edge connector A one-piece receptacle containing female contacts, designed to receive the edge of a PCB and interconnect, on which the male contacts are etched or printed. The connector may contain either a single or double row of female contacts. Both thermoplastic and thermosetting insulating materials are used.

edge definition The fidelity of reproduction of a pattern edge relative to the production master.

electroless copper deposition Process in which base laminate is coated with a layer of copper through chemical deposition.

electromagnetic compatibility Principle in which any electronic or electrical appliance should be able to operate without causing electromagnetic interference, and without being affected by electromagnetic interference. Also known as EMC.

electrostatic discharge (ESD) A transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field.

embedding Encapsulation process using thick protective material.

emissivity The ratio of the emissive power of a body to the emissive power of a blackbody at the same temperature.

emulsion (1) A material such as polyvinyl acetate that is built up on a printing screen to block portions of the screen. The open portions define the pattern for depositing solder paste on a PCB. (2) The light-sensitive silver halide coating of photographic films that produces an image after exposure and development.

encapsulation Term referring to the protection of assemblies, reducing the effects of environmental conditions. (See Figure 8 on following page.)

entrapment The damaging admission and trapping of air, flux, and fumes. It is caused by contamination and plating.

environmental stress screening (ESS) Manufacturing stage in which all assemblies are subjected to abnormal stresses, with the aim of forcing all early failures to occur. Also known as reliability testing.

environmental test A test or series of tests used to determine the sum of external influences affecting the structural, mechanical, and functional integrity of any given package or assembly.

epoxy (1) A polymer thermosetting resin able to form a chemical bond to plastic and metal surfaces. (2) A polymeric resin material. A family of thermosetting resins used in the packaging of semiconductor devices that form a chemical bond to many metal surfaces.

epoxy smear Epoxy resin that has been deposited onto the surface or edges of the conductive pattern during drilling. Also called resin smear.

etch factor The ratio of the depth of etch (conductor thickness) to the amount of lateral etch (undercut).

etchant Solution used to remove unwanted copper from non-circuit areas on printed circuit boards.

etchback The controlled removal of all components of base material by a chemical process on the side wall of holes in order to expose additional internal conductor areas.

etching The process of removing unwanted metallic substance bonded to a base via chemical or chemical and electrolytic means.

etching resists Materials deposited on the surface of a copper-clad base material that prevent the removal by etching of the conductive areas they cover.

eutectic The alloy of two or more metals that has the lowest melting point. Eutectic alloys, when heated, transform directly from a solid to a liquid without experiencing a plastic region.