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1 Live! © 2012
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Live!
© 2012
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Laser Welding of Transparent Plastics Clear-to-clear Polymer Bonding with High-Wavelength Lasers
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Our presenters
© 2012
Shane Stafford Market development representative, LPKF Laser & Electronics North America Josh Brown Laser plastic welding sales associate, LPKF Laser & Electronics North America Dr. Tony Hoult West coast general manager, IPG Photonics
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Questions
• Submit questions via…
• Your GoTo Webinar panel • Twitter
• #LPKF • @LPKF_USA
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Topics
1. What is LWTP?
2. How it works
3. Industries
4. Materials
5. Applications
6. Equipment
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1. What is LWTP?
Laser Welding of Transparent Plastics
• Polymer bonding with laser energy • Clear-to-clear bonding (also translucent/natural polymers) • Requires no special additives or absorbers • AKA - 2µm welding (2 micron)
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A new type of laser welding
Through-transmission Laser Welding
(TTLW)
Laser Welding of Transparent Plastics
(LWTP)
Absorbing layer required Requires NO absorbers, can bond clear/natural/translucent
thermoplastics
800nm – 1064nm wavelengths 1500nm – 2000nm wavelengths
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2. How it works
• Changes in laser wavelength affect transmission/absorption in thermoplastics
Natural polycarbonate
X-axis – wavelength in nanometers Y-axis – % of
laser radiation transmitted by PC
Near 100% transmission Partial, natural absorption
Goldilocks' Zone
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How it works (continued)
Goldilocks' Zone
• Right balance of transmission and absorption
Volumetric Heating
• Laser passes through all pieces, but enough
energy is absorbed in each to create melt
“Lens” Effect
• Majority of energy tends to stay at interface
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• Laser beam with a wavelength >1500 nm • 2 or more clear/natural/translucent thermoplastics • Clamping force • Material compatibility (i.e. similar melt temp, surface energy and
chemical makeup)
Requirements
Clamping force Clamping force
Transparent plastic
Transparent plastic
Workpiece carrier
Weld zone
material fusion
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Laser Motion Control
• Beam controlled by galvo-scanning mirrors, traces joint pattern • Typical travel speeds 20 – 80mm/s, usually a single pass
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Advantages of Laser Welding
LWTP Specific Advantages • No absorbers! • New possibilities for laser entry/joint designs • Great for films and multilayer applications
Laser welding v. other joining methods (i.e. gluing, ultrasonic, vibration) • Particulate free – cleanroom rated process up to class 5 • Localized heat • No mechanical stress • Hermetic seals • High strength bonds • Excellent repeatability/low maintenance - excellent for high-volume
production • Flexible process • Low scrap/reject rates
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No absorbers!
Disadvantages of absorbers • High cost • Even “optically clear” absorbers have some color effect • Difficult/costly to apply • Disadvantageous for approval procedures (e.g. FDA-certification)
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3. Industries
Medical • Microfluidics and lab-on-a-chip • Catheters/tubing • Bags and connectors
Biotech • Cell culture flasks/cases
Consumer - broad • Design elements and aesthetics
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4. Material Compatibility
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Notable materials for LWTP
Rigid • Polycarbonate • PMMA (acrylic) • PS • COP/COC • PEEK
Flexible • TPU/TPE • PET • PVC
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Welding of 2 PMMA-foils (thickness 250 µm)
5. Applications
1 mm
Quadratic weld seam
0,25 mm
0,4 mm
PMMA-foil PMMA-foil
Weld zone
Scale-up of weld seam
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Welding multiple foil-layers
Fields of application
Four layers of a PU-foil
5 mm
4 PU-foils
Weld zone
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Welding one PC-foil between two PMMA-sheets
Fields of application
PMMA-sheet (1,0 mm)
PMMA-sheet (0,8 mm)
PC-sheet (0,1 mm)
Example of a weld contour
1,5 mm
0,9 mm
5 mm
Scale-up of weld seam
PC foil
Weld zone PMMA-sheet
PMMA-sheet
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COC-Foil (150 µm) on a microfluidic-sheet (COC)
Fields of application
COC foil
Weld zone
COC-microfluidic
Weld seam embed channel
Microfluidic channels
Weld seam in a microfluidic channel system
1 mm
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Fields of application
Plane welding of a foil on a microfluidic-sheet (thickness 1,0 mm)
Plane welding
Unharmed channel boarders
2,5 mm
2,5 mm
Scale-up of weld area
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Fields of application
Two translucent PC-sheets (thickness 1 mm)
Weld zone
PC-sheet PC-sheet
Weld contour: LPKF-logo (width of weld seam: 0,6 mm)
10 mm
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Two super-transparent PC-sheets (thickness 1 mm)
Fields of application
Weld contour: LPKF-logo (width of weld seam: 1 mm)
10 mm
Weld zone PC-sheet PC-sheet
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Fields of application
Appearance of fracture of two transparent PC-sheets
Appearance of fracture (welding of two transparent PC-sheets)
Material break-out
3 mm Weld zone PC-sheet PC-sheet
Material break-out
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New color options
• Clear PC welded to an optically opaque, yet laser transmissive black dyed PC
• Laser could theoretically enter from either side as both parts are transmissive to the laser
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Long wavelength laser welding of polymers
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New approach: • Long wavelength
approach produces volumetric absorption of the laser beam
• More recognizably a welding process
• Enables butt welds or lap welds
• Obeys Beer-Lambert absorption law
22 layers of 0.1 mm thick LDPE
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PMMA (acrylic) welding
• volumetric absorption
• no absorption enhancers
• no material modification
Test results:
• 3 mm thick samples, fig. 1
• Melt features on surface
• 30W, 100 mm/s speed
• 163 mm scan lens
• Films can be welded onto
PMMA surface
1” PMMA discs Figure 1.
Figure 2.
Micro-welding polymers with 2um lasers
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0.8 mm thick flexible TPU
Range of fibers can be incorporated into film
Welded Tritan® co-polyester containers
Weld line, single pass
Weld line, 3 pass
Polymer Joining Example
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T Joint
Weld widths and joints
Beam spot size = joint width • Can vary from <100µm to 3mm • Depends on optics set and focal depth
Joint Types
Lap Joint Butt Joint
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Clamping – Glass Plate
• Clamping force ensure contact between parts • Workpiece carrier provides support along entire joint • Glass clamp plate – must be glass, not acrylic (acrylic will absorb laser)
Workpiece carrier
Glass Clamp Plate
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Clamping – Metal Tools
• All metal tooling provides support as close to joint as possible without blocking beam
Workpiece carrier
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Fiber Lasers
Details • Not “fiber delivered” - fiber lasers use actual optical fiber as the lasing
chamber rather than a gas or crystal • 120 watt – average power, scalable in future • CW – continuous wave • Can create very small beam spot profiles < 100 µm Diode Lasers – also available in >1500nm wavelengths • Requires special wafers to reach higher wavelengths, can be expensive • Wattages tend to be lower than fiber lasers • Shorter focal length lenses required
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Systems
Easily integrated into existing standard laser welding systems, requires only a different laser source, usually a fiber laser at 1940nm.
Automation Integrated Systems
Stand-alone Systems for Automated Cells or Manual Loading
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Cleanroom Compliant
• Laser welding is a particulate free process making it ideal for cleanrooms • LPKF application center cleanroom is rated at ISO Class 5
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Thank you for your attention! LPKF Laser & Electronics · 12555 SW Leveton, Tualatin, OR 97062 Josh Brown – 503.454.4231, [email protected] – www.lpkfusa.com
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Questions
Submit questions via…
• Your GoTo Webinar panel • Twitter
• #LPKF • @LPKF_USA
© 2012
