Printed Wiring Board Terms

Standard Technical Engineering Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

Editor note; All the PWB terms are listed below. The alphabetic links above will switch to the main general engineering dictionary, so scroll down the page for definitions related to Printed Wiring Boards.

'A' to 'Ge', 'Gr' to 'O', 'P' to 'R', 'S', 'T' to 'Z'

Ground. The point in a circuit used as a common reference point for measuring purposes. To connect some point of an electrical circuit or some item of electrical equipment to earth or to the conducting medium used in lieu thereof. A conducting connection, whether intentional or accidental, between a circuit or piece of equipment and the earth, or some body serving as earth; a place of zero electrical potential.

Ground Bounce. Ground bounce refers to the ringing on an output signal when one or more outputs on the same device are being switched from HIGH to LOW. Ground bounce is associated with the inductance and resistance of the ground connection in the integrated circuit. More detailed definition of Ground Bounce.

Ground Fill: About the same as a ground island, as some portion of a PWB is covered [filled] with copper which is grounded. Smaller ground fill islands are 100% copper, while larger islands are stitched or broken up. Ground Fill is only used on portions of the PWB with no parts, while a ground island may have a component soldered to it.

PCB Ground Fill
PWB Ground Fill

Ground Grid: Ground gridding is a network of orthogonal connections between traces carrying ground. A Ground Grid uses less copper than ground fill or a ground island.

Ground Island. A small copper layer contained on one or more layers of a Printed Wiring Board which is only connected to ground. A Ground Island is always much smaller than a ground plane. Ground Islands may be 100% copper fill or hatched to reduce the amount of copper. A solid ground island is shown to the right.

PCB Ground Island
Ground Island

Ground Loop: An unwanted current that flows in a conductor connecting two points that are nominally at the same potential, i.e., ground, but are actually at different potentials. Enhanced definition of Ground Loops Description of Ground Loops.

Ground Plane. A large copper layer contained on one or more layers of a Printed Wiring Board [PWB] which is only connected to ground. In most cases a ground plane covers most if not all of the PWB layer it resides on. The portion of a ground-plane antenna that acts as ground.

Ground Planes. Copper planes used to minimize interference between circuits and from external sources. The large islands or complete planes are connected to ground.

Ground Potential. Zero potential with respect to the ground or earth. Engineering note; Ground does not have to mean 0 volts.

Ground Stitching: Normally used with a ground island or ground fill to insure the island makes a good connection with the ground plane. Ground Fill Stitching is shown in the picture to the right, while Ground Island Stitching is shown in the third graphic on the right, below. Note the small vias in the ground fill to the right, near the edge of the ground fill, next to the ICs. Note the PWB is a DDR memory Stick.

PCB Ground Island Stitching
PWB Ground Island Stitching

Guard Ring: A ground-connected track that does not carry a return current for the circuit under normal operation.

Hatched Ground Plane: [cross hatch] Also called Meshed Planes. A ground plane that does not use 100 percent copper fill to reduce the amount of metal used for better solderability, to even out the amount of copper used on both sides of a pwb or to make the plane more flexible.

Impedance. The total opposition a trace offers to the flow of current, consisting of resistance and reactance [capacitance and inductance].

equivalent Trace Impedance
Trace Impedance

Jumper Wire. A wire used to repair an error in a PWB, so that the circuit card does not have to be re-fabed. The Jumper Wire corrects trace wiring error with simple re-work. May also be called a 'white wire'.

Jumper Wire repair
PWB Jumper Wire

Keep-Out: A clearance area around ICs and other components that should not be populated because it would interfere with mounting parts, trouble-shooting, air-flow and so on. A buffer zone around the perimeter of a PCB to keep components from be mounted to near the edge of a board, or traces from running to near the edge. A board layer or small section of a board layer in which traces are not allowed to be routed.

Laminate: A product made by bonding two or more layers together, usually of different materials, under heat and pressure to form a single structure.

Land Pattern. A combination of lands intended for the mounting, interconnection, and testing of a particular part. The graphic shows a 20-pin surface mount DIP SOIC Land Pattern, with no component installed. Note the ground fill. Also note the via placed between the power pin and the by-pass capacitor, not a good design practice.

SOIC PWB Land Pattern
PWB Lands

Lands: Pads on the PWB designed to accept IC legs, as in landing pads for solder connections. A Land(s) is the point that a component is soldered down on. Lands are normally on the outter layers on the PCB used for the purposes of soldering surface mount components Also see Lifted lands.

PWB Land
PWB Land

Layout: Text in review

Lead (Pb): A soft, heavy metal used in solder compositions and other alloys.

Lifted lands. A Land that has become delaminated from the board. A Land that is not longer attached to the substrate. There shall be no lifted lands on the deliverable printed wiring board.

Mask. A device used to deposit materials on a substrate in the desired pattern.

Master Drawing. Refer to the definition from MIL-STD-100.

MCM: Multi Chip Module. Refer here for vendors and more data; MCM IC Packaging.

Microstrip: Traces that are adjacent to a continuous reference plane. In a Printed Circuit Board [PCB] stack-up, the microstrips are on the primary and secondary layers [Top and Bottom layers]. The reference plane used may either be a ground plane or power plane.

MicroStrip Topology
Microstrip Traces

MIL. The diameter of a conductor equal to 1/1000 (.001) inch.

Minimum Annular Ring. The minimum distance between the edge of a PCB pad and its via. A Minimum Annular Ring distance will be difference between an out layer and an inner layer. Refer to this page for Minimum Annular Ring Graphics and Definition.

Mounting Methods. Refer to a graphic on Transistor Can Mounting

Mounting Standoff. See Stand-Off.

metal Can Mounting

Multilayer Board: [MLB] See Multilayer Printed Wiring Board below.

Multilayer Printed Wiring Board. A rigid, flexible, or rigid-flex printed wiring board having three or more printed wiring board layers that are mechanically bonded together and electrically interconnected. A two layer board would only have copper layers on the top and bottom layers and is not normally considered a Multilayer Board. The graphic to the right shows a MLB PCB, with the copper on one layer, then the traces that appear black followed by the traces the appear read, each on a separate layer.

Multilayer PCB

NASA Specs: Relevant NASA Specifications;
NASA-STD-8739.3 - Soldered Electrical Connections
NASA-STD-8739.4 - Crimping, Interconnecting Cables, Harnesses, and Wiring
NASA-STD-8739.5 - Fiber Optic Terminations, Cable Assemblies, and Installation
NAS 5300.4(3J-1) - Workmanship Standard for Staking and Conformal Coating of Printed Wiring Boards and Electronic Assemblies
NAS 5300.4(3M) - Workmanship Standard for Surface Mount Technology
NASA-STD-8739.7 - Standard for Electrostatic Discharge Control (Excluding Electrically Initiated .."text removed".. Devices)
Editor note; I have no way of knowing if these standards are still in service or withdrawn without replacement.

Netlist. A report which gives a name to each net on a PCB and the points it connects to.

Non-Plated-Through-Hole: [NPTH] A non-plated-through hole is one formed without a deposition of metal on the inside surface of a through-hole. See also Plated-Through-Hole.

Nonwetting: A condition whereby a surface has contacted molten solder, but the solder has not adhered to all of the surface; basis metal remains exposed.

PC motherboard

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