Finishing Technology for Consumer Electronics:
A Manufacturer’s Perspective
James Wrezel, Bing Diao & Sarah Severson
Motor...
2Page
Introduction
• Our mission is to connect millions of people with affordable
devices that don’t compromise on quality...
3Page
So Why UV-Curable Coatings?
Property Advantages
Scratch Resistance Better than 2K PU Coatings
Yellowing Better than ...
4Page
Critical UV Coating Performance Testing
Paint Supplier and Component Specifications
require conformance to appropria...
5Page
Topics
• Full Gloss UV Clearcoat Composite Housings
• Low Gloss UV Clearcoat – Mar Resistance
• Low Gloss UV Clearco...
6Page
Full Gloss UV Clearcoat Composite Housings
• Full gloss UV coatings enable a high quality finish suitable for specif...
7Page
Scratch Resistance Characterization – Steel Wool
• Measurement of gloss change as a function of steel wool reciproca...
8Page
Scratch Resistance of Different UV Clearcoatings
0
10
20
30
40
50
60
70
80
90
100
0 5 20 50 100 160
GlossChange
Stee...
9Page
High Gloss Surface Cleanability
WCA
Reference Improved
1 88.4 111.0
2 86.9 112.1
3 80.3 123.0
4 99.7 109.0
5 86.6 10...
10Page
High Gloss Clearcoat Printing
• Personalization is driving the requirement for post-processing, including pad
print...
11Page
Low Gloss UV Clearcoats – Mar Resistance
• Mar resistance is critical for low gloss UV clearcoats as gloss changes ...
12Page
Low Gloss Basecoat / UV Clearcoat System – Tumbler Testing
Gloss 1-2 Gloss 4-6
Tumbler testing identified surface s...
13Page
Color (description)
Basecoat Thickness
(Spec = 8-13 microns)
Clearcoat Thickness
(Spec = 10-15 microns)
White – Goo...
14Page
Low Gloss Basecoat / UV Clearcoat – Clearcoat FTIR Analysis
• Greater surface organic-to-filler ratio can reduce ma...
15Page
Low Gloss UV Coatings – Gritty Surface Texture
Gritty area below M-logo
Turquoise “Grit” – 400X
Matting
Agent
Solid...
16Page
Low Gloss UV Clearcoats – Plastic Contamination
• Fingerprint marks observed after temperature/humidity exposure. N...
17Page
Low Gloss UV Coatings – Pad Printing Adhesion
• A silver pad print ink was found to have poor scrape adhesion over ...
18Page
Conclusions
• Full gloss UV coatings can provide high scratch resistance when
modified accordingly. Smudge resistan...
19Page
Future Development Needs in UV Coatings
• Anti-Smudge UV Clearcoats – Available option within a coating family
• Po...
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Finishing Technology for Consumer Electronics: A Manufacturer’s Perspective

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"Finishing Technology for Consumer Electronics:
A Manufacturer’s Perspective" given by James Wrezel, Bing Diao & Sarah Severson from Motorola Mobility LLC, a Google Company.

The presentation was given at RadTech UV & EB Technology Expo & Conference 2014. To learn more about UV and EB Curing Technology, visit http://www.radtech.org.

Published in: Technology
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Finishing Technology for Consumer Electronics: A Manufacturer’s Perspective

  1. 1. Finishing Technology for Consumer Electronics: A Manufacturer’s Perspective James Wrezel, Bing Diao & Sarah Severson Motorola Mobility LLC, a Google Company RadTech UV/EB 2014 Technology Expo & Conference May 12 – 14, 2014 Chicago, IL
  2. 2. 2Page Introduction • Our mission is to connect millions of people with affordable devices that don’t compromise on quality, experiences or style. Every time someone powers on a Motorola device, we like to think it's charging up the world — making someone smile, say "wow," get a little more out of their day. • Coatings are creating the quality look and feel in a device that is affordable • Delighting the consumer with attractive materials, surfaces and coatings that promote a feeling of quality and a device that is something special and personal • Growing desire for housing interchangeability & personalization • UV coatings allow us to vary the user experience and provide color, gloss and haptic options which are production capable
  3. 3. 3Page So Why UV-Curable Coatings? Property Advantages Scratch Resistance Better than 2K PU Coatings Yellowing Better than 2K PU (appropriate photoinitiator) Perceived Quality Appearance, Feel, Color Depth Testing Rapid Cure, No Post Cure Yield Reduced FM Contamination Handling / Packaging Hardness and Fast Property Development Coating Adaptability Monocoat & Base/Clear Mixing / Pot Life Long Pot Life Fat Edge / Orange Peel Reduced vs. 2K PU Coatings
  4. 4. 4Page Critical UV Coating Performance Testing Paint Supplier and Component Specifications require conformance to appropriate specifications which translate to a high quality product for the consumer • Pencil Hardness & Scrape Resistance • Abrasion Resistance – Static and Dynamic Load • Cross-Cut Tape Adhesion • Chemical Resistance – Solvents & Staining Media • Color & Gloss – Spectrophotometer and Gloss Meter
  5. 5. 5Page Topics • Full Gloss UV Clearcoat Composite Housings • Low Gloss UV Clearcoat – Mar Resistance • Low Gloss UV Clearcoat – Production Issues
  6. 6. 6Page Full Gloss UV Clearcoat Composite Housings • Full gloss UV coatings enable a high quality finish suitable for specific end-users and premium products • Concerns for the implementation of full gloss UV surface decoration - scratch resistance - thermal stability - cleanability - printability • Early testing identified a performance risk due to the ease of scratching and gloss reduction that would be deemed objectionable to the consumer and lead to early life failures Microscratching obvious at various viewing angles Gloss reduced from abrasion
  7. 7. 7Page Scratch Resistance Characterization – Steel Wool • Measurement of gloss change as a function of steel wool reciprocating cycling • Engaged multiple UV coating suppliers to develop improved scratch resistant finishes that exceeded the performance of their standard coatings Linear Taber Scratch Test Using Steel Wool
  8. 8. 8Page Scratch Resistance of Different UV Clearcoatings 0 10 20 30 40 50 60 70 80 90 100 0 5 20 50 100 160 GlossChange Steel Wool Cycles GlossChange vs. Steel Wool Cycles Competitor Normal PU Normal UV Droid Ultra • An improved full gloss UV scratch resistant clearcoat was identified which exceeded the performance of existing coatings and competitive products • The coating system is processable using conventional UV lamps and compatible with basecoats and surface primers. Multiple coating applicators have been introduced to this coating system in mass production.
  9. 9. 9Page High Gloss Surface Cleanability WCA Reference Improved 1 88.4 111.0 2 86.9 112.1 3 80.3 123.0 4 99.7 109.0 5 86.6 108.0 Avg. 88.4 112.6 • Full gloss UV coatings can offer the consumer advantages in cleanability when combined with anti-smudge additives • Such coatings can be tested in a variety of ways depending on use conditions • Water and other liquid contact angle measurements can be used to characterize the coated surface WCA = 88.4 Good Wetting WCA = 112.6 Poor Wetting Greater water contact angle (WCA) provides a surface that is easier to clean
  10. 10. 10Page High Gloss Clearcoat Printing • Personalization is driving the requirement for post-processing, including pad printing • Regulatory and carrier logos require similar level of decoration performance and reliability as the UV clearcoat New test methods developed to replace subjective test methods, including localized scrape and mar resistance Poor scratch resistance of pad printing observed with UV clearcoat + anti-smudge additive
  11. 11. 11Page Low Gloss UV Clearcoats – Mar Resistance • Mar resistance is critical for low gloss UV clearcoats as gloss changes can be observed with consumer use • Early supplier involvement is required to ensure performance meets requirements 0 1 2 3 4 5 6 0 10 20 40 GlossChange Steel Wool Cycles GlossChange vs. Steel Wool Cycles Supplier A - 8 Gloss Supplier B- 8 Gloss Original User Trial Steel Wool Performance Testing
  12. 12. 12Page Low Gloss Basecoat / UV Clearcoat System – Tumbler Testing Gloss 1-2 Gloss 4-6 Tumbler testing identified surface staining and marring which was gloss dependent even within desired scope of a “low gloss” surface finish
  13. 13. 13Page Color (description) Basecoat Thickness (Spec = 8-13 microns) Clearcoat Thickness (Spec = 10-15 microns) White – Good (4-6 gloss) 8 – 10 10 – 12 White – Failure (1-2 gloss) 6 – 10 5 - 8 Good White (1000X) – Smooth, even clear coat Bad White (1000X) – Rough, thin clear coat Substrate Substrate Base coat Base coat Clear coat Clear coat Low Gloss Basecoat / UV Clearcoat – Coating Thickness Maintaining proper UV clearcoat thickness is critical, as well as surface roughness
  14. 14. 14Page Low Gloss Basecoat / UV Clearcoat – Clearcoat FTIR Analysis • Greater surface organic-to-filler ratio can reduce marring in low gloss coatings • Basecoat gloss may require abnormally high levels of matting agent in the UV clearcoat vs. that required in a one-coat system to meet clearcoat gloss targets • Possible interaction between basecoat & clearcoat from basecoat drying conditions Gloss IRIntensity 1720cm-1 vs1060 cm-1 1720cm-1 1060cm-1 Bad Paper White 1-2 0.543 0.876 0.62 Good Paper White 4-6 0.871 0.892 0.98 Known Reference 1-2 0.826 0.904 0.91 Substrate Gloss Reading Plastic 9 Basecoat 29-31 (Line A)
  15. 15. 15Page Low Gloss UV Coatings – Gritty Surface Texture Gritty area below M-logo Turquoise “Grit” – 400X Matting Agent Solid Particle • 45 micron solid debris particle observed • Good part cleaning and UV clearcoat filtration needed
  16. 16. 16Page Low Gloss UV Clearcoats – Plastic Contamination • Fingerprint marks observed after temperature/humidity exposure. No impact to cross-cut adhesion. • Poor operator handling of phone housings during placement on painting jigs • Important to wear proper gloves and handle parts by edges only
  17. 17. 17Page Low Gloss UV Coatings – Pad Printing Adhesion • A silver pad print ink was found to have poor scrape adhesion over a low gloss UV clearcoat • Ink supplier reformulated the ink for better UV coating adhesion • Plasma treatments can offer improved ink adhesion when applied to fully cured UV coatings Cross-cut tape adhesion pad printing failures Improved pad printing adhesion
  18. 18. 18Page Conclusions • Full gloss UV coatings can provide high scratch resistance when modified accordingly. Smudge resistance and easy cleanability need improvement to promote personalization and regulatory marking. • Pad printing needs to be developed for compatibility with UV clearcoats for high field performance • Mar resistance of low gloss UV coatings must be tailored to maximize perceived quality and reliability • Production problems with regard to coating filtration and plastic handling must be offset with controlled processing and proper operator handling
  19. 19. 19Page Future Development Needs in UV Coatings • Anti-Smudge UV Clearcoats – Available option within a coating family • Post-Processing – Suppliers should optimize coatings beyond typical use conditions and consider that the coating itself may be a substrate • Mar Resistant UV Clearcoats – Improved stain and gloss retention when abraded • Future UV coating system development requires careful thought for plastic substrate interactions and use limits

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