A UV flood lamp sized too small forces multiple exposures, fixture repositioning, or scanning — all of which introduce dose variation and slow production. A flood lamp sized too large wastes energy, increases equipment cost, and exposes parts of the assembly to UV that should not be exposed. Sizing a UV flood lamp correctly requires defining the cure area, the required irradiance and dose, and the constraints of the production process before evaluating equipment. Define the Cure Area First The starting point for UV flood lamp sizing is the largest substrate or assembly you need to cure in a single exposure. Define the cure area precisely: What is the maximum substrate dimension? (Length × width for rectangular parts; diameter for circular substrates) Do you need to cure the entire substrate surface, or only specific regions? Is the assembly positioned in a tray or fixture that defines a consistent cure zone? Will multiple parts be loaded onto a tray or pallet for simultaneous curing? The lamp's active cure area must encompass the full cure zone, with usable irradiance extending to the edges of the substrate. If the lamp's active area exactly equals the substrate size, irradiance uniformity at the edges may be insufficient. Design in a margin — the lamp's usable cure area should typically be 10–20% larger than the substrate to maintain acceptable irradiance at the part edges. Irradiance Requirements at the Substrate After defining the cure area, establish the required irradiance at the substrate surface: From the adhesive or coating supplier: obtain the minimum irradiance (mW/cm²) required for cure at the lamp's emission wavelength and the minimum dose (mJ/cm²) for full cure. Calculate the required exposure time: Exposure time (s) = Dose (mJ/cm²) ÷ Irradiance (mW/cm²). Confirm this exposure time is compatible with your production cycle time. Confirm the irradiance at your working distance: The working distance for a flood lamp is the distance between the lamp face and the substrate surface. Irradiance decreases with distance. Request irradiance data at the working distance your fixture or enclosure establishes, not at the lamp's face. UV LED vs. Mercury Arc Flood Lamps UV LED flood lamps dominate new installations. They emit at a fixed narrow peak wavelength, have long LED lifetimes (20,000–50,000 hours to L70), generate less infrared than mercury arc sources, and can be turned on and off instantly. Available in modular array configurations that can be scaled to cover large cure areas. Mercury arc and metal halide flood lamps provide broad-spectrum UV output, covering UV-C through UV-A wavelengths. Used for adhesives and coatings requiring broad-spectrum activation or UV-C wavelengths not available from UV LED sources. Bulb lifetime is 1,000–2,000 hours, requiring scheduled replacement. Require warm-up and cool-down periods that affect production workflow. For most new UV curing installations with UV-A compatible adhesives and coatings, UV LED flood lamps are the appropriate technology. Lamp Area Coverage and Array Configurations UV LED flood lamps are available as single-head units covering areas from approximately 50 mm × 50 mm to 150 mm…

A UV LED spot lamp purchase that looks straightforward at the quote stage often reveals hidden complexity during installation — a wavelength that doesn't match the adhesive, an irradiance specification that doesn't hold at production working distance, or a controller that lacks the features needed for process documentation. Asking the right questions before signing a purchase order prevents these discoveries from becoming production problems. Questions About Wavelength and Spectral Output What is the peak emission wavelength of the lamp? UV LED lamps are available at 365 nm, 385 nm, 395 nm, and 405 nm. Confirm the peak wavelength against the absorption spectrum of your adhesive or coating. A nominal "365 nm" lamp from different suppliers can have peaks ranging from 360 nm to 370 nm — the difference matters for some adhesive systems. What is the spectral FWHM of the emission peak? UV LED emission is narrow — typically 10–25 nm FWHM. Confirm the actual spectral bandwidth, not just the peak wavelength. A photoinitiator with a narrow absorption peak may not respond to a lamp whose peak is at the edge of its absorption band, even if the nominal wavelengths sound compatible. Can you provide the emission spectrum of the lamp? Request a plot of emission intensity versus wavelength. This confirms the peak wavelength and bandwidth from measured data, not just the nominal specification. Questions About Irradiance and Working Distance What is the irradiance at my working distance? Suppliers often specify peak irradiance at the lamp face or at a short reference distance (5–10 mm). Ask for irradiance data at your actual production working distance — the distance between the light guide tip and the adhesive surface in your fixture. If the supplier cannot provide irradiance data at your working distance, ask for the irradiance-versus-distance curve so you can interpolate. How is irradiance measured? Ask whether irradiance values are measured with a calibrated radiometer traceable to a national standard, or derived from theoretical calculations. Measured values are more reliable. Confirm the measurement geometry matches your intended use (same light guide diameter, same spot size configuration). Does irradiance remain stable over the cure cycle? For high-duty-cycle production curing, irradiance should be stable from the first second of exposure to the last. Ask whether the controller uses closed-loop irradiance feedback (maintaining constant output as the LED heats up) or open-loop power control (delivering constant power, with output varying as LED temperature changes). For process-critical applications, closed-loop regulation is preferable. Questions About Spot Size and Coverage What is the spot size at my working distance? Spot size increases with working distance as the beam diverges. Confirm that the spot covers your entire bond area within the irradiance threshold required for cure. Ask for spot size data at the working distance you intend to use, not at the lamp's reference distance. What irradiance threshold is used to define the spot size? Some suppliers define spot size at 1/e² (13.5% of peak irradiance), others at 50% or 80% of peak. Understand the definition and confirm…

Selecting a UV LED lamp supplier is not just a procurement decision — it is a process engineering commitment. The supplier you choose will determine whether your curing process runs reliably for years, whether you have access to technical support when problems arise, and whether replacement parts are available when equipment ages. Evaluating UV LED lamp suppliers on the right criteria prevents expensive regrets. Technical Capability Wavelength options and irradiance range. A capable supplier offers UV LED lamps across the wavelengths your applications require — 365 nm, 385 nm, 395 nm, and 405 nm at minimum. They should be able to specify irradiance values at multiple working distances with supporting measurement data, not just peak irradiance at the lamp face. Application engineering support. Can the supplier review your adhesive specifications and recommend a lamp configuration? Can they calculate the irradiance and dose delivered at your working distance? Can they advise on spot size, light guide selection, and fixturing? A supplier who can engage technically on your process is more valuable than one who can only quote equipment from a catalog. Calibration data. Ask whether irradiance values in the specification sheet are manufacturer-measured with calibrated equipment or derived from theoretical calculations. Request the measurement method and calibration traceable to a national standard (NIST or equivalent). Spectral data. Request the emission spectrum of the lamp, showing peak wavelength and FWHM (full width at half maximum) spectral bandwidth. Confirm that the emission peak falls within the absorption band of your adhesive system. Equipment Quality and Reliability Thermal management. UV LED lamps generate heat at the LED junction. Adequate thermal management — heat sink design, forced-air cooling, or liquid cooling for high-power units — is essential for stable output over the cure cycle and long LED lifetime. Ask the supplier how thermal management is implemented and what junction temperature the LED array operates at under rated conditions. LED lifetime specification. Request the rated LED lifetime (in hours) and the definition used — typically L70, the point at which output degrades to 70% of initial value. Ask for lifetime data for the LED source at rated operating conditions, not at reduced power. Output stability. Does the lamp maintain constant irradiance over a cure cycle, or does output drop as the system heats up? Ask whether the controller uses feedback control (closed-loop irradiance regulation) or open-loop power control. Closed-loop systems maintain irradiance despite LED temperature variation; open-loop systems do not. Controller features. Evaluate the controller for programmable exposure time, adjustable irradiance, dose monitoring, alarm output for below-specification output, and data logging capability. Industrial UV curing applications in regulated industries require controller data logging for process traceability. If you would like to discuss technical specifications with an Incure applications engineer before evaluating suppliers, Email Us and we will help you define the evaluation criteria for your specific process. Application Testing and Demonstrations Will the supplier provide a demonstration unit? A capable supplier should offer application testing — either at their facility or by loaning a demonstration unit…

An undercured UV adhesive bond looks identical to a fully cured one until it fails. The surface may be tack-free, the assembly may pass a visual inspection, and the bond may survive initial handling — but the mechanical properties are compromised, and the bond will fail under service conditions at a fraction of its rated strength. Minimum UV dose is the threshold parameter that separates a structurally sound bond from an assembly defect. Understanding what it means and how to apply it is fundamental to any UV adhesive curing process. What UV Dose Means UV dose is the total UV energy delivered to the adhesive surface per unit area, expressed in joules per square centimeter (J/cm²) or millijoules per square centimeter (mJ/cm²). It is the product of irradiance (W/cm²) and exposure time (seconds): Dose (J/cm²) = Irradiance (W/cm²) × Time (s) Dose represents the photochemical work done on the photoinitiators in the adhesive. Each unit of dose drives a proportional number of photoinitiation events, generating free radicals that add monomer units to growing polymer chains. A minimum cumulative dose is required to drive the polymerization reaction to a conversion level that produces the adhesive's rated mechanical properties. Below this minimum dose threshold, polymerization conversion is incomplete. The adhesive is undercured. Mechanical properties — tensile strength, shear strength, elongation — are below specification. Resistance to environmental factors (humidity, temperature, solvents) is compromised. The adhesive may pass visual inspection and short-term handling but will fail under sustained load or environmental stress. Tack-Free Dose vs. Full Cure Dose Most UV adhesive data sheets specify two dose thresholds: Tack-free cure (surface cure) dose: The minimum dose at which the adhesive surface becomes non-tacky. Surface cure occurs when photoinitiators at the surface are consumed and oxygen inhibition (which keeps the surface liquid) is overcome. A tack-free surface is achievable at lower dose than full structural cure. Full cure dose (functional cure dose): The minimum dose required for the adhesive to reach its rated mechanical properties throughout the bond line. Full cure dose is always higher than tack-free dose and may be 2–10× higher depending on the adhesive formulation. Using tack-free dose as the process target produces assemblies that handle without visible problems but have mechanical properties well below specification. Only full cure dose ensures the bond meets its design intent. How Adhesive Suppliers Specify Minimum Dose Reputable UV adhesive suppliers specify minimum cure dose as a condition for achieving rated mechanical properties. The data sheet may state: "Minimum dose: 500 mJ/cm² at 365 nm for full cure" "Recommended dose: 1,000–3,000 mJ/cm² at 385 nm" "Minimum irradiance: 100 mW/cm²; exposure time: 10 seconds for full mechanical properties" If the data sheet expresses minimum cure conditions in irradiance and time rather than dose, calculate the equivalent dose. If the specification is for a wavelength different from your lamp, confirm with the adhesive supplier whether the dose requirement changes at the lamp's emission wavelength. If the adhesive you are using does not have dose specifications from the supplier,…

The decision between a UV spot lamp and a UV conveyor system shapes the production process architecture for years. Both technologies cure UV adhesives and coatings effectively, but they serve fundamentally different process requirements. Understanding the technical and operational basis for choosing between them prevents expensive equipment decisions that don't match actual production needs. The Core Distinction A UV spot lamp delivers focused UV energy to a specific, stationary bond point. The part is held in a fixture, the lamp is positioned over the cure location, and UV exposure occurs over a defined dwell time at that position. The cure cycle is a discrete event — start, expose, stop. A UV conveyor system moves parts through a continuous UV exposure zone on a belt. The lamp array — typically a flood lamp or series of flood lamps — is fixed above the belt. Parts pass through the cure zone at a controlled belt speed, receiving UV dose that is the product of the belt irradiance and the time the part spends beneath the lamp array. The cure process is continuous, not discrete. This architectural difference determines which technology fits which application. When UV Spot Lamps Are the Right Choice Point bonding and precision assembly. When cure is needed at a specific joint location — a bonded lens, a connector seal, a wire tack point — and the bond area is small (typically less than 20–30 mm), a spot lamp delivers energy precisely where needed without exposing surrounding components. Low-to-medium throughput assembly. Manual or semi-automated assembly lines where parts are processed one at a time, with operators positioning each part for cure, are well matched to spot lamp technology. Dwell times of 5–30 seconds per cure cycle are compatible with most manual assembly rates. Accessible but fixed bond locations. When the bond joint is accessible from above or through a defined delivery path, a spot lamp mounted in a fixture or on a robot arm can reach the cure location reliably. Applications with multiple cure points on a single assembly — three wire tacks, four corner bonds — can use multiple light guides from a single controller to cure all points simultaneously. Heat-sensitive substrates with large components. Spot lamps expose only the bond area to UV energy. Conveyor systems expose the entire assembly passing beneath the lamp array. When surrounding components cannot tolerate UV exposure — sensitive electronics, photo-reactive coatings, human-readable labels — a spot lamp allows selective exposure. Flexible production with frequent changeovers. Spot lamp setups can be reconfigured for different part geometries by adjusting the fixture and repositioning the lamp. Conveyor systems are more process-specific in their configuration and require more significant setup changes for different substrates. When UV Conveyor Systems Are the Right Choice High-volume, continuous throughput. Conveyor systems are designed for continuous production. Parts enter the cure zone continuously, cure as they travel through, and exit already cured. Throughput rates are determined by belt speed and lane width — industrial conveyor UV systems can cure thousands of…

Spot size is one of the most overlooked variables in UV LED system selection — until a production line is running and the cure results are inconsistent. Engineers who define the required spot size before specifying equipment build processes that cure reliably and predictably. Engineers who assume any UV spot lamp will cover their bond area discover edge-undercure problems after the equipment is installed. This is the guide for getting spot size right the first time. What Spot Size Means Spot size is the diameter (or area) of the UV light pattern delivered by the lamp at a specified working distance. For circular spots, it is typically expressed as a diameter in millimeters at the 1/e² intensity boundary (where irradiance falls to 13.5% of peak) or at the 80% or 50% irradiance level, depending on the manufacturer's convention. Different irradiance contours matter for different purposes. The area within which irradiance exceeds the adhesive's minimum required irradiance is the effective cure zone. Adhesive that falls outside this zone — at the spot edges where irradiance is below threshold — will not receive sufficient UV energy to cure completely. Always ask the lamp supplier which irradiance threshold their spot size specification refers to, and confirm that the threshold used is above your adhesive's minimum required irradiance. Defining Your Required Cure Area Before selecting a UV LED system, define the geometry of your bond joint: What is the shape of the adhesive bond line? (Circular, rectangular, linear bead, irregular pattern?) What is the maximum dimension? (Diameter of a lens seat, length of an edge bond, width of a potted area?) What is the minimum dimension the lamp must cover? The lamp's effective cure spot must encompass the entire bond area within the usable irradiance zone. If the bond area is circular and 8 mm in diameter, the lamp's spot must deliver irradiance above the adhesive's minimum threshold across the full 8 mm diameter at your production working distance. If the bond area is larger than available spot sizes from a single lamp, evaluate whether multiple light guides from a single controller can cover the full area simultaneously, or whether a UV flood lamp with a larger cure area is the appropriate tool for the application. Working Distance and Spot Size Relationship Spot size increases with working distance. As the light guide is moved farther from the substrate, the beam diverges and the illuminated area expands. Irradiance decreases as the spot expands, because the same total power is distributed over a larger area. The tradeoff between spot size and irradiance at working distance is fundamental to UV spot lamp selection. A lamp that delivers a 5 mm spot at 10 mm working distance with 2,000 mW/cm² irradiance may deliver a 12 mm spot at 30 mm working distance but with irradiance reduced to 300 mW/cm². Whether the 300 mW/cm² at 30 mm is sufficient to cure your adhesive within your cycle time is determined by the adhesive requirements — not by the lamp alone.…

The photoinitiators in a UV adhesive absorb light at specific wavelengths. The UV lamp must emit at wavelengths that fall within those absorption bands. An otherwise well-designed curing process will fail completely if this fundamental match is missing — and the failure can be subtle, producing bonds that appear cured on the surface but remain structurally weak at the interface. Getting the wavelength match right is the starting point for every UV adhesive curing process. The Role of Photoinitiators UV-curable adhesives polymerize when photoinitiators — light-sensitive molecules blended into the formulation — absorb UV photons and generate reactive free radicals or cations that initiate chain-growth polymerization. Each photoinitiator has a characteristic absorption spectrum: a range of wavelengths over which it absorbs UV energy efficiently, with one or more absorption peaks where efficiency is highest. If the UV lamp does not emit at wavelengths within the photoinitiator's absorption spectrum, the photoinitiator cannot absorb energy from the lamp and the polymerization reaction will not initiate. The adhesive remains liquid or produces an incompletely polymerized, mechanically weak gel rather than a cured solid. Reading the Adhesive Absorption Spectrum The photoinitiator absorption spectrum is typically expressed as a curve of molar absorptivity or extinction coefficient versus wavelength, with units of L/(mol·cm). The peaks in this curve identify the wavelengths at which the photoinitiator is most efficient at absorbing UV energy. Most industrial UV adhesives use photoinitiators with absorption peaks in the UV-A range (315–400 nm). Common peaks include: 365 nm: One of the most widely used UV-A wavelengths. Photoinitiators such as bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (BAPO) and hydroxycyclohexyl phenyl ketone variants absorb in this range. 385 nm: A common peak for photoinitiators used in dental, optical, and industrial adhesive formulations. 405 nm: Near-visible violet wavelength. Used in some modern adhesive formulations and digital printing inks; closer to visible blue than deep UV. Some adhesives use blends of multiple photoinitiators with absorption peaks at different wavelengths to broaden their spectral response. These formulations may cure effectively under multiple lamp wavelengths. Obtaining Spectral Data from the Adhesive Supplier Request the photoinitiator absorption spectrum or the recommended curing wavelength from your adhesive supplier. The technical data sheet for most industrial UV adhesives specifies: Recommended curing wavelength (e.g., "cure with 365 nm UV") Irradiance range and dose required for complete cure at that wavelength Spectral sensitivity range where cure is effective If the data sheet only lists a single recommended wavelength, ask the supplier whether the adhesive will also cure at adjacent wavelengths (e.g., 385 nm if the recommendation is 365 nm). Some adhesives have sufficient photoinitiator absorption at ±20 nm of the primary peak to cure effectively at an adjacent LED wavelength. This flexibility matters when lamp availability or process integration considerations favor a specific wavelength. If you need help evaluating whether your adhesive is compatible with a specific UV LED wavelength, Email Us and an Incure applications engineer will review the adhesive specifications and lamp options. UV LED Lamp Emission Characteristics UV LED lamps emit at a narrow peak…

Irradiance is the variable most engineers underspecify when setting up a UV adhesive curing process. The number on a lamp's data sheet tells you what the lamp can deliver at a specific distance under laboratory conditions. The number that matters is the irradiance actually reaching your adhesive surface at your production working distance — and whether that value is sufficient to drive the polymerization reaction to a complete, structurally sound cure. What Irradiance Means Irradiance is UV radiant power per unit area: watts per square centimeter (W/cm²) or milliwatts per square centimeter (mW/cm²). It represents the intensity of UV energy hitting a surface at a given moment. Irradiance is not the same as dose — dose (J/cm²) is irradiance integrated over the exposure time and represents the total UV energy delivered to the adhesive. Both irradiance and dose must meet minimum thresholds for complete cure. An adhesive can receive a sufficient total dose at low irradiance over a long exposure time, but cure kinetics are not always linear. Very low irradiance can result in incomplete photoinitiation even with extended exposure. Very high irradiance can drive rapid surface cure while the adhesive interior remains undercured, particularly in thick bond lines or pigmented adhesive systems. Adhesive Supplier Specifications The starting point for determining required irradiance is the adhesive technical data sheet. Reputable UV adhesive suppliers specify: Recommended irradiance range (mW/cm²) Required cure dose (J/cm²) at the specified wavelength Minimum tack-free surface cure dose Minimum structural cure dose for full mechanical properties If the data sheet does not specify irradiance and dose, contact the adhesive manufacturer directly. A supplier who cannot provide cure parameter guidance is a supplier to evaluate carefully. Use the adhesive's specified wavelength for all measurements. Irradiance specifications apply at a specific emission wavelength — irradiance measured at 365 nm is not the same as total UV irradiance, and using the wrong measurement wavelength produces incorrect dose calculations. Typical Irradiance Ranges by Application Industrial UV adhesive applications span a wide range of irradiance requirements: Low irradiance (10–50 mW/cm²): Ambient or low-power UV curing, suitable for slow-curing adhesives with high photoinitiator loading. Rarely used in production environments due to slow cycle times. Medium irradiance (50–500 mW/cm²): Standard range for most UV spot lamp industrial applications. Covers the majority of UV-curable adhesive formulations used in assembly. Cycle times of 2–30 seconds are typical. High irradiance (500 mW/cm² – 5 W/cm²): UV LED spot lamps and high-power flood lamps in the upper irradiance range. Used for fast-cure applications requiring sub-second or 1–3 second cycle times. Some adhesive formulations are specifically designed for high-irradiance cure. Very high irradiance (>5 W/cm²): Concentrated UV sources for specialized applications. Requires careful evaluation of substrate thermal tolerance, as even low-infrared UV LED sources can heat substrates significantly at very high irradiance. If you are uncertain whether your target irradiance is achievable with available UV LED lamps for your working distance and spot size requirements, Email Us and an Incure applications engineer will model the irradiance for your process…

A UV flood lamp that performs well on paper but fails on the production floor is a common and expensive mistake. The specifications that matter — irradiance uniformity, wavelength output, cooling capacity, and control integration — are often not the ones prominently featured in a product brochure. This guide gives manufacturing and process engineers a structured framework for evaluating UV flood lamps for industrial curing applications. What UV Flood Lamps Are Used For UV flood lamps cure adhesives, coatings, and encapsulants over large areas. Unlike spot lamps, which concentrate energy on a single bond point, flood lamps deliver UV energy uniformly across a defined cure zone — a panel, a board, a tray of assembled parts, or a substrate on a conveyor. Industrial flood curing applications include conformal coating cure, structural adhesive cure on bonded panels, UV ink cure, gasket and seal cure, and potting compound surface cure. The defining characteristic of a flood lamp is area coverage with acceptable irradiance uniformity. A flood lamp that delivers high irradiance at the center and low irradiance at the edges creates a cure gradient — parts near the center cure faster and more completely than parts at the edges. Understanding the uniformity specification of a flood lamp is as important as knowing its peak irradiance. Wavelength Selection UV flood lamps are available at 365 nm, 385 nm, and 405 nm from UV LED sources, and at broad-spectrum output from mercury arc and metal halide sources. Select the wavelength based on the photoinitiator absorption spectrum of your adhesive or coating. For most UV-A curable adhesives and conformal coatings, 365 nm or 385 nm UV LED flood lamps are appropriate. For UV-curable inks and some optical coatings, 365 nm or 405 nm may be specified. Confirm the required wavelength with your material supplier before specifying equipment. If your facility uses multiple UV-curable materials with different wavelength requirements, evaluate whether a single lamp wavelength can cover all materials or whether separate lamps are needed for different process stations. Irradiance and Dose Irradiance (W/cm² or mW/cm²) is the UV power delivered per unit area at the substrate surface. Dose (J/cm²) is irradiance multiplied by exposure time. The adhesive or coating supplier specifies the minimum dose required for complete cure at a given irradiance. Evaluate flood lamp irradiance at the working distance you will use in production — not the manufacturer's specified maximum irradiance at minimum distance. Irradiance drops with increasing distance from the lamp. Measure irradiance with a radiometer calibrated to the lamp wavelength at the actual production working distance and confirm the value meets your cure requirements. Irradiance uniformity across the cure zone matters as much as peak irradiance. Request uniformity data — typically expressed as the ratio of minimum to maximum irradiance across the cure area — from the lamp manufacturer. A uniformity of ±10–15% across the cure zone is acceptable for most industrial applications. Applications with tight cure specification windows may require tighter uniformity. Cure Area and Coverage Specify the cure area —…

The choice of UV spot lamp determines whether your adhesive bonds cure reliably, at the right speed, and without damaging the parts underneath. Engineers who approach UV spot lamp selection systematically — matching the lamp's output to the adhesive chemistry, the substrate geometry, and the production process — build curing processes that hold up under production conditions. Engineers who pick a lamp based on price or availability alone routinely discover cure failures, thermal damage, and process inconsistency after installation. This guide covers the variables that matter. What a UV Spot Lamp Does A UV spot lamp concentrates UV energy from a small-area emitter onto a defined cure zone. The lamp delivers a controlled UV dose — irradiance (W/cm²) over an exposure time — to activate the photoinitiators in a UV-curable adhesive and drive the polymerization reaction to completion. Spot lamps are used where cure is needed in a localized area: a bonded lens, a sealed connector, a wire-tacked component, a medical device joint. The output characteristics of the spot lamp must be matched to the requirements of the adhesive. A mismatch in wavelength, irradiance, or spot size produces an incompletely cured bond or damages the substrate through excessive UV or heat. Wavelength Matching UV adhesives cure when their photoinitiators absorb UV energy at a specific wavelength range. Most UV adhesives absorb in the 365 nm range (UV-A), and many also respond at 385 nm or 405 nm. Some specialized adhesives cure at 254 nm (UV-C) or at multiple wavelength peaks. UV LED spot lamps emit at defined peak wavelengths — 365 nm, 385 nm, or 405 nm are common in industrial systems. The lamp wavelength must fall within the adhesive's absorption spectrum. An adhesive optimized for 365 nm may cure slowly or incompletely under a 405 nm source, even at the same irradiance. Obtain the photoinitiator absorption spectrum from your adhesive supplier. Match the lamp wavelength to the peak absorption band. If the adhesive formulation is fixed and the available lamp outputs don't match, work with your adhesive supplier to reformulate with a compatible photoinitiator. Irradiance Requirements Irradiance is the UV power density delivered to the adhesive surface, measured in W/cm² or mW/cm². The adhesive supplier specifies a minimum irradiance required to initiate cure and a recommended operating range for complete cure at specified exposure times. Operating below minimum irradiance results in surface cure with an uncured interior — the surface forms a skin that prevents oxygen inhibition but the adhesive beneath remains tacky or liquid. Operating above maximum irradiance accelerates cure but can generate excess heat at the adhesive surface and in the substrate. Measure irradiance at the adhesive surface — not at the lamp head. Irradiance decreases with distance from the lamp, and the reduction is significant over even small distances. Use a UV radiometer calibrated to the lamp's emission wavelength to measure irradiance at the working distance you intend to use in production. Spot Size and Coverage A UV spot lamp delivers energy over a defined spot…