Introduction
The world of Printed Circuit Board (PCB) manufacturing is filled with technical terms and industry-specific jargon. This comprehensive glossary aims to demystify the language of PCB production, providing clear definitions and explanations for over 200 terms commonly used in the field. Whether you're a novice engineer, a seasoned professional, or someone looking to expand their knowledge of electronics manufacturing, this guide will serve as an invaluable resource.
Basic PCB Terminology
Board Types
FR-4
FR-4 (Flame Retardant 4) is the most common material used for PCB substrates. It's a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant.
Rigid PCB
A rigid PCB is a circuit board that is inflexible and cannot be bent. It's typically made from FR-4 or similar materials.
Flexible PCB
A flexible PCB, also known as a flex circuit, is a circuit board that can bend and flex. It's usually made from materials like polyimide or polyester.
Rigid-Flex PCB
A rigid-flex PCB combines both rigid and flexible board technologies in a single circuit board.
Board Layers
Single-Sided PCB
A PCB with conductive material (usually copper) on only one side of the board.
Double-Sided PCB
A PCB with conductive material on both sides of the board.
Multilayer PCB
A PCB with three or more conductive layers. These layers are separated by insulating material and connected through vias.
Board Components
Conductor
The conductive material on a PCB, typically copper, that forms the circuit paths.
Substrate
The base material of the PCB, usually made of fiberglass reinforced epoxy resin (FR-4).
Solder Mask
A thin lacquer-like layer of polymer applied to the copper traces of a PCB to prevent oxidation and to prevent solder bridges from forming between closely spaced solder pads.
Silkscreen
A layer of text and symbols printed on the PCB to identify components, test points, and other areas of importance.
PCB Design Terms
CAD
Computer-Aided Design, the use of computer systems to aid in the creation, modification, analysis, or optimization of a design.
Gerber File
The standard file format used by PCB manufacturing equipment to photo plot the copper layers, solder mask, silkscreen, and other PCB features.
Schematic
A diagram that represents the electrical connections and components of a circuit using standardized symbolic representations.
Netlist
A list of the electronic components in a circuit and the nodes they connect to.
DRC
Design Rule Check, an automated process that verifies whether a PCB design complies with the manufacturing constraints.
DFM
Design for Manufacturing, the practice of designing products in a way that makes them easy to manufacture.
Footprint
The physical space and connection points that a component occupies on a PCB.
Trace
A conductive path or track on a PCB that carries electrical signals or power.
Pad
A conductive area on a PCB where component leads or surface mount devices are soldered.
Via
A plated hole that connects conductive layers in a multilayer PCB.
PCB Manufacturing Processes
Photolithography
The process of transferring a pattern onto a substrate using light.
Photoresist
A light-sensitive material used in photolithography to form a patterned coating on a surface.
Exposure
The process of projecting an image of the circuit pattern onto the photoresist-coated board.
Development
The process of removing the unexposed (or exposed, depending on the type of photoresist) areas of photoresist after exposure.
Etching
The process of removing unwanted copper from the PCB, leaving only the desired circuit pattern.
Etchant
A chemical solution used to remove unwanted copper from the PCB during the etching process.
Drilling
The process of creating holes in the PCB for component leads, vias, and mounting.
CNC Drilling
Computer Numerical Control drilling, a highly precise method of drilling holes in PCBs using computer-controlled machinery.
Laser Drilling
A method of creating very small holes (microvias) in PCBs using a laser.
Plating
The process of depositing a thin layer of metal onto the PCB.
Electroless Plating
A method of plating that uses a chemical reaction to deposit metal without the use of electrical current.
Electroplating
A method of plating that uses electrical current to deposit metal onto a conductive surface.
Lamination
The process of bonding multiple layers of a PCB together under heat and pressure.
AOI
Automated Optical Inspection, a process that uses cameras and image processing software to check for defects in PCBs.
Flying Probe Testing
A method of electrical testing that uses moving probes to check for opens, shorts, and component values on a PCB.
Surface Finish Types
HASL
Hot Air Solder Leveling, a process where the PCB is dipped in molten solder and then leveled with hot air knives.
ENIG
Electroless Nickel Immersion Gold, a surface finish that deposits a layer of nickel, then a thin layer of gold over exposed copper surfaces.
OSP
Organic Solderability Preservative, a thin organic coating applied to copper surfaces to preserve their solderability.
Immersion Tin
A surface finish where a thin layer of tin is chemically deposited on exposed copper surfaces.
Immersion Silver
A surface finish where a thin layer of silver is chemically deposited on exposed copper surfaces.
Component Types and Mounting Technologies
Through-Hole
Components with leads that are inserted through holes in the PCB and soldered on the opposite side.
SMD
Surface Mount Device, a type of electronic component designed to be mounted directly onto the surface of a PCB.
BGA
Ball Grid Array, a type of surface-mount packaging used for integrated circuits, notable for its high pin count.
QFP
Quad Flat Package, a surface mount integrated circuit package with leads extending from all four sides.
SMT
Surface Mount Technology, the method of producing electronic circuits in which the components are mounted or placed directly onto the surface of PCBs.
Wave Soldering
A bulk soldering process used for both through-hole and surface mount components.
Reflow Soldering
A process in which a solder paste (a sticky mixture of powdered solder and flux) is used to temporarily attach one or more electrical components to their contact pads, after which the entire assembly is subjected to controlled heat.
Quality Control and Testing
ICT
In-Circuit Testing, a powerful method of testing PCBs by powering up the circuit and measuring performance against expected parameters.
Functional Testing
Testing that verifies a PCB performs its intended function correctly.
X-ray Inspection
A non-destructive testing method that uses X-rays to inspect the internal structures of a PCB, particularly useful for inspecting BGAs and other hidden solder joints.
Burn-in Testing
A stress test that involves operating a newly manufactured PCB for an extended period to identify any components that might fail early in their lifetime.
Advanced PCB Technologies
HDI
High-Density Interconnect, a PCB with a higher wiring density per unit area than conventional PCBs.
Microvia
A very small via, typically with a diameter of 150 microns or less, used in HDI boards.
Embedded Components
Electronic components that are embedded within the PCB itself rather than mounted on the surface.
Controlled Impedance
A characteristic of PCB traces designed to have a specific impedance, crucial for high-speed signal integrity.
RF PCB
Radio Frequency PCB, a specialized type of PCB designed to handle high-frequency signals.
Environmental and Regulatory Terms
RoHS
Restriction of Hazardous Substances, a directive that restricts the use of certain hazardous materials in electrical and electronic products.
WEEE
Waste Electrical and Electronic Equipment Directive, a European Community directive on the treatment of electrical and electronic waste.
UL Certification
Underwriters Laboratories certification, a safety certification for electronic products.
IPC Standards
Standards for the design, production, and assembly of electronic equipment, developed by the Association Connecting Electronics Industries (IPC).
Materials and Chemicals
Flux
A chemical cleaning agent used to facilitate the soldering process by removing oxidation from the metals to be soldered.
Solder Paste
A material used in the manufacture of printed circuit boards to connect surface mount components to pads on the board.
Conformal Coating
A protective chemical coating or polymer film that conforms to the contours of a PCB to protect the components and circuitry.
Prepreg
Pre-impregnated composite fibers used in the lamination process of multilayer PCBs.
Specialized PCB Types
Metal Core PCB
A PCB that uses a metal base as its substrate, typically aluminum or copper, to enhance heat dissipation.
High-Frequency PCB
PCBs designed to handle signals at very high frequencies, often used in RF and microwave applications.
Heavy Copper PCB
A PCB that uses thicker copper layers, typically 3 oz or more, to handle higher currents or improve heat dissipation.
Backplane
A large PCB that serves to connect several smaller PCBs, often used in servers and networking equipment.
PCB Assembly Terms
Pick and Place
The process of placing SMD components onto a PCB using automated machinery.
Stencil Printing
The process of applying solder paste to a PCB using a metal stencil and squeegee.
Reflow Profile
The time/temperature relationship that a PCB experiences during the reflow soldering process.
DFT
Design for Testability, a design technique that adds certain testability features to a PCB to make it easier and more cost-effective to test.
PCB Defects and Troubleshooting
Open Circuit
A break in the conductive path of a PCB that prevents current from flowing.
Short Circuit
An unintended connection between two points in an electrical circuit.
Solder Bridge
An unintended solder connection between two adjacent pads or pins.
Tombstoning
A defect where a surface mount component stands on one end due to uneven solder reflow.
Pad Cratering
A defect where the pad lifts from the PCB substrate due to stress.
Advanced Manufacturing Concepts
Lean Manufacturing
A systematic method for waste minimization within a manufacturing system without sacrificing productivity.
Six Sigma
A set of techniques and tools for process improvement, aimed at reducing defects and variability in manufacturing processes.
Industry 4.0
The trend towards automation and data exchange in manufacturing technologies and processes.
Digital Twin
A digital replica of physical assets, processes, and systems that can be used for various purposes.
Emerging Technologies in PCB Manufacturing
3D Printed Electronics
The use of 3D printing technology to create electronic circuits and PCBs.
Flexible Hybrid Electronics
A technology that combines elements of conventional printed electronic processes with novel materials to create flexible, conformable, and stretchable electronics.
Biodegradable PCBs
PCBs designed to decompose naturally at the end of their lifecycle, reducing electronic waste.
Photonic PCBs
PCBs that integrate optical waveguides alongside traditional electrical traces for high-speed data transmission.
Tables
Common PCB Materials
| Material | Properties | Common Uses |
|---|---|---|
| FR-4 | Flame retardant, good electrical insulator | Standard PCBs |
| Polyimide | Heat resistant, flexible | Flex PCBs, High-temp applications |
| PTFE | Low dielectric constant, low loss | High-frequency PCBs |
| Aluminum | Excellent thermal conductivity | Metal core PCBs, LED applications |
| Ceramic | High thermal conductivity, high frequency performance | RF and Microwave PCBs |
PCB Layer Count and Typical Applications
| Layer Count | Typical Applications |
|---|---|
| Single Layer | Simple electronics, LED boards |
| Double Layer | Consumer electronics, IoT devices |
| 4-6 Layer | Computers, industrial controls |
| 8-16 Layer | Servers, networking equipment |
| 18+ Layer | High-end telecommunications, aerospace |
Common Surface Finishes
| Finish | Pros | Cons |
|---|---|---|
| HASL | Low cost, good solderability | Poor planarity, not suitable for fine pitch |
| ENIG | Excellent surface planarity, good for fine pitch | Higher cost, potential "black pad" issue |
| OSP | Low cost, flat surface | Short shelf life, single reflow only |
| Immersion Tin | Good solderability, flat surface | Relatively short shelf life |
| Immersion Silver | Good solderability, suitable for high frequencies | Prone to silver migration, tarnishing |
PCB Hole Sizes and Drilling Methods
| Hole Size | Typical Drilling Method | Common Uses |
|---|---|---|
| > 0.3 mm | Mechanical Drilling | Through-hole components, larger vias |
| 0.1 - 0.3 mm | Mechanical Drilling (with special care) | Small vias, some SMT pads |
| 50 - 100 μm | Laser Drilling | Microvias in HDI boards |
| < 50 μm | Laser Drilling | Ultra-fine microvias, advanced HDI |
Frequently Asked Questions
- Q: What is the difference between a rigid PCB and a flexible PCB? A: A rigid PCB is made from a solid substrate material (usually FR-4) and cannot be bent, while a flexible PCB is made from flexible materials like polyimide and can be bent or flexed. Rigid PCBs are more common and less expensive, while flexible PCBs are used in applications where space is limited or the board needs to conform to a specific shape.
- Q: What does "PCB stackup" mean? A: PCB stackup refers to the arrangement of copper and insulation layers in a multilayer PCB. It includes the number of layers, their thicknesses, and the order in which they are arranged. The stackup is crucial for controlling impedance, reducing electromagnetic interference, and ensuring proper functioning of the PCB.
- Q: Why is solder mask important in PCB manufacturing?
A: Solder mask is important because it:
- Prevents solder bridges between closely spaced solder pads
- Protects the copper traces from oxidation
- Provides electrical insulation
- Improves the board's appearance and readability
- Q: What is the purpose of vias in a PCB?
A: Vias serve several purposes in a PCB:
- They connect traces on different layers of a multilayer PCB
- They can be used to conduct heat from one layer to another
- They can be used as test points
- In some designs, they help with signal integrity by providing a return path for high-frequency signals
- Q: What is the difference between HASL and ENIG surface finishes? A: HASL (Hot Air Solder Leveling) involves dipping the PCB in molten solder and then leveling it with hot air knives. It's a cost-effective option but can result in an uneven surface. ENIG (Electroless Nickel Immersion Gold) deposits a layer of nickel, then a thin layer of gold over exposed copper surfaces. ENIG provides a very flat surface finish, making it suitable for fine-pitch components, but it's more expensive than HASL.
No comments:
Post a Comment