Technical glossary

Electronics Glossary

Here you will find the definitions of the most common electronics terms, explained in clear English to help you better understand our discussions and technical proposals. This glossary covers PCB design, industrial assembly, components, IoT connectivity and regulatory certifications.

PCB Design

PCB — Printed Circuit Board: The PCB (printed circuit board) is the physical support on which all of a product's electronic components are mounted and interconnected. It is made up of copper layers separated by an insulating material (most often FR4, an epoxy reinforced with glass fibre). It is the heart of every piece of electronic equipment, from the smartphone to the industrial machine. Its design directly determines the performance, reliability and manufacturing cost of the final product.
Gerber Files: Gerber files are the standard format used to send a PCB's manufacturing data to the fabrication shop. They describe, layer by layer, the position of the tracks, holes and copper areas. Without these complete files, it is impossible to start industrial manufacture of the board. Codium generates and checks these files before any production release to avoid non-conformities.
BOM — Bill of Materials: The BOM is the exhaustive list of all the components needed to manufacture an electronic board: manufacturer part number, quantity per board, value, package and preferred suppliers. It is the starting document for all procurement and the basis for calculating the material cost. A well-structured BOM avoids purchasing errors and makes future changes to the product easier.
Schematic: The schematic is the electrical diagram of the circuit: it graphically represents, using standardised symbols, all the components and their electrical connections. It is the first step of the design process, carried out before the physical printed circuit is drawn. It serves as a permanent reference for understanding how the product works, diagnosing faults and making changes. It can be compared to the plans of a building before it is constructed.
Routing: Routing is the operation of physically drawing the conductive tracks that connect the components on the PCB, while respecting electrical, thermal and mechanical constraints. It is a delicate phase that calls for expertise, particularly for high-speed signals, high currents or radio circuits. Careful routing is the guarantee of compliant electrical performance and good behaviour in EMC certification.
DRC — Design Rule Check: The DRC is an automatic check carried out by the design software to ensure that the PCB layout complies with all of the fabrication shop's manufacturing rules: minimum spacing between tracks, hole size, conductor width, distance to the board edges. It is run before the files are sent to production and detects errors that are invisible to the naked eye and that would make the board impossible to manufacture or prone to failure.
DFM — Design for Manufacturability: DFM is an in-depth analysis carried out before manufacture to ensure that the board can be produced industrially under good conditions. It takes into account the constraints of the assembly equipment, manufacturing tolerances, accessibility for testing and the risk of defects. At Codium, DFM is an integral part of the design process, to guarantee a high success rate from the very first runs and avoid costly rework. Read our article on Design for Manufacturing.
Layers: A PCB can be made up of several stacked conductive layers separated by insulators. A simple board has 2 layers (top and bottom); complex boards can have 4, 6, 8 or more. Adding layers makes it possible to route very dense circuits while reducing the board area. The higher the number of layers, the more expensive the manufacture — but the board gains in compactness and electromagnetic performance.
Via: A via is a plated hole that passes through one or more layers of the PCB to electrically connect two levels of tracks. There are through-hole vias (running right through the board), blind vias (between the surface and an inner layer) and buried vias (between two inner layers). Laser microvias, used in high-density HDI boards, allow very compact assemblies such as those found in smartphones.
Pad: A pad is a defined copper area on the PCB, intended to receive and solder an electronic component. Its shape, dimensions and position are defined precisely according to the component manufacturer's specifications. A poorly sized pad can cause cold solder joints, short circuits or mechanical lift-off — it is a critical element of assembly quality.
Footprint (Land pattern): The footprint is the physical representation of a component in the PCB design software's library: it groups together the solder pads, the silkscreen outline and the courtyard around the component. Each component part number has a standardised footprint matching its physical package. A footprint error is one of the most frequent causes of non-conformity discovered during the first prototypes.

Assembly & Production

SMT / SMD — Surface Mount Device: An SMT component (also known as an SMD, for Surface Mount Device) is soldered directly onto the surface of the PCB, without passing through the board. These small components allow high assembly density and are placed by automatic Pick & Place machines, then soldered in a reflow oven. Almost all modern electronic boards mainly use SMT components — find out how our production line assembles them.
Wave soldering: Wave soldering is an industrial soldering process intended for through-hole components (THT): the board travels over a wave of molten liquid solder that simultaneously solders all the pins on the copper side. This fast process is suited to large production runs of boards fitted with connectors, relays or power components. It is often supplemented by manual soldering for delicate areas or heat-sensitive components.
Reflow soldering: Reflow soldering is the standard process for soldering SMT components. Solder paste is first applied to the pads through a stencil, the components are placed by the Pick & Place machine, then the whole assembly passes through a reflow oven that melts and solidifies the paste according to a precise temperature profile (ramp-up, melting plateau, controlled cooling). This process guarantees repeatable, high-quality solder joints across the entire board.
AOI — Automated Optical Inspection: AOI is a quality control system using high-resolution cameras that automatically inspects every board after assembly. It checks the presence, polarity and solder quality of each component by comparing the board against a reference model. AOI detects missing components, misplaced components and cold solder joints. At Codium, AOI is systematic on all of our production runs to guarantee a consistent quality level.
ICT — In-Circuit Test: The ICT test electrically checks each component individually on the assembled board, using a bed of nails that contacts dedicated test points on the PCB. It measures the values of resistors, capacitors and inductors, checks continuity and detects short circuits. Complementary to AOI (which checks visual appearance), ICT reveals invisible electrical defects. It is particularly cost-effective for medium and large production runs.
Functional test: The functional test simulates the real conditions of use of the product to validate its overall correct operation: communication, measurement, control, user interface. It is the last control step before shipping, guaranteeing that every board delivered meets the customer's specifications under conditions close to final use. Codium develops custom test benches for each project in order to automate this step in series production.
Pick & Place: The Pick & Place machine is a precision assembly robot that picks up SMT components from their packaging (reels, trays, tubes) and positions them on the board coated with solder paste, with an accuracy of less than a tenth of a millimetre. Its throughput can reach tens of thousands of components per hour. It is the central machine of the SMT assembly line, and programming it correctly is essential for placement quality.
Stencil: The stencil is a stainless steel template, precisely laser-cut, used to deposit solder paste only at the locations of the solder pads. Its thickness determines the quantity of paste deposited, which directly influences solder joint quality. A well-designed stencil is essential to obtain uniform, repeatable deposits, particularly on small SMT components and fine-pitch packages such as QFPs or BGAs.
Selective soldering: Selective soldering is an automated soldering process for through-hole (THT) components on mixed boards (SMT + THT). Unlike wave soldering, which exposes the whole board to the solder, a fine nozzle precisely applies molten tin only to the areas to be soldered. It is the preferred solution when SMT components on the bottom side cannot go through wave soldering, or when very localised treatment is needed to avoid damaging heat-sensitive components.
Solder paste: Solder paste is a mixture of metal-alloy solder microspheres (lead-free in compliance with RoHS: SAC305 SnAgCu alloy) and a chemical flux that promotes wetting. It is applied to the PCB pads through the stencil before assembly. As it passes through the oven, the paste melts and forms the solder joints that fix the components to the board and connect them electrically.

Electronic components

Through-hole component (THT — Through-Hole Technology): A through-hole component has pins that pass through holes in the PCB and are soldered on the opposite side. Less compact than SMT, it offers better mechanical resistance to vibration and remains essential for certain robust connectors, power capacitors or transformers. It is soldered by wave soldering in series production, or manually for small quantities.
Resistor: The resistor is the most widespread passive electronic component. It opposes the flow of electric current according to its value, expressed in ohms (Ω). It is used to limit a current, divide a voltage, bias a transistor or adapt signal levels. Modern SMT resistors come in very small sizes (0402 or 0201 formats) and are practically invisible to the naked eye on an assembled board.
Capacitor: The capacitor is a passive component able to store and release electrical energy in the form of charge. It is essential for filtering power supplies, decoupling integrated circuits (which prevents high-frequency noise) and stabilising voltages. Its value is expressed in farads (F), most often in microfarads (µF) or picofarads (pF) in embedded electronics.
Inductor: The inductor (or coil) stores energy in the form of a magnetic field and opposes rapid changes in current. It is essential in DC-DC power converters (which convert one voltage into another), electromagnetic interference filters and radio circuits. Its value is expressed in henrys (H), most often in microhenrys (µH) or nanohenrys (nH) for embedded electronics.
Microcontroller (MCU): The microcontroller is an integrated circuit that combines a processor, program memory (Flash) and built-in peripherals (communication interfaces, converters, timers, GPIO) in a single chip. It is the “brain” of most embedded electronic products: it runs the firmware that defines the product's behaviour. The choice of microcontroller determines performance, power consumption, available connectivity and the cost in series production.
FPGA — Field-Programmable Gate Array: An FPGA is a reprogrammable logic circuit that can be configured after manufacture to carry out specific digital processing at very high speed in parallel. Unlike a microcontroller, which executes instructions in sequence, the FPGA directly implements logic functions in hardware. It is used for image processing, high-speed acquisition or proprietary communication protocols. Programming it in VHDL or Verilog requires specialist skills.
BGA — Ball Grid Array: The BGA is an integrated component package whose electrical connections are solder balls arranged in a grid under the component — invisible once soldered onto the board. This very compact format is used for processors, radio modules and high-density memories. Using it requires specialised equipment and conventional inspection is not enough: an X-ray scan is needed to check the quality of the solder joints hidden under the package.
QFP — Quad Flat Package: The QFP is a flat rectangular package with leads emerging on all four sides. Commonly used for microcontrollers, processors and logic circuits, it offers a good compromise between integration density and ease of visual inspection of the solder joints. Its fine lead pitches (0.4 to 0.8 mm) require precise alignment during assembly, but rework in the event of a defect is easier than with a BGA.
Active & passive components: Passive components (resistors, capacitors, inductors) do not need a power supply of their own and simply absorb, store or release energy. Active components (transistors, integrated circuits, microcontrollers) need a supply voltage and can amplify signals or switch currents. An electronic board always combines these two families to perform its functions.
Component obsolescence: Obsolescence occurs when a component manufacturer discontinues production of a part number (PCN/EOL notification). This can block the manufacture of a product or force a partial redesign in order to find and validate an equivalent. Codium maintains active monitoring of the critical components in your projects and proposes proactive solutions — building up stock, searching for substitutes — to avoid production interruptions.

RF & Radio Frequencies

Antenna: An antenna is a device that converts an electrical signal into a radiated electromagnetic wave (transmission) or the reverse (reception). Its performance depends on its geometry, on its dimensions — intrinsically linked to the wavelength of the signal — and on the environment in which it is integrated into the product. A plastic enclosure, a ground plane that is too close or a poorly shielded cable can significantly degrade its real-world characteristics. At Codium, the design, simulation and optimisation of antennas is carried out in-house by our RF engineer in our RF laboratory.
Antenna gain: The gain of an antenna measures its ability to concentrate radiated energy in a preferred direction, expressed in dBi (decibels relative to a theoretical isotropic antenna that would radiate uniformly in all directions). A gain of 0 dBi corresponds to an ideal omnidirectional antenna. A directional antenna can reach 6, 9 or 12 dBi by concentrating its radiation. For IoT, an omnidirectional antenna with moderate gain is often preferable for covering devices in varying positions.
VSWR — Voltage Standing Wave Ratio: The VSWR (Voltage Standing Wave Ratio) measures the impedance match between the RF source (transmitter, amplifier) and the antenna. A VSWR of 1:1 is ideal — all of the energy is delivered to the antenna and radiated. A high VSWR (2:1, 3:1…) means that a significant share of the energy is reflected back to the transmitter, degrading range and potentially damaging the amplifier in the long term. Matching is achieved with networks of discrete components (capacitors, inductors) or impedance transformers integrated into the PCB routing.
50 Ω impedance: Almost all radio-frequency systems use a characteristic impedance of 50 ohms as a common reference (coaxial cables, SMA connectors, spectrum analyser inputs, transmitter outputs). The routing of RF tracks on the PCB — known as microstrip or coplanar lines — must strictly respect this impedance by controlling the track width and the substrate thickness, otherwise reflection losses and degraded radio performance will result.
DECT NR+: DECT NR+ (Digital Enhanced Cordless Telecommunications New Radio) is an open standard developed by ETSI for industrial IoT. It operates in the 1.9 GHz band (away from the congestion of the 2.4 GHz and 868 MHz ISM bands), with no usage licence required in Europe. It makes it possible to create robust mesh networks with data rates of up to 2 Mbps, a range of 100 to 500 m per hop and deterministic latency suited to control and command applications. Its self-healing mesh topology guarantees network resilience even if a node fails — ideal for workshops and industrial environments. Learn more: our DECT NR+ page.
Anechoic chamber: An anechoic chamber (or RF-shielded anechoic room) is a shielded enclosure whose walls are covered with absorbing materials that eliminate reflections of electromagnetic waves. It recreates an ideal measurement environment, isolated from external disturbances, in which to characterise antennas (radiation pattern, gain, VSWR) and carry out electromagnetic compatibility (EMC) tests. Codium's RF laboratory has an anechoic chamber that makes it possible to measure and optimise antennas directly on the final product.

Connectivity & IoT

LoRa / LoRaWAN: LoRa (Long Range) is a radio technology that makes it possible to transmit small amounts of data over very long distances (1 to 15 km depending on the environment) with very low energy consumption. LoRaWAN is the network protocol built on top of LoRa to create long-range IoT networks. This technology is ideal for industrial sensors, meter management or asset tracking that must run for several years on a battery.
LPWAN — Low Power Wide Area Network: LPWAN covers the family of radio network technologies designed specifically for autonomous connected objects: long range, very low power consumption and low data rate. The main LPWAN technologies are LoRaWAN, Sigfox and LTE-M (4G CAT-M). They make it possible to connect sensors or equipment over wide geographical areas with batteries that last several years, without costly infrastructure to deploy.
MQTT: MQTT (Message Queuing Telemetry Transport) is a lightweight and efficient network communication protocol designed for resource-constrained connected objects. It works on the publish / subscribe model: devices publish their data to a central server (the broker) to which client applications subscribe in order to receive it in real time. MQTT is very widespread in industrial IoT systems, supervision dashboards and connected home automation.
Zigbee: Zigbee is a short-range (10 to 100 m), very low-power radio communication standard based on the IEEE 802.15.4 specification. It makes it possible to create mesh networks of sensors or actuators in which each node can relay the data of the others, extending coverage without additional infrastructure. It is very widespread in home automation, connected lighting and industrial sensor networks where many devices coexist.
Bluetooth LE — Bluetooth Low Energy: Bluetooth LE (Low Energy) is a version of Bluetooth optimised for battery-powered connected objects. It allows short, occasional data exchanges over a range of a few metres to a few tens of metres, with minimal energy consumption between transmissions. It is built into wearable health sensors, location beacons, industrial handheld tools and wireless configuration equipment.
NFC — Near Field Communication: NFC allows data to be exchanged between two devices at very short range (less than 10 cm). This technology is used for contactless payment, configuring devices by tapping a smartphone, reading smart tags or secure identification. Passive NFC mode can even power a small sensor electrically without a battery, simplifying the design of very compact devices.
LTE-M / 4G CAT-M1: LTE-M (LTE for Machines, also written CAT-M1) is a variant of the 4G network designed specifically for low-power connected objects. It uses the operators' existing infrastructure (Orange, SFR, Bouygues) with no intermediate gateway to deploy — a simple SIM card is enough. Compared with standard 4G, it offers better indoor penetration, reduced power consumption thanks to the PSM and eDRX modes, and voice support (VoLTE). It is suited to mobile sensors, remotely monitored alarms, connected meters and telemetry equipment requiring immediate nationwide coverage. Learn more: our LTE-M guide.
NB-IoT — Narrowband IoT: NB-IoT is a cellular LPWAN technology standardised by 3GPP, deployed on the operators' 4G frequencies. It is optimised for applications that transmit very little data (a few bytes per day) with extremely low power consumption. Unlike LTE-M, NB-IoT does not support mobility or voice, but it offers better penetration underground and in difficult areas. Typical use cases: water meters, parking sensors, presence detectors, fixed beacons.

Certifications & Regulatory Compliance

CE marking: CE marking (Conformité Européenne) is mandatory for any electronic product placed on the market in the European Economic Area. It attests that the product complies with the applicable European directives (electrical safety, electromagnetic compatibility, radio emissions…). It is not a quality label but a declaration of regulatory conformity that binds the manufacturer. Codium supports its customers in preparing technical files and anticipating the tests needed to obtain CE marking — see our guide to CE certification for electronics.
FCC: FCC (Federal Communications Commission) certification is mandatory for any equipment emitting radio signals that is sold in the United States. It guarantees that the device does not interfere with other communication equipment and complies with the emission limits set by US regulations. This certification requires testing in an accredited laboratory and is essential for any project targeting the North American market.
RoHS — Restriction of Hazardous Substances: The RoHS directive (2011/65/EU) restricts the use of hazardous substances in electronic equipment placed on the European market: lead, mercury, cadmium, hexavalent chromium and certain brominated flame retardants. It requires the use of lead-free solders and certified compliant components. RoHS compliance is verified through supplier documentation and is a necessary condition for CE marking.
REACH: REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) is the European regulation governing the management of chemical substances used in industrial and consumer products. It obliges manufacturers to identify and declare the presence of substances of very high concern (SVHC) above certain concentration thresholds. For electronics, this concerns component materials, PCB surface finishes and certain plastics used in connectors.
WEEE — Waste Electrical and Electronic Equipment: The WEEE directive requires manufacturers and distributors of electronic equipment to take charge of the collection and recycling of their products at end of life. In practice, this means registering with an approved compliance scheme and funding recycling through a contribution. The crossed-out wheelie bin symbol found on electronic products indicates that they are subject to the WEEE directive and must not be thrown away with household waste.
CRA — Cyber Resilience Act: The Cyber Resilience Act is a European regulation coming into force in stages until 2027, which imposes mandatory cybersecurity requirements on all connected products placed on the European market. It covers: security by design (built in from the design stage), vulnerability management throughout the product's lifetime, security updates, technical documentation and the reporting of incidents to the authorities. It applies to all IoT objects, connected industrial equipment, radio modules and embedded systems. Codium integrates these requirements from the design phase to anticipate the compliance of your products.
IEC 62443 — Industrial cybersecurity: IEC 62443 is the international cybersecurity standard for industrial control systems (ICS/SCADA) and connected embedded components. It defines four security levels (SL1 to SL4) and precise technical requirements: network segmentation, strong authentication, encryption of communications, access management and traceability of security events. It is the essential reference for integrators and manufacturers of connected OT (Operational Technology) systems, consistent with the requirements of the Cyber Resilience Act (CRA).
EMC — Electromagnetic Compatibility: Electromagnetic compatibility is the ability of equipment to operate correctly in its electromagnetic environment without disturbing other nearby devices or being disturbed itself. EMC tests check both the radiated and conducted emissions of the device, as well as its immunity to external disturbances (electrostatic discharge, radiated fields, surges). EMC must be anticipated from the PCB routing stage — ground planes, decoupling, shielding — because late corrections are costly. It is a condition for obtaining CE marking.

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