Light is all around us, but how does it help in gluing things together? In this post we explore the fundamentals of light curing technology, the specialty of UV curing technology, UV curing material, and our top UV curing adhesives.
What is Light Curing?
Light is made up of a wide spectrum of electromagnetic radiation, with different wavelength regions corresponding to different amounts of energy, such as infrared, visible, and ultraviolet (UV). As the wavelength of light decreases (and the frequency increases), the energy it carries increases. Therefore, as shown in the diagram below, γ (gamma) and X rays carry much more energy than radio waves.
Every chemical reaction requires a minimum amount of energy applied to it before it can start off; this is called the activation energy. The different amounts of energy provided by the different wavelengths of light are able to trigger and activate different chemical reactions, acting as their activation energy. UV light, which carries a relatively high amount of energy, can be used to start chemical reactions which have a high activation energy. Microwaves, which carry a relatively low amount of energy, can be used to start chemical reactions which have a low activation energy.
Curing, a chemical process during which an adhesive and its substrate toughen and harden into a cross-linked product, can be initiated or accelerated through the use of light. Different adhesives require different activation energies for their curing process. Adhesives that can be heat-cured are initiated by infrared radiation; UV curing adhesives are initiated by ultraviolet radiation; and so on.
UV curing is one of the most common types of light curing due to its high energy and therefore instantaneous curing effect at a low cost and risk. Typical cure speeds of 1 to 30 seconds are typical for surface cures, with higher intensity light leading to faster cures. UV curing resins can also tolerate overexposure from 100% to 500% without any degradation. Two simple ways of increasing the light intensity include reducing the gap between the light and the substrate, and adding another UV lamp onto the production line.
The rapid curing speed of UV light leads to shorter cycle times, improved lead times for customers, and reduced labour costs for the manufacturer. UV curing is also relatively easy to manage, only requiring simple UV-curing dispensing equipment, and no racks or ovens – in contrast to heat curing. Since most UV curing material are also single component, there is no need for mixing, therefore bypassing the potential issues that come with it. Finally, UV curing technology is environmentally friendly due to the lack of harmful chemicals involved in its process; this produces less chemical waste and reduces the regulatory and disposal costs for the manufacturer. High intensity UV light, however, is regarded as ionizing radiation which can cause harm to the skin and bodily functions; therefore, sufficient care must be taken when handling UV equipment.
What Equipment Do I Need for UV Curing?
- UV curing kit
- Radiometer to monitor and record the UV curing process, ensuring the apparatus is working effectively and that the operator is shielded from the UV light
- UV shield
- UV-protective eye goggles
UV Curing Material
A wide range of industrial materials on the market can be UV cured. These range from:
- Adhesives – offering rapid curing, strong and clear bonds with a good aesthetic.
- Coatings – regularly used on printed circuit boards (PCBs) to protect the components from harmful agents.
- Potting compounds – used extensively in electronic applications.
- Maskants – providing surface protection.
UV Curing Adhesives
Permabond have a long, proven history of supplying UV curing adhesives to many industries, ranging from munitions to decorative art glasses. Permabond offers single component UV curing adhesives that are ideal for use on glass or plastics as they give translucent, odourless and strong bonds very quickly.
Permabond UV630 is a low viscosity, plastic bonding UV curing adhesive that offers a fast cure and very high shear strength with low-power lamps. Due to its excellent elongation and impact resistance, it is ideal for applications requiring substrates with different coefficients of thermal expansion.
Permabond UV681 is a tack-free, low viscosity, UV curing adhesive which is ideal for conformal coating, protecting against environmental and vibrational damage. Due to being translucent and tack free, it is suitable for coating smart card microchips. It provides an even, bubble-free coating with high resistance to temperature, making it resist wave-soldering as well.
Permabond UV683 is a tack-free, UV curing adhesive with an ideal viscosity for doming. Due to this, and its high temperature resistance which makes it resist wave-soldering, it is perfectly suitable for the encapsulation of electronic components. It is able to cure on demand very quickly even with low-power lamps.