for rare or hard-to-find parts.


Copper Weight

The thickness is of copper is measured in a variety of units depending on the region.  In America, for historical reasons, the thickness is measured in the pseudo-unit [ounces], which is short for [ounces]/[foot]².  Other regions measure it in [micrometers], while others measure in [grams]/[millimeter]².


Courtyard

The smallest circumscribed rectangle that surrounds a component body and land pattern.


Image from blogs.mentor.com


Cut tape

Integrated Circuits and Passive Components are shipped in a variety of packing options that make them easy to use with automated machinery.  One option is to place the components in either a paper or plastic housing that has sprocket holes along one edge.  The automated machinery uses the sprocket holes to feed the parts into the pick and place machine and index the location of parts.  When an entire reel of parts is purchased and fed into the machine, it is referred to as a reel.  When only a portion of that reel is purchased, the specified number of components will be counted off and cut away from the reel, leaving the customer with a cut tape.

SMT Feeder Bank

Above is a series of reels (left) and cut tapes (right) ready to be fed into an SMT machine.  Image from smtcaddy.com

The machines do have their limitations -- cut tapes cannot feed single parts, and a minimum tape length is required.  This leads to something manufacturers call overage.


D

Derating

The numbers specified in datasheets are usually only accurate in ideal, laboratory conditions.  And the real world is nothing like a laboratory.  So individual values will fluctuate with temperature, age, voltage, current, etc...

The process of adjusting the value down from the specified value is referred to as derating.  It is done by either looking at a graph, called a derating curve, or by following an equation.


Design for Manufacture

Not everything that can be drawn in a cad program can be made in a factory.  Design For Manufacture is a series of checks that ensure that a printed circuit board can be built in a factory.


Digi-Key Electronics Corporation

Digikey is a major North American parts distributor and one of the sponsors of the course.

Visit their website here:  https://digikey.com


E

E-series

Inductors, Resistors, Capacitors, etc... have standard values based largely on the equation

E Series Approximation

where m is an E-Series value m=3\times2^x\;x\in {1,2,3,4,5,6}={6,12,24,48,96,192} and n is a positive integer less than m.

Each order-of-magnitude is logarithmically broken into a set number of values.  For E24 series, those values are 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.9, 3.2, 3.5, 3.8, 4.2, 4.6, 5.1, 5.6, 6.2, 6.8, 7.5, 8.3, 9.1

\sqrt[24]{10^0}=1.0 \sqrt[24]{10^1}\approx 1.1 \sqrt[24]{10^2}\approx 1.2 \sqrt[24]{10^3}\approx 1.3 \sqrt[24]{10^4}\approx 1.5 \sqrt[25]{10^5}\approx 1.6
\sqrt[25]{10^6}\approx 1.8 \sqrt[25]{10^7}\approx 2.0
1.0 Ω
1.1 Ω 1.2 Ω 1.3 Ω 1.5 Ω 1.6 Ω 1.8 Ω 2.0 Ω
10 Ω 11 Ω 12 Ω 13 Ω 15 Ω 16 Ω 18 Ω 20 Ω
100 Ω 110 Ω 120 Ω 130 Ω 150 Ω 160 Ω 180 Ω 200 Ω
1 kΩ 1.1 kΩ 1.2 kΩ 1.3 kΩ 1.5 kΩ 1.6 Ω 1.8 Ω 2 kΩ

\sqrt[24]{10^8}=2.2 \sqrt[24]{10^9}\approx 2.4 \sqrt[24]{10^10}\approx 2.6\\ \Rightarrow2.7 \sqrt[24]{10^11}\approx 2.9\\ \Rightarrow3.0 \sqrt[24]{10^12}\approx 3.2\\ \Rightarrow 3.3 \sqrt[25]{10^13}\approx 3.5\\ \Rightarrow3.6
\sqrt[25]{10^14}\approx 3.8\\ \Rightarrow3.9 \sqrt[25]{10^15}\approx 4.3
2.2 Ω 2.4 Ω 2.7 Ω 3.0 Ω 3.3 Ω 3.6 Ω 3.9 Ω 4.3 Ω
22 Ω 24 Ω 27 Ω 30 Ω 33 Ω 36 Ω 39 Ω 43 Ω
220 Ω 240 Ω 270 Ω 30 Ω 330 Ω 360 Ω 390 Ω 430 Ω
2.2 kΩ 2.4 kΩ 2.7 kΩ 3.0 kΩ 3.3 kΩ 3.6 kΩ 3.9 kΩ 4.3 kΩ

\sqrt[24]{10^16}=4.6\\ \Rightarrow 4.7 \sqrt[24]{10^17}\approx 5.1 \sqrt[24]{10^18}\approx 5.6 \sqrt[24]{10^19}\approx 6.2 \sqrt[24]{10^20}\approx 6.8 \sqrt[25]{10^21}\approx 7.5
\sqrt[25]{10^22}\approx 8.3\\ \Rightarrow 8.2 \sqrt[25]{10^23}\approx 9.1
4.7 Ω 5.1 Ω 5.6 Ω 6.2 Ω 6.8 Ω 7.5 Ω 8.2 Ω 9.1 Ω
47 Ω 51 Ω 56 Ω 62 Ω 68 Ω 75 Ω 82 Ω  91 Ω 
470 Ω 510 Ω 560 Ω 620 Ω 680 Ω 750 Ω 820 Ω 910 Ω
4.7 kΩ  5.1 kΩ 5.6 kΩ 6.2 kΩ 6.8 kΩ 7.5 kΩ 8.2 kΩ 9.1 kΩ

and the series would repeat for each multiple of 10 up into the MΩ range.

See https://en.wikipedia.org/wiki/E_series_of_preferred_numbers for more information


Eutectic

Pure substances undergo phase changes at specific temperatures.  Mixtures undergo phase changes over a range of temperatures.  At a specific ratio of substances, the solidus and liquids temperatures intersect at the Eutectic point.  At this point, the substance transitions directly from solid to liquid and back without entering an intermediate phase.

Phase Diagram

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F

FR-4

FR-4 is a designation for the most common dielectrics used in a printed circuit board.  It describes woven fiberglass and epoxy substrate that is Fire Resistant.

Core

The FR4 designator can be applied to a wide array of laminates.


Full-Duplex

In full-duplex communication, data is able to move bi-directionally during a data transaction.  Both nodes are capable of simultaneous transmit/receive.


G

GPIO

General Purpose Input Output pins are microcontroller pins that can be configured for a variety of tasks such as digital or analog inputs and output, PWM outputs, and data buses.


H

Half-Duplex

In half-duplex transmission, data is able to move bidirectionally, but only in one direction at a time during a data transaction.  Both nodes have the ability to transmit and receive but are only capable of one function at a time.


I

I2C

Inter-integrated circuit (I2C or I²C) is a half-duplex synchronous data bus that transfers data between two integrated circuits.  I2C is a popular interface, but suffers from low speed and limited transmission range compared to SPI and UART transmission protocols


K

Keysight Technologies


L

Land

A land or pad is a conductive part of a printed circuit board that is meant to connect to the pin of an integrated circuit.  

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LED

Light Emitting Diode.  These are devices that convert electrical energy into light.


Liquidus

Pure substances undergo phase changes at specific temperatures.  Mixtures undergo phase changes over a range of temperatures.  Liquidus is the temperature at which all solids have melted in a warming mixture.

Phase Diagram


LPI Soldermask

Liquid Photo Imagable Solder Mask is the outermost coating on a printed circuit board that sits between the copper and the components -- it's what gives PCBs their color.

Colored SolderMask

LPI is applied as a liquid coat that covers an entire PCB.  Then patterns of light are projected on the liquid and the high energy photons cause the material to harden and adhere to the PCB.

LPI protects copper traces and prevents liquid solder from migrating during the reflow process.


M

metalized

The tops of printed circuit boards and the bottoms and sides of discrete components are often made of a variety of metals or are coated with a thin layer of a metallic compound to make the surface-layer conductive.  These areas can then be soldered or further processed.  


Microchip

Microchip Technologies is an electronic component manufacturer based in North America.  Among their very popular offerings is the Atmel328P, the main microcontroller in the Arduino.


Minimum Order Quantity

The minimum order quantity is the absolute lowest number of parts that can be ordered at a time.  Below this quantity, the manufacturer or distributor's profit margins are so low, it doesn't make sense to invest employee time or company resources to sell the item.


N

Net

A net is a network of pads, traces, and copper pours that are electrically connected.  The theoretical resistivity of a net is zero.  Nets can extend from layer to layer through vias, but nets do not extend through components.

All nets should be given meaningful names.

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P

pad

A pad is a conductive copper shape on a PCB that is meant to act as a connection point for pins or probes.


Panelization

Printed Circuit Boards are made from sheets of material that comes in standard sizes of 12" x 18", 18" x 24", or 24" x 36".  To keep manufacturing costs down, multiple printed circuit boards are combined on a panel during fabrication.  

The entire panel is not available for usable space.  A 1" margin is used for tooling and test coupons.


Passive Components

Passive components cannot provide power gain in a circuit.  Examples include resistor, capacitors, inductors.


Pin

A pin is a metallic component connector that is soldered to a pad.


Prepreg

Prepreg is short for preimpregnated.  It refers to an adhesive dielectric layer that contains thermally activated epoxy.

The cores and the prepreg are pressed tightly together in a hot-oil hydraulic press for several hours, permenantly binding the materials.


PTH

PTH stands for Plated Through-Hole.  This is a hole that is drilled through all layers of a PCB and then plated with copper.

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R

RefDes

Short for Reference Designator.  Every component in every schematic and board file needs a unique identifier.  These can be any alphanumeric character string, but the convention and best practice is to use a letter to indicate the component type and a number that is incremented with each successive component type. 

For example, three resistors on a board would be labeled R1, R2, and R3, even if they had identical values.


Common Reference Designators
Prefix Component
A Assembly
B Battery
C Capacitor
 D Diode
DS  Display
 F  Fuse
FB   Ferrite Bead
J  Jack
 L  Inductor
 Motor
 MK  Microphone
 Plug
 Transistor
 Resistor
 Switch
 Transformer
 TP  Test Point
 U  Integrated Circuit
VR   Voltage Regulator
XTAL   Crystal
 Y  Oscillator


Resistor

These components restrict current flow between two nets in an electrical circuit.  The amount of current is proportional to the potential difference between the two nets.  Resistors are passive components.


Royal Circuit Solutions

Royal Circuit Solutions and Royal Flex Circuits are companies in California that specialize in small-batch, prototype, and custom printed circuit boards.  Royal Circuit Solutions is the principal sponsor of this course.

Visit their website here:

https://royalcircuits.com

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S

Schematic

A schematic is a pictorial representation of circuit components and their connections.  Symbols used in a schematic can vary depending on the convention used and a designers preferences.


SCL

Serial Clock Line is the synchronous timing line on the I2C data bus.


SDA

Serial Data is the data transmission part of the I²C data bus.


Slash-sheet

Slash-sheets are dielectric material specifications sheets detailed in an appendix to IPC-4101.  The pages provide material specifications, such as coefficient of thermal expansion, glass transition temperature, resin content, glass type, etc...

Material vendors such as DuPont, Isola, Rogers, etc... create cores that satisfy particular requirements, for example /28 or /41.  PCB engineers that specifically require Isola-370HR might pay more than an engineer that simply request a material that satisfies /98 or /99, since a manufacturer might have a similar product on hand from a different manufacturer.


Solidus

Pure substances undergo phase changes at specific temperatures.  Mixtures undergo phase changes over a range of temperatures.  Solidus is the temperature at which solids begin to form in a cooling mixture.  

Solder Phases


Specmanship

The process of selecting and presenting data about a part in a favorable, and often inconsistent way.  This tends to give engineers false impressions about the performance of a product. 

There are companies that purchase products from all manufacturers in a product class and independently test multiple samples in a controlled environment.  These companies then sell their results to engineers.  

Hard Way Hughes

"Specmanship is looked down upon by engineers as it can lead to costly mistakes.  I know of several engineers that will stop using parts from companies they believe are manipulating datasheet data.  Here's an example from two real companies (names redacted, and data changed) I talked to at Sensor Expo last year when I was trying to select a gyroscope for a project.

Example:

Company A markets a gyroscope with a bias instability of 0.4 °/hr.  Company B markets a gyroscope with a bias instability of 1.4 °/hr.

You'd choose company A, right?

Hold on -- company B suggested that I request the bias instability over the entire temperature operating range for product A.

Specmanship Example

What isn't presented in marketing materials is that when the gyroscopes were characterized over the entire operating temperature range of -55° C to 125°C, company A chose to present the best number, while company B chose to present the worst-case scenario."


SPI

A Serial Peripheral Interface is a data bus that transfers data between two or more integrated circuits.

It has the benefits of high speed and full-duplex communication.


T

Traveler

A traveler is a set of instructions that assembly line workers follow to construct a PCB.

Traveler


V

via

VIA stands for Vertical Interconnect Access.

Electrical connections between components are referred to as interconnects.  Traces and copper pours connect make in-plane (horizontal) connections, and formed cylinders called VIAs make the out-of-plane (vertical) connections.

Vias

This image was made by digitally removing all non-copper features from a printed circuit board.  From left to right, a buried via, a blind via, a through-hole via, stacked microvia, and staggered microvia.
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