UV Curing Glossary
UV Spot Curing Glossary
The vocabulary of UV spot curing, in plain English, from dose and irradiance to oxygen inhibition, shadowing, and dual-cure. Every term links to the how-to that puts it to work.
- UV spot curing
- Curing a UV-reactive adhesive, coating, or ink at a specific point by aiming a concentrated beam of ultraviolet light at it, rather than flooding a whole part or oven. A spot source delivers high intensity to a small area for a fast, localized cure.
- Dose (UV)
- The total ultraviolet energy delivered to the joint, equal to intensity multiplied by exposure time (measured in millijoules per square centimetre, mJ/cm²). Cure is driven by dose: to cure faster you raise intensity so the same dose arrives in less time.
- Irradiance / intensity
- The UV power arriving per unit area at the working plane (milliwatts per square centimetre, mW/cm²). It falls off quickly with distance from the guide tip, which is why a close, repeatable working distance matters.
- Radiometer
- An instrument that measures UV intensity (and often accumulated dose) at the working plane. It turns "it looks cured" into a number, so you can verify a new lamp, catch an aging guide, balance splitter legs, and reproduce a process.
- Wavelength
- The colour of the UV, measured in nanometres (nm). Common curing bands are 365, 385, 395, and 405 nm. Cure only happens where the source wavelength overlaps the adhesive initiator’s absorption, so wavelength must be matched to the chemistry.
- UVA / UVB / UVC
- Bands of the ultraviolet spectrum by wavelength: UVA (about 315–400 nm) does most adhesive curing; UVB (about 280–315 nm) and UVC (about 100–280 nm) are shorter and more energetic. Most substrates block UVB/UVC and pass UVA.
- Photoinitiator
- The ingredient in a UV adhesive that absorbs UV and starts the cure reaction. Its absorption band sets the wavelength the source must provide; a source that doesn’t hit the initiator’s band will not cure the adhesive.
- Oxygen inhibition
- The quenching of a free-radical (acrylate) cure at the exposed surface by atmospheric oxygen, leaving a thin tacky skin over a hard bulk. Overcome it with more surface dose, a nitrogen blanket or cover film, or an air-cure chemistry.
- Shadowing
- Any part of a joint that the UV cannot reach directly. Shadowed adhesive stays liquid. The fixes are lighting the joint from more angles (a splitter), repositioning, or a dual-cure adhesive for volume the light can’t reach.
- Dual-cure adhesive
- An adhesive that cures by UV where light reaches and by a secondary mechanism, heat, moisture, or an activator, where it doesn’t. It is the reliable answer for joints with unavoidable shadowed volume, such as blind holes.
- Light guide
- The flexible conduit, a liquid-filled or fiber cable, that carries UV from the source to the work. Its diameter sets the spot size and intensity; it is a consumable that loses transmission as it ages and fouls.
- Liquid light guide
- A light guide with a liquid-filled core, common on arc systems like the SunSpot 2. It transmits a broad spectrum efficiently; respect its minimum bend radius and temperature rating to protect the core.
- Splitter (multi-pole) guide
- A light guide that divides one source into two or four legs so several joints cure in one exposure. Per-leg intensity drops as the light divides, so the legs are balanced (typically within about ten percent) and dose is verified at each tip.
- Working distance
- The gap between the light-guide tip and the joint. Because intensity falls off quickly with distance, a short and repeatable working distance is one of the easiest ways to raise intensity and cut cure time.
- Arc lamp (metal-halide)
- A high-intensity broad-spectrum UV source, as used in the SunSpot 2, emitting across a wide band (about 275–650 nm). It cures nearly any UV chemistry but its output dims gradually over the lamp’s life.
- UV LED source
- A solid-state UV source emitting a specific narrow band (such as 365, 385, 395, or 405 nm), as used in the SkyBeam and SkyWand. It offers instant on/off, long life, low heat, and no warm-up, but the wavelength must match the adhesive.
- Broad-spectrum cure
- Curing with a source that emits many wavelengths at once (an arc lamp), so whatever band an adhesive’s initiator needs is present. It removes wavelength matching as a variable and cures unqualified or mixed chemistries.
- Tacking
- A fast, small UV cure that holds a component in place before a later structural bond or a soldering/reflow step. A tack fixes placement in one to three seconds; it is not the final structural joint.
- Staking
- Locking a wire, lead, or component to a board or bobbin with a dab of UV adhesive so it resists vibration and handling. Several small stakes along a long lead cure more completely than one large bead.
- Conformal coating
- A thin protective film over a circuit assembly. UV-cure conformal coatings let a reworked area be re-coated and cured in seconds without oven-baking the whole board, ideal for touch-up and repair.
- Potting / encapsulation
- Filling or sealing a component or assembly with resin for protection. UV-cure encapsulants set on demand but only as deep as the light penetrates, so deep pots are cured in layers or use a dual-cure resin.
- Cure depth
- How far into a resin or adhesive film the UV cure reaches. It depends on wavelength, intensity, and the resin’s own rating. Beyond the rated depth, cures are done in layers or with a dual-cure chemistry.
- Shutter
- A mechanical gate on an arc source that blocks the beam except during a deliberate exposure, usually triggered by a foot pedal. It keeps the beam off the bench and the operator between cures.
- Heat filter
- An optical filter that removes infrared from an arc source’s output so the work isn’t thermally heated during cure, important for optics, glass, and heat-sensitive assemblies.
- Interlock
- A safety circuit that prevents a UV source from firing when a guard or enclosure is open. Essential on enclosed and automated curing stations so the intense UV can’t expose an operator.
- PLC integration
- Wiring a curing system to a programmable logic controller so a production line can trigger the cure, hold a fixed programmed dose, and gate it with interlocks. LED systems with a command interface suit this best.
- Lamp module
- The replaceable lamp assembly in an arc system. The SunSpot 2 uses a quick-change 200 W module (UV1866, with UVB-enhanced and visible-cure variants) so an aged lamp is swapped at the bench without optical realignment.
- Substrate transmission
- How much UV a material passes. A part can look clear yet block short UV, glass and polycarbonate pass longer UVA/visible but absorb UVB/UVC, so curing through a substrate means matching the wavelength to what it transmits.
- MAP (Minimum Advertised Price)
- A manufacturer policy setting the lowest price a reseller may advertise. An authorized distributor confirms in writing what it may publish before advertising prices, to stay within any MAP agreement.
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