Swaged Lead

A component lead wire that extends through a hole in a printed board and its lead extension is flattened(swaged)to secure the component to the board during  manufacturing operations.

Surfactant

A chemical added to the cleaning solution to lower surface tension and to promote wetting.

Surface Tension

The natural, inward, molecular attraction force that inhibits the spread of a liquid at its interface with a solid material.

Surface Mounting

The electrical connection of components to the surface of a conductive pattern that does not  utilize component holes.

Surface Leakage

The passage of current over the boundary surface of an insulator as distinguished from passage through its volume.

Surface Insulation Resistance(SIR)

A measure in ohms of an insulating material’s (as in FR-4) electrical resistance between conductors.

Surface Insulation Resistance(SIR)Test

Test for the level of resistance of an insulating material, such as FR-4.between conducting members of a board (traces, contacts).

Supported Hole

A hole in a printed board that has its inside surface plated or otherwise reinforced.

Subtractive Process

A process for obtaining conductive patterns by selective removal of unwanted areas of conductive foil from a metal clad base material.

Substrate

See Base Material.

Stripline

A type of transmission line configuration which consists of a single narrow conductor parallel and equidistant to two parallel ground planes.

Strain

The deformation resulting from a stress.

Straight-through Lead

A component lead that extends through a hole and is terminated without subsequent forming.

Step-and-repeat

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

Step Soldering

The making of solder connections by sequentially using solder alloys with successively lower melting temperatures.

Statistical Process Control(SPC)

The use of statistical techniques to analyse the outputs of processes with the results guiding actions taken to adjust and/or maintain a state of quality control.

Stamped Printed Wiring

Wiring which is produced by die stamping and which is bonded to an insulating base.

Spurious Signal

See Cross-talk.

Solidus

The highest temperature at which filler metal(Solder) is completely solid.

Solderless Wrap

A method of connecting a solid wire to a square, rectangular, or V-shaped terminal by tightly wrapping the wire around the terminal with a special tool.

Soldering

 A process of joining metallic surfaces with solder, without the melting of the base metals.

Soldering Iron Tip

The portion of a soldering iron that is used for the application of the heat that melts the solder.

Solderability

The ability of a metal to be wetted by molten solder.

Solderability Testing

The evaluation of a metal to determine its ability to be wetted by solder.

Solder Side

The side of a printed board which is opposite to the component side.

Solder Resist

An ink, lacquer, photo-resist or metal coating which is not wetted by molten solder.  It is applied to specific areas of a PCB to stop them from being solder-coated, usually when mass soldering.

Solder Projection

An undesirable protrusion of solder from a solidified solder joint or coating.

Solder Plug

A core of solder in a plated through-hole.

Solder Paste

Finely divided particles of solder, with additives to promote wetting and to control viscosity, tackiness, drying rate, etc.

Solder oil (Blanket)

Liquid formulations that are used in intermix wave soldering and as coverings on static and wave soldering pots in order to eliminate dross and to reduce surface tension during the soldering process.

Solder Mask, Solder Resist

Coating with mask and insulate areas of a circuit pattern where solder is not desired.

Solder Masks

A screening defect characterized by prints having jagged edges, the result of incorrect moving pressure.

Solder Levelling

 The process of immersing printed circuit boards into hot liquids. Often referred to as HASL or HAL (Hot Air Levelling).

Solder Fillet

A preferable concave surface of solder that is at the interconnection of the metal surfaces of a solder connection.

Solder Connection Pinhole

A small hole that penetrates from the surface of a solder connection to a void of indeterminate size within the solder connection (process indicator).

Solder Bridging

The unwanted formation of a conductive path of solder between conductors.

Solder (Soft)

A metal alloy with a melting temperature that is below 450℃.

Soak

The period after pre-heat and before re-flow peak temperature where the internal temperature differences between parts allowed to equalize.

Snap-off

The return of a stencil to normal level after deflection by the pressure of the squeegee moving across the surface.

Snap-off Distance

The space between the top surface of the substrate and the underside of the stencil when the squeegee is not in play.

SMT

Surface Mount Technology. Defines the entire body of processes and components which create printed circuit assemblies without components with leads that pierce the board.

SMOBC

Solder Mask Over Bare Copper.

Smear

Resin, smeared over the edge of an internal copper layer of a multi-layer board during drilling, which prevents the layer from making electrical contact with the barrel of the hole.

SMD

Surface Mounted Device. Any component or hardware element designed to be mounted to a printed circuit board (PCB) without penetrating the board.

Slump

A spreading of the solder paste after printing but before re-flow soldering. If excessive, a loss of definition may result.

Single-image Production Master

A production master used in the process of making a single printed board.

Shingle-sided Board

A printed board with a conductive pattern on one side only.

Simulation

The process of creating a virtual representation(a computer model)of an electronic component, circuit board, or system and applying virtual test signals to the model to verify its functionality and possibly its timing.

Silkscreen

Often used for legend print and means the printed reference designators on a printed wiring boards.

Signal

An electrical impulse of a pre-determined voltage, current, polarity and pulse width.

Signal Plane

A conductor layer intended to carry signals, rather than serve as a ground or other fixed voltage function.

Signal Conductor

An individual conductor used to transmit an impressed signal.

Short

Short-circuit, An abnormal connection of relatively low resistance between two points of a circuit or conductors from different nets either touch or some closer than the minimum spacing allowed for the design rules being used.

Shielding, Electronic

A physical barrier, usually electrically conductive, designed to reduce the interaction of electric or magnetic fields upon devices, circuits or portions of circuits.

Shadowing

A condition occurring during etching in which the dielectric material, in intimate contact with the foil, is incompletely removed though acceptable etching may have been achieved elsewhere. In re-flow soldering, a condition in which component bodies block the infra-red energy from certain areas of the board. In wave soldering, the solder fails to wet some parts leads due to other devices blocking the flow of solder.

Sensitizing

See Activating.

Semi-aqueous Cleaning

A technique involving the use of a solvent followed by hot-water rinses and drying.

Semi-additive process

A process for obtaining conductive patterns by a combination of electroless metal deposition with etching and/or electroplating. A semi-additive process is used in conjunction with a metal clad base material.

Screen

A network of metal or fabric standards mounted tautly on a frame and upon which the PCB’s circuit pattern is superimposed by photographic means.

Screen Printing

A process for transferring an image to a surface by forcing suitable media through a stencil screen with a squeegee. Also called silk screening.

Schematic Diagram

A drawing that shows, by means of graphic symbols, the electrical connections, components and functions of a specific electronic circuit arrangement.

Saponifier

An aqueous organic or inorganic base solution with additives that promote the removal of flux.