Solving UV Curing Mysteries with Measurement. Jim Raymont

Transcription

1 Solving UV Curing Mysteries with Measurement Jim Raymont October 25, 2017

2 Agenda UV Overview Measurement Lessons Repeat the same mistake and not learn Learn from your mistake The smartest person learns from the mistake of others UV LED Measurement Ask questions as we go Presentation available as a PDF Please calibrate me

3 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 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

4 Round Up The Usual Suspects Suspect 1A: The Formulator Suspect 1B: The Equipment Supplier

5 Please Describe the.. Abrasion Resistance Scratch Resistance Chemical Resistance Hardness Weatherability Non-Yellowing Flexibility 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?

6 The UV Process-Analogy Cake: Bake at 350 F for 30 minutes 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 350 X 30 = 10,500 Equal Degree Minute Options 700 F for 15 minutes? 175 F for 60 minutes? What if the cake mix only gave you the time?

7 Speaking the Same Terminology Irradiance (Intensity) Expressed in watts or milliwatts per square centimeter (W/cm 2 or mw/cm 2 ) Total radiant power of (all) wavelengths passing from all incident directions onto an infinitesimally small area (cm 2 ) Depth of cure, penetration through pigments and opaque colors, adhesion to the substrate Energy Density (Dose) Expressed in Joules (J/cm 2 ) or millijoules (mj/cm 2 ) 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

8 Speaking the Same Terminology Peak Irradiance Time Communication Process Development Transition to Production Production Within a company With Supply Chain

9 Speaking the Same Language Broadband UV Spectrum UVA: nm Black light, UV Inks, adhesion UVB: nm Toughness, skin response UVC: nm, germicidal (254 nm), surface cure, tack, chemical or scratch resistance UVV: nm, opaque/white, thick coats, adhesion, depth of cure Broadband Instrument Responses Instrument Bandwidths are not defined and vary from manufacturer to manufacturer and how they are specified EIT UVA nm, Full Width Half Max (FWHM), CWL 365 nm IL UVA nm CWL 365 nm EIT UVA nm IL UVA nm UV LEDs Discussed Later

10 Variable: UV Energy Wavelength Mercury Gallium Iron Courtesy Heraeus Fusion UV

11 Process Window I am loose and tight in all the wrong places

12 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

13 Process Window Starting Point: Formulator Guidelines Testing can define a process window Lab testing is less expensive than production testing or no process window Variables: Line speed Lamp distance Lamp output Bulb Type Source Type Coating

14 Process Window Normal Operating Window Caution 20% Undercure Buffer Range Stop!Undercure Limit Over cure or over temperature?

15 Gathering UV Evidence We can t ask a UV lamp or a power supply to confess, but we can gather evidence using other means

16 Gathering UV Evidence Did you perform the maintenance? Did You?

17 Gathering UV Evidence Right Tools? Right Tests? Right Expectations? Documentation?

18 Gathering UV Evidence = Gather and preserve evidence to use it for when conditions change

19 Preserving UV Evidence 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 Poor chain of custody Date Line Speed Dwell Time FPM/RPM UV System: North Line Lamp: 2 Ind. Actual. Power WPI Hour Meter Irradiance (W/cm 2 ) Energy Density (J/cm 2 ) 10/

20 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

21 Gathering UV Evidence Profiling Radiometers Profile helps determine focus of system and tracks changes Lamp types Break down multi-lamp systems Focused lamp UV W/cm 2 Non-Focused lamp Time in seconds Distance Change-Same lamp FOCUSED 858 mw/cm 2 UV W/cm 2 UV W/cm 2 NON-FOCUSED 290 mw/cm mj/cm 2 Dimensional Curing 1707 mj/cm 2 Gloss Control Time in seconds Time in seconds

22 Gathering UV Evidence Differences in: Irradiance values Lamp Types Focus of Lamps Speed collected A typical Irradiance Profile

23 Gathering UV Evidence In God we trust, all others bring data Dr. W. Edwards Deming

24 Gathering UV Evidence Ref Readings Unit Readings % Deviation Unit Power Puck II Power Puck II s/n Speed (f/m) 25 feet/min 25 feet/min UVA mj/cm2 mw/cm2 mj/cm2 mw/cm2 mj/cm2 mw/cm % -1.11% % +4.30% % -4.57% Average % -0.46% % STEDV 2.496% 2.001% 4.855% 2.537% 7.142% 4.488% Repeat for other UV bands

25 Real World Lessons

26 Human Error Temperature Reading UV Readings Unit was sent through UV system upside down

27 Arc lamp performance-data 55 (140 cm) bulb Irradiance mw/cm 2 Data collected 3/24/16 Band Left Center Right Highest Delta UVA % UVB % UVC % UVV % Energy Density mj/cm 2 UVA % UVB % UVC % UVV % Bulb not installed correctly in UV system

28 Arc Lamp Performance-Graph Graphically display UV across width of bulb

29 How Old Are You? Hour Meter

30 UV Sources: Spectral Output With 600 hours of run time would you change this bulb? OLD NEW UVA Energy Density: 537 to 487 mj/cm 2 UVA Irradiance: 309 to 290 mw/cm 2

31 UV Sources: Spectral Output Change Now? OLD NEW UVV Energy Density: 737 to 1331 mj/cm 2 UVV Irradiance: 397 to 734 mw/cm 2

32 Lamp Symptoms - Aging Devitrification / Clouding Mirroring Blackening / Erosion Contaminated Airflow

33 Aged Arc Lamp Middle End 440mW/cm 2 in the middle vs. 317 mw/cm 2 at the end How wide is your line compared to the product?

34 Variable: UV Energy Wavelength Ratio of different bands to identify bulb type

35 The Real World: Readings Profiling Radiometers Trouble shoot two identical production lines (Speed, bulb types) UVA Line 1 UVV Blue UVA Line Speed Changed UVV Bulb Type Changed Red UVV UVA Line 2

36 Intensity Bulbs: Buy on Value vs. Price Hours Courtesy: Efsen Engineering

37 Bulbs: Buy on Value vs. Price Watch purchasing staff getting specials

38 Neglect of UV curing system

39 Mystery: Bad Reflectors Dirty, damaged and improper reflectors can be detected by their distinctive UV fingerprints on a profiling radiometer.

40 Process Variables-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 Abrasion Resistance Toughness Adhesion Adhesion & TiO 2 Cure A multi-channel radiometer allows you to compare short & long wave ratios and identify changes UVC: UVA UVC: UVV

41 Lamp Symptoms Inadequate Cooling The bowed lamp (left) overheated due to a damaged cooling system (right)

42 Diagnosing Inadequate Cooling/Airflow End Middle Sagging-15 % difference in irradiance levels middle to end

43 Mystery: Operator Error

44 Mystery: Operator Error Changing the distance from the UV System to the substrate FOCUSED 858 mw/cm 2 Non-focused is not always bad. Useful for gloss control for example 2096 mj/cm 2 NON-FOCUSED 290 mw/cm mj/cm 2 The effect of moving the UV housing away from the cure surface

45 Mystery: Operator Error Lamp Symptoms Distance to Part Varying the distance from the UV source to the substrate is a common source of process problems Substrate Height?

46 LED Sources

47 relative spectral radiance Traditional UV Source Spectral Output 100 Hg spectra modified with added materials 90 Gallium Mercury Iron wavelength [nm] Hg Ga Fe

48 EIT Bandwidth Responses

49 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) Images courtesy Baldwin, Dymax, Integration Technology, Excelitas & Phoseon Technology

50 Measurement of 395 nm LED Using UVA to measure a 385 nm or 395 nm LED Δ = 60% Δ = 95%

51 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

52 Define the right band? Theoretical Band Account for variation in the LED CWL L395 LED Output Spectra Showing + 5nm Spread of Cp Along with Required Filter Response to Obtain 2% Measurement

53 Optics Design

54 L395 Instrument Response Total Measured Optical Response

55 LED-R Series LEDCure Radiometer L395 Total Optics Response Single Band, Cosine Response Two Options: Standard & Profiler 40 Watt Dynamic Range Suggested Operating Range L395 Start Threshold 400 mw/cm 2 to 40 W/cm mW/cm 2 Patented Optics Response

56 Summary 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

57 Questions Jim Raymont 309 Kelly s Ford Plaza SE Leesburg, VA USA Phone: New EIT Facility for Manufacturing, Sales and Service