Glossary

Adhesion promotion
The chemical process of preparing a surface to enhance its ability to be bonded to another surface, as in a layer of conformal coating.

Adhesion failure
The rupture of an adhesive bond such that the separation appears to be at the adhesive-adherent interface.

ARUR
Abbreviation standing for acrylic resin and urethane resin combination chemistries.

Bridging
Fillet or meniscus formation of coating around the leads of a component caused by capillary action.

Creep
Strain, deformation, or movement of coatings caused by time and/or temperature.

Cross-linking
The formation of chemical bonds between molecules in a thermosetting resin during a polymerization reaction.

CTE
(Coefficient of Thermal Expansion) Linear dimensional change with respect to an original dimension due to a change in temperature.

Cure
A change in the physical properties of a polymer by a chemical reaction.

Degradation
Decrease in quality or integrity. Loss of desired physical, chemical or electrical properties.

Delamination
A separation between a conformal coating layer and the surface it is adhering to.

De-wetting
The propensity of the coating material to refuse to wet the surface evenly.

Dielectric constant
The ratio of the capacitance of a configuration of electrodes with a specific material as the dielectric between them to the capacitance of the same electrode configuration with a vacuum or air as the dielectric.

Dielectric strength
The maximum voltage that a dielectric can withstand under specified conditions without resulting in a voltage breakdown, usually expressed as volts per unit dimension.

Dilution
Reduction in viscosity. Can be achieved by mixing a nonreacting, soluble agent into the material.

Dissipation factor
A value that represents the tendency of insulating or dielectric materials to absorb some of the energy in an alternating-current signal.

Durometer
A measure of the degree of hardness or the resistance to be deformed or fractured.

Filler
A substance that is added to a material to modify its solidity, bulk, or other properties.

Fish eyes
A surface defect to the conformal coating that resembles the eyes of a fish.

Gel time
Time taken for a liquid polymer to begin to exhibit pseudo-elastic properties or to be Îimmobilized.Ì

Glass transition temperature TG
The temperature at which an amorphous polymer, or the amorphous regions in a partially-crystalline polymer, changes from being in a hard and relatively-brittle condition to being in a viscous or rubbery condition.

Hardness
A property that indicates the ability of a material to resist penetration of a specific type of indentor when forced into the material under specified conditions. Indentuation hardness is inversely related to the penetration and is dependent on the elastic modulus and viscoelastic behavior of the material.

Insulation resistance
A measure of the capability of a material to electrically insulate adjacent conductors from each other.

Masking
The process of applying a temporary film, tape boot or plug that prevents the area covered from being coated.

Monomer
A chemical compound that can undergo polymerization.

MSDS
(Material Safety Data Sheet) Provided by the manufacturer, contains relevant properties of the material with regards to safety concerns.

Multi-layering
The process of applying more than one layer of coating to make up the desired thickness.

Orange peeling
A surface defect to the conformal coating that resembles the surface or skin of an orange.

Outgassing
The gaseous emission from a processed coating layer when it is exposed to heat or reduced air pressure, or both.

Permeability
The ability of molecules of one material to flow through the matrix of another material. The degree of permeability is dependant on the molecular structure of both materials.

Polymerization
The formation of a matrix of cross-linked long chain molecular structure from short chain monomer molecules.

Pot life
The length of time a material, substance, or product can be left in an open package or dispenser, while it meets all applicable specification requirements and remains suitable for its intended use.

Rework
The act of reprocessing noncomplying articles, through the use of original or alternate equivalent processing, in a manner that assures compliance of the article with applicable drawings or specifications.

RTV
(Room Temperature Vulcanizing) The development of desired dry film properties at room temperature..

Shelf life
The length of time a material, substance, or product can be stored, under specific environmental conditions, while it meets all applicable specification requirements and remains suitable for its intended use.

Shrinkage
Reduction in volume as a wet, freshly applied layer dries/cures into a coating film with desired properties.

Solids content
The proportion of resin or polymer material to the solvent carrier.

Stripping
The process of eroding a material by chemical reaction. Stripping agents can be used to remove certain types of conformal coating for the purpose of rework or repair.

Surface tension
The natural, inward, molecular-attraction force that inhibits the spread of a liquid at its interface with a solid material.

Viscosity
The property of a polymer to frictionally resist internal flow that is directly proportional to the applied force.

VOC
(Volatile organic compound) Regulated compounds containg carbon that have measurable vapor pressures.

Wetting
The formation of a relatively uniform, and adherent film of materials on a surface.

Credit for the glossary belongs to IPC. For more information, visit www.ipc.org.

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