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Live!

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Laser Welding of Transparent Plastics Clear-to-clear Polymer Bonding with High-Wavelength Lasers

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Our presenters

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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, jbrown@lpkfusa.com – www.lpkfusa.com

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Questions

Submit questions via…

• Your GoTo Webinar panel • Twitter

• #LPKF • @LPKF_USA

© 2012