Rosin

 A hard, natural resin (nowadays also synthetic),consisting of abietic and primaric acids and their isomers, some fatty acids and terpene hydrocarbons, that is extracted from pine trees and subsequently refined.

Rosin Flux

The mildest of solder fluxes and generally requiring added organic activating agents.

Roadmap

A printed pattern of non-conductive material by which the circuitry and components are delineated on a board to aid in service and repair of the board.

Right-angle Edge connector

A connector which terminates conductors at the edge of a printed board, which bringing the terminations our at right angles to the plane of the board conductors.

Ribbon Cable

A flat cable with round conductors.

Rheology

Science of flow ,is the study of the flow and deformation of matter and is particularly important with regard to colloidal systems.

Re-working

The act of repeating one or more manufacturing operations for the purpose of improving the yield of acceptable part.

Re-work

A manufacturing step or process that is repeated to bring a non-performing or non-conforming component or circuit to a functional condition.

Reverse Image

The film pattern on a printed circuit board enabling the exposure of conductive areas for subsequent plating.

Resist

Coating material used to mask or to protect selected areas of a pattern from the action of an etchant, solder, or plating. Also see Dry Film, Resists, Plating Resists and Solder Resists.

Resin

A high-molecular-weight organic material with no specific melting point. A polymer.

Resin Smear

Resin transferred from the base material onto the surface or edge of conductive pattern normally caused by drilling. Sometimes called epoxy smear.

Residue

Any visual or measurable form of process-related contamination.

Repeatability

The ability of a system to return to a specific parameter, said of equipment when evaluating its consistency of processing.

Repair

The process of restoring the functional capability of a defective component or circuit.

Reliability

The probability that a component, device or assembly will function properly for a defined period of time under the influence of specific environment and operational conditions.

Relative Humidity

The radio of the quantity of water vapour present in the air to the quantity which would saturate the air at the given temperature.

Registration

The alignment of a pad on one side of the printed circuit board or layers of a multi-layer board to its mating pad on the opposite side.

Register Mark

A symbol used as a reference point to maintain registration.

Re-flowing

The melting of an electro-deposit followed by solidification.

Re-flow Spike

The portion of the re-flow soldering process during which the temperature of the solder is raised to a value that is sufficient to cause the solder to melt.

Re-flow Soldering

Joining components to substrates by placing the parts into solder paste and then melting the paste to achieve re-flow and the interconnection.

Reference Edge

The edge of cable or conductor from which measurements are made.

Radial Lead

 A lead extending out of the side of a component, rather than from the end.