Practical Applications of Laser Technology for Semiconductor Electronics MOPA Single Pass Nanosecond Laser Applications for Semiconductor / Solar / MEMS & General Manufacturing Mark Brodsky US Application Laboratory Manager
Overview General Industrial Laser Overview Sources and variables MOPA vs Q-Switch Lasers Typical laser uses for Electronics Gaussian vs Single Pass Pulses Benefits of High khz and Peak power Application Examples
Wide Spectrum-Rules of Thumb 1.064 is industrial starting place for smaller but powerful spots Cut wavelength in half at Triple the price and less power Less absorption depth comes at a price of thermal stability
Lasers in Electronics MicroMachining A range of infra red, visible and ultra violet laser sources give fast machining of a wide range of materials Via Drilling CO2 Laser drilling machine: Package, Printed circuit board, Ceramic device Material: Glass-epoxy, Epoxy, Green sheet) UV Laser drilling machine: Package, Printed circuit board, Flexible board material: Glass-epoxy, Epoxy, Polymide) Stencil Cutting CO2 Laser drilling machine: Package, Printed circuit board, Ceramic device Material: Glass-epoxy, Epoxy, Green sheet) UV Laser drilling machine: Package, Printed circuit board, Flexible board material: Glass-epoxy, Epoxy, Polymide)
Marking Apps Plastic Ceramic Through Plating Strip / Remark
Nanosecond Lasers Predominantly solid state 1micron sources Rod - Nd:YAG, YVO 4 Disk Yb+:YAG Fiber - Yb+
Pulsed MOPA Fiber Laser directly modulated LD Amplifier Chain (GTWave Technology) Seed Laser Pre-Amp Post-Amp Advantages of MOPA architecture: Pulse parameters can be controlled independently at different stages Extensive pulse energy and peak power parameter space
MOPA Laser Technical Description Seed Optical Pulses Yb GTWave TM Pre-Amplifier Yb GTWave TM Power-Amplifier Fibre Optic Beam Delivery Output Pulses Seed Laser Diode Pump Laser Diode Pump Laser Diodes Seed Laser Driver Pump Laser Driver Pump Laser Driver Main Control and Monitoring Electronics User Control Electronics MOPA architecture optical seed pulse generated by a single-mode semi-conductor (master-oscillator) laser diode dual-stage Yb GTWaveTM fibre amplifier system pumped by multi-mode 9xx nm laser diodes fibre-optic beam delivery cable terminated with collimator, optical isolator and optional telescopes
SPI s PulseTune Optical Pulses Directly Modulated @ 20W New Waveforms 20W Q-Switched Fiber laser @ 20W Power (kw) 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 80 khz 0.0-50 0 50 100 150 200 250 300 Time (s) 25 khz peak power (kw) 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 50 100 150 200 250 300 350 time (ns) 80 khz 20 khz 30 khz 40 khz 60 khz 80 lhz 20 khz Increasing rep rate by using different Wave Forms with shorter pulse lengths limits peak power reduction Increased rep rate significantly reduces peak power
Marking Optics Galvo Systems Beam Expander Aperture Scan Head Mirror(2) ibdo Spacer F-Theta Lens Marking Plane Pupil Spacer Spot Size
Short Duration High Peak Power Equals High Speed Processing
Spot Overlap: Marking quality up-close (one of several quality measures) Half the story! No Spot Overlap visible mark poor resolution dotted-line Spot overlap is a key Greater overlap produces a more continuous mark appearance >60% overlap desired for many marking applications <5% Spot Overlap improved mark low resolution scallop edge >60% Spot Overlap desired mark high resolution smooth line edge To increase spot overlap Slow down the mark until the pulses overlap Or (better put) Increase the pulse repetition rate at your desired marking speed!
Higher KHz provides smoother ablation Spot overlaps only works when transition energy is has been passed. Less ablation, more material conversion
Solar Energy/Display Technology Scribing Transmissive Conducting Oxide (TCO) Typically Indium Tin Oxide (ITO) Careful control of the pulse energy is crucial to; completely remove the film, produce minimal burr to the patterned edge, lack of cracking/delamination of the TCO no damage to the glass substrate. 20W; 25kHz WF0 1m/s scan speed 80µm scribe width 20W; 125kHz WF2 1m/s scan speed 40µm scribe width
Different Beam Quality & Pulse Energy The right tool for every job! Series SM RM/HS HM M 2 <1.3 <2 ~3.2 Power 10W / 20W 10W / 12W / 20W 30W / 40W Key attribute Fine feature Multi purpose Wider lines <25micron 35-80micron >60micron Application Scribing (P1) Fine marking General marking and micro-machining Wide marks deep engrave area/logo
Comparison of M 2 on Application What is best for Snap and break in ceramic 20W SM 1.1 20W HS 1.8 40W HM 3.2 Pulse with smallest M 2 has highest power density but may not be best for the application!
Flexible Tool - Diverse Applications Images and samples courtesy of: Miyachi Unitek, Electrox, LMCo & Orotig
Silicon Processing Scribing and Cutting Low rep rate 25kHz Deep scribe High level of debris High rep rate >100kHz Shallow scribe Low level of debris Drilling Similar effect to above >400holes/s in 200µm Si wafers with 20W laser Diameter circa 50 µm Marking Can be smooth on surface But no circuitry can be below
Molybdenum thin film ablation P1 scribe Electrically conducting back contact film for CIGS or CIS modules 0.25-1 µm thick 125kHz, 4 m/s 30-40µm wide lines on 0.2 mm pitch
Enhanced Ohmic conduction Annealing of thin metallic film Array or overlapping spot fill techniques Enhanced contact with underlying layer Control of pulse to minimise damage
Glassy Carbon Machining Difficult to process TG ~3000 C ns Pulsed fiber laser 20W HS Good solution for micromachining
Other Machining Fired and Green Ceramic Half mm Copper Heat
Processing Rubber Cutting Drilling Mould cleaning Micro-machining
Laser Processing Applications The majority of laser materials processing applications are impacted by: Peak pulse power - which is typically required to overcome processing thresholds. kw Pulse energy - which governs the amount of thermal energy available to effect any material processing. mj Pulse duration - impacts beam-material interaction time. ns Power Density which reflects the intensity of the laser energy on the substrate. W/mm 2 Average Power typically governs productivity and processing speed W Pulse M 2 Spike, Hammer, or Hoss Hat It is often a combination of these parameters that needs to be considered in pulsed laser materials processing applications.
Conclusions MOPA ns pulsed fiber lasers offer: Front end loaded pulse energy High peak power - High khz processing for speed Expanding application space