PCB Glossary : D to G

Defect:
Any nonconformance to specified requirements by a unit or product.

Definition:
The fidelity of reproduction of pattern edges, especially in a printed circuit relative to the original master pattern.

Delamination:
A separation between any of the layers of the base of laminate or between the laminate and the metal cladding originating from or extending to the edges of a hole or edge of board.

Design Rule Checking:
The use of a computer program to perform continuity verification of all conductor routing in accordance with appropriate design rules.

Desmear:
The removal of friction-melted resin and drilling debris from a hole wall.

Dewetting:
A condition that results when molten solder has coated a surface and then receded, leaving irregularly shaped mounds separated by areas covered with a thin solder film and with the base material not exposed.

Dielectric:
An insulating medium that occupies the region between two conductors.

Dimensional Stability:
A measure of the dimensional change of a material that is caused by factors such as temperature changes, humidity changes, chemical treatment, and stress exposure.

Double-Sided Board:
A printed board with a conductive pattern on both sides.

Drilling:
The act of forming holes (vias) in a substrate by mechanical or laser means.

Dry-Film Resists:
Coating material specifically designed for use in the manufacture of printed circuit boards and chemically machined parts. They are suitable for all photomechanical operations and are resistant to various electroplating and etching processes.

Dry-Film Soldermask:
Coating material (dry-film resist) applied to the printed circuit board via a lamination process to protect the board from solder or plating.

Electroless Copper:
A thin layer of copper deposited on the plastic or metallic surface of a PCB from an autocatalytic plating solution (without the application of electrical current).

Electroplating:
The electrodeposition of an adherent metal coating on a conductive object. The object to be plated is placed in an electrolyte and connected to one terminal of a direct current (DC) voltage source. The metal to be deposited is similarly immersed and connected to the other terminal.

Epoxy:
A family of thermosetting resins. Epoxies form a chemical bond to many metal surfaces.

Epoxy Smear:
Epoxy resin that has been deposited on edges of copper in holes during drilling either as uniform coating or in scattered patches. It is undesirable because it can electrically isolate the conductive layers from the plated-through-hole interconnections.

Etchback:
The controlled removal of all components of the base material by a chemical process acting on the sidewalls of plated-through holes to expose additional internal conductor areas.

Etching:
The chemical, or chemical and electrolytic, removal of unwanted portions of conductive materials.

Flying Probe:
A testing device that uses multiple moving pins to make contact with two spots on the electrical circuit and send a signal between them, a procedure that determines whether faults exist.

FR-4:
The UL-designated rating for a laminate composed of glass and epoxy that meets a specific standard for fire-retardance. FR-4 is the most common dielectric material used in the construction of PCBs.

Gerber:
A software format used by the photoplotter to describe the printed circuit board design.

Golden Board:
See Known Good Board.

Ground Plane:
A conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding, or heat sinking.