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PCB Terminology

Printed Circuit Board Terminology

When customers talked with us ,we may have some misunderstandings.Especially for some new designers and students,they may not know much about Printed Circuit Boards,so here,we list some common words in the industry.Hope it helps all people.

  • Annular Ring: This term refers to the copper pad area that is left after a hole is drilled through it. This ring is measured from the edge of the pad to the edge of the hole and is an important consideration in PCB design, as it allows an electrical connection to be made from one side of the hole to the other.
  • AOI: Short for automated optical inspection, AOI refers to a type of inspection method used to find potential problems concerning soldering performance in multi-layer PCBs with components mounted on. The AOI equipment finds these issues by capturing images of the inner PCB surfaces, looking for any possible issues in terms of displacement, polarity etc.
  • Aspect Ratio: Aspect ratio refers to the ratio between a PCB's thickness and diameter of its minimum via. It's best to keep aspect ratios low to improve plating quality and minimize potential via failures.that is if the min hole is 0.1mm, the board thickness can not be 1.6mm.
  • Assembly Drawing: An assembly drawing is a reference depicting the assembly requirements of a PCB. These drawings will usually include the placements of components as well as the construction technologies, methods and parameters needed to make it happen.
  • Back Drilling: Primarily applied in multi-layer PCB fabrication, back-drilling helps improve signal integrity by removing stubs from plated through-holes. These stubs are unnecessary portions of via that extend into the hole, potentially causing reflections and other disturbances that damage signals.
  • BGA: Short for ball grid array, this is a type of component packaging used in integrated circuits (ICs) for surface mounting. They can ensure high-speed efficiency since they use columns of balls instead of pins. BGAs are usually used to mount devices like microprocessors on PCBs permanently.
  • Bare Board: This term refers to a circuit board with no components mounted on it.
  • Bare Copper:No solder mask,no finishing on the PCB,just copper .
  • Buried Via: This term is used to refer to a via connecting a top layer to one or more inner layers. In other words, a buried via can only be seen from one side of the board when looking at it from the outside.
  • Blind Via:the via is from inner layer to another inner layer,that is we can not see the via from outside.
burried via ,blind via
B is burried via,A and C is blind via
  • CAM Files: CAM is an acronym for computer-aided manufacturing, and the files produced by this software are used for PCB manufacturing. There are multiple types of CAM files, including Gerber files for photoplotters and NC Drill files for NC Drill machines. These files are usually sent off to board and assembly houses for refinement and eventual manufacturing.
  • Carbon Mask: This is a type of conductive carbon paste that is added to the surface of a pad. Made with a combination of resin and carbon toner, carbon masks are heat-cured and are typically applied to jumpers, keys, etc.
  • Ceramic Substrate Printed Board: This type of board is made with a ceramic substrate, to which other materials are bonded with alumina or aluminum nitride. The primary selling points for ceramic substrate boards are their excellent insulation capabilities, thermal conductivity, soft solderability and adhesive strength.
  • COB: Shorthand for chip-on-board, this term is a type of bare chip SMT technology. COB involves directly mounting integrated circuits to a PCB instead of packaging them first. Common in mass-produced gadgets and toys, COB can be identified by a black glob of plastic on a PCB, called a glob top. Underneath the glob, the chip connects to the board with fine wires.
  • Copper Weight: This term is used to indicate thickness of copper foil on each layer of a PCB. It's typically expressed in ounces of copper per square foot.1OZ (0.035mmm)is standard weight,the max copper we made is 12OZ,that is thick copper PCB
  • Countersink Holes: These are cone-shaped holes that are drilled into a PCB. To allow a countersunk screw to sit flush with the PCB surface.Unlike the normal holes,the countersink hole has two dimensions,one side is bigger,another side is small.
countersink hole
  • DIP: An abbreviation for a dual in-line package, a DIP is a kind of housing for integrated circuits. This housing will typically come in the form of a molded plastic container with two rows of attachment pins.
  • Double-Sided PCB: A type of PCB that features traces and pads on both sides, rather than a single side.
  • DRC: An acronym for design rule check, this is a software verification of a PCB layout. These are often used on PCB designs before production to ensure the design doesn't contain any potential sources of error, like small drill holes or traces placed too close together.
  • Dry Film Solder Mask: This is a type of solder mask film that is applied to a printed board that results in a higher resolution mask with finer line designs. This method tends to be more expensive than liquid solder masks.
  • Edge Connector: This type of connector is designed for the edge of a PCB, and it is most often used to facilitate an add-on card.
  • Edge Plating: This is a term used for copper plating that stretches from the top to the bottom of a surface and along the edges of a board, allowing for edge soldering and connections.
edge plating
  • FR4: This is a material rating for a flame-resistant material. It also refers to the most commonly used PCB substrate material. The name specifies that the resin material is capable of automatically extinguishing when it is aflame.
  • Gerber File: A type of CAM file used to control a photoplotter. It's a standard way of communicating board specifications with manufacturers.
  • Gold Fingers: These are connectors found on the edge of a PCB after the board has been plated with gold. Hard, smooth and flat, these fingers are excellent conductors, supporting edge-to-edge connections. Gold fingers are usually hard gold with at least 5 micro inch.
  • Half-Cut/Castellated Holes: This refers to holes that are drilled on the edge of a board and plated, resulting in a half-circle hole on the edge of the PCB. This is common for PCBs designed for microchip testing.Also,we call it half hole plating. Castellated Holes are usually used in modules which will load on another main printed circuit board.
  • Laminate: This term refers to the combination of different materials through heating, adhesive and welding methods to create a new material with multiple layers. The resulting material has greater strength and stability than the individual materials combined to create the laminate.
  • Legend: This is a shorthand guide for marking component names and positions. Legends help ease the assembly and maintenance processes.Also,it calles with silkscreen,overlay.
  • Multi-Layer PCB: This is a type of PCB with at least three conductive layers of trace and components.
  • NC Drill: This is a more common name for a Numeric Control drill machine. This type of machine is what assemblers use to drill holes in PCBs
  • NPTH: An acronym for non-plated through hole, NPTH refers to a hole with no plated copper on the hole wall. This means no electric connections can be made using the walls of this hole.
  • Pad: This is one of the most basic composition units of a PCB assembly. A pad is a contact point used to connect components with a via and is the point to which the components are soldered.
  • Panel: A panel is a combination of boards produced simultaneously to improve efficiency during the manufacturing process. Once the process is finished, these panels are typically broken apart into their singular units before being used.
  • Panelize: This is the act of grouping multiple PCBs into a panel to improve manufacturing efficiency. An alternative term is panelization.
  • Pick-And-Place: A method of SMT assembly where a machine automatically picks up SMDs and places them in the correct positions on the board.
  • Plated-Through Hole: Alternatively called a PTH, this is a procedure in which a through-hole is plated so that the hole wall can be conductive. This is often used as a contact point for through-hole components and can be used as a via.
  • Prepreg: Also called PP, is the key material for multi-layer PCB manufacturing. it is primarily composed of resin and strengthening material that is then classified into glass-fiber cloth, paper base, compound material etc.
  • Press Fit Holes: This is a hole through which a contact terminal can be pressed into a PCB.The tolerance for press fit hole is 0.05mm(2mil). it is very strict.
  • Reference Designator: Alternatively called "Ref Des, " this is the name of a component on a PCB. Typically, the component name begins with a letter or two, indicating the component class, followed by a number. These designators are usually printed on the silkscreen to help identify each component.
  • RF: Short for radio frequency, RF is an electromagnetic frequency ranging between 300KHz and 300GHz. RF can also be a type of high-frequency electromagnetic signal.
  • Silkscreen: This is a layer of epoxy ink applied to a PCB that contains component names and positions. The labels included on silkscreens help to direct workers through the assembly process. Typically, silkscreens are white, which helps the labels stand out against the PCB's solder mask.
  • Slot Hole: Non-round holes on a PCB that may or may not be plated. These are often required for specific components but are costly due to the labor needed to cut them.
  • Solder Mask/Solder Resist: This is a layer of material, usually consisting of an epoxy resin, which isn't compatible with solder. This material is applied to the entire PCB, except those areas where content needs to be soldered. This process helps to physically and electrically insulate traces, preventing shorts. Solder masks are often green in color, though red and black are also common.
  • Surface Finish: Since copper tends to oxidize in natural environments, a surface finish protects the layer from doing so. Oxidation can cause the tin paste to fail or solder incorrectly. The primary types of surface finishes include HASL, ENIG, ENEPIG, OSP and others.
  • Tented Via: This is a type of via that has a dry film solder mask covering both its pad and its plated-thru hole. This solder mask insulates the via completely, protecting the PCB against shorts. Some vias are tented only on one side to allow for testing on the other.
  • Via: This term refers to plated through-holes that connect signals between traces on different layers of a PCB. These holes have conductive copper interiors to maintain an electrical connection.
  • Via Filled With Resin/Via Plugged: This is a via that is filled with an epoxy resin. Once filled, copper can be soldered to the surface of the resin without influencing the final product.
  • Via in Pad: Also called a thru-hole on the pad, a via in pad functions as an electric connection between layers. It is useful for multi-layer components or for fixing the positions of components.Vin in pad are mostly at BGA area,there is no enough room to rout trace,so a hole at BGA pad to another layer is very helpful.
via in pad
  • V-Scoring: This is an incomplete cut through a panel, which is often used to help break apart panels of PCBs into single units.we also call it V-cut ,V-groove.