Technical glossary

Electronics Glossary

Find here the definitions of the most common electronics terms, explained in plain English to help you better understand our exchanges 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 electronic components of a product are fixed and interconnected. It consists of copper layers separated by an insulating material (most commonly FR4, a fibreglass-reinforced epoxy). It is the heart of every electronic device, from a smartphone to an 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 transmit PCB manufacturing data to the workshop. They describe layer by layer the location of tracks, holes and copper areas. Without these complete files, it is impossible to launch industrial manufacturing of the board. Codium generates and verifies these files before any production run to avoid non-conformities.
BOM — Bill of Materials: The BOM is the exhaustive list of all components required to manufacture an electronic board: manufacturer reference, quantity per board, value, package and preferred suppliers. It is the starting document for all procurement and the basis for material cost calculation. A well-structured BOM prevents purchasing errors and facilitates future product revisions.
Schematic: The schematic is the electrical plan of the circuit: it graphically represents using standardised symbols all components and their electrical connections. It is the first step in the design, carried out before drawing the physical printed circuit board. It serves as a permanent reference for understanding the product's operation, diagnosing faults and making revisions. It can be compared to a building's blueprints before construction.
Routing: Routing is the operation of physically drawing the conductive tracks connecting components on the PCB, respecting electrical, thermal and mechanical constraints. It is a delicate phase requiring expertise, particularly for high-speed signals, high currents or radio circuits. Careful routing guarantees electrical performance conformance and good EMC certification results.
DRC — Design Rule Check: The DRC is an automatic verification performed by the design software to ensure that the PCB drawing respects all workshop manufacturing rules: minimum spacing between tracks, hole sizes, conductor thickness, distance to board edges. It runs before sending files to production and detects errors invisible to the naked eye that would make the board unmanufacturable or defective.
DFM — Design for Manufacturability: DFM is an in-depth analysis performed before manufacturing to ensure the board can be industrially produced under good conditions. It takes into account the constraints of assembly equipment, manufacturing tolerances, test accessibility and defect risks. At Codium, DFM is an integral part of the design process to guarantee a high success rate from the first series and avoid costly rework. Read our article on Design for Manufacturing.
Layers: A PCB can be composed of several stacked conductive layers, separated by insulators. A simple board has 2 layers (top/bottom); complex boards can have 4, 6, 8 or more. Adding layers enables very dense circuits to be routed while reducing the board's footprint. The higher the layer count, the more expensive the manufacturing — but the board gains in compactness and electromagnetic performance.
Via: A via is a metallised hole that passes through one or more PCB layers to electrically connect two levels of tracks. There are through vias (all the way through the board), blind vias (between the surface and an inner layer) and buried vias (between two inner layers). Laser microvias, used in HDI high-density boards, enable very compact assemblies as found in smartphones.
Pad: A pad is a defined copper area on the PCB, designed to receive and solder an electronic component. Its shape, dimensions and positioning are precisely defined according to the component manufacturer's specifications. A poorly sized pad can cause cold joints, short circuits or mechanical tearing — it is a critical element of assembly quality.
Footprint: The footprint is the physical representation of a component in the PCB design software library: it groups the solder pads, the outline silkscreen and the courtyard area around the component. Each component reference has a standardised footprint corresponding to its physical package. A footprint error is one of the most common causes of non-conformity discovered during first prototypes.

Assembly & Production

SMD / SMT — Surface Mount Device / Technology: An SMD (Surface Mount Device) component is soldered directly onto the PCB surface, without going through the board. These small-size components enable high assembly density and are positioned by automatic Pick & Place machines, then soldered in a reflow oven. The vast majority of modern electronic boards primarily use SMD components — discover how our production line assembles them.
Wave soldering: Wave soldering is an industrial soldering process for through-hole (THT) components: the board passes over a wave of molten liquid solder that simultaneously solders all leads on the copper side. This fast process is suited to large series of boards with connectors, relays or power components. It is often complemented by manual soldering for delicate areas or heat-sensitive components.
Reflow soldering: Reflow soldering is the standard process for soldering SMD components. Solder paste is first deposited on pads via a stencil, components are placed by the Pick & Place, then the whole assembly passes through a reflow oven that melts and solidifies the paste according to a precise temperature profile (temperature ramp, melting plateau, controlled cooling). This process guarantees reproducible, 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 each board after assembly. It verifies the presence, polarity and solder quality of each component by comparing the board to a reference model. AOI detects missing, misaligned or cold-soldered components. At Codium, AOI is systematic on all our production runs to guarantee consistent quality levels.
ICT — In-Circuit Test: ICT electrically verifies each component individually on the assembled board, via a bed-of-nails probe that contacts dedicated test points on the PCB. It measures resistor, capacitor and inductor values, verifies continuities 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 series production.
Functional test: The functional test simulates the real usage conditions of the product to validate its overall correct operation: communication, measurement, control, user interface. It is the final inspection step before shipment, guaranteeing that every delivered board meets client specifications under conditions close to final use. Codium develops custom test benches for each project to automate this step in series production.
Pick & Place: The Pick & Place machine is a precision assembly robot that picks SMD components from their packaging (reels, trays, tubes) and positions them on the board coated with solder paste with sub-tenth-of-a-millimetre accuracy. Its throughput can reach tens of thousands of components per hour. It is the central machine of the SMT assembly line, and its correct programming is essential for placement quality.
Stencil: The stencil is a precisely laser-cut stainless steel template used to deposit solder paste only at solder pad locations. Its thickness determines the amount of paste deposited, which directly influences solder quality. A well-designed stencil is essential for achieving homogeneous and reproducible deposits, particularly on small SMD components and fine-pitch packages such as QFP or BGA.
Solder paste: Solder paste is a mixture of solder micro-balls in metal alloy (lead-free in RoHS compliance: SAC305 SnAgCu alloy) and chemical flux facilitating wettability. It is deposited on PCB pads via the stencil before assembly. During oven processing, the paste melts and forms solder joints that mechanically fix and electrically connect the components to the board.

Electronic Components

Through-hole component (THT — Through-Hole Technology): A through-hole component has leads that pass through the PCB holes and are soldered on the opposite side. Less compact than SMD, it offers better mechanical resistance to vibration stress and remains indispensable 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 current, divide voltage, bias a transistor or adapt signal levels. Modern SMD resistors exist 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 capable of storing and releasing electrical energy as charge. It is essential for power supply filtering, integrated circuit decoupling (which prevents high-frequency noise) and voltage stabilisation. 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 current variations. It is indispensable in DC-DC power converters (which transform one voltage to another), electromagnetic interference filters and radio circuits. Its value is expressed in henries (H), most often in microhenries (µH) or nanohenries (nH) for embedded electronics.
Microcontroller (MCU): The microcontroller is an integrated circuit that combines in a single chip a processor, programme memory (Flash) and integrated peripherals (communication interfaces, converters, timers, GPIO). It is the "brain" of most embedded electronic products: it executes the firmware that defines the product's behaviour. The choice of microcontroller determines performance, power consumption, available connectivity and series cost.
FPGA — Field-Programmable Gate Array: An FPGA is a reprogrammable logic circuit that can be configured after manufacturing to perform specific digital processing at very high speed in parallel. Unlike a microcontroller that executes instructions sequentially, the FPGA directly implements logic functions in hardware. It is used for image processing, high-speed acquisition or proprietary communication protocol applications. Its programming in VHDL or Verilog requires specialised expertise.
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 on the board. This very compact format is used for processors, radio modules and high-density memories. Its implementation requires specialised equipment and standard inspection is insufficient: X-ray inspection is needed to verify the quality of hidden solder joints under the package.
QFP — Quad Flat Package: The QFP is a flat rectangular package with leads protruding on four sides. Commonly used for microcontrollers, processors and logic circuits, it offers a good balance between integration density and ease of visual solder inspection. Its fine lead pitches (0.4 to 0.8 mm) require precise alignment during assembly, but rework in case of defect is easier than with a BGA.
Active & passive components: Passive components (resistors, capacitors, inductors) need no 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 both families to accomplish its functions.
Component obsolescence: Obsolescence occurs when a component manufacturer discontinues a reference (PCN/EOL notification). This can halt production of a product or require a partial redesign to find and validate an equivalent. Codium actively monitors critical components in your projects and proposes preventive solutions — stock building, substitute search — to avoid production interruptions.

Connectivity & IoT

LoRa / LoRaWAN: LoRa (Long Range) is a radio technology that transmits small amounts of data over very long distances (1 to 15 km depending on 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 battery.
LPWAN — Low Power Wide Area Network: LPWAN groups the family of radio network technologies specifically designed for autonomous connected objects: long range, very low power consumption and low data rates. The main LPWAN technologies are LoRaWAN, Sigfox and LTE-M (4G CAT-M). They enable sensors or equipment to be connected over vast geographic areas with batteries lasting 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 operates on the publish/subscribe model: devices publish their data to a central server (the broker) to which client applications subscribe to receive them 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) low-power radio communication standard based on the IEEE 802.15.4 standard. It enables creation of mesh networks of sensors or actuators where each node can relay data from 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 Bluetooth version optimised for battery-operated connected objects. It enables short and occasional data exchanges over a range of a few to a few tens of metres, with minimal energy consumption between transmissions. It is integrated into portable health sensors, location beacons, industrial handheld tools and wireless configuration equipment.
NFC — Near Field Communication: NFC enables data exchange between two devices at very short range (less than 10 cm). This technology is used for contactless payment, device configuration by approaching a smartphone, reading smart tags or secure identification. Passive NFC mode can even electrically power a small sensor without a battery, simplifying the design of very compact devices.
4G / LTE CAT-M: LTE CAT-M (also called LTE-M or 4G CAT-M1) is a 4G variant specifically designed for connected objects. Compared to standard 4G, it offers better indoor and underground penetration, reduced power consumption and extended battery life. It is suited to mobile sensors, alarm systems or telemetry equipment that must remain permanently connected via the cellular network.

Certifications & Regulatory Compliance

CE Marking: CE marking (European Conformity) is mandatory for any electronic product marketed in the European Economic Area. It attests that the product conforms to applicable European directives (electrical safety, electromagnetic compatibility, radio emissions…). It is not a quality label but a regulatory conformity declaration binding the manufacturer. Codium supports its clients in preparing technical files and anticipating the tests required for CE marking — see our guide on CE certification for electronics.
FCC: FCC (Federal Communications Commission) certification is mandatory for any radio-emitting equipment marketed in the United States. It guarantees that the device does not interfere with other communication equipment and respects emission limits set by US regulations. This certification requires tests 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 requires 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 responsibility for the collection and recycling of their end-of-life products. In practice, this translates into registration with an approved eco-organisation and financing recycling via a contribution. The crossed-out wheelie bin symbol present on electronic products indicates they are subject to the WEEE directive and must not be disposed of with household waste.
EMC — Electromagnetic Compatibility: Electromagnetic compatibility refers to the ability of equipment to operate correctly in its electromagnetic environment without disturbing other surrounding devices, nor being disturbed itself. EMC tests verify both the radiated and conducted emissions of the device, as well as its immunity to external disturbances (electrostatic discharges, radiated fields, surges). EMC must be anticipated from PCB routing — ground planes, decoupling, shielding — as late corrections are costly. It is required for CE marking.

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