PCB Terminology Glossary

Printed circuit board is a crucial component of electronic applications. As such, it is essential to have a comprehensive understanding of the terminology associated with them. Familiarity with PCB terminology promotes effective collaboration between enterprises, enables enthusiasts to pursue DIY electronic projects, and expands the knowledge base of users. In line with our commitment to providing cutting-edge technology solutions, TechSparks is pleased to present the most exhaustive list of PCB glossaries available online. We invite you to utilize this resource for your reference and stay ahead of the curve in the ever-evolving world of electronics.

PCB Manufacturing Terminology

PCB Manufacturing Terminology
PCB
That is, the printed circuit board, as the core component of modern electronics, is called the “mother of electronics”. Its role is to serve as the carrier of electronic components and provide the necessary conditions for electrical connections. When we refer to PCB we usually refer to a bare board, which is a board that does not contain electronic components and consists of a non-conductive sheet with printed wires.
PWB
The full name is Printed Wire Board, which was the early term for PCB. In the early stages of technology, it emphasized the wires and connections on the board, hence the use of “Wire.” However, as electronic technology increasingly demanded higher circuit performance, it was renamed Printed Circuit Board. This term not only encompasses the wiring on the board but also emphasizes the layout, connections, and pins of the components. Essentially, the terms PWB and PCB are interchangeable.
Substrate
While a printed circuit board is composed of multiple components, regardless of the type of PCB, they share the same materials, with the only distinction being the substrate material. The substrate layer, serving as the core of the PCB, is the material that gives the PCB its name. Within the internal structure of the PCB, the substrate layer achieves insulation purposes and provides mechanical support, ensuring the stable operation of the circuit.
Inner Layer
This is a concept involved in multi-layer circuit structures, where each inner layer includes elements such as traces, copper foils, signal planes, power planes, etc. Since inner layers are situated within the internal structure of the PCB, achieving circuit connections relies on vias, which allow the transfer of current, signals, or electrical connections from one layer to another.
Via
A generic term referring to holes on a printed circuit board, encompassing various types. The design and manufacturing of PCB vias are determined by the requirements of different projects. Regardless of the type, their ultimate purpose is to achieve electrical connections between different layers. Such connections allow designers to arrange more components and functions on the limited surface of the PCB, providing crucial support for a compact circuit layout.
PTH and N-PTH
These are two similar concepts used in the treatment of holes on a PCB. PTH stands for Plated Through Hole, where a layer of conductive copper is added to the hole walls, enabling the passage of current between different layers. On the other hand, N-PTH, or Non-Plated Through Hole, is primarily used for mechanical support and positioning, unrelated to circuit performance.
Stackup
This term is associated with multi-layer circuits and refers to the process of layering different components in a more strategic manner to construct a more complex and powerful circuit board structure. Stackup in design should adhere to strict PCB design rules and maintain a symmetrical structure to achieve superior electrical performance.
Lamination
A printed circuit board is akin to a sandwich made up of multiple different layers stacked together to form a whole. The lamination process is the key to laminating multiple copper layers and insulation layers together through high temperature and high pressure to make them inseparable.
Milling
A machining technique utilizing Computer Numerical Control (CNC) machines, milling is employed in various processes such as removing excess copper foil, drilling holes, and V-groove cutting during PCB manufacturing. Despite the ongoing iterations and updates in technology, laser processing is emerging with more sophisticated techniques. However, milling processes persist in the PCB manufacturing industry, maintaining their prominence due to their cost-effectiveness.
Silkscreen
In PCB industry, silkscreen refers to the characters on the surface of the PCB used to identify components, circuit layouts, circuit descriptions, and manufacturer information. On one hand, it aids in the assembly process, and on the other hand, it provides necessary support for rework. Unlike inner layers, the silkscreen layer is typically directly printed onto the solder mask layer without the need for stacking and lamination.
Solder Mask
This is the protective layer of the PCB, located at the topmost part. The green portion we see on the PCB belongs to the solder mask, although it can also be of other colors depending on the solder mask ink used. Serving as a primary component of the PCB, it plays a dual role. On one hand, it shields against external threats such as dust, moisture, and chemicals. On the other hand, it covers the exposed copper traces and pads on the circuit board, preventing short circuits during assembly and operation.
Coverlay
As flexible circuits can be bent and folded, the protective layer on their surface needs to possess the capability to flex. Coverlay is essentially the solder mask, but with a distinction—it is specifically used to protect flexible circuits. Some also refer to coverlay as flexible solder mask. The most common material for coverlay is polyimide, renowned for its excellent thermal stability, chemical resistance, and mechanical strength.
Surface Finish
A process involving specific chemical or physical treatments of the surface of a printed circuit board to enhance its surface performance, corrosion resistance, and solderability. This procedure aims to ensure higher reliability and stability of the PCB in practical applications. Given the diverse design and application requirements, there are various PCB surface finishes available to cater to specific needs.
FR4
Glass Fiber Reinforced Epoxy Resin, is one of the most common materials in the PCB industry. It features high flame resistance, primarily composed of glass fiber cloth and flame-retardant epoxy resin. In flame tests, it can withstand continuous burning for over 10 seconds without dripping, categorized into different grades based on test results, with a total of 5 grades. FR4 material is widely popular due to its outstanding performance and cost-effective pricing.
Rogers
Rogers is a materials technology company based in the United States, specializing in the research, development, manufacturing, and sale of high-performance materials and products. The Rogers laminates they develop, although expensive, are highly effective for radio frequency (RF), microwave, and other high-frequency applications.
Multilayer PCB
The visible part of a PCB to the naked eye consists of the outer layers, namely the top layer and the bottom layer. However, when the need arises to accommodate more components, a more densely packed circuit is required. To incorporate more circuits without increasing the surface area of the PCB, we opt to arrange them internally, forming a multilayer structure. Typically, a PCB with three layers or more is referred to as a multilayer PCB, where “layers” refer to copper foil layers, as the final circuits will be arranged on these copper foils. This design significantly enhances the integration and performance of the circuit while maintaining the compact size of the PCB.
Double-Sided PCB
Refers to a PCB where both the top and bottom have conductive patterns, allowing components to be installed on both surfaces simultaneously. The primary objective is to optimize the overall volume of the product by fully utilizing the PCB surfaces. In comparison to single-sided PCB, double-sided PCB require soldering on both surfaces, which increases manufacturing complexity and costs.
Gerber Files
Before production, manufacturers need to obtain design-related information. However, design files may lack detailed explanations for specific aspects. In such cases, Gerber files become an irreplaceable bridge. They contain precise graphics of various layers of the PCB, key information such as circuit traces, pads, and through-holes, providing necessary guidance for production. Before manufacturing, Gerber files need to be generated for each PCB layer, and RS-274-X has become the most common format. This standardized format enables manufacturers to accurately interpret and understand design intent, ensuring the precision and consistency of PCB production.
ODB++
Are considered the next-generation standard in the PCB manufacturing field. Utilizing an easily readable ASCII format, they facilitate the upload and download of data, simplifying the process compared to traditional Gerber files. However, it’s essential to note that ODB++ is not just an evolution of Gerber files; rather, it functions as a comprehensive and intelligent solution for transmitting PCB manufacturing information. This aids in reducing the occurrence of human errors.
IPC
Originally known as the “Institute for Interconnecting and Packaging Electronic Circuits,” plays a pivotal role in guiding and standardizing the electronic manufacturing industry globally. With members spanning across suppliers, manufacturers, assembly companies, and various other sectors, IPC forms a diverse and influential community, providing extensive consensus and standards for the electronics industry. The IPC standards established by this organization are considered a universal language applicable worldwide, contributing to ensuring the consistency, reliability, and manufacturability of products.
BGA
The full name is Ball Grid Array, which is a packaging technology used for chips and other components. Its notable feature is a grid-like array of solder balls on the bottom of the chip, which connects to corresponding solder pads on the printed circuit board through soldering. The introduction of BGA is primarily due to its higher pin layout and excellent heat dissipation performance, making it a mainstream technology in modern chip packaging.
HASL
Short for Hot Air Solder Leveling, is a common and cost-effective surface treatment process typically applied to standard PCB. In the HASL process, the PCB is heated to the melting point of the solder, and then liquid solder is uniformly sprayed onto the surface using hot air or nitrogen. This forms a protective layer of tin, enhancing the reliability of soldering and preventing oxidation.
OSP
Short for Organic Solderability Preservative, is a surface treatment aimed at protecting the copper surface of PCB to prevent oxidation in the air, thereby enhancing solderability. Its advantages include lower cost and environmental friendliness. However, compared to other technologies, OSP may slightly lag in terms of heat resistance and mechanical strength.
ENIG
Short for Electroless Nickel Immersion Gold. It involves coating the copper surface with a layer of nickel, followed by immersion in a solution containing gold ions. A chemical reaction occurs, and the gold layer adheres to the nickel layer, forming a gold finish on the copper surface.
ENEPIG
Abbreviation for Electroless Nickel Electroless Palladium Immersion Gold, is considered an upgraded version of ENIG. It introduces a thin layer of palladium on top of the electroless nickel layer to enhance the connection between gold and nickel, providing superior heat resistance and corrosion resistance. Despite its relatively higher cost, ENEPIG is the preferred choice in applications with extremely high demands for performance and reliability due to its outstanding characteristics.
Immersion Tin
Involves depositing a layer of tin metal onto the copper surface of a PCB to provide protection and improve solderability. In the processing, the copper surface is first cleaned and activated, and then the board is immersed in a solution containing tin salts, allowing a tin layer to deposit on the copper surface through a chemical reaction. Immersion Tin offers advantages such as good solderability, suitability for small pitch components, and relatively lower costs. However, it tends to have poorer corrosion resistance and wear resistance compared to other methods.
Immersion Silver
This involves immersing a PCB in a solution containing silver ions, forming a silver layer on the copper surface. The immersion silver process is characterized by strong conductivity, excellent corrosion resistance, and robust metal connectivity, making it highly favored in specific applications. However, it comes with a relatively higher cost.
Gold Fingers
Refer to a row of metal connection points along the edge of a PCB, presenting a neatly arranged strip, hence the name ‘gold fingers‘, also known as edge fingers. These gold fingers are typically formed through electroplating, using alloy materials to ensure excellent durability, making them resistant to damage even during repeated insertion and removal processes. Once inserted into a slot, gold fingers can reliably connect to other PCB, facilitating electrical and data transmission between devices.

PCB Assembly Terminology

PCB Assembly Terminology
PCBA
The term “PCBA” is an abbreviation for Printed Circuit Board Assembly. From observations, when users search for “PCBA” on Google, search results often focus on “PCB vs PCBA“. This might be the reason why the term has not become widely popular. However, in China, PCBA is one of the most commonly used terms.
PCB Assembly
Refers to the process of installing components onto the surface of a printed circuit board and soldering them in place. In electronics, the bare board serves as the substrate, while the components act as the functional elements. The PCB assembly process connects these two parts, allowing current to flow along the traces on the PCB to the component pins, enabling the components to perform their functions. Simply speaking, the PCB assembly process involves: applying solder paste→mounting components→high-temperature soldering→testing.
Solder Paste Printing
This is a common process in PCB assembly that involves applying solder paste to a specific stencil. The solder paste is then evenly spread onto the printed circuit board by applying uniform pressure using a squeegee. For DIY enthusiasts, this process might be a bit intricate and can be accomplished using a syringe. However, for commercial projects involving large-scale production and requiring consistency, automated equipment is typically used for solder paste printing.
SMT
Short for Surface Mount Technology, is the most widely used technology in modern PCB assembly processes, specifically designed for mounting surface-mount components. In the SMT process, a pick-and-place robot uses a vacuum nozzle to pick up components from feeders and precisely places them at designated positions on the PCB. This technology is highly popular due to its applicability to miniaturization and high-density designs. Additionally, it contributes to cost reduction and increased production efficiency through automated manufacturing processes.
THT
Stands for Through-Hole Technology, is a relatively traditional yet reliable PCB assembly technique suitable for through-hole components. In the THT assembly process, the first step involves drilling holes at predetermined locations on the PCB. Subsequently, electroplating is performed to create a metal layer on the hole walls. The component pins are then inserted through these holes and soldered in place.
PCB Stencil
Also known as SMT stencil or solder paste stencil, the PCB stencil is a crucial tool used in the solder paste printing stage of SMT assembly. Typically made of aluminum or stainless steel, it features a surface with holes corresponding to the soldering points. During the solder paste printing process, solder paste is applied to the surface of the stencil, and then a squeegee is used to accurately deposit the solder paste onto the solder points. This tool significantly enhances the efficiency and precision of solder paste printing.
SMD
It is an abbreviation for surface mount device, which includes different shapes and sizes, such as rectangular, cylindrical, composite, and special-shaped components. These components are smaller in size compared to through-hole components, making them more suitable for miniaturization and densification of electronic products.
DIP/DIL
Also known as dual in-line package, is a commonly used packaging method for integrated circuits. The integrated circuit is shaped like a rectangle with two rows of parallel metal pins, known as headers, on each side. Components in DIP packages can be soldered into through-holes on a printed circuit board or plugged into DIP sockets. The components are generally referred to as DIPn, where n represents the number of pins. For instance, a 15-pin integrated circuit is called DIP15.
Wave Soldering
Refers to a soldering technique used for through-hole components, achieving soldering by melting the tin on the pins at high temperatures. In the wave soldering process, the board is inclined as it enters the machine, and the solder wave presents a series of wavelike forms on the underside of the PCB, resembling ocean waves, hence the term “wave.”
Reflow Soldering
It is a soldering process used for surface-mount components, named for the characteristics of solder melting and reflow. In the reflow soldering process, components are first mounted on the PCB and then transported to the soldering area via a conveyor belt. After going through the three stages of preheating, soldering, and cooling, a reliable solder connection is formed.
Conformal Coating
It is a coating or material applied in a colloid form to the surface of a PCB, commonly used in the engineering and manufacturing fields. Through exposure to UV light in a curing machine, this coating gradually solidifies to form a protective layer, shielding the circuit from moisture, physical impacts, and chemical factors. Depending on the specific application of the PCB, different types of chemical materials can be chosen to prepare conformal coatings to meet specific environmental conditions and requirements.
Potting
It is a process of filling electronic devices containing electronic components and circuits with high molecular insulation materials such as polyurethane, silicone, epoxy resin, etc., either through machinery or manual methods. Subsequently, the material cures at room temperature or under heating conditions. After potting a PCB, it forms a high-performance thermosetting insulation layer, achieving bonding, sealing, potting, and protective coating for the circuit. In appearance, it resembles amber.

PCB Design Terminology

PCB Design Terminology
Footprint
Refers to the actual physical layout and pin arrangement of a component on a PCB, defining the position, spacing, size, and connection method of the component’s pins to the solder pads on the PCB. A correct PCB footprint contributes to ensuring the reliability of the PCB. Typically, this information is provided by the component manufacturer or can be found in the library of design tools.
Pad
This refers to the metallic area on a PCB used to connect components. Serving as the point of connection between component pins and the PCB surface, pads secure them together through the application of solder paste and the soldering process. Generally, PCB pads are divided into two main types: through-hole pads for plug-in components and surface mount pads for SMD components.
Window Opening Design
Window opening design refers to the process of removing the solder mask at specific locations on the PCB surface, also known as solder mask opening. This encompasses various forms such as pad opening, via opening, gold finger opening, and more. The primary objective is to provide a more convenient soldering environment. Designers can execute this operation using design software and subsequently output files for manufacturers to use in production.
HDI
Short for High-Density Interconnect, refers to a set of technologies and design methods implemented in printed circuit boards to achieve more and complex electrical interconnections within limited space. These design methods include multi-layer design, stacking/layering techniques, microvia technology, and more.
Blind Vias
Similar to other vias, blind vias primarily serve the purpose of connecting components to the circuit. However, what sets them apart is that they enter from one side of the PCB surface but do not emerge from the other side. Typically, blind vias are combined with technologies such as SMT and HDI. Taking SMT as an example, due to the shorter pins of components mounted on blind vias, the power of SMT is often leveraged for surface mount assembly.
Buried Via
A type of via concealed within the interior of a PCB and not visible on the surface, its purpose is not for installing components but rather to establish interlayer connections. Based on its concept, buried vias are exclusive to multilayer PCBs, as single-layer and double-layer configurations lack sufficient inner layers for buried via designs.
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High-Frequency Circuit
High-frequency circuits are designed to handle signals in the range of hundreds of kilohertz to several gigahertz. These circuits aim to provide faster and more comprehensive signal processing, primarily applied in advanced fields such as radio frequency (RF), microwave, and millimeter-wave technologies. In high-frequency environments, electronic systems face various interferences and challenges, making the design and manufacturing of high-frequency PCB more demanding.
Radio Frequency Circuit
Short for RF circuit, is a specialized circuit designed to handle radio frequency signals within the range of 300 kHz to 300 GHz. It is primarily employed in communication systems, radar, radio, and various wireless communication devices. In high-frequency environments, RF circuit design involves several critical aspects, including substrate material characteristics, signal transmission, and impedance matching.
Ground Plane
The ground plane is a special layer in PCB design, typically a copper layer that covers the entire PCB. Its main purpose is to provide a path for the return of electric current, ensuring signal integrity. When designing a ground plane for a PCB, it is essential to ensure circuit continuity and choose an appropriate grounding strategy based on project characteristics.
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  2. Low-frequency circuit: The term refers to a circuit that operates at a frequency ranging from tens of Hz to hundreds of kHz. It is characterized by a low frequency and long wavelength. Compared to high-frequency circuits, its design and manufacturing processes are simpler. Low-frequency circuits are commonly used in audio amplification, signal processing, and power applications.
  3. Power Layer: This is a PCB design terminology used in design work, where power and ground planes are added between layers of insulating materials to provide a stable power distribution network and to prevent short circuits and interference between different circuit layers.
  4. Insulation layer: This is a layer made of non-conductive materials, such as glass fiber-covered resin or polyimide, which is located between the conductive layers of a PCB. Its purpose is to provide insulation and prevent short circuits, signal interference, and other issues between circuit layers.
  5. ALIVH: Stands for Advanced Layer-Interleaved Via Hole, which is a high-density interconnection technology that uses electrical measurement technology between multi-layer staggered vertical jacks and multi-layer metal circuit layers. This technology can achieve high-density layouts and a large number of interconnections.
  6. Analog Circuit: Is a common terminology in circuit design that is used to process continuous electrical signals such as sound, light, and temperature. The output of these circuits is non-binary and can be amplified, filtered, conditioned, converted, and mixed to suit different application needs.
  7. Annular Ring: Refers to the copper pad area that remains after drilling around the hole on a printed circuit board Usually, the annular ring is designed to match the pins inserted into the holes to ensure reliable pin connections.
  8. Aspect Ratio: The ratio of the length to width of a PCB. It is a critical factor that determines the shape and size of the board, as well as the reliability and cost of the PCB. Smaller aspect ratios are easier to manufacture, but for specific applications, larger PCB sizes or higher aspect ratios may be required to accommodate necessary components and circuits.
  9. Buried Resistance: Terminology in PCB design, resistors on a PCBA board is typically mounted on the board through assembly, whereas buried resistor boards refer to PCBs that have an inner layer resistor added during the design phase to achieve the required resistance value and accuracy.
  10. Node: Is a connection point that links two or more electronic components in a circuit, either physically or virtually. These nodes play a crucial role in simplifying a circuit diagram and help identify areas where improvements or modifications can be made. In PCB design, each node is assigned a unique net name, and all components connected to that net are considered part of the same circuit. Efficient management of nodes is important in ensuring the overall performance and functionality of the circuit.

PCB Test Terminology

PCB Test Terminology
AOI
Short for Automatic Optical Inspection, is a technology used for surface inspection of circuit board manufacturing and assembly quality. For PCBA manufacturers, AOI inspection is essential and is often integrated into the production line. The operation process of AOI systems involves using high-resolution cameras and lighting to illuminate the surface of the PCB, generating images. These images are then compared to predefined standards, utilizing image processing and matching techniques to detect any defects that deviate from the standards.
FPT
Short for Flying Probe Test, and as the name suggests, this testing method utilizes a set of tiny probing needles, also known as flying probes, to conduct electrical performance testing at various points. During testing, the flying probes make direct contact with the testing points on the PCB, identifying key parameters such as resistance, current, and voltage to ensure correct circuit connections and performance. However, due to its relatively lower coverage, it is not suitable for large-scale production and is often used in prototype and small-batch production scenarios.
X-Ray
X-ray is a high-energy, penetrating electromagnetic wave widely employed in quality inspections for PCB manufacturing and assembly. Its uniqueness lies in the ability to penetrate the external layers of PCB, revealing the intricate structures of internal circuits to identify issues such as inner layer short circuits or interlayer open circuits. Additionally, the images generated through X-ray inspections can track the pathways, providing guidance for subsequent repair work.
ICT
Short for In-Circuit Test, is a technology that utilizes custom test fixtures to verify the connectivity and functionality of components on a PCB, with a focus on the electrical performance of the PCB. While custom test fixtures come with a high cost for users, it has long been considered worthwhile and is widely used in modern electronics manufacturing.
Functional Testing
It is a method of testing the entire PCB as a complete unit to verify that its functionality operates as expected. Typically positioned at the end stages of a PCBA project, functional testing requires more time and investment due to its comprehensive nature. However, it is considered worthwhile, as statistics show that PCBA functional testing can reduce a failure rate of 0.003 to one hundred times less.
Multimeter
For enthusiasts, acquiring professional testing equipment is often an impractical endeavor. The multimeter steps in to fill this void. It is a versatile and portable testing device, consisting of a display head, probes, and function buttons. With a multimeter, hobbyists can troubleshoot PCBs, diagnose faults, and measure parameters like current, voltage, and resistance.
Open Circuit
Refers to the discontinuity in the continuity of current flow, where there should be a connection in the circuit. This interruption can be a result of intentional design choices or circuit malfunctions, such as switch configurations or component burnouts. Generally, an open circuit is not considered to pose severe hazards like fire, but it can lead to equipment malfunctions.
Short Circuit
A short circuit refers to the unintended creation of a low-impedance path between conductors in two circuits, causing the current to bypass the original circuit path. The ultimate result may include serious consequences such as circuit overload, equipment damage, or even fire.
Solder Bridging
It is a common soldering defect that refers to the unintentional connection of solder in places where it shouldn’t be, resulting in issues such as short circuits that affect the performance of the circuit. Solder bridging typically occurs due to excessive solder, pins being too close together, and other related factors.
  1. Burn-In Test: Used to screen components and PCBs for defects that may not be detected in standard tests. It involves running PCBs or components at elevated temperatures and voltages for extended periods of time to accelerate component aging and failure.
  2. AQL: The terminology used for quality control inspections in PCB projects, with its full name being Acceptable Quality Level. During the project, the manufacturer will conduct sampling inspections of the produced PCBs to determine the defect rate. The lower the AQL value, the higher the requirement for product quality, and consequently, the more samples need to be inspected.

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