Thermocompression Bonding

The joining of two materials without an intermediate material by the application of pressure and heat in the absence of electrical current.

Thermoplastic

Polymer materials that can be repeatedly melted without significant change in their properties.

Thermosetting

Describes the property of an epoxy, to set or become rigid and non-meltable when heated with or without pressure.

Thermosetting Plastic

Polymer materials that cure (irreversably polymerize) at specific temperature and time conditions.

Thixotropic Ratio

An indication of thixotropy as a ratio of viscosities at two different shear rates.

Thixotropy

The property of a paste or fluid to thicken or set up to a paste or semi-gel when allowed to stand. Agitation breaks it down but further standing will again permit a viscosity rise.

Torsional Strength

The torque required to separate adhesive bonded (and cured) materials and/or components.

Transceiver

A device that performs, within one chassis, both telecommunicafion transmitting and receiving functions.

Transistor

An active semiconductor device capable of providing power amplification. Transistors have three or more terminals.

Solvent Cleaning

A cleaning method employing chlorinated and fluorinated hydrocarbon liquids.

Solvent Extraction

The removal of one or more components from a liquid mixture by intimate contact with a secondary liquid that is nearly insoluble in the first liquid and which dissolves the impurities and not the substance to be purified.

Specific Gravity

The ratio of the weight of any volume of a mass or substance to the weight of an equal volume of water at given temperature. The specific gravity of a substance times the density of water equals the density of the substance.

Specific Heat

The ratio of a material’s thermal capacity to that of water at 15°C.

Spread

The distance a substance (e.g., an adhesive) moves after it has been applied at ambient conditions.

Stencil

A metal mask in which patterns or apertures matching the component locations on the PCB are made so a suitable material can be forced through the apertures by a squeegee onto a substrate.

Stencil Printing

Deposition of a specific material, such as solder paste, using a stencil.

Storage life

The period of time during which a packaged epoxy or curing agent can be stored under specific temperature conditions and remain stable for use. Sometimes called shelf life.

Stress

An applied force or pressure, as tension or shear, exerted on a body which produces a resultant strain on the material. The ability of material to withstand a stress depends on the strength of its cohesive force or molecular resistance.

Substrate

A material upon the surface of which an epoxy is spread for any purpose, such as bonding or coating.

Substrate Geometry

Substrate dimensions, typically dimensions critical to implement a successful bonding process, including the following