How to Select UV Curing Adhesives
UV curing adhesives use ultraviolet (UV) light or other sources of radiation to initiate curing and form a permanent bond without heating.
Ultraviolet (UV) or visible light cures or polymerizes a combination of monomers and oligomers into a UV adhesive. UV adhesives are also known as radiation curing or radiation curing adhesives because UV rays are a source of radiant energy.
Electron beam curable adhesives are another type of radiation curable adhesives. Light or radiation sources used in the UV or visible light curing process include medium pressure mercury lamps, pulsed xenon lamps, LEDs, or lasers.
UV-curable adhesives consist of monomers, oligomers, photoinitiators, additives, and sometimes UV-transparent fillers. The UV photoinitiator component generates free radicals or actions when exposed to UV light, which initiate crosslinking between unsaturation sites in the monomers or oligomers.
Benefits of UV curing adhesives
The ability of UV curable adhesives to cure quickly without heat saves energy and increases productivity. Energy savings occur because capital expenditures and production space required for expensive ovens required for thermal curing adhesives are eliminated. Thermally cured adhesives can take hours to cure compared to UV adhesives, which can cure in seconds or minutes.
UV curing adhesives can be "100% solids" meaning that all of the adhesive becomes a solidified bond joint. As a result, no water or solvents are released into the environment, which is better for the environment (no emissions) and safety (no flammable fumes), as well as parts that are sensitive to water or solvents.
Some UV-curable adhesives contain additional modifiers, such as fillers, pigments, or staple fiber reinforcements. Others contain solvent-based tackifying resins that use a volatile organic compound (VOC) to thin or alter viscosity. Solvent-based, UV-curable adhesives generally pose greater environmental or regulatory concerns.
Physical properties
Physical and processing properties include void fill, the space or gap between the substrate and the adhesive or sealant; and viscosity, a measure of a fluid's resistance to flow.
Curing time is another important property to consider. With UV curing adhesives, the setting or curing time is the time required to fully cure or set a bonding system. In thermosetting, hydraulic or other chemically setting systems, the time will vary depending on the actual curing temperature. However, for UV curing adhesives, the cure time can be quite fast.
Some styles of UV curing adhesives adhere instantly upon application of UV light. Others, which are more common, begin to turn when they come into contact with UV rays, but still require a certain period of time to fully set. Longer cure times will be required for lower cure temperatures.
Thermal properties
Use Temperature: The range of temperatures to which products can be exposed without degrading structural or other required end-use properties.
Thermal Conductivity: The linear heat transfer per unit area through a material for a given applied temperature gradient.
Coefficient of Thermal Expansion (CTE) – The amount of linear expansion or contraction that occurs in UV curing adhesives with a change in temperature.
Electrical and optical properties
Dielectric Strength – The maximum voltage field that UV curing adhesives can withstand before electrical failure occurs.
Resistivity - The longitudinal electrical resistance (ohm-cm) of a uniform rod of unit length and unit cross-sectional area.
Dielectric Constant: The relative permittivity of a material compared to a vacuum or free space.
The refractive index - A measure of the speed of light in a material. This is the amount of light transmitted through a material.
About Us
DeepMaterial is an innovative company specializing in adhesives for semiconductor and electronic applications and surface protection materials for chip packaging and testing. Based on the core technolo- gy of adhesives, DeepMaterial has developed adhesives for chip packaging and testing, circuit board-level adhe-sives, and adhesives for electronic products. Based on adhesives, it has developed protective films, semiconductor fillers, and packaging materials for semiconductor wafer processing and chip packaging and testing.