laser from virginia

Charles L. Brown Department of Electrical and Computer Engineering

Mool C. GuptaLangley Distinguished Professor & NSF I/UCRC Center Director

Department of Electrical & Computer Engineering

University of Virginia

Workshop, November 10, 2010

Laser Based Manufacturing


Outline

I. Introduction & Laser matter Interaction Process

II. High Power Lasers

III.Optical, Thermal and Electrical Properties of

Materials

IV. Beam Delivery and Scanning systems

V. Examples of Laser Applications

VI. Laser Process Monitoring

VII. Laser Market and Future Prospects

Outline


Section I. Introduction & laser

matter interaction process


National Science Foundation Center

For Laser Based Manufacturing

Develop Science, Engineeringand Technology Base for

Laser and Plasma Processing of Materials, Devices and

Systems for Advanced Manufacturing

Center Mission


Partnership

Projects

Industry

Fed. LabsUniv.

State NSF

MembershipMembership

Mem

bers

hip

CIT

Over

head

&

Facil

ity

Funds& National

Recognition

University of Virginia (Lead)

University of Michigan-Ann Arbor

University of Illinois

Southern Methodist University

NSF Industry University Cooperative

Research Center for Laser Based

Manufacturing


AREVA Inc. NAVAIR

GE Global Research A Army Research Lab.

NASA-Langley

General Motors R&D Trinity Industries

Trumpf Lasers

Lockheed Martin Lee Lasers

Halliburton Lesker Corp

Focus Hope Huettinger

Cymer Corp. Dexter

FIT Star Fire

IMRA Begnaud

Industrial Advisory Board Members

http://www.areva.com/servlet/ContentServer?pagename=arevagroup_en/homehttp://www.leelaser.com/index.htmlhttp://www.focushope.edu/default.htmhttp://www.nasa.gov/http://www.cymer.com/


$30k membership allows

Technical project for 1 year

Access to center facility

Access to center technology

Interaction with all center board members

Benefit from other NSF supported projects

NOTE: Board Members have access to

center research of over $1M with an

investment of $30k in membership. NSF

report shows $7 return for every dollar

invested.

NSF I/UCRC Center


Laser Welding: - Laser welding of light materials

-Rapid manuf. by e-beam welding

-Gas tungsten arc welding

-Galvanized steel welding

Laser Micromachining: -Laser texturing of Mo for solar

-Laser micromachining for fluidics

- Laser drilling of Ni superalloys

Laser Cladding: -Laser sintering of inconel 690

- Laser Cladding for erosion

Laser Diagnostics- -Laser corrosion detection-Navair

-Composition diagnostics during DMD

Plasma Processing: -Transparent coatings, pulsed plasma

Summary of Center Projects


Laser and Optics Lab Two fiber lasers (IPG), 50 ns pulse width

High power CW diode laser (250W)

Fs laser

Two Nd-YAG laser (10 ns pulse width)

Optical measurement equipment

Computer controlled stages and galvo systems

Clean Room Facility for Microfabrication Optical Lithography, e-Beam Lithography,

sputtering, e-beam deposition, ion etching

Characterization Facility- SEM, TEM, AFM, X-ray, ..

Sensor and Photovoltaic Device Fabrication and Characterization Labs

Research Infrastructure


Diode pump Solid state laser

Diode laser

IPG fiber laser

YAG laserYAG laser

Research Infrastructure


Automotive

Panel hole cutting

Surface modification

Sheet metal welding

Aerospace

Laser cutting & welding

Laser brazing

General manufact.

Micromachining

Microfabrication

Others

Laser crystallization

Pulsed laser deposition

Medical

Eye surgery

Tissue removal

Biostimulation

Military

Laser weapons

Army laser goggles

Laser designator

Brazing

Cladding

Soldering

Seam welding

Spot welding

Diode pumping

Surface melting

Epoxy curing

Laser sintering

Laser welding

Paint stripping

Laser forming

Medical applications

Laser illumination

Composite forming

Free form fabrication

Laser Applications


LaserMaterial

Beam Delivery & scanning

Power source

& electronicsX-Y-Z computer

controlled stage

Process

monitor &

safetyEnvironment

Fundamentals of Laser Matter

Interactions


Laser material interactions

Laser systems

Optics and beam delivery systems

Materials and metallurgical aspects

Process sensing and control

Application specific process

Various Aspects of Laser Based Manufacturing


Light Absorption

Temperature Rise

Melting

Vaporization

Cooling and

solidification

Material

Laser

beam

Ablated particles

Laser parameters

Optical properties of materials

Thermal properties of

materials

Electrical properties

Plasma

Plume

Light

emission

Laser Matter Interactions


http://ej.iop.org/links/q35/KI7QquaireEtwti,zstKpA/oa3451.pdf

Interaction

time


Laser rod

100 %

Reflecting

mirror

Partially

reflecting

mirror

Coherent

radiation

Pump source

High Power Lasers


Beam profile: GaussianSpectral Information

Pulse widthPolarization

-15 -10 -5 0 5 10 15

Re

lative

in

ten

sity

Time (ns)

Temporal Profile of a ns laser pulse

Pulse width at

FWHM

-6 -4 -2 0 2 4 6

Beam

width

Re

lative

in

ten

sity

Distance

I = Io exp[-r2/a]

Spatial distribution of intensity of a laser beam

Outp

ut p

ow

er

Wavelength (nm)

T.E

T.M

Laser Parameters


Laser Beam Profile


http://www.etechnologie.fh-stralsund.de/Daten/Fundamentals%20of%20laser%20drilling.pdf

Laser pulse characteristics


pp

apeak

ft

PP

Tf p

1

ppeakp tPPdtE

p

ppeak

At

E

A

PI

A

tP

A

EW

ppeakp

Peak Power

Intensity

Pulse energy

Fluence

Repetition ratetp=pulse width

Pa =Average power

A=area

Ppeak = Peak power

Ep = peak energy


I. Continuous (CW)- Important parameter is the power in Watts Between 100W and 20kW

for materials processing

II. Pulsed - Important parameters are Joules

per Pulse and number of Pulses per Second

Energy per pulse: 1mJ -1kJ

Pulse length: 1ms -1ns-100 fs

Pulse repetition rate: 0.1/s to 1 MHz

Lasers

Charles L. Brown Department of Electrical and Computer Engineeringhttp://www.electro-optics.org//files/laser%20workshop/martukanitz.pdf#search

Laser

Types


Important commercial lasers

Excimer 193-248nm Pulsed 10s of Watts

Nd-YAG 1064 nm CW or Pulsed kW

CO2 10600 nm CW or Pulsed kW

Cu-Vapor 534 nm Pulsed 10s of Watts

Ti-Sapphire 700-1000 nm CW or Pulsed 10s of Watts

Other gas Solid State & Semiconductor Lasers

Important Commercial Lasers


Power density of welding and others

http://www.uni-ulm.de/ilm/AdvancedMaterials/Presentation/Admasulaserconductionwelding.pdf

Laser Power Density Regimes


http://t1.gstatic.com/images?q=tbn:ANd9GcRDgYhJ4I0kfhbHS83UQcsA0nWgSd0aQsdYPeuJRU2rS1jSsY0&t=1&usg=

__eqVU_YCOd-vi4yZ7qTvs_5iwyRs=

Fiber Laser Nd:YAG laser

Lasers


Section III. Optical, thermal and electrical

properties of materials


Reflectivity

Thermal Conductivity

Specific Heat

Latent Heat

The lower these parameters the more

efficient the process since less energy is

required to melt and vaporize the material.

Important Physical Parameters


Beer Lamberts Law

I = I0 exp (-4d/)

Where: = extinction coefficient; =

Wavelength; I = Intensity at depth d; I0 =

Intensity at the surface

Beer Lamberts Law


http://www.intel.com

Absorption coefficeint for various semiconductors


Table: Complex refractive index and reflection coefficient

for some materials to 1.06 micron radiation

Source: W. M. Steen

Optical Properties


Figure: Reflectivity of steel to polarised 1.06 micron radiation,

Source: W. M. Steen

Reflectivity variation with angle


Figure. Reflectivity of some common metals for normal incidence as

a function of wavelength. (After F. A. Jenkins and E. White, Fundamentals of Optics, 4th ed., McGraw-Hill, 1976)

Reflectivity vs. Wavelength

Charles L. Brown Department of Electrical and Computer Engineeringhttp://free.pages.at/bastieh/download/source/vortrag/lama.pdf

Absorption vs Wavelength


http://www.ensc.sfu.ca/people/faculty/chapman/e894/e894l15g.pdf

Schematic variation of absorption with temperature for a typical metal

surface for both the YAG and CO2 laser wavelength

Absorption and

reflectivity are very

temperature

dependent

Often undergo

significant changes

when material melts

eg Silicon, steel

becomes highly

reflective on melting

Temperature

effect on

absorption

Charles L. Brown Department of Electrical and Computer EngineeringLaser Material Processing by W. Steen

Thermal properties of metals and

semiconductors


Temperature Distribution

tqerIAz

TK

t

TPc zp

.

2

2

P= mass density, = specific heat, k= thermal

conductivity

; I(r) = radial distribution of laser beam

Represents attenuation of beam in z-direction a = optical

Absorption coefficient. A is absorptivity (between 0 and 1)

For flat beam

pc pPcK

D

ze

constIrI 0

Dt

zicrfc

K

DtAIztT

2

2, 0




Temperature vs time


Figure: Temperature vs. depth by copper


Temperature vs Depth


Section IV. Beam delivery and scanning

systems


http://www.electro-optics.org//files/laser%20workshop/martukanitz.pdf#search

Hard Optic Delivery

(CO2, Nd:YAG, and Excimer Lasers)

Fiber Optics Delivery

(Primarily Nd:YAG Lasers)

Mirrors must be properly aligned and

clean

Can be used with practically any

wavelength

Hard optical systems are fairly

reliable

Versatile delivery to work station

No practical fiber materials for

use with CO2 lasers (10.6 micron

radiation)

Require high fiber bend radius

(approx 0.2m) to prevent leakage

Destroys coherency of beam,

resulting in larger focal spot

Focus HeadFibersLaser

Optics

Moving

Workplaces

Moving

Optics

Beam delivery systems for laser processing

Charles L. Brown Department of Electrical and Computer Engineeringhttp://www.aerotech.com/pressbox/uk/release.cfm/ID/254.html

http://www.laserod

.com/mirrors.shtm

Laser Scanning Systems

Charles L. Brown Department of Electrical and Computer Engineeringhttp://www.uslasercorp.com/catalog/fobd.html

Fiber optic beam delivery system


Section V. Applications


Surface Processing

Alloying

Surface Hardning

Cladding

Annealing & Doping

Crystallization

Texturing

Patterning

Direct writing

Bulk Processing

Cutting

Drilling Holes

Marking

Welding

Etching & Coating

Pulsed Laser

Depostion

Laser CVD

Applications


Laser micromachining


Laser Micro-machiningEDM

Sharp notch tip

Smaller heat effected zone

Laser micro notch fabrication


AFM Image of

Double Grating in

Si

Diffraction Pattern

from Double

Grating

Micro/nano fabrication


Laser marking for CD disks


Schematic of laser cleaning process


Wavelength: 800 nm

Pulse Repetition Rate: 1 KHz

Pulse Energy: 1 mJ

Laser texture-experimental setup


Laser surface texture


Laser surface texture of thin films


Surface Reflectivity Control


Laser Generated Nanopores


Superhydrophobic Surfaces


Cell growth on laser textured surface


Laser Marking


Lasers for Photovoltaics


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.51E16

1E17

1E18

1E19

1E20

1E21

Rsheet

= 9 ohms / sq

P C

on

cen

tra

tio

n (

ato

ms/

cm3)

Depth (m)

V=6 ; 10X Scan; P=28 W

V=6 ; 1X Scan; P=39 W

Rsheet

= 45ohms/sq

Laser Doping


200 400 600 800 1000 1200

0

20

40

60

80

100Q

ua

ntu

m E

ffic

ien

cy

(%

)

Wavelength (nm)

300 nm junction with passivation

300 nm junction without passivation

Laser Textured Surfaces for Photodetector


Laser imaging of weld pool surface


http://www.cohr.com/Downloads/Paper5713Afinal.pdf#search=

Displays


1 m

Laser texturing

Laser notch

formation

Laser sintering

Laser surface cleaning

Laser

microma

chining

Examples of Laser Processing


Inconel 690 laser cladding on Inconel 600 for nuclear applications

Laser Aided Manufacturing for Nuclear Energy

SEM cross-section

Improve corrosion resistance of coolant

pipes by laser cladding

lower cost / higher processing speed

good adhesion & high density

minimal residual stress in base material

good chemical/mechanical/thermal

stability

avoid premature failure & enhance life

reduce repair costs

maintain generator safety, efficiency,

and up-time

transfer technology of laser metal

cladding

http://people.virginia.edu/~tcb9y/Gupta/AREVA/SMU4.wmv


x

y

Nd:YAG LaserMirror

Lens

Argon gas environment

Nd:YAG Laser

High power CW laser

Stage

Advantages:

-Non-contact process, eliminating

contamination from walls

-Achieving extremely high temperature

(>4000C), and the control of rapid

heating and cooling rates

-Sintering to high density, with minimal

post processing requirements

Objectives:

-Provide basic understanding of laser

sintering mechanism for ultra high

temperature ceramics (UHTCs)

-Fabrication of cladding layer and 3-D

structures using UHTCs for Air Force

applications.

Laser processing of ultra high temperature ceramics


0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120

2 Theta (degree)

Inte

ns

ity (

a.u

.)

-

Laser sintering of nanoparticles


Laser generated nanofibers and rods


LASER-DRIVEN COMPRESSIVE WAVE

GENERATION

Turbine Blade & Vessel in Power Plants

Medical applications

Laser shot peening


Section VII. Process monitoring


Welding

Cutting

Sintering

Surface cleaning

Micromachining

Texturing

Peening

Types of Laser Processes


Types of Physical Phenomenon for

Sensing

Optical

Emission

Absorption

Reflection

Fluorescence

Direct imaging

Plasma related

Sheath voltage, thickness etc

Density

Temperature

Acoustic

Acoustic emission from melt pools

Structural modification

Defect generation


Example : Laser Welding

Optical signals

Acoustic signals

Plasma signals

Process signal during laser

welding

Shao et al., Journal of Physics: Conference Series 15 (2005) 10110


Imaging in harsh environments

Better spectral and spatial resolution

Compact, reliable, low cost

High speed

Fiber optic based systems

Future prospects for laser process monitoring


Section VII. Laser market and future prospects


5%3%

11%

12%

13%

24%

32%

Marking

Cutting

Engraving

Microprocessing

Welding

Drilling

Other

Worldwide, by Units Sold

Source: Industrial Laser Solutions

2005 Laser Applications


http://www.optoiq.com/index/photonics-technologies-applications/lfw-display/lfw-article-display/283868/articles/laser-focus-world/volume-43/issue-2/features/laser-marketplace-2007-diode-laser-market-takes-a-breather.html

Commercial Laser Market


Lasers provide a competitive edge in

manufacturing

Significant growth is expected in Laser Based

Manufacturing

Progress in high power diode, fiber and disk

lasers will generate lower cost, compact , better

efficiency and hands free operation laser

systems.

Desktop manufacturing may be possible

Our Center has long experience in laser based

process development and sensor monitoring with

excellent infrastructure and resources for

education and training

Future Prospects


THANK YOU

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