laser transmission microjoining technology for … · 2020. 9. 3. · laser technology...
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Fraunhofer USA Center for Laser Technology
MICROMANUFACTURING 2009, APRIL 1-2, MINNEAPOLIS, MN
LASER TRANSMISSION MICROJOINING TECHNOLOGY
FOR PACKAGING OF MEMS
R. Patwa1, H. J. Herfurth1, S. Heinemann1, Golam Newaz2
1 Fraunhofer USA, Center for Laser Technology, 46025 Port Street, Plymouth, MI 48170, USA
2 Wayne State University, Detroit, MI 48232, USA
Fraunhofer USA Center for Laser Technology
Outline
• Introduction - Fraunhofer CLT
• Laser Transmission Microjoining Applications
• Joining Dissimilar Materials
• Results
• Process Characterization
• Joining Similar Materials
• Conclusions
Fraunhofer USA Center for Laser Technology
Key Competencies at Fraunhofer CLT
Unbiased Applied R&D in:
Process Development
(from Chips to Ships)
Consulting to Production Validation
Special Optics
Engineering of Advanced Lasers
- Diode Lasers
- Fiber Lasers
Unique Turn-Key Systems
Fraunhofer USA Center for Laser Technology
Outline
• Introduction - Fraunhofer CLT
• Laser Transmission Microjoining Applications
• Joining Dissimilar Materials
• Results
• Process Characterization
• Joining Similar Materials
• Conclusions
Fraunhofer USA Center for Laser Technology
Biomedical Applications
Cochlear Implant to
restore partial hearing
Challenges
• Hermetic sealing
• Localized bonding
• Long term stability
• Biocompatibility
Next-generation retinal
prosthesis Source: California
Institute of Technology
Source: Advanced
Bionics, Corp. Housing of MEMS /
Hermetic sealing
Glass MEMS Device
Silicon base
Fraunhofer USA Center for Laser Technology
Laser Transmission Joining Principle
During laser transmission microjoining process -
The laser radiation is transmitted through the partially transparent top material.
It is absorbed at the surface of the bottom material.
The laser radiation is converted into heat energy directly at the interface.
Schematic of sample in fixture Schematic of the sample undergoing
the bonding process
Fraunhofer USA Center for Laser Technology
Different Joining Methods
Quasi-simultaneous Mask Simultaneous
Fraunhofer USA Center for Laser Technology
Basic Joint Designs
laser beam
transparent
material
absorbing
transparent
material
absorbing
material
laser beam
laser beam
transparent
material
absorbing
material
laser beam
material
transparent
material
absorbing
material
Fraunhofer USA Center for Laser Technology
Laser Transmission Joining Setup
Laser Sources
cw Yb- doped fiber laser (JDSU)
• Wavelength : 1110 nm
• Maximum Power : 25 W
• Fiber Size : 9 µm
cw Diode laser (Fraunhofer)
• Wavelength : 808 nm
• Maximum Power : 27 W
• Fiber Size : 800 µm
cw Nd:YAG laser (Trumpf)
• Wavelength : 1064 nm
• Maximum Power : 1000 W
• Fiber Size : 600 µm
Sample
Laser
optic
Fixture
Fraunhofer USA Center for Laser Technology
Material Combination Matrix
Imid
ex®
Teflo
n®
PE
BA
X®
PV
DF
Poly
ure
thane
PE
EK
Boro
silic
ate
gla
ss
PA
PM
MA
Nitinol X X
Chromium coating X X
Stainless steel X X X
Titanium X X X
Silicon X
Titanium coated glass
X X X
ABS X
PA X
Absorbing
Transparent
Metal - Polymer Ceramic – Metal/Ceramic Polymer - Polymer
Fraunhofer USA Center for Laser Technology
Optical Properties of Materials
0
1
2
3
4
5
6
7
8
0 2 4 6 8
Applied Laser Power (W)
Me
as
ure
d L
as
er
Po
we
r (W
)
Cover glass + Imidex
Cover glass + PEEK
No Cover glass & NoPolymer
Transmissivity of Imidex with cover glass = 79.8 %
Transmissivity of PEEK with cover glass = 80.9 %
Absorption (),
Transmission (∆)
Polymer
Silicon
Glass
Fraunhofer USA Center for Laser Technology
Process Optimization
Metal-Polymer
Process parameter window is determined to optimize bond formation process.
25
30
35
40
45
50 150 250 350 450 550
Speed [mm/min]
La
ser
po
we
r [W
]
good bond
no bond
temporarily bonded
partially melted
completely melted
Glass-Silicon
0
2
4
6
8
10
12
10 100 1000 10000 100000
(Log) Speed (mm/min)
Laser
Pow
er
(W)
--
no effect
Imidex changes color
Weak Bond
Bond
Strong Bond
Very Strong Bond
Burned
Fraunhofer USA Center for Laser Technology
Outline
• Introduction - Fraunhofer CLT
• Laser Transmission Microjoining Applications
• Joining Dissimilar Materials
• Results
• Process Characterization
• Joining Similar Materials
• Conclusions
Fraunhofer USA Center for Laser Technology
Metal-Polymer Bonding
View
As is bond surface
top view
Titanium - Imidex
Titanium - PVDF
Chromium - PEEK
Nitinol - PEEK
Nitinol - Imidex
Chromium - Imidex Titanium - Polyurethane
Fraunhofer USA Center for Laser Technology
Metal-Polymer Bonding
Titanium coated glass/
Imidex bond
Bond line
Stainless steel/PEBAX
bond
Fraunhofer USA Center for Laser Technology
Material – Silicon (Top) , Borosilicate Glass (Bottom)
Nd:YAG laser
35 W, 200 mm/min
Diode laser
30 W, 60 mm/min
Fiber laser
Spot Bond
Silicon-Glass Joining
Fraunhofer USA Center for Laser Technology
Temperature Control for Plastic Welding
0 50 100 0
5
10
15
20
25
distance [ mm ]
laser
pow
er
[ W
]
0
100
200
300
400
500
600
tem
pera
ture
[°C]
0 50 100 0
5
10
15
20
25
distance [ mm ]
Laser
pow
er
[ W
]
0
100
200
300
400
500
600
tem
pera
ture
[°C]
Diode laser; 5 m/min
signal processor
temperature
detector
laser beam
focussing
lens
focussing
lens
workpiece
filter
laser power
detector
optical fibre
T
TL
L
L
temperature
radiation
Custom optic for
temperature control
Fraunhofer USA Center for Laser Technology
Joint Characterization – Failure Load Limit
0
1000
2000
3000
4000
5000
6000
0 0.2 0.4 0.6 0.8 1
Displacement (mm)
Lo
ad
(g
ram
s)
Nitinol/Imidex
Chromium/Imidex
Chromium/PEEK
Nitinol/PEEK
Titanium/Imidex
Polymer-Polymer Metal-Polymer
400
600
800
1000
1200
1400
0.0 1.0 2.0 3.0 4.0
Speed (m/min)
Failu
re L
oad
(N
)
Thickness - 3.1mm
Thickness - 2.4mm
Thickness - 1.9mm
Fraunhofer USA Center for Laser Technology
Joint Characterization – Shear Pull Strength
0
5
10
15
20
3 4 5 6 7 8 9 10
Laser Power (W)
Pu
ll S
tre
ng
th (
N/m
m2
)
Nitinol/PEEK
0
5
10
15
Niti
nol/I
mid
ex
Niti
nol/P
EEK
Chr
omiu
m/P
EEK
Chr
omiu
m/Im
idex
Titani
um/Im
idex
Ma
xim
um
Pu
ll S
tre
ng
th (
N/m
m2
)
Metal-Polymer
Fraunhofer USA Center for Laser Technology
Joint Characterization –Degradation in Cerebrospinal fluid (CSF)
Material combination:
Glass: Pyrex 7740 Ti-coated
Imidex: 0.177 mm thick
Laser: Fiber laser
Average failure load as bonded: 21.5 N/mm2
0
5
10
15
20
25
0 2 4 6 8 10 12 14
Weeks in CSF Solution at 37 oC
Fa
ilu
re L
oa
d (
N/m
m2)
Fraunhofer USA Center for Laser Technology
Joint Characterization – Pressure Testing
Sample
Titanium: 3 mm x 5 mm; hole diameter = 1 mm
Imidex: O. D. 2 mm
Pressure test setup Result
Burst pressure: 80 bar
Tensile strength: 8 N/mm2
Fraunhofer USA Center for Laser Technology
Helium detector/
Mass
spectrometer
Helium
Vacuum
Laser Bond
Laser: Fiber laser
Power: 4.2 W
Speed: 100 mm/min
Polyimide to Titanium
Substrate: 2.6 x 10-6 Std. cc/sec/cm2
Bond: 3.4 x 10-6 Std. cc/sec/cm2
Leak rate slightly higher
Joint Characterization – He-Leak Testing
Fraunhofer USA Center for Laser Technology
Joint Characterization – SEM Analysis
Fraunhofer USA Center for Laser Technology
Joint Characterization –XPS Analysis
Titanium Surface
Ti2p lines
XPS Signal
Collection Area
Material combination:
Imidex/Titanium Bond
Lines
C1S lines
Fraunhofer USA Center for Laser Technology
Competing Technologies
• Laser Micro-joining
Advantages
- Highly localized
- Precise bond lines
- Heat affected zone (HAZ) confined to very small volume of material
- Encapsulation design flexibility
- Non-contact process
• Ultrasonic Welding
Advantages
- Lower initial equipment cost
• Adhesive Bonding
Advantages
- Good for area bonds
Fraunhofer USA Center for Laser Technology
Outline
• Introduction - Fraunhofer CLT
• Laser Transmission Microjoining Applications
• Joining Dissimilar Materials
• Results
• Process Characterization
• Joining Similar Materials
• Conclusions
Fraunhofer USA Center for Laser Technology
Butt Joint (33 W, 100 mm/min) Cross-section
Material: Glass wafer
(Pyrex 7740)
Thickness: 0.5 mm
Laser: Pulsed CO2
(Rofin SC x10)
Power: 65 W
Speed: >25.0 m/min
Multiple scans
Glass-to-Glass Welding
Fraunhofer USA Center for Laser Technology
T - Joint Fillet Edge Joint
0.25 mm
0.25 mm
Fillet Edge Joint
Cross-section Cross-section
Glass-to-Glass Welding
Fraunhofer USA Center for Laser Technology
Conclusions
• Laser transmission microjoining of similar and dissimilar material
combinations has been successfully achieved.
• The results demonstrate the similarities and differences between the different
material systems and underscored the importance of laser microjoining
technology for such applications.
• This study provides a database of novel joining combinations that can be
commercialized for industrial applications.
• This technology clearly exhibits a high potential for laser joining processes to
address the increasing demand for packaging applications.
Fraunhofer USA Center for Laser Technology
Thank you for your attention!
CONTACT-
Rahul Patwa
rpatwa@clt.fraunhofer .com
www.clt.fraunhofer.com
Fraunhofer Center for Laser Technology
46025 Port Street
Plymouth, Michigan 48170
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