PCB glossary R-S

PCB Glossary starting with R

Reference designator (abbrv. "ref des"): The name of a component on a printed circuit by convention beginning with one or two letters followed by a numeric value. The letter designates the class of component; eg. "Q" is commonly used as a prefix for transistors. Reference designators appear as usually white or yellow epoxy ink (the "silkscreen") on a circuit board. They are placed close to their respective components but not underneath them, so that they are visible on the assembled board. By contrast, on an assembly drawing a reference designator is often placed within the boundaries of a footprint --a very useful technique for eliminating ambiguity on a crowded board where reference designators in the silkscreeen may be near more than one component.

Reference Dimension: A dimension without a tolerance that is used only for informational purposes that does not govern inspection or other manufacturing operations.

Reflow Soldering: Melting, joining and solidification of two coated metal layers by application of heat to the surface and predeposited solder paste.

Reflowing: The melting of an electrodeposited tin/lead followed by solidification. The surface has the appearance and physical characteristics of being hot-dipped.

Registration: The degree of conformity to the position of a pattern, or a portion thereof, a hole, or other feature to its intended position on a product.

Resin (Epoxy) Smear: Resin transferred from the base material onto the surface of the conductive pattern in the wall of a drilled hole.

Resist: Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder or plating.

RF (radio frequency) and wireless design: A circuit design that operates in a range of electromagnetic frequencies above the audio range and below visible light. All broadcast transmission, from AM radio to satellites, falls into this range, which is between 30KHz and 300GHz.

Rigid-Flex: A PCB construction combining flexible circuits and rigid multi layers usually to provide a built-in connection or to make a three dimensional form that includes components.

Route (or Track): A layout or wiring of an electrical connection.

PCB Glossary starting with S

Scanning Electron Microscopy: Scanning Electron Microscopy is a scanning method, which utilizes a microscope with 200 times magnification or greater.

Schematic: A diagram which shows, by means of graphic symbols, the electrical connections and functions of a specific circuit arrangement.

Scoring: A technique in which grooves are machined on opposite sides of a panel to a depth that permits individual boards to be separated from the panel after component assembly.

Screen Printing: A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeegee.

Semiconductors: Semiconductors are materials whose properties fall between those of insulators and conductors, and is also the term used for all electronic components made from semiconductor material. Semiconductors, most commonly silicon and germanium, are the basic foundation of nearly all solid-state electronic devices.

Short: Short circuit. An abnormal connection of relatively low resistance between two points of a circuit. The result is excess (often damaging) current between these points. Such a connection is considered to have occurred in a printed wiring CAD database or artwork anytime conductors from different nets either touch or come closer than the minimum spacing allowed for the design rules being used.

Signal layer: Layer of a board, in which traces can be placed. For a two-sided board two signal layers are available - the Top and the Bottom layers.

Silk Screen (Silk Legend): Epoxy-ink Legend printed on PCB. The most common colors used are white and yellow.

Single-Sided Board: A printed board with conductive pattern on one side only.Small Outline Integrated Circuit (SOIC): An integrated circuit with two parallel rows of pins in surface mount package.

Small-Outline J-lead (SOJ): Small-Outline J-lead (SOJ) is a type of chip module, which utilizes inward extending J-shaped pins to attach chips to a printed circuit board surface.

SMD: Surface Mount Device.

SMOBC: Solder mask Over Bare Copper. A method of fabricating a printed circuit board that results in final metallization being copper with no protective metal. The non-coated areas are coated by solder resist, exposing only the component terminal areas. This eliminates tin lead under the mask.

SMT: Surface Mount Technology. Defines the entire body of processes and components which create printed circuit board assemblies with lead less components.

Solder: An alloy that melts at relatively low temperatures and is used to join or seal metals with higher melting points. A metal alloy with a melting temperature below 427°C (800°F).

solder balls: The round solder balls bonded to a transistor contact area and used to make connection to a conductor by face-down bonding techniques.

Solder Bridging: Solder connecting, in most cases, misconnecting, two or more adjacent pads that come into contact to form a conductive path.

Solder Bumps: Round solder balls bonded to the pads of components used in face-down bonding techniques.

Solder Coat: A layer of solder that is applied directly from a molten solder bath to a conductive pattern.

Solder Leveling: The process by which the board is exposed to hot oil or hot air to remove excess solder from holes and lands.

Solder Mask or Solder resist: Coating to prevent solder to deposit on.

Solder Mask: Non-preferred term for solder resist.

Solder Mask or Solder resist: Coating to prevent solder to deposit on.

Solder Wick: A band of wire removes molten solder away from a solder joining or a solder bridge or just for desoldering.

Space transformer — Abbreviated ST: A major component of certain high-density probe cards. It provides pitch reduction, high routing density and localized mid-frequency decoupling. A major developer of ATE systems which use space transformers is Wentworth Labs.

SPC: Statistical Process Control. The collection of process data and creation of control charting is a tool used to monitor processes and to assure that they remain In Control or stable. Control charts help distinguish process variation due to assignable causes from those due to unassignable causes.

Static Random Access Memory (SRAM): Static Random Access Memory (SRAM) is a type of non-volatile memory commonly used in caching, which is faster (and more expensive) than dram because it does not require "refreshing".

Step-And-Repeat: A method by which successive exposures of a single image are made to produce a multiple image production master.

Stuff: Attach and solder components to (a printed wiring board).

Sub-panel: A group of printed circuits (called modules) arrayed in a panel and handled by both the board house and the assembly house as though it were a single printed wiring board. The sub-panel is usually prepared at the board house by routing most of the material separating individual modules, leaving small tabs. The tabs are strong enough so that the sub-panel can be assembled as a unit, and weak enough so that final separation of assembled modules is easily done.

Substrate: A material on whose surface adhesive substance is spread for bonding or coating. Also, any material which provides a supporting surface for other materials used to support printed circuit patterns.

Surface Mount Technology (SMT): Surface Mount Technology (SMT) is the principal technology for the assembly of printed circuit boards by soldering electrical components directly to a board substrate that uses less space than the pin-through-hole method. SMT is a highly flexible technology that can be continually reconfigured to meet customer-specific product requirements. Each SMT assembly line is designed to have PCB screen printing, component placement and solder reflow capabilities.

Symbol: A simplified design representing a part in a schematic circuit diagram.

Synchronous Dynamic Random Access Memory (SDRAM): Synchronous Dynamic Random Access Memory (SDRAM) is a relatively new type of dram, which synchronizes itself with the CPU's bus and is capable of running at higher clock speeds than conventional memory.

System Design and Engineering: System Design and Engineering is a series of processes for taking an electrical product from customer-supplied requirements to volume production, with focuses on functionality, cost, size, manufacturability, scalability, compatibility, durability, safety and serviceability. The process includes hardware design, product architecture, circuit design and schematic capture, technology assessment and selection, component selection, parts sourcing and production quantity ordering, printed circuit board layout, mechanical design, software development, concurrent and sustaining engineering, sub-assembly integration and interconnection, enclosure and packaging design, functional and environmental compliance and prototyping, as well as programmable device software development and other services.