John A. Patten, Amir R. Shayan, H. Bogac Poyraz, Deepak Ravindra and Muralidhar Ghantasala

reelingripebeltUrban and Civil

Nov 15, 2013 (3 years and 9 months ago)

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John A. Patten, Amir R. Shayan, H. Bogac Poyraz, Deepak Ravindra and
Muralidhar Ghantasala



Western Michigan University

Kalamazoo, MI







Increasing

industrial

demand

in

high

quality,

mirror
-
like

and

optically

smooth

surfaces



High

machining

cost

and

long

machining

time

of

semiconductors

and

ceramics



Reduce

the

cost

in

precision

machining

of

hard

and

brittle

materials

(semiconductors

and

ceramics)


Motivation


Tool wear


Machining time


Semiconductor wafers

Optical lens

Machining cost


60
-
90%

Ceramic seals

Grinding

Polishing

Lapping

Diamond Turning

Potential Applications




Semiconductors

and

ceramics

are

highly

brittle

and

difficult

to

be

machined

by

conventional

machining



Lapping, fine grinding and polishing



High tool cost



Rapid tool wear



Long machining time



Low production rate

Background

Micro
-
Laser Assisted Machining (µ
-
LAM)

Solution ?

High Pressure Phase Transformation (HPPT
)

SiC

HPPT is one of the process mechanisms involved in ductile
machining of semiconductors and ceramics


addresses

roadblocks

in

major

market

areas

(
such

as

precision

machining

of

advanced

materials

and

products)


uses

a

laser

as

a

heating

source

to

thermally

soften

nominally

hard

and

brittle

materials

(such

as

ceramics

and

semiconductors)


represents

a

new

advanced

manufacturing

technology

with

applications

to

the

many

industries,

including


Automotive


Aerospace


Medical

Devices


Semiconductors

and

Optics

Micro
-
Laser Assisted Machining (µ
-
LAM)


The

objective

of

the

current

study

is

to

determine

the

effect

of

temperature

and

pressure

in

the

micro
-
laser

assisted

machining

of

the

single

crystal

4
H
-
SiC

semiconductors

using

scratch

tests
.


Objective



The

scratch

tests

examine

the

effect

of

temperature

in

thermal

softening

of

the

high

pressure

phases

formed

under

the

diamond

tip,

and

also

evaluate

the

difference

with

and

without

irradiation

of

the

laser

beam

at

a

constant

loading

and

cutting

speed
.





The

laser

heating

effect

is

verified

by

atomic

force

and

optical

microscopy

measurements

of

the

laser

heated

scratch

grooves
.


Scratch

T
ests

Experimental Procedure



Laser



Furukawa

1480
nm

400
mW

IR

fiber

laser

with

a

Gaussian

profile

and

beam

diameter

of

10
μm
.



Tool



90


conical

single

crystal

diamond

tip

with

5
μm

radius

spherical

end
.



Workpiece



single

crystal

4
H
-
SiC

wafers

provided

by

Cree

Inc
.


NOTE:

The primary flat is the {1010} plane with the flat face parallel to the <1120>
direction. The primary flat is oriented such that the chord is parallel with a specified
low index crystal plane. The cutting direction is along the <1010> direction.

Diamond Tip Attachment

Diamond tip

(5

m radius)

Ferrule

(2.5mm diameter)


(a)
5 µ
m

RADIUS DIAMOND TIP

ATTACHED ON THE END OF THE

FERRULE USING EPOXY

(b)
CLOSE UP ON DIAMOND TIP EMBEDDED IN THE SOLIDIFIED EPOXY
.


(b)

(
a
)

Laser output power measurements with and without the diamond tip attached.

Total Power coming out of the tip : 43%


Total Power Calibration

Laser Beam Profile

2
-
D

2
-
D

3
-
D

B
efore attachment of the diamond tip

After
attachment of the diamond tip

T
he laser driving current is 580mA

(~75mW)


T
he laser driving current is
214
mA

(~60mW)


Out of focus

On focus

On focus

Experimental Setup of µ
-
LAM System

Design of Experiments

Scratch

No.

Loading

g (
mN
)

Machining
Condition

Cutting

speed

(µm/sec)

Laser
Power
(mW)

1*

2.5 (25)

w/o laser

305*

0

2*

2.5 (25)

w/ laser

305*

350

3

2.5 (25)

w/o laser

1

0

4

2.5 (25)

w/ laser

1

350

*Experiments performed previously by Dong and Patten (2005).

SPECIFICATIONS OF THE SCRATCHES

Results and Discussion



AFM

measurements

have

been

used

to

measure

the

groove

size

and

to

study

the

laser

heating

effect

of

the

scratches

made

on

4
H
-
SiC
.

AFM

IMAGE

OF

THE

SCRATCH

#
3


NO LASER HEATING

AFM IMAGE OF THE SCRATCH #4

W/ LASER HEATING

Results and Discussion Cont’d

Scratch #

Machining
Condition

Cutting

speed

(µm/sec)

Average
Groove
Depth
(nm)

Relative
Hardness

(
GPa
)

1*

w/o laser

305*

41

39

2*

w/ laser

305*

46

35

3

w/o laser

1

54

30

4

w/ laser

1

90

18

AVERAGE GROOVE DEPTHS MEASURED WITH AFM

Thr ust For ce = 25
mN

*Experiments performed previously by Dong and Patten (2005).

Results and Discussion Cont’d


AVERAGE GROOVE DEPTH MEASURED WITH AFM IN (nm) WITH
2 DIFFERENT CUTTING SPEEDS , W/LASER AND W/O LASER

Mechanical Energy and Heat

0
5
10
15
20
25
30
25
700
3200
27.3

8

0

0

0.16

0.9

Energy (
nW
)

Temperature (
°
C)

Mechanical
Work
Heat
µ
-
LAM System

Laser
Head

UMT
Tribometer

Laser
Cable
and BDO

Diamond
Cutting
Tool

UMT
Computer

Diamond Tools In
μ
-
LAM

Chardon
Diamond
Tool

K&Y Diamond Tool

WMU Diamond
Tool

Conclusion




Laser

heating

was

successfully

demonstrated

as

evidenced

by

the

significant

increase

in

groove

depth

(from

54

nm

to

90

nm),

i
.
e
.
,

reduced

relative

hardness

~
40
%
,

indicative

of

enhanced

thermal

softening

~
700
°
C
.





AFM

measurements

of

the

laser
-
heat

assisted

scratch

grooves

show

deeper

and

wider

grooves

compared

to

scratches

made

without

the

laser

heating

assisted

methods
;

which

indicates

favorable

thermal

softening

effects

~
700
°
C
.



Acknowledgement


Dr
.

Valery

Bliznyuk

and

James

Atkinson

from

PCI

Department


Kamlesh

Suthar

from

MAE

Department


Support

from

NSF

(CMMI
-
0757339
)


Support

from

MUCI


Hardness
-
Temperature, 6H
-
SiC

0
5
10
15
20
25
30
20
300
400
500
600
700
800
990
1100
1300
1500
1580
Hardness (GPa)

Temperature (


C)

Hardness (GPa)
Hardness
-

Temperature

RELATIVE HARDNESS OF THE 90
nm

AND 95
nm

DEEP SCRATCHES
w
/LASER AND
w/o LASER

CUTTI NG SPEED = 1
µm/sec

Scratch

Depth

(nm)

Machining Condition

Thrust Force

(
mN
)

Relative Hardness

(
GPa
)

90

w/laser

25

18

95

w/o laser

70

62