Solving UV Curing Mysteries with Measurement

Jim Raymont

Whodunit? Whodat?

UV Can Be Mysterious Unless You Understand It• Cannot see it with the visible eye • Wavelength is a nanometer (nm)-a billionth of a meter • Reduce UV mysteries and process variables to

increase profit

• Ask questions as we go • Will share this presentation as PDF • Here to help during the SGIA show (Booth 2800)

Solving UV Mysteries

Anything that you can measure, you have a better chance of controlling. Things that you do not measure become the cause of mysterious problems

Larry Goldberg-Beta Industries

Producing a large amount of product before detecting a problem.

UV Curing-Crime Scene

Round Up The Usual Suspects

Suspect 1A: The Formulator

Suspect 1B: The Equipment Supplier

� Abrasion Resistance

� Scratch Resistance

� Chemical Resistance

� Hardness

� Weatherability

� Non-Yellowing

� Flexibility

Please Describe the ……..

� Tensile Strength

� Gloss

� Coating Viscosity

� Film Thickness

� Ability to Over Coat

� TBD

� TBD

What properties are formulation driven?

What properties are process/UV source driven?

The UV Process

What if the cake mix only gave you the time?

• 350° X 30 = 10,500

Equal Degree Minute Options

• 700°F for 15 minutes?

• 175°F for 60 minutes?

Cake: Bake at 350°F for 30 minutes

The UV Process-Analogy

Oven Temperature ( °F) is similar to Irradiance (Watts/cm 2)

Bake Time (Minutes or seconds) is similar to Energy Density (Joules/cm 2)

Not Specified: Oven Type

Changing the Cake Process Window

Speaking the Same TerminologyIrradiance (Intensity)• Expressed in watts or milliWatts per square centimeter (W/cm2 or

mW/cm2)

• Total radiant power of (all) wavelengths passing from all incidentdirections onto an infinitesimally small area (cm2)

• Depth of cure, penetration through pigments and opaque colors, adhesion to the substrate

Energy Density (Dose)• Expressed in Joules (J/cm2) or milliJoules (mJ/cm2) per square

centimeter

• Incorporates time as part of the measurement

• One watt for One second = One Joule

• Area under the irradiance curve

• Often the only UV exposure guide number supplied

Speaking the Same Terminology

Time

Peak Irradiance

Communication

• Process Development

• Transition to Production

• Production

• Within a company

• With Supply Chain

IL UVA

250-415 nmEIT

UVA 320-390 nm

Speaking the Same Language

Broadband Instrument Responses • Instrument Bandwidths are not defined and vary from manufacturer to

manufacturer and how they are specified• EIT UVA 320-390 nm, Full Width Half Max (FWHM), CWL 365 nm• IL UVA 250-415 nm CWL 365 nm

Broadband UV Spectrum• UVA: 320-390nm “Black light”, UV Inks, adhesion• UVB: 280-320nm “Toughness” , skin response• UVC: 200-280nm, germicidal (254 nm), surface cure, tack, chemical or

scratch resistance• UVV: 395-445nm, opaque/white, thick coats, adhesion, depth of cure

UV LEDs Discussed Later

“I am loose and tight

in all the

wrong places”

Process Window

• The range in which a process will work with the desired results

– Adhesion, hardness, flexibility, gloss, texture, stain or scratch resistance, chemical rub, cross hatch, abrasion rub, color ID, registration

– Often a compromise

• Invest before production & confirm when things are working!

– Starting guidelines from formulator?

– Define your lower limits and document the readings

– Increase line speed/decrease applied power until you undercure, note readings and cushion by 20%

– Upper limits?

• Monitor your readings by job, hour, shift or day as required to maintain quality

• Establish your process window during the design/development phase and start monitoring from day one in production

Process Window

Variables:

• Line speed

• Lamp distance

• Lamp output

• Bulb Type

• Source Type

• Coating

Process Window

• Starting Point: Formulator Guidelines

• Testing can define a process window

• Lab testing is less expensive than production testing or

no process window

Stop!Undercure Limit

Caution 20% Undercure Buffer Range

Normal Operating Window

Over cure or over temperature ?

Process Window

We can’t ask a UV lamp or a power supply to

confess, but we can gather evidence using

other means…

Gathering UV Evidence

“ Did you perform the maintenance? Did You?”

Gathering UV Evidence

Gathering Evidence

Gathering UV Evidence

• Right Tools?

• Right Tests?

• Right Expectations?

• Documentation?

=

Gathering UV Evidence

Gather and preserve evidence to use it

for when conditions change

Date

Line Speed Dwell Time

FPM/RPM

UV System: North Line Lamp: 2

Ind. Actual. PowerWPI

Hour Meter

Irradiance(W/cm 2)

Energy Density (J/cm 2)

10/9 25 22 400 780 0.859 1.45

For each UV lamp system• Hour meter • Indicated vs. actual process speed• Power settings (WPI, Amps)• Irradiance (W/cm 2)• Radiant Energy Density(J/cm 2)• Lamp matched to chemistry• Focus/Reflector condition• TBD

Preserving UV Evidence

Poor chain of custody

Focused

lamp

Time in seconds

UV

W/c

m2

Non-Focused lamp

UV

W/c

m2

Time in seconds

FOCUSED

858 mW/cm2

2096 mJ/cm2

NON-FOCUSED

290 mW/cm2

1707 mJ/cm2

Dimensional Curing

Gloss Control

Distance Change-Same lamp

Profiling Radiometers

• Profile helps determine

focus of system and

tracks changes

• Lamp types

• Break down multi-lamp

systems

Time in seconds

UV

W/c

m2

Gathering UV Evidence

A typical Irradiance Profile

Differences in:• Irradiance values• Lamp Types• Focus of Lamps• Speed collected

Gathering UV Evidence

Gathering UV Evidence

In God we trust, all others bring data Dr. W. Edwards Deming

Gathering UV Evidence

• What Data (Evidence) Is Needed? • Consistent Data Collection Techniques• Fooled by the Equipment?• Do not contaminate the crime scene or

measurement tools

Gathering UV Evidence

Ref ReadingsUnit Readings % Deviation

Unit Power Puck II

Power Puck II

s/n 15678 17654Speed (f/m) 25 feet/min 25 feet/min

UVA mJ/cm2 mW/cm2 mJ/cm2 mW/cm2 mJ/cm2 mW/cm21 109.000 450.000 99.000 445.000 -9.17% -1.11%2 105.000 442.000 103.000 461.000 -1.90% +4.30%3 104.000 460.000 109.000 439.000 +4.81% -4.57%

Average 106.000 450.667 103.667 448.333 -2.09% -0.46%% STEDV 2.496% 2.001% 4.855% 2.537% 7.142% 4.488%

Repeat for other UV bands

A Scandal in Bohemia

Analyzing the UV Evidence

Inspector Jacques Clouseau: It's amazing how he fell perfectly into

the chalk outline on the floor.

Ponton: I think they drew the outline after he was shot.

Inspector Jacques Clouseau: Ah! We must be working with some

kind of mastermind!

My Best Cases

Cases of Absent Minded Staff

Human Error …

Unit was sent through UV system upside down

Temperature Reading

UV Readings

55” (140 cm) bulb

Irradiance mW/cm2 Data collected 3/24/16

Band Left Center Right Highest Delta

UVA 797 983 635 35.4%

UVB 713 888 573 35.5%

UVC 200 257 167 35.0%

UVV 612 757 492 35.0%

Energy Density mJ/cm2

UVA 243 282 234 17.0%

UVB 206 239 195 18.4%

UVC 58 68 55 19.1%

UVV 231 264 222 15.9%

Arc lamp performance-Data

Bulb not installed correctly in UV system

Graphically display UV across width of bulb

Arc Lamp Performance-Graph

Instrument Care

• Radiometers work better when properly maintained

Optics & Sensor Care

• Optics work better when properly maintained

Irradiance W/cm2 Data Collected 3/24/16

Band Before After Difference

UVA 1223 983 -19.6%

UVB 1066 888 -16.7%

UVC 277 257 -7.2%

UVV 889 757 -14.9%

Energy Density J/cm2

Band Before After Difference

UVA 349 282 -19.2%

UVB 284 239 -15.9%

UVC 75 68 -9.33%

UVV 309 264 -14.6%

Before: Data collected with contaminated optics

After: Data collected after cleaning

UV Measurement Challenges

• Two recommended methods:

o Lint/Detergent free wipes or IPA with cotton swab

• Advantages and disadvantages to each method

• First do no harm

• Avoid shirt sleeve, shop towel, etc.

• Avoid ‘dry’ cleaning instrument

UV Measurement Challenges

You Tube Video Link on EIT website

UV Measurement Challenges

The Case of the

Missing ID

How Old Are You?

Hour Meter

Devitrification / Clouding Mirroring

Blackening / Erosion Contaminated Airflow

Lamp Symptoms - Aging

440mW/cm2 in the middle vs. 317 mW/cm2 at the end

How wide is your line compared to the product?

MiddleEnd

Aged Arc Lamp

Variable: UV Energy Wavelength

Mercury

Gallium Iron

Courtesy Heraeus Fusion UV

Variable: UV Energy Wavelength

Ratio of different bands to identify bulb type

Line 1

Line 2

Blue

UVA

Red UVV

Profiling Radiometers• Trouble shoot two ‘identical’ production lines (Speed, bulb types)

Line Speed Changed Bulb Type Changed

UVA

UVA

UVV

UVV

The Real World: Readings

UVA Energy Density: 537 to 487 mJ/cm 2

UVA Irradiance: 309 to 290 mW/cm 2

NEWOLD

With 600 hours of run time would you change this bu lb?

UV Sources: Spectral Output

Change Now?

OLDNEW

UVV Energy Density: 737 to 1331 mJ/cm2

UVV Irradiance: 397 to 734 mW/cm2

UV Sources: Spectral Output

The Case of the Misguided

Purchasing Staff

Bulbs: Buy on Value vs. Price

Courtesy: Efsen Engineering

Hours

Inte

nsity

Watch purchasing staff getting ‘specials’

Bulbs: Buy on Value vs. Price

The Case of the

Missing Maintenance Team

Neglect of UV curing system

Dirty, damaged and improper reflectors can be

detected by their distinctive “UV fingerprints” on a

profiling radiometer.

Mystery: Bad Reflectors

A CLEAN BULB AND REFLECTOR DELIVERS ALL THE UV SPECTRUM IN THE RANGES OF UVA, UVB, UVC

AND UVV

A DIRTY BULB AND REFLECTOR DELIVERS VERY

LITTLE OF THE UV SPECTRUM IN UVC & UVB ,

AND REDUCED AMOUNTS OF UVA AND UVV

A multi-channel radiometer allows you to compare short

& long wave ratios and identify changes

UVC: UVAUVC: UVV

Abrasion

Resistance

Toughness Adhesion Adhesion

& TiO2

Cure

Process Variables -Reflectors

The Case of the

Overheated Lamp

The bowed lamp (left) overheated due to a damaged

cooling system (right)

Lamp Symptoms – Inadequate Cooling

Sagging-15 % difference in irradiance levels

middle to end

End

Middle

Diagnosing Inadequate Cooling/Airflow

The Case of the

Restless Operator

Mystery: Operator Error

The effect of moving the UV housing away from the cure surface

FOCUSED

858 mW/cm 2

2096 mJ/cm 2

Changing the distance from the UV System to the substrate

NON-FOCUSED

290 mW/cm 2

1707 mJ/cm 2

Non-focused is not

always bad. Useful

for gloss control for

example

Mystery: Operator Error

• Varying the distance from the UV source to the

substrate is a common source of process problems

• Substrate Height?

Lamp Symptoms – Distance to Part

Mystery: Operator Error

The Case of

Unexpected Gremlins

(Mr. Murphy)

Quantitative, routine

maintenance Real-time

status monitoring

Periodic vs. Real-Time UV Measurement

Without an early warning system, the dipstick is useless.

Periodic vs. Real-Time UV Measurement

• Works for applications where a radiometer will not fit or is not practical– Web– Bank of multiple lamps– Lamps high off ground

• Continuous feedback about UV conditions– Certificate of Conformance – Tight Process Windows– High Value Products

• Continuous monitoring of lamp intensity

• Communication– Percentage readings – Coordinate with absolute radiometer

When to Use?

Sensor Locations

Display/Conditioning Options

Panel Mount• One Sensor• Display plus 0-10V

Output

Din Rail• One Sensor, 0-10V Output

Quartz Rod

Making a Case For

New Lamp Sources

One Bullet Barney……

Hg spectra modified with added materials

0

10

20

30

40

50

60

70

80

90

100

200 250 300 350 400 450 500

wavelength [nm]

rela

tive

spec

tral

rad

ianc

e

Hg Ga Fe

Mercury

Gallium

Iron

Traditional UV Source Spectral Output

EIT Bandwidth Responses

Images courtesy Baldwin, Dymax, Integration Techno logy, Excelitas & Phoseon Technology

UV LEDs

Wide variety of UV LED sources • Multiple suppliers with wide level of expertise,

support, finances• Match source to your application & process• Economics of source selected (ROI)

Adoption Curve

Adoption: Digital-Standard

Suppliers: End Users:

Courtesy

Courtesy

Adoption: Digital-Standard

Adoption: Digital , Custom

Suppliers: End Users:

Courtesy

Courtesy

Adoption: Digital , Custom

Adoption: Screen, simple

Suppliers: End Users:

Courtesy

Adoption: Screen, Industrial

Suppliers: End Users:

Courtesy

EIT Bandwidth Responses

Δ = 60%

Measurement of 395 nm LED

Δ = 95%

Using UVA to measure a 385 nm or 395 nm LED

Evaluate LED Output

• Width of the LED at the 50% Power Point

• Variations between suppliers:• Binning• Longer wavelengths• Sold as +/- 5 nm from center

wavelength (CWL)

395 nm LED array output measured on a spectral radiometer at EIT

L395 LED Output Spectra Showing + 5nm Spread of Cp A long with Required Filter Response to Obtain 2% Measurem ent

Define the right band?

Theoretical Band

Account for variation in

the LED CWL

Optics Design

L395 Instrument Response

Total Measured Optical Response

LED-R™ Series

LEDCure™ Radiometer• L395 Total Optics Response

• Single Band, Cosine Response

• Two Options: Standard & Profiler

• 40 Watt Dynamic Range

• Patented Optics Response

Suggested Operating Range L395

400 mW/cm2 to 40 W/cm2

Start Threshold

16-48mW/cm2

LEDCure L395 Performance

Data collected at EIT February 9, 2017

• A 395nm UV LED source was calibrated to 16W/cm² using the EIT L395.

• The UV LED source was then measured with another NIST traceable radiometer.

• The two radiometers matched to within 4% at different irradiance levels.

Data Courtesy of Phoseon Technology

LEDCure L395 Feedback

• The EIT measurement differed from the calculated value by less than 1%.

• The other NIST traceable radiometer differed from the calculated value by more

than 13%.

LEDCure L395 Feedback

Data Courtesy of Phoseon Technology

0

1

2

3

4

5

6

7

8

9

10

11

Ene

rgy

Den

sity

(J/

cm²)

Energy Density Measurements

EIT L395 Other NIST Meter Calculated

• Measurements at different irradiance settings were made with the

EIT L395 radiometer, and compared to the expected values.

• The L395’s linearity across a 3:1 dynamic range is excellent.

LEDCure L395 Feedback

Data Courtesy of Phoseon Technology

LEDCure L395 Performance

LEDCure vs. National Standard

Working Distance

(mm)

Primary Standard: Integrating

Sphere(W/cm2)

LEDCure L395

(W/cm2)

Difference

5 9.01 9.23 2.4%10 7.74 7.74 0.0 %15 6.66 6.63 - 0.5%20 5.74 5.83 1.6%25 5.04 5.08 0.8%

Data Courtesy Lumen Dynamics/Excelitas

Image courtesy Hamamatsu

UV LEDs

Future• Shorter wavelength

LEDs• Improvement in life

& power in the shorter wavelengths

• Chemistry continues to improve to reach more applications

• Dual 365 & 395 nm Source

� Establish a baseline.

� Establish a process window.

� Make measurements routinely.

� Measure consistently. Same location, speed, device

� Document test procedures

� Use right tools

� Label & mark equipment

� Calibrate all of your tools

� Communicate & Involve Supply Chain

Crime Prevention Tips

Jim RaymontEIT Instrument Markets

Director Sales

Member ASDPT

Want a copy of this presentation?

Send me an Email or give me a card

Open Discussion-Questions

703-478-0700

jraymont@eit.com

www.eit.com

SGIA Booth 2800