laser based manufacturing - university of virginia … l. brown department of electrical and...

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Section I. Introduction & laser

matter interaction process

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Partnership

Projects

Industry

Fed. LabsUniv.

State NSF

MembershipMembership

Member

ship

CIT

Overhead &

Facility

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

Charles L. Brown Department of Electrical and Computer Engineering

•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

Charles L. Brown Department of Electrical and Computer Engineering

•$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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

• 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

Charles L. Brown Department of Electrical and Computer Engineering

Diode pump Solid state laser

Diode laser

IPG fiber laser

YAG laserYAG laser

Research Infrastructure

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

LaserMaterial

Beam Delivery & scanning

Power source

& electronicsX-Y-Z computer

controlled stage

Process

monitor &

safetyEnvironment

Fundamentals of Laser Matter

Interactions

Charles L. Brown Department of Electrical and Computer Engineering

•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

Charles L. Brown Department of Electrical and Computer Engineering

•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

Charles L. Brown Department of Electrical and Computer Engineering

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

Interaction

time

Charles L. Brown Department of Electrical and Computer Engineering

Laser rod

100 %

Reflecting

mirror

Partially

reflecting

mirror

Coherent

radiation

Pump source

High Power Lasers

Charles L. Brown Department of Electrical and Computer Engineering

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Laser Beam Profile

Charles L. Brown Department of Electrical and Computer Engineering

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

Laser pulse characteristics

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Important commercial lasers

Excimer 193-248nm Pulsed 10’s of Watts

Nd-YAG 1064 nm CW or Pulsed kW

CO2 10600 nm CW or Pulsed kW

Cu-Vapor 534 nm Pulsed 10’s of Watts

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

Other gas Solid State & Semiconductor Lasers

Important Commercial Lasers

Charles L. Brown Department of Electrical and Computer Engineering

Power density of welding and others

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

Laser Power Density Regimes

Charles L. Brown Department of Electrical and Computer Engineering

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

__eqVU_YCOd-vi4yZ7qTvs_5iwyRs=

Fiber Laser Nd:YAG laser

Lasers

Charles L. Brown Department of Electrical and Computer Engineering

Section III. Optical, thermal and electrical

properties of materials

Charles L. Brown Department of Electrical and Computer Engineering

•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

Charles L. Brown Department of Electrical and Computer Engineering

Beer Lambert’s Law

I = I0 exp (-4παd/λ)

Where: α = extinction coefficient; λ =

Wavelength; I = Intensity at depth d; I0 =

Intensity at the surface

Beer Lambert’s Law

Charles L. Brown Department of Electrical and Computer Engineering

http://www.intel.com

Absorption coefficeint for various semiconductors

Charles L. Brown Department of Electrical and Computer Engineering

Table: Complex refractive index and reflection coefficient

for some materials to 1.06 micron radiation

Source: W. M. Steen

Optical Properties

Charles L. Brown Department of Electrical and Computer Engineering

Figure: Reflectivity of steel to polarised 1.06 micron radiation,

Source: W. M. Steen

Reflectivity variation with angle

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Temperature Distribution

tqerIAz

TK

t

TPc z

p

.

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

pcpPc

KD

ze

constIrI 0

Dt

zicrfc

K

DtAIztT

2

2, 0

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Temperature vs time

Charles L. Brown Department of Electrical and Computer Engineering

Figure: Temperature vs. depth by copper

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

Temperature vs Depth

Charles L. Brown Department of Electrical and Computer Engineering

Section IV. Beam delivery and scanning

systems

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Section V. Applications

Charles L. Brown Department of Electrical and Computer Engineering

• 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

Charles L. Brown Department of Electrical and Computer Engineering

Laser micromachining

Charles L. Brown Department of Electrical and Computer Engineering

Laser Micro-machiningEDM

● Sharp notch tip

● Smaller heat effected zone

Laser micro notch fabrication

Charles L. Brown Department of Electrical and Computer Engineering

AFM Image of

Double Grating in

Si<100>

Diffraction Pattern

from Double

Grating

Micro/nano fabrication

Charles L. Brown Department of Electrical and Computer Engineering

Charles L. Brown Department of Electrical and Computer Engineering

Laser marking for CD disks

Charles L. Brown Department of Electrical and Computer Engineering

Schematic of laser cleaning process

Charles L. Brown Department of Electrical and Computer Engineering

Wavelength: 800 nm

Pulse Repetition Rate: 1 KHz

Pulse Energy: 1 mJ

Laser texture-experimental setup

Charles L. Brown Department of Electrical and Computer Engineering

Laser surface texture

Charles L. Brown Department of Electrical and Computer Engineering

Laser surface texture of thin films

Charles L. Brown Department of Electrical and Computer Engineering

Surface Reflectivity Control

Charles L. Brown Department of Electrical and Computer Engineering

Laser Generated Nanopores

Charles L. Brown Department of Electrical and Computer Engineering

Superhydrophobic Surfaces

Charles L. Brown Department of Electrical and Computer Engineering

Cell growth on laser textured surface

Charles L. Brown Department of Electrical and Computer Engineering

Laser Marking

Charles L. Brown Department of Electrical and Computer Engineering

Lasers for Photovoltaics

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Laser imaging of weld pool surface

Charles L. Brown Department of Electrical and Computer Engineering

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

Displays

Charles L. Brown Department of Electrical and Computer Engineering

1 μm

Laser texturing

Laser notch

formation

Laser sintering

Laser surface cleaning

Laser

microma

chining

Examples of Laser Processing

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

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

(>4000°C), 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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Laser generated nanofibers and rods

Charles L. Brown Department of Electrical and Computer Engineering

LASER-DRIVEN COMPRESSIVE WAVE

GENERATION

Turbine Blade & Vessel in Power Plants

Medical applications

Laser shot peening

Charles L. Brown Department of Electrical and Computer Engineering

Section VII. Process monitoring

Charles L. Brown Department of Electrical and Computer Engineering

• Welding

• Cutting

• Sintering

• Surface cleaning

• Micromachining

• Texturing

• Peening

Types of Laser Processes

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

Example : Laser Welding

• Optical signals

• Acoustic signals

• Plasma signals

Process signal during laser

welding

Shao et al., Journal of Physics: Conference Series 15 (2005) 101–10

Charles L. Brown Department of Electrical and Computer Engineering

• 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

Charles L. Brown Department of Electrical and Computer Engineering

Section VII. Laser market and future prospects

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

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

Charles L. Brown Department of Electrical and Computer Engineering

•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

Charles L. Brown Department of Electrical and Computer Engineering

THANK YOU