The strength of a UV-cured bond does not come from the adhesive alone. It depends on delivering the correct dose of ultraviolet energy to every part of the bond line, in the wavelength band the adhesive is formulated to absorb. Get that relationship wrong and even a well-chosen adhesive underperforms. What the UV Bonding Ratio Means Unlike a two-part adhesive with a fixed mix ratio, the ratio in UV bonding describes the relationship between the light energy supplied and the adhesive's cure requirement. Four variables set it: Irradiance, the power density reaching the adhesive surface, measured in milliwatts per square centimeter. Higher irradiance generally cures faster. Exposure time, the duration under the lamp, in seconds. Spectral match, whether the lamp output overlaps the adhesive's photoinitiator absorption. Common LED peaks are 365, 385, and 405 nm; arc lamps are broadband. Bond line geometry, since thick sections and opaque substrates block light from reaching the full adhesive volume. The product of irradiance and time is the energy dose, in millijoules per square centimeter. Each adhesive has a minimum dose within its absorption band that drives the photoinitiator to full polymerization. That dose, delivered uniformly, is the target. Why Dose Control Is Not Optional Under-curing produces a predictable set of failures. The surface stays tacky and attracts dust. Mechanical properties fall short, so bonds fail early under shear or impact. Resistance to moisture, solvents, and temperature drops. Unreacted monomer can outgas and fog nearby optics or leave residue on electronics. Over-curing is less common but real. Excess exposure can embrittle some formulations, and optically clear grades can yellow. The larger production risk is variability: if irradiance drifts as a lamp ages, or exposure time changes with line speed, quality wanders batch to batch and specifications become hard to hold. How Incure Helps You Hit the Ratio Predictable Formulations Incure UV adhesives are built around defined photoinitiator systems with published absorption data. Technical data sheets state the recommended wavelength, the minimum and optimal irradiance, and the total dose for full cure, which removes most of the trial and error. Dual-cure grades add a secondary moisture or heat mechanism for shadowed joints where light cannot reach the entire bond line. Curing Equipment That Matches the Job The right delivery system depends on part size and throughput. Incure L9000 spot lamps concentrate high irradiance on a small area for precision work. L-Series flood lamps cover larger footprints. For continuous production, the CDM conveyor moves parts under a fixed lamp head at a controlled speed, which converts line speed directly into a repeatable dose. Our guide to matching a conveyor lamp head to line speed and part width covers that selection in detail. Process Validation Incure specialists help build a validation routine centered on a calibrated radiometer. Lamp output declines with hours of use, and periodic measurement at the bond line is the only reliable way to know the delivered dose is still in range. This also catches contamination on lamp windows and light guides before it…

UV adhesives cure in seconds and let an operator align a part before locking it. Their weakness is simple: the light has to reach the adhesive. In an assembly with opaque covers, deep joints, or shadowing components, part of the bond line never sees UV and stays liquid. Dual-cure adhesives close that gap. This article explains how dual-cure chemistry works, what it buys, and how to run it in production. How a dual-cure adhesive works A dual-cure adhesive is a single-component system with two cure mechanisms. UV light drives a fast primary cure that fixes the joint in seconds. A second mechanism then cures the material the light did not reach: UV plus heat. A bake at a defined temperature and time completes the cure through the bulk and shadowed regions. UV plus moisture. The adhesive reacts with ambient humidity over hours to finish shadowed areas, with no oven required. UV plus anaerobic. The adhesive cures where it is confined between close-fitting metal surfaces, out of contact with air. The UV step gives immediate handling strength; the secondary step gives full properties everywhere. What dual cure solves Shadowed bond lines. The main reason to use it. Opaque substrates, tight tolerances, and complex geometry all block UV somewhere. The secondary cure ensures no adhesive is left uncured, which would otherwise mean weak spots, corrosion risk from mobile monomer, or slow property drift. Fixture-free assembly. Because the UV tack cure holds the parts in seconds, jigs and clamps come off the line. Parts are handled immediately while the secondary cure proceeds. Consistent final strength. A bond that is fully cured across its whole area, including the hidden parts, is stronger and more predictable than one that relies on a partial UV cure alone. Broad substrate range. Dual-cure formulations bond plastics, metals, glass, and ceramics, and the chemistry can be tuned for flexibility to handle thermal-expansion mismatch, the failure mode covered in how CTE mismatch causes adhesive bond failure. The trade-offs Dual cure is not free. The secondary step adds a process stage, an oven or a humidity-controlled dwell area, and time before parts reach full strength. Moisture-cure grades depend on ambient humidity and slow down in dry conditions or thick sections. Heat-cure grades need components that tolerate the bake. If an assembly is fully UV-accessible, a straight UV adhesive is simpler. Running it in production Map the shadows. Identify exactly where UV cannot reach. That determines which secondary mechanism fits and how the cure area is laid out. Set the UV dose. The illuminated areas still need their target energy, in mJ/cm2, from a UV LED source matched to the adhesive's absorption wavelength. Verify it with a radiometer, since lamp output falls as sources age. Validate the secondary cure. For heat, confirm oven temperature and dwell give full cure in the shadowed regions, not just the surface. For moisture, establish the humidity and time needed at your maximum bond thickness. Dispense cleanly. Complex parts need consistent adhesive volume in every joint. Automated…

Potting components into a metal housing combines two hard problems: getting a UV-curable resin to bond well to metal, and curing resin that the opaque metal keeps in shadow. Both are solvable, but they shape which grade you choose and how you set up the cure. This article covers adhesion to metal substrates, the line-of-sight limit, and how to run UV potting on metal parts. Why UV cure is attractive for metal work Encapsulating parts in metal enclosures has traditionally meant thermal-cure epoxy and an oven. UV cure offers an alternative where it fits: Seconds instead of hours to handling strength, so parts clear the line fast. Working time on demand. The resin stays liquid until the lamp fires, so operators align components and inspect fill first. Low heat. Useful when potting temperature-sensitive electronics mounted on a metal chassis that would otherwise act as a heat path during an oven cure. Adhesion to metal Metal surfaces carry oxide, oils, and machining residue. A UV potting compound bonds to what is on the surface, so preparation drives the result: Degrease with a solvent wipe to remove cutting fluid, drawing compound, and handling oil. Abrade or blast where the joint is structural, to remove loose oxide and add texture for mechanical keying. Consider a primer or adhesion promoter on aluminum and stainless, which form tenacious but sometimes weakly bonded oxide layers. Choose a grade formulated with adhesion promoters for metal and with low cure shrinkage, so the resin does not pull away from the housing wall as it hardens. Low shrinkage also reduces stress on encapsulated components. The shadow problem UV energy cures only what it illuminates. In a metal housing, anything the walls or a component block stays liquid. Uncured resin under a part can remain tacky, corrode the metal, or outgas later. Three responses: Design for access. Keep the resin surface open to the lamp and avoid overhangs where possible. Use a dual-cure grade. These start with a UV surface cure for immediate handling, then complete through the bulk and shadowed areas by heat or ambient moisture. This is the standard answer for components fully enclosed by metal. Fall back to thermal cure for deep, fully enclosed cavities where even a dual-cure UV step adds little value. Our comparison of UV and epoxy systems covers where each belongs. Running the process Curing hardware. Metal parts often have irregular geometry, so lamp placement matters. A UV LED flood lamp with adjustable height covers a bench station; a conveyor system gives uniform dose across parts on a line. Match the lamp wavelength to the compound's absorption. Dose. Set the target energy from the data sheet, measured in mJ/cm2, and validate cure-through at the real resin depth. Check lamp output with a calibrated radiometer on a schedule, since UV sources lose intensity with age. Thermal expansion. Metal expands far less than most potting resins. Across the service temperature range, that difference loads the bond line and can lift the resin from the wall…

Potting a printed circuit board means encapsulating it, or a section of it, in a cured resin that shields the electronics from moisture, vibration, contamination, and electrical faults. The protection is real, but potting also adds weight, complicates rework, and can stress components if the resin is wrong for the job. This article covers what PCB potting delivers, the chemistry choices, and how to select a compound for a given assembly. What potting protects against Moisture and contamination. A cured barrier keeps humidity, condensation, dust, salt fog, and corrosive vapor off conductors and solder joints. Mechanical stress. The resin damps vibration and absorbs shock, protecting fine-pitch components and lead frames in automotive, rail, and portable equipment. Electrical faults. Potting compounds have high dielectric strength, which suppresses arcing, tracking, and corona in higher-voltage sections and maintains spacing that conformal coating alone cannot. Heat. Thermally conductive grades move heat away from hot components into a housing. Tampering. An opaque, hard encapsulant resists probing and reverse engineering. The cost of leaving a board unprotected in a harsh environment is premature field failure, so for outdoor, mobile, or industrial electronics potting is often not optional. The chemistry choices Epoxy. Highest modulus and adhesion, best chemical and moisture resistance, good dielectric performance. The rigidity is a liability if the board carries components with very different thermal expansion, where cure and thermal-cycle stress can crack solder joints or the resin. Best for rigid assemblies in stable-temperature service. Polyurethane. Softer and more flexible than epoxy, good for vibration damping and wide temperature swings, with moderate chemical resistance. Sensitive to moisture during cure. Silicone. Widest temperature range, very low stress on components, easy to remove for rework, but lower mechanical strength and adhesion. UV-curable and dual-cure. Cure in seconds under a lamp, which suits high-volume lines and shallow pots. UV alone needs light to reach the resin; dual-cure grades finish shadowed regions by heat or moisture. See our UV versus epoxy comparison for the general trade-off. Matching compound to assembly Work through these questions: Service temperature range. Wide swings favor a flexible chemistry or a toughened epoxy; stable indoor service allows a rigid epoxy. Component mix. Tall electrolytic capacitors, connectors, and bare die each set constraints on stress and cure temperature. A low-stress or low-exotherm grade protects sensitive parts. Thermal expansion spread. A large coefficient-of-thermal-expansion difference between resin, board, and components drives cyclic stress, the failure mode covered in how CTE mismatch causes adhesive bond failure. Pot depth and geometry. Deep or enclosed cavities rule out UV-only cure. Rework expectation. If a board may need component replacement, a softer polyurethane or silicone, or a partial pot, keeps that option open. Throughput. High volume favors UV or dual-cure with a conveyor curing system; lower volume suits a room-temperature or oven-cure epoxy. Partial potting and glob-top as alternatives Full encapsulation is not always the right level of protection: Glob-top covers only a wire-bonded die or a single sensitive component with a small dome of resin. It protects the most vulnerable…

With a two-part epoxy, the mix ratio determines whether it cures. With a UV potting compound there is no mix ratio. The equivalent variable is UV dose, the combination of light intensity and exposure time, and controlling it is the difference between a fully protective encapsulant and a tacky, under-cured one. This article explains what UV dose is, why an incorrect dose causes specific failures, and how to set and hold it in production. What "dose" means for a UV potting compound UV potting compounds are single-component systems. Their cure is driven by delivered energy, not a chemical blend. Two quantities define it: Irradiance (intensity): the optical power reaching the resin surface, in mW/cm2. Higher intensity cures faster. Exposure time: how long the resin sees the light, in seconds. Their product is dose, expressed in mJ/cm2. A given compound needs a minimum dose at a suitable wavelength (commonly 365 or 405 nm) to reach full properties. The data sheet states that target. What happens when the dose is wrong Under-cure (dose too low). The compound stays soft, tacky, or poorly adhered. That degrades every function it was chosen for: lower chemical resistance, reduced mechanical and vibration protection, weaker dielectric strength, and slow property drift that turns into field failures and warranty claims. Under-cured resin can also outgas and corrode nearby metal. Over-cure (excessive dose). Less common, but prolonged high-intensity exposure can embrittle some formulations and yellow optically clear grades. It also wastes lamp life and energy. Inconsistent dose across a batch. Variation in lamp output, part position, or conveyor speed produces parts with different cure states and unpredictable service life, which is harder to catch than a uniform under-cure. The variables that move dose in real production Lamp aging. UV sources lose output over hundreds to thousands of hours. A recipe validated on a new lamp can drift below the minimum dose months later. This is the same degradation mechanism described in what causes UV light guide degradation over time. Pot depth. Light attenuates as it passes through resin, especially filled or pigmented grades. A dose that cures a 2 mm section may not cure 6 mm. Thick sections need higher intensity, longer time, or a dual-cure grade. Distance and geometry. Irradiance falls with distance from the source. Parts sitting lower in a fixture, or angled away from the lamp, receive less. Shadowing. Any component that blocks the line of sight leaves resin beneath it under-cured regardless of the nominal dose. Setting and holding the dose Start from the compound data sheet for target dose and wavelength. Choose curing hardware that can deliver it consistently: a UV LED flood lamp for bench work, a conveyor system for volume with repeatable belt speed and lamp height. Then instrument the process: Measure dose with a calibrated radiometer at the part surface, not the nominal lamp rating. Log it on a schedule and set a replacement or recalibration trigger when intensity drops below the minimum plus a margin. Validate cure-through at your real…

Potting protects a component by encasing it in a cured resin. Traditional two-part epoxies and silicones do this well but tie up floor space for hours and often need an oven. UV-curable potting compounds reach handling strength in seconds under a lamp, which changes what a potting line can look like. This article explains how UV potting works, where it fits, where it does not, and how to build a reliable process around it. How UV potting differs A UV potting compound is a single-component, 100 percent solids resin that stays liquid until it absorbs UV energy, at which point photoinitiators trigger rapid polymerization. Practical consequences: Cure in seconds to a minute rather than hours, so parts move off the line immediately. Unlimited working time until the lamp switches on, so operators can place components and inspect fill before committing. No solvent and no mix ratio, which removes VOC handling, pot-life waste, and mix-error scrap. Low exotherm, so heat-sensitive parts are not stressed during cure. Where UV potting works well UV potting fits shallow-to-moderate pot depths on parts where light can reach the resin surface: sensor assemblies, connector back-shells, LED modules, coil terminations, and small control boards in open housings. Optically clear grades suit LED and sensor work; filled grades give higher modulus and better abrasion resistance. The cured compound provides the same protection a thermal potting resin would: a moisture and contamination barrier, shock and vibration damping, and dielectric isolation. Grades are formulated across a hardness range, from flexible compounds that absorb vibration to rigid ones that lock components in place. Where UV potting does not fit The hard constraint is line-of-sight. UV energy cures only what it reaches. A deep pot, an opaque cover over the resin, or a component that shadows part of the cavity leaves uncured material underneath. Uncured resin can stay tacky, corrode metal, or outgas. Two ways around it: keep the design UV-accessible, or use a dual-cure grade that starts with UV and finishes shadowed regions by heat or ambient moisture. For fully enclosed cavities, a thermal-cure epoxy remains the better choice. Our comparison of UV and epoxy systems covers the general trade-off. Building the process Curing hardware. Match the source to the throughput. A UV LED flood lamp covers a bench station; a conveyor system handles volume with uniform dose; a cure chamber suits batch work. The compound's absorption peak has to match the lamp output, commonly 365 or 405 nm. Dose control. Cure depends on delivered energy, intensity multiplied by exposure time, measured in mJ/cm2. Follow the compound's data sheet for target dose and adjust for pot depth: thicker sections need more energy to cure through. Dispensing. Slow, controlled fill or automated dispensing with degassing keeps voids out. Voids are weak points and moisture traps. Quality control. Check lamp output with a calibrated radiometer on a schedule, because UV sources lose intensity as they age. Confirm full cure with a surface-tack check and a hardness reading, and run thermal-cycling and humidity tests…