Laser transmission microjoining technology for

Laser transmission microjoining technology for

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
Next-generation retinal
prosthesis
Source: California
Institute of Technology
Glass
Source: Advanced
Bionics, Corp.
•
•
•
•
Challenges
Hermetic sealing
Localized bonding
Long term stability
Biocompatibility
Cochlear Implant to
restore partial hearing
Fraunhofer USA
Center for
Laser Technology
MEMS
Device
Silicon base
Housing of MEMS /
Hermetic sealing
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 the sample undergoing
the bonding process
Fraunhofer USA
Center for
Laser Technology
Schematic of sample in fixture
Different Joining Methods
Simultaneous
Quasi-simultaneous
Fraunhofer USA
Center for
Laser Technology
Mask
Basic Joint Designs
laser beam
laser beam
transparent
material
transparent
material
absorbing
material
absorbing
material
laser beam
transparent
material
laser beam
transparent
material
absorbing
material
Fraunhofer USA
Center for
Laser Technology
absorbing
material
Laser Transmission Joining Setup
Laser Sources
cw Yb- doped fiber laser (JDSU)
• Wavelength
• Maximum Power
• Fiber Size
: 1110 nm
: 25 W
: 9 µm
Laser
optic
cw Diode laser (Fraunhofer)
• Wavelength
• Maximum Power
• Fiber Size
Sample
: 808 nm
: 27 W
: 800 µm
Fixture
cw Nd:YAG laser (Trumpf)
• Wavelength
: 1064 nm
• Maximum Power : 1000 W
• Fiber Size
: 600 µm
Fraunhofer USA
Center for
Laser Technology
Material Combination Matrix
X
Chromium coating
X
X
Stainless steel
X
Titanium
X
X
X
PMMA
X
PA
Nitinol
Borosilicate
glass
PEEK
Polyurethane
PVDF
PEBAX®
Teflon®
Absorbing
Imidex®
Transparent
X
X
Silicon
X
Titanium coated
glass
X
X
X
ABS
X
PA
X
Metal - Polymer
Fraunhofer USA
Ceramic – Metal/Ceramic
Center for
Laser Technology
Polymer - Polymer
Optical Properties of Materials
Glass
Polymer
8
Measured Laser Power (W)
Cover glass + Imidex
7
Cover glass + PEEK
6
No Cover glass & No
Polymer
5
4
3
Absorption (),
2
1
Transmissivity of Imidex with cover glass = 79.8 %
Transmissivity of PEEK with cover glass = 80.9 %
0
0
2
4
6
Silicon
8
Applied Laser Power (W)
Transmission (∆)
Fraunhofer USA
Center for
Laser Technology
Process Optimization
Process parameter window is determined to optimize bond formation process.
Metal-Polymer
Glass-Silicon
12
45
8
6
no effect
Imidex changes color
Weak Bond
4
Bond
Laser power [W]
Laser Power (W) --
10
40
35
good bond
no bond
30
temporarily bonded
Strong Bond
2
partially melted
Very Strong Bond
completely melted
Burned
25
0
10
100
1000
10000
100000
150
250
350
450
Speed [mm/min]
(Log) Speed (mm/min)
Fraunhofer USA
50
Center for
Laser Technology
550
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
Chromium - PEEK
Titanium - Imidex
View
Nitinol - PEEK
As is bond surface
top view
Nitinol - Imidex
Titanium - PVDF
Chromium - Imidex
Fraunhofer USA
Center for
Laser Technology
Titanium - Polyurethane
Metal-Polymer Bonding
Bond line
Titanium coated glass/
Imidex bond
Fraunhofer USA
Center for
Laser Technology
Stainless steel/PEBAX
bond
Silicon-Glass Joining
Material – Silicon (Top) , Borosilicate Glass (Bottom)
Diode laser
30 W, 60 mm/min
Fraunhofer USA
Nd:YAG laser
35 W, 200 mm/min
Center for
Laser Technology
Fiber laser
Spot Bond
Temperature Control for Plastic Welding
25
signal processor
focussing
lens
filter
laser beam
laser power
detector
L
400
15
300
10
200
5
0
100
0
L
50
L
0
100
distance [ mm ]
25
T
focussing
lens
temperature
radiation
workpiece
Fraunhofer USA
Center for
Laser Technology
500
20
400
15
300
10
200
5
0
0
Custom optic for
temperature control
600
100
50
distance [ mm ]
Diode laser; 5 m/min
0
100
temperature [°C]
laser power [ W ]
optical fibre
Laser power [ W ]
T
500
20
temperature [°C]
temperature
detector
600
Joint Characterization – Failure Load Limit
Metal-Polymer
6000
Polymer-Polymer
1400
Nitinol/Imidex
Chromium/Imidex
5000
Chromium/PEEK
1200
Titanium/Imidex
4000
Failure Load (N)
Load (grams)
Nitinol/PEEK
3000
2000
1000
800
Thickness - 3.1mm
600
1000
Thickness - 2.4mm
Thickness - 1.9mm
0
400
0
0.2
0.4
0.6
0.8
1
1.0
2.0
Speed (m/min)
Displacement (mm)
Fraunhofer USA
0.0
Center for
Laser Technology
3.0
4.0
Joint Characterization – Shear Pull Strength
Nitinol/PEEK
Metal-Polymer
20
Maximum Pull Strength (N/mm2)
15
10
5
10
5
0
3
4
5
6
7
8
9
10
Laser Power (W)
iti
no
l/I
m
id
ex
N
iti
no
l/P
EE
C
K
hr
om
iu
m
/P
EE
C
K
hr
om
iu
m
/Im
id
ex
Ti
ta
ni
um
/Im
id
ex
0
N
Pull Strength (N/mm2)
15
Fraunhofer USA
Center for
Laser Technology
Joint Characterization –Degradation in Cerebrospinal fluid (CSF)
Material combination:
Laser:
Fiber laser
2
Failure Load (N/mm )
Glass: Pyrex 7740 Ti-coated
Imidex: 0.177 mm thick
25
20
15
10
5
0
0
2
4
6
8
10
12
14
Weeks in CSF Solution at 37 oC
Average failure load as bonded: 21.5 N/mm2
Fraunhofer USA
Center for
Laser Technology
Joint Characterization – Pressure Testing
Sample
 Titanium:
 Imidex:
3 mm x 5 mm; hole diameter = 1 mm
O. D. 2 mm
Result
Burst pressure: 80 bar
Tensile strength: 8 N/mm2
Pressure test setup
Fraunhofer USA
Center for
Laser Technology
Joint Characterization – He-Leak Testing
Polyimide to Titanium
Substrate: 2.6 x
Bond:
10-6
Std.
cc/sec/cm2
Helium
Laser Bond
3.4 x 10-6 Std. cc/sec/cm2
Leak rate slightly higher
Vacuum
Laser: Fiber laser
Power: 4.2 W
Speed: 100 mm/min
Fraunhofer USA
Center for
Laser Technology
Helium detector/
Mass
spectrometer
Joint Characterization – SEM Analysis
Fraunhofer USA
Center for
Laser Technology
Joint Characterization –XPS Analysis
Titanium Surface
Material combination:
Imidex/Titanium
Bond
Lines
XPS Signal
Collection Area
C1S lines
Fraunhofer USA
Center for
Laser Technology
Ti2p lines
Competing Technologies
•
•
Laser Micro-joining
Ultrasonic Welding
Advantages
Advantages
-
Highly localized
- Lower initial equipment cost
-
Precise bond lines
-
Heat affected zone (HAZ) confined
to very small volume of material
-
Encapsulation design flexibility
-
Non-contact process
Fraunhofer USA
Center for
Laser Technology
•
Adhesive Bonding
Advantages
- Good for area bonds
Outline
• Introduction - Fraunhofer CLT
• Laser Transmission Microjoining Applications
• Joining Dissimilar Materials
• Results
• Process Characterization
• Joining Similar Materials
• Conclusions
Fraunhofer USA
Center for
Laser Technology
Glass-to-Glass Welding
Material:
Glass wafer
(Pyrex 7740)
Thickness: 0.5 mm
Laser:
Power:
Speed:
Pulsed CO2
(Rofin SC x10)
65 W
>25.0 m/min
Multiple scans
Butt Joint (33 W, 100 mm/min)
Fraunhofer USA
Center for
Laser Technology
Cross-section
Glass-to-Glass Welding
0.25 mm
T - Joint
Fillet Edge Joint
Fillet Edge Joint
0.25 mm
Cross-section
Fraunhofer USA
Center for
Laser Technology
Cross-section
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!
CONTACTRahul Patwa
rpatwa@clt.fraunhofer .com
www.clt.fraunhofer.com
Fraunhofer Center for Laser Technology
46025 Port Street
Plymouth, Michigan 48170
Fraunhofer USA
Center for
Laser Technology