When a bond is small, buried, or surrounded by parts that must not see ultraviolet light, a spot lamp is the right tool. A high-intensity UV spot lamp concentrates energy through a light guide onto a point a few millimeters across, curing adhesives in seconds without flooding the whole assembly.
Arc and LED Spot Lamps
Two technologies dominate spot curing:
- Mercury arc spot lamps produce a broadband output from roughly 240–450 nm at very high intensity at the guide tip. The wide spectrum cures pigmented and shadowed bonds well. The trade-offs are a warm-up period, a bulb life on the order of 2,000 hours, and consumable reflectors and filters.
- UV LED spot lamps emit a narrow band at 365, 385, or 405 nm, switch on instantly, run cool, and last beyond 20,000 hours. They are the better fit where the chemistry matches an available band and heat must be kept low.
Incure offers both: the S20 UV arc spot lamp for broadband high intensity and the L9000 UV LED spot lamp for narrow-band, low-heat curing.
Dose at the Guide Tip
The energy an adhesive absorbs equals irradiance at the guide tip in mW/cm² multiplied by exposure time. Tip irradiance depends on guide diameter, guide length, working distance, and guide condition. A short, large-core guide held close delivers the highest energy; a long, thin guide trades intensity for reach. Fix the tip-to-part gap with a holder so the dose repeats.
Selecting a Spot Lamp
- Spectrum or wavelength: Broadband arc for pigmented or shadowed bonds; matched LED band for clear or thin-section work.
- Intensity: Enough tip irradiance to cure within the cycle time, with headroom for source aging.
- Guide count: Single guide for one point; multi-guide heads for several cure points on one part.
- Working distance and access: The guide must reach the bond without fouling adjacent parts.
- Consumables: For arc lamps, factor in bulb, reflector, and filter replacement intervals.
Total Cost of an Arc Spot Lamp
An arc spot lamp’s running cost is more than the bulb. Over a year of single-shift use, plan for two or more bulb changes, periodic reflector replacement, and light-guide replacement as transmission falls. Each bulb change also needs a re-verification of tip irradiance and often a small recipe adjustment. An LED spot lamp removes the bulb and reflector consumables entirely and shifts the only wear item to the guide, which is common to both technologies. Where the chemistry allows an LED band, that difference compounds over the equipment life.
Matching Guide Diameter to the Feature
Guides commonly range from about 3 mm to 12 mm core diameter. A 3 mm guide concentrates energy onto a single small joint and fits into crowded assemblies; an 8 mm or larger guide covers a wider fillet or a cluster of close pins in one exposure but needs more standoff to avoid a hot center with a weak edge. Choose the smallest guide that covers the bond in one shot.
Curing in Shadowed Geometry
When part of the bond sits in shadow behind a component, a single spot exposure leaves that region under-cured. Options are to expose from two angles, to use a secondary-cure adhesive that finishes shadowed resin by heat or moisture, or to move to a flood approach that floods light in from multiple directions.
For help choosing between arc and LED spot curing for your bond, Email Us.
Applications
Spot lamps serve electronics component tacking, connector and sensor potting, optical fiber and lens bonding, small mechanical assembly, and localized coating repair. Where the whole part or a large area needs curing, a flood lamp or cure chamber is the better choice.
Process Control and Maintenance
Measure tip irradiance with a band-matched radiometer on a schedule. Light guides lose transmission as they age and discolor, so rotate or replace them when output falls below the recipe assumption; the causes are covered in this guide to UV light guide degradation. For arc lamps, replace the bulb at its rated hours rather than waiting for a cure defect.
Frequently Asked Questions
Q: Arc or LED spot lamp?
A: Broadband arc for pigmented, thick, or shadowed bonds and chemistries needing short wavelengths. Matched-band LED for clear or thin-section work where low heat and long source life matter and the chemistry fits an available band.
Q: What guide diameter should I use?
A: The smallest core that covers the bond in one exposure. A 3 mm guide concentrates energy on a single small joint; an 8 mm or larger guide covers a wider fillet but needs more standoff.
Q: Why does an otherwise stable arc lamp drift toward under-cure?
A: Usually the light guide. Transmission falls as guides age and discolor, so rotate or replace them when tip irradiance drops below the recipe assumption.
To specify a UV spot curing lamp for a precise process, Contact Our Team.
Visit www.incurelab.com for more information.