Light Cure Factors

There are a number of control variables in the curing process. All variables are related to the characteristics of the substrate being cured and the type of adhesive being used.

Considerations for the irradiance level, wavelength, exposure time, substrate, substrate temperature, UV adhesive, spectral output, and environment should be made before UV light curing.

When determining adhesives, select the most suitable chemistry for the desired results. Adhesives are an engineered material that is specifically formulated to accomplish different tasks: one specific formula does not fit all desired applications. The adhesive properties that should be considered in various applications include:

Cure Shrinkage	Adhesive Strength	Operating Temperature Range
Index of Refraction	Viscosity	Elongation
Hardness	Modulus of Elasticity	Tensile Strength
Shear Strength	Peel Strength	Cohesive Strength
Outgassing	Moisture Resistance	Glass Transition Temperature
Rate of Creep	Thermal Conductivity	Thermal expansion Coefficient
Cure Time	Degree of Cure	Degree of Cross-Linking
Shelf Life

Light dose - What settings are appropriate?

• Irradiance (mW/cm²) multiplied by Exposure Time (seconds)
• Many adhesive data sheets continue to provide exposure information in terms of Dose
• It is expressed in mJ/cm²
• 1 mW x 1 sec = 1 mJ

Unfortunately there are many settings possible for the same dosage. For example:

If you want 100 mJ/cm2;

• 2 mW/cm² x 50 sec
• 5 mW/cm² x 20 sec
• 10 mW/cm² x 10 sec
• 20 mW/cm² x 5 sec
• 50 mW/cm² x 2 sec

All these settings provide same dose. Specifying a dose level provides no information on how best to cure the adhesive.