Post on 16-Apr-2018
1
Structured wire in
multi-crystalline silicon
wafer mass production:
An efficient alternative to
diamond wire
Oliver Anspach
PV Crystalox Solar Silicon
GmbH, Germany
5th Annual c-Si PVMC
workshop
at Intersolar NA -
Wednesday July 13, 2016
2 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
England
Ingot / Block
Production
in Oxfordshire
Germany
Wafer
Production
in Erfurt
Clear focus on the crystalline silicon wafer technology
Independent Si-wafer manufacturer with European content and
low carbon foot-print
3 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
$0,50
$0,55
$0,60
$0,65
$0,70
$0,75
$0,80
$0,85
$0,90
$0,95
$1,00
Aug-12 Mar-13 Oct-13 Apr-14 Nov-14 May-15 Dec-15 Jun-16
Wafer price 2012 - 2016
Motivation
Average spot market price for
156 mm Multi-Si Solar Wafer
1) Source: PVinsights.com
1)
Wafer price 2011 - 2013
4 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Challenges in Wafering
Thinner wires
Thinner wafers
Higher throuhput
Less consumables
Fixed Abrasives Diamond wire
Loose Abrasives Structured wire
Higher yield
Higher precision
Less breakage
• Only coolant needed – no loose abrasives
necessary
• High cutting speeds
• Wafer surface structure / breakage / texture
• New wire saws mandatory
• Differences in cutting of mono- or multi-Si
• Conventional slurry / wire system
• Higher cutting speeds / less wire
• Less slurry
• Less kerf loss
• Conventional wire saws
2) D. Heppner et al.; AMAT; 26th EUPVSEC, Hamburg, 2011.
2)
5 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire
Wafering Squaring
6 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire
Patents
Charles Hauser, 1990, WO 90/12670
„wire with active surface“
NV Bekaert S.A., 1999, WO 99/28547
„wire with waved elements“
NV Bekaert S.A., 2012,
WO 2012/069314
„structured wire with
helicoidal shape“
Sodetal, 2013,
WO 2013/076400
„twisted wire with a helix“
Trefilarbed (Arcelor), HCT Shaping
Systems (AMAT), 2006,
WO 2006/067062
„monofilament metal wire with crimps“
7 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Progress in wafer mass production using structured wire
121%
273%
0%
50%
100%
150%
200%
250%
300%
mo
nth
01
mon
th 0
2
mon
th 0
3
mo
nth
04
mon
th 0
5
mon
th 0
6
mo
nth
07
mon
th 0
8
mon
th 0
9
mon
th 1
0
mon
th 1
1
mon
th 1
2
mon
th 1
3
tod
ay
R&
D
table speed
Structured wire
production process:
• More than 150 % higher
throughput possible
• Similar throughput to
diamond wire process
possible
Vertical force
Diamond wire
process table
speed range
Straight wire process = 100 %
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
3)
8 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Progress in wafer mass production using structured wire
Structured wire
production process:
• More than 150 % higher
throughput possible
• More than 50 % less wire
consumption possible
Vertical force
121%
273%
84% 46%
0%
50%
100%
150%
200%
250%
300%
mo
nth
01
mon
th 0
2
mon
th 0
3
mo
nth
04
mon
th 0
5
mon
th 0
6
mo
nth
07
mon
th 0
8
mon
th 0
9
mon
th 1
0
mon
th 1
1
mon
th 1
2
mon
th 1
3
tod
ay
R&
D
table speed
wire consumption
Straight wire process = 100 %
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
3)
9 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
The faster the cutting process the less power is needed!
0
100
200
300
400
500
600
Su
m p
ow
er
co
nsu
mp
tio
n [
kW
h]
time
straight wire process
structured wireprocess
Structured wire
production process:
• More than 150 % higher
throughput possible
• More than 50 % less wire
consumption possible
• Less power consumption
needed (3rd main cost
driver)
10 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Progress in wafer mass production using structured wire
121%
273%
39%
84% 46%
0%
50%
100%
150%
200%
250%
300%
mo
nth
01
mon
th 0
2
mon
th 0
3
mo
nth
04
mon
th 0
5
mon
th 0
6
mo
nth
07
mon
th 0
8
mon
th 0
9
mon
th 1
0
mon
th 1
1
mon
th 1
2
mon
th 1
3
tod
ay
R&
D
table speed
slurry consumption
wire consumption
Structured wire
production process:
• More than 150 % higher
throughput possible
• More than 50 % less wire
consumption possible
• Less power consumption
• More than 50 % less
slurry consumption
possible
Roughness
0,0
0,5
0 50 100 150 200 250
Ra
[µ
m]
distance from wire entry [mm]
straight wirestructured wire
Straight wire process = 100 %
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
3)
11 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Structured wire does not use small particles for cutting!
0,0
0,5
0 50 100 150 200 250
Ra [
µm
]
distance from wire entry [mm]
straight wirestructured wire
Roughness
0
0,2
0,4
0,6
0,8
1
0,1 1 10 100Freq
uen
cy d
istr
ibu
tio
n
Geometric particle diameter in µm
SiC-particlesSi-particlessum
wire
large particles
cut at the
wire entry
small particles
cut at the
wire exit
Particle size
entry both
wires
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
4) Anspach et al., Proceedings of the 24th EUPVSEC (2009).
3)
4)
12 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Structured wire does not use small particles for cutting!
0,0
0,5
0 50 100 150 200 250
Ra [
µm
]
distance from wire entry [mm]
straight wirestructured wire
Roughness
wire
large particles
cut at the
wire entry
small particles
cut at the
wire exit
Particle size classifi-
cation straight wire
Particle size
entry both
wires
0
0,2
0,4
0,6
0,8
1
0,1 1 10 100Freq
uen
cy d
istr
ibu
tio
n
Geometric particle diameter in µm
SiC-particlesSi-particlessum
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
3)
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
4) Anspach et al., Proceedings of the 24th EUPVSEC (2009).
4)
13 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Structured wire does not use small particles for cutting!
0,0
0,5
0 50 100 150 200 250
Ra [
µm
]
distance from wire entry [mm]
straight wirestructured wire
Roughness
wire
large particles
cut at the
wire entry
small particles
cut at the
wire exit
Particle size classifi-
cation straight wire
Particle size
entry both
wires
Particle size class.
structured wire
0
0,2
0,4
0,6
0,8
1
0,1 1 10 100Freq
uen
cy d
istr
ibu
tio
n
Geometric particle diameter in µm
SiC-particlesSi-particlessum
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
4) Anspach et al., Proceedings of the 24th EUPVSEC (2009).
3)
4)
14 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Structured wire does not use small particles for cutting!
0,0
0,5
0 50 100 150 200 250
Ra [
µm
]
distance from wire entry [mm]
straight wirestructured wire
Roughness
wire
large particles
cut at the
wire entry
small particles
cut at the
wire exit
Particle size classifi-
cation straight wire
Particle size
entry both
wires
Particle size class.
structured wire
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
4) Anspach et al., Proceedings of the 24th EUPVSEC (2009).
3)
4)
15 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
What about higher kerf loss with structured wire? Kerf loss
140
145
150
155
160
165
170
0 100 200
Slo
t w
idth
[µ
m]
structrured wire entry structured wire exit
straight wire entry straight wire exit
• In 2012 standard 120 µm straight wire
• 900 mm block length with 345 µm pitch
• Introduction of 115 µm structured wire
120
125
130
135
140
145
150
155
160
0 1000 2000
calc
. kerf
lo
ss [
µm
]
corresponding wafer #
pitch
new pitch
• 200 µm thin wafers
• New median pitch 4 µm
less than standard
• Pitch correction of wire
guiding rollers possible
today
3) Anspach et al., Solar Energy Materials & Solar Cells 131 (2014) 58–63.
3)
16 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Why such a decrease of more than 20 µm kerf loss?
• Straight wire showed around 5 µm diameter loss due to wire wear
• Structured wire kerf loss is defined by a combination of:
Fresh wire Used wire 0°
Used wire 90 °
Wire wear
• Non-uniform
wire wear
• Brass coating
partly evident
• 0 - >20 µm
diameter loss
17 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Why such a decrease of more than 20 µm kerf loss?
Straight wire showed around 5 µm diameter loss due to wire wear
Structured wire kerf loss is defined by a combination of:
Wire wear
• Non-uniform
wire wear
• Brass coating
partly evident
• 0 - >20 µm
diameter loss
Structure
amplitude
• Manufacturer
defines
amplitude
• Structure
(effective
amplitude)
looses with
increasing
wire wear
• Structure
stiffness
+
18 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Why such a decrease of more than 20 µm kerf loss?
• Straight wire showed around 5 µm diameter loss due to wire wear
• Structured wire kerf loss is defined by a combination of:
Wire wear
• Non-uniform
wire wear
• Brass coating
partly evident
• 0 - >20 µm
diameter loss
Structure
amplitude
• Manufacturer
defines
amplitude
• Structure
(effective
amplitude)
looses with
increasing
wire wear
• Structure
stiffness
Wire tension
• Wire tension
defines
effective
amplitude
• Loss of wire
tension in wire
web + +
0 µm
2 µm
4 µm
6 µm
8 µm
10 µm
12 µm
14 µm
16 µm
18 µm
20 µm
0 N 10 N 20 N
Eff
ec
tive
am
pli
tud
e
19 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
Why such a decrease of more than 20 µm kerf loss?
• Straight wire showed around 5 µm diameter loss due to wire wear
• Structured wire kerf loss is defined by a combination of:
Wire wear
• Non-uniform
wire wear
• Brass coating
partly evident
• 0 - >20 µm
diameter loss
Structure
amplitude
• Manufacturer
defines
amplitude
• Structure
(effective
amplitude)
looses with
increasing
wire wear
• Structure
stiffness
Wire tension
• Wire tension
defines
effective
amplitude
• Loss of wire
tension in wire
web
Speed ratio
• The higher the
speed ratio …
• … the higher
wire wear
• … the higher
wire tension
• … the less
effective
amplitude
+ + +
20 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – wafer mass production
High table to wire speed ratios cause loss of effective amplitude!
182
184
186
188
190
192
194
196
0 20 40 60
Cen
ter
wafe
r th
ickn
ess [
µm
]
Speed ratio [µm/min * (m/s)-1]
21 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Structured wire – summary
Structured wire shows still high cost
reduction potential
Save cost in the short + mid term range
without invest
Still standard wire sawing equipment ready
for even thinner wires
One has to take care with the structure of
the wire
Balance between wire wear and wire tension
and effective amplitude
What is the best structure and why?
Where is the physical and economical limit
of Si load in slurry?
22 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Wafering – near term challenges (1-3 years)
Reduce cost by 15-20 % per year
Reduce wire diameter down to less than 100 µm
Find optimal and stiff structure for thin wires
< 100 µm (take state of wear into account)
Steel wire with high breaking load
Structure wire
Reduce cost by 15-20 % per year
Reduce wire diameter down to 60 µm and get it work
in mass production
Very thin steel wire with high breaking load
Diamond wire
23 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Wafering – long term challenges (4+ years)
Reduce cost by 15-20 % per year
Be aware of …
Conventional wire sawing
Show mass production capability
Show cost advantage after
development phase
Mono: Very high
performance n-type Si
needed
… New technologies
24 5th Annual c-Si PVMC workshop
July 13, San Francisco, USA
Slurry
Thank you for your attention!
wire
Si-block
Acknowledgement:
R&D + Engineering Team at PV Crystalox Solar Silicon GmbH