This document discusses laser micro joining processes and applications in research and development. It outlines laser beam sources and beam manipulation strategies used for micro joining applications in energy storage, electronics, and lightweight construction. Current approaches in research include welding copper with spatial and temporal power modulation to increase weld depth and quality. Developments aim to enable precision melt engineering through dynamic beam manipulation and modeling of laser micro joining processes.

1. LASER MICRO JOINING - PROCESSES AND
APPLICATIONS IN RESEARCH AND DEVELOPMENT
A. Gillner, B. Mehlmann, A. Olowinsky, A. Roesner, F. Schmitt
Eindhoven, 06 December 2012
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2. OUTLINE
1. Applications for Laser Micro Joining
2. Laser Beam Sources for Micro Joining
3. Beam Manipulation Strategies
4. Process Simulation
5. Current Approaches in Research and Development
6. Developments in System Technology
7. Questions of the Future
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3. 1. Applications for Laser Micro Joining
Energy, Electronics and Lightweight Construction
Welding Glass Soldering Plastic welding Soldering
High Power
Energy storage CRP/ GRP Photovoltaics
Electronics
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4. 1. Applications for Laser Micro Joining
Energy, Electronics and Lightweight Construction
Requirements for welding of CRP
 Thermoplastic matrix
 Joining area visible for laser
beam
 Translucent joining partner
(GF) with minimum
transmission of 25%for laser
radiation
 Laser absorbing joining
partner (CF/GF carbon-black
filled)
 Appropriate contact between
joining partners by adapted
clamping device
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5. 1. Applications for Laser Micro Joining
Energy, Electronics and Lightweight Construction
15
Laser Beam
Penetration
Line Energy [J/m m ]
Al 0,5
Conductors 10 Cu 0,3
5
Pouch Cell
Plate Cooler Not Connected
0
0 50 100 150 200
Feed [mm/s]
Welding geometry:
 Overlap, Al conductor
top Requirements for welding process
 Linear weld seam  Stabilized process in small working range
Parameter:
 Enlarged cross-section for enhanced conductivity
 df = 80 µm
 P = 500 - 1 000 W  Welding of dissimilar materials

Page 5 v = 50 - 200 mm/s
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6. 2. Laser Beam Sources for Micro Joining
New Approaches on the Horizon
Source: Philips Source: IFSW Source: Trumpf
High Power Ultra-Short Wavelength Single-Mode 1500-2300 nm 515 nm
VCSEL Pulsed Laser multiplexing Fiber Laser Emission Emission
(532+1064 nm) Wavelength Wavelength
Soldering and Welding of Increasing Welding of Welding of Welding of
Plastic Welding Glass Process Stability materials with polymer parts highly
Processes in Copper high thermal and bonding reflective
Welding conductivity of silicon materials
Source: Roth, SPIE, 7920, Source: IFSW
2011
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7. 2. Laser Beam Sources for Micro Joining
Influence of Intensity Distribution
 Comparison PC / PBT @100 mm/s 3500 3500
 PC: 16.4 W
Intensity in counts
Intensity in counts
3000 3000
 PBT: 47.8 W
2500 2500
 Both welding processes at
optimum 2000 2000
 Steep edge in temperature
Thermosensorik GmbH IR Sy stem Thermosensorik GmbH IR Sy stem
distribution visible in
thermography for PC
 Widened welding zone by
scattering for PBT
Modified energy input by
scattering
Intensity distribution defined by
laser source and optics
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8. 3. Beam Manipulation Strategies
Variable Intensity Profile in Time and Space
Intensität [W/ cm²] Intensität [W/ cm²]
0,0E+00 0,0E+00
0,2 0,2 2,8E+03 1,9E+03
5,5E+03 3,8E+03
8,3E+03 5,6E+03
1,1E+04 7,5E+03
1,4E+04 9,4E+03
1,7E+04 1,1E+04
y [mm]
y [mm]
1,9E+04 1,3E+04
0,0 0,0 2,2E+04 1,5E+04
2,5E+04 1,7E+04
2,8E+04 1,9E+04
3,0E+04 2,1E+04
3,3E+04 2,3E+04
3,6E+04 2,4E+04
3,9E+04 2,6E+04
-0,2 -0,2 4,1E+04 2,8E+04
4,4E+04 3,0E+04
4,7E+04 3,2E+04
-0,2 0,0 0,2 -0,2 0,0 0,2
x [mm] x [mm]
Beam Shaping Spatial Power Temporal Power
Modulation Modulation
• M-Shape • Fast Beam • Rising Time
• Circle Deflection • Frequency
• Diffractive Optical • Lissajous- • Different
Elements (DOE) oscillation modulation shapes
geometries
• Amplitude
• Frequency
• Amplitude
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9. 4. Process Simulation
Integrative Process Simulation - Polymer Welding
 Procedure of Integrative Measurement of transmission and reflection (flat
Process Simulation leads specimen)
to:
Identification of scattering and absorption
 A-priori estimation of coefficient and scattering angle (independent from
weldability thickness)
 Laser wavelength
Computation of intensity distribution in the
 Intensity distribution transparent joining partner (arbitrary specimen)
 Irradiation strategy
 Appropriate system Simulation of heating and melting processes
technology
 Design of Selection of irradiation strategy and appropriate
Components (DoC) laser beam source
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10. 4. Process Simulation
Polymer Welding with Spatial Power Modulation
Computer Model:
 Heat conduction equation
 Input: geometry, material data
 c pT 
   KT   Q,
t
: mass density, cp: specific heat capacity, K: heat
: mass density, c : specific heat capacity, K: heat conductivity, Q: source term.
conductivity, Q: source term
p
Computer model output:
 Temperature field Top view – welding area HAZ in cross section Temperature profile
Parameters:
 df = 80 µm
 P=4W
 v = 50 mm/s
 f = 1000 Hz
 a = 0.2 mm
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11. 4. Process Simulation
Polymer Welding with Lateral Power Modulation
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12. 5. Current Approaches in Research and Development
Welding of Copper with Spatial Power Modulation
Increase of welding
depth by 30%
Increase of welding
width by 30%
v = 30 mm/ s v = 50 mm/ s v = 200 mm/ s
0 µm 150 µm 0 µm 150 µm 0 µm 150 µm
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13. 5. Current Approaches in Research and Development
Welding of Copper with Spatial Power Modulation
 Optimum of oscillation amplitude dependent on material and welding speed in
the range of 0.2-0.3 mm
 Instabilities and holes/ pores in welding zone for high oscillation amplitudes
 Increase of tensile strength by 50-150%
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14. 5. Current Approaches in Research and Development
Combined Laser Welding (515 + 1030 nm)
45 1200
37
Cu-ETP
Penetration Depth in µm
40
Melt Ejections per Weld
1100
35
30 1000
25
19
900
20
15 12 800
10
Melt Ejections 700
5 Penetration Depth 1
0 600
IR cw IR and Green IR modulated IR modulated
cw Green cw v = 6 m/min,
Pav = 1700 W, f = 500 Hz
 Increase in penetration depth by combined laser welding
 Decrease in number of melt ejections
Page 14  Smoother weld seam surface
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15. 5. Current Approaches in Research and Development
Welding of Copper with Temporal Power Modulation
 Different shapes
of modulation
type:
 Sinusoidal
 Saw tooth
 Significant
reduction of
defects between
600-800 Hz
 Increasing
number of
defects with
high frequency
Page 15
modulation
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16. 5. Current Approaches in Research and Development
Welding of Copper with Temporal Power Modulation
100 Hz
1 mm
200 Hz
1 mm
700 Hz
1 mm
5000 Hz
1 mm
P = 250 W ( 58 W)
v = 50 mm/s
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17. 6. Developments in System Technology
Ultra-High Speed Beam Deflection
Galvano- Polygon- AOD MEMS Digital Mirror
meterscanner scanner Device (DMD)
• Proven • Uniform • Beam de- • Miniatu- • Miniatu-
Concept geometry flection by rization rization
• High laser • High laser diffraction • Fixed • Moderate
power power of laser oscillation laser power
beam frequency
• Moderate • Very fast • High
dynamics beam • Oscillation oscillation
deflection frequencies frequency
up to 500
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kHz
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18. 7. Questions of the Future
Precision Melt Engineering
 Manipulation of the liquid melt by temporal and spatial power
modulation leading to an increase in welding precision
 Welding of joining partners in the thickness below 10 µm (e.g.
welding on metallic coatings)
 Best suited intensity distribution depending on characteristics of
materials or laser beam sources
 Adaptions in modelling and simulation in neglected 3. dimension
 Simultaneous welding like in E-beam welding
 Process control for highly dynamic beam manipulation
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19. Thank you very much for your attention!
Dipl.-Ing. Benjamin Mehlmann
Fraunhofer-Institut für Lasertechnik
Tel.: +49 (0) 241 89 06 -613
Fax: +49 (0) 241 89 06 -121
Email: benjamin.mehlmann@ilt.fraunhofer.de
Thanks to:
Andreas Heider, Axel Hess (IFSW Stuttgart)
Stephan Gronenborn, Holger Mönch (Philips)
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