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Benjamin Mehlmann - Fraunhofer Institute

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Benjamin Mehlmann - Fraunhofer Institute

  1. 1. LASER MICRO JOINING - PROCESSES ANDAPPLICATIONS IN RESEARCH AND DEVELOPMENTA. Gillner, B. Mehlmann, A. Olowinsky, A. Roesner, F. SchmittEindhoven, 06 December 2012© Fraunhofer ILT
  2. 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 FuturePage 2© Fraunhofer ILT
  3. 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 ElectronicsPage 3© Fraunhofer ILT
  4. 4. 1. Applications for Laser Micro Joining Energy, Electronics and Lightweight ConstructionRequirements 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 devicePage 4© Fraunhofer ILT
  5. 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© Fraunhofer ILT
  6. 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 2011Page 6© Fraunhofer ILT
  7. 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 opticsPage 7© Fraunhofer ILT
  8. 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 • AmplitudePage 8© Fraunhofer ILT
  9. 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 sourcePage 9© Fraunhofer ILT
  10. 10. 4. Process Simulation Polymer Welding with Spatial Power ModulationComputer 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 pComputer model output: Temperature field Top view – welding area HAZ in cross section Temperature profileParameters: df = 80 µm P=4W v = 50 mm/s f = 1000 Hz a = 0.2 mmPage 10© Fraunhofer ILT
  11. 11. 4. Process Simulation Polymer Welding with Lateral Power ModulationPage 11© Fraunhofer ILT
  12. 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 µmPage 12© Fraunhofer ILT
  13. 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%Page 13© Fraunhofer ILT
  14. 14. 5. Current Approaches in Research and Development Combined Laser Welding (515 + 1030 nm) 45 1200 37 Cu-ETP Penetration Depth in µm 40Melt 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 ejectionsPage 14  Smoother weld seam surface© Fraunhofer ILT
  15. 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 frequencyPage 15 modulation© Fraunhofer ILT
  16. 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/sPage 16© Fraunhofer ILT
  17. 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 500Page 17 kHz© Fraunhofer ILT
  18. 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 manipulationPage 18© Fraunhofer ILT
  19. 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)© Fraunhofer ILT

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