- Sagging : After printing of solder paste, the slow loss of definition of the print as the board rests under the influence of gravity. - Saponifier : A chemical that changes organic material (e.g. oil, fat, colophony not soluble in water) into a chemical soap (soluble in water) - SCC : A chip carrier [Square Chip Carrier] with a square body. - SCC : Solder Column Connector. Form of the BGA-family, where short solder columns are used instead of the spherical balls. - Screen : In screen-printing the weave (metal or plastic) onto which a pattern is created by means of an epoxy coating (emulsion) which determines the print. The screen is stretched into a frame prior to printing. - Screen mesh : The woven fibers or metal wires used to support the emulsion and allow the solder paste to flow through for printing. The diameter and spacing (number per inch) of the fibers determine the "size" of the mesh. - Screen-Printing : A printing process that presses paste through a screen onto the PCB. - Screenability : The qualitative characteristic of the solder paste with respect to how easy it spreads and prints without any detrimental behavior. - Semiaqueous Cleaning : A cleaning method employing a first chemical process that changes soils on the assembly into water soluble residues and then washing those off by a water rinse process - Shadowing : A general condition in IR and some Convection Reflow equipment where parts do not receive the intended amount of energy for heating. This can occur due to direct blocking of radiation or due to laminar convective flow - SMA : Surface Mounted Assembly. Any electronic assembly or module that is manufactured with surface mounted components and using surface mount technology. - SMC (SMD) : Surface Mounted Components (Surface Mounted Devices). Any electrical or mechanical component that can be attached to the surface of a substrate with solder. - SMT : Surface Mount Technology. The technology used to manufacture electronic assemblies using components that are soldered directly to the substrate or PWB. - Snap-Back : The action of a screen or stencil to return into its original position after having been deflected by a squeegee during non-contact printing - Snap-Off : The action of return during non-contact printing of the screen just after the squeegee passes. - Snap-Off Distance : The distance setting between a screen or stencil during non-contact printing. - SO : Small Outline. A package resembling a flat pack with leads on only two sides. - Soft soldering : is characterized by a more-or-less arbitrary limit for the value of the melting point of the third metal or alloy: in particular 450°C (approx. 840°F) - Soft Water : Water that is naturally 'soft' or that has gone through a water-softening process. Such a process replaces 'hard' ions by 'soft' ions - SOIC : Small Outline Integrated Circuit. A plastic IC package for surface mounting applications that has leads on two opposite sides. - SOJ : A plastic IC package with "J" leads on two sides. It resembles a plastic DIP, except for lead spacing and forming. - SOL (SOW) : Small Outline - Large (Small Outline - Wide). SO generally refers to a package that is approximately 150 mils wide, while SOL/SOW refers to packages that are approximately 300 mils wide. - Solder : Relatively low melting metals or alloys [< 450 ºC] which are used to join relatively high melting metals. - Solder Alloy : this is given according to the standard QQ-S-571 - Solder Ball : Individual spheres of solder found on the assembly after soldering. Their mechanism of creation is different in flow (wave) soldering and reflow soldering. - Solder dip : taking the PCB to the solder by a dipping movement of the conveyor - Solder Fillet : The entirety of solidified solder between pad and lead - Solder Joint : A conductive joint which was created by soldering between the conductors of the PCB and the leads (or metallizations) of the component. - Solder Paste : A mixture of small solder particles in a flux and viscosity moderating solvent. - Solder paste, also called solder cream : consists mainly of solder particles and flux and is a rather complicated concoction of these elements and is distinguished according to: Metal content - Solder Slump : The flow of solder paste after the printing process that occurs under the force of gravity - Solderability : Evaluations of the capability of any surface, either component or PWB land, to wet with molten solder. - soldering : is that process in which two metals, each having a relatively high melting point, are joined together by means of a third metal or alloy having a relatively low melting point - Solids Content : The amount (by weight) of non-volatile chemicals in a flux - Solidus : highest temperature at which a metal is completely solid. - Solvent Extraction Method : A cleanliness test method that uses a mixture of alcohol and water to remove polar contaminants from the soldered assembly. By measuring the change in conductivity of the fluid a deduction is madeabout the soil removed from the product - SOT : Small Outline Transistor. A plastic leaded package for diodes and transistors used in surface mounting applications. - Spray fluxing : a flux application which employs a method of producing tiny solder droplets and directing them onto the bottom of the PCB. it is the only system that can control the amount of flux deposited and newer spray fluxers always provide fresh flux. - Spring-Loaded Probes : Spring-loaded needles of a bed-of-needle fixture that contact the assembly at pre-determined points for test purposes. - Squeegee : A blade used to press paste or adhesive through a screen or stencil during printing - Squeegee Downstop : The distance, which the squeegee has to traverse in z-direction to reach the stencil or screen - Squeegee Pressure : The pressure exerted by the squeegee on the stencil during printing - Squeegee Speed : The velocity with which the squeegee travels over the stencil or screen during printing - Squeegee Stroke : The distance that the squeegee travels over the stencil during printing - Stencil : A foil (mostly metal) into which apertures are made to reflect the pattern to be printed and which is used for printing purposes - Step-and-Repeat : The repetition of the same pattern on the PCB - Step-Down Stencil : A stencil that has areas, which have been thinned out to allow for thinner solder paste deposition when compared to the thicker areas - Substrate : The base material which is used to support the printed interconnections and the components of the electronic assembly. - Surface Insulation Resistivity [SIR] Test : A test which measures the level of resistivity of a dielectric (e.g. FR-4) between conductive parts [comb pattern]. - Surface Mount Device : A component intended for use on the surface of a PCB - Surface mounted : a method to supply an assembly with components where the components are mounted to the board without the use of through-holes. leadless components ("leadless" is a misnomer; plenty of leadless components have leads)