2. LEDs for General Lighting

3. LEDs for General Lighting & UV Curing

4. LEDs for UV Curing Support Performance Price Quality Brand
Energy Savings
Life
Specs
Service
Vendor Relationship
Form Factor
Process Control
ROI

5. How do we improve our UV LED selection & application success?
LEDs for UV Curing
How do we improve our UV LED
selection & application success?

6. Characterizing UV LED Curing Systems
UV Output
Electrical Input
Form Factor
Uniformity of Output
Use of Optics
Product Life
Thermal Management and Cooling
Ruggedness and Reliability
Intended Use & Process Window
Understanding UV LED system characteristics drastically improves product selection & application success!

7. UV Output in Theory
Wavelength (nm) - distance between corresponding points of a wave.
Peak Irradiance (Watts/cm2) - radiant power arriving at a surface per unit area at a point in time.
Energy Density (Joules/cm2) - radiant energy arriving at a surface per unit area over time. It is the integral of irradiance over time.
Time
Energy Density
Irradiance

8. UV Output in Practice
Wavelength (nm) – must be matched to formulation of ink, coating, or adhesive. 395 nm most typically used. 365, 385, and 405 nm also available nm in development.
Peak Irradiance (Watts/cm2) – beneficial for penetration and surface cure.
Energy Density (Joules/cm2) – promotes more thorough cure and faster line speed.
Time
Energy Density
Irradiance

9. UV Output in Practice
Formulations need a minimum Peak Irradiance (W/cm2) to react.
High Peak Irradiance (W/cm2) doesn’t necessarily mean
high Energy Density (J/cm2).
New evidence suggests there may be a maximum
Peak Irradiance (Watts/cm2) for formulations.
High Energy Density (J/cm2) needed for fast line speeds and more thorough cure.

10. Irradiance vs Distance

11. Irradiance vs Energy Density
Higher Power
Lower Total Energy
Higher Power
Higher Total Energy
Lower Power
Lower Total Energy
Lower Power
Higher Total Energy
Energy Density

12. Irradiance vs Energy Density
System A is 16 W/cm2 and 20 x 150 mm wide at the emitting window. Irradiance profile measures 2.34 J/cm2 in energy density with 1.2 KW input.
A and B deliver similar energy density (area under irradiance curves) but may not cure the chemistry similarly.
System B is 8 W/cm2 and 40 x 150 mm wide at the emitting window. Irradiance profile measures 2.53 J/cm2 in energy density with 1.4 KW input.

13. Nominal Power (Watts/in)
Electrical Input vs Irradiance
Product
Wavelength
(nm)
Length
(mm/in)
UV Head DC Supply Power
(Watts)
Nominal Power (Watts/in)
Irradiance
(Watts/cm2)
LED – FL400
395
450/18
4,361 DC
240 16
5,451 DC
300 20
5,775 DC
320 24
Mercury
Broad Band
5,400 AC
1 – 2
7,200 AC
400
2 – 3
9,000 AC
500
3 - 4
10,800 AC
600
4 - 5
*For purposes of comparison, all lamps are 450 mm (18”).
**Calculations do not include chillers, exhaust blowers, or make-up air. Strictly a comparison of lamp supply power and output irradiance.
***Irradiance for UV LED curing systems is specified at the emitting window. Conventional UV systems are typically at 2” from lamp head.

14. Nominal Power (Watts/in)
Electrical Input vs Energy Density
Product
Emitting Window
L x W (mm)
Irradiance
(Watts/cm2)
DC Supply
(Watts)
Nominal Power (Watts/in)
Energy Density
(Joules/cm2) A
80 x 10 8
145 45
0.56 B
75 x 20
670
225
1.10 C
960
325 D
75 x 40
1400
475
2.40
*For purposes of comparison, all four air-cooled products have flat glass emitting windows and are 395 nm.
**Irradiance for UV LED curing systems is specified at the emitting window.
***Energy density measured at same belt speed using an EIT L395 radiometer. Top of radiometer was 5 mm from emitting window. A B C D

15. Energy Density (J/cm2) Varies Significantly Across Market Offerings
Diode
Power
Design
Raw diode selection
Diode qty. / packing density
Packaging methods
Peak irradiance
DC power input
Driver technology
Model variations
Cooling effectiveness
Window width
Quantity of heads
Quality
Maintenance
Uniformity
Ingress resistance
Amount of degradation over time
Quality & consistency of clean room mfg.
Chiller & plumbing
Air filters
Emitting window

16. Thermal Management & Cooling
This is not radiated IR energy but energy created by inefficiencies
Approximately 30% to 40% of input power is converted to useable UV output
Approximately 60 to 70% of input power is converted to unwanted heat
Cannot exceed maximum LED junction temperature
Cooling is designed to optimize the efficiency of the LEDs
Cooling can be air or liquid

17. Poor Thermal Management
Factors
Impact
Result
Junction and solder joint temps over 110°C
Uneven cooling
Liquid coolant below 25°C
Unsealed heads
Affects curing uniformity
along length of heads
Condensation
Foreign matter on LEDs creating hot spots and failures
Gradual & catastrophic diode failures
Decrease in irradiance & energy density
Reduced ability to fully cure & drive press speed

18. Ruggedness & Reliability
Clean room assembly practices
Sealed heads
Water resistance
20K to 50K lifetime ON hours
Robust and cleanable quartz emitting window
Impact resistance
Cooling systems designed to operate at higher temperatures

19. Form Factor Smaller lengths scaled end-to-end to cover web
Single length heads to span full web width
Air-cooled or Liquid-cooled configurations

20. Form Factor – Scaled Lamps

21. Intended use drives LED selection, integration, and process window
Intended Use & Process Window
LEDs AVAILABLE IN CONFIGURATIONS TO SPAN ANY WEB WIDTH OR
Trend is towards air-cooled systems
Irradiance over 20W/cm2 often unnecessary
Air-cooled
Up to 20 W/cm2
Water-cooled
Up to 50 W/cm2
A PROPERLY CHARACTERIZED UV LED SYSTEM SPECIFIES:
Wavelength
Energy Density
Irradiance W/cm2
Intended use drives LED selection, integration, and process window + +
280 nm in development
365 nm
385 nm
395 nm
405 nm
Faster press speeds
More thorough cure
Major differences across products and vendors
A high peak irradiance (W/cm2) DOES NOT guarantee a high energy density (J/cm2).
Peak irradiance provides NO insight into delivered energy density

22. Intended Use & Process Window
Physical properties of final cure – drive chemistry formulation
Formulation - matched to wavelength and irradiance (Watts/cm2)
Working Distance - lamp peak irradiance or head optics selected to deliver needed irradiance at cure surface
Process Line Speed – determines needed energy density (Joules/cm2)
Plant Environment & Preference - drives cooling selection (air or water)
Mounting location – available application space / web width drives lamp form factor
Lamp proximity / orientation to unwanted cure surfaces – influences use of optics and shielding

23. Characterizing UV LED Curing Systems
UV Output
Electrical Input
Form Factor
Uniformity of Output
Use of Optics
Product Life
Thermal Management and Cooling
Ruggedness and Reliability
Intended Use & Process Window
Understanding UV LED system characteristics drastically improves product selection & application success!

24. Thank You!
Jennifer Heathcote Phoseon Technology Global Director of Business Development +1 (312)

25. Uniformity of Output
Uniformity Improves with web distance from LED Source.
Peak irradiance at web decreases with distance.

26. Optics
Flat Glass
Rod Lens
External Reflector
Internal Reflector
A single row of LEDs or a narrow matrix of LEDs must be used with optics and reflectors to be effective. Typically results in less energy density.

27. Optics: Irradiance (Watts/cm2) vs. Energy Density (Joules/cm2)
Flat Glass
Use of optics can increase peak irradiance above that for flat glass (nominally 100%). But optics are most effective with narrow emitters and typically emit less total energy density.

28. Over 2 Million hours of total SLM Lifetime Testing
LED On-Time
UV Intensity
10K
20K
30K
40K
100%
70%
LED
90%
80%
50K
Conventional Lamps: Replaced every 2,500 hours
70K Hours
60K
Over 2 Million hours of total SLM Lifetime Testing