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IMEC - INTECDepartment of Information Technologyhttp://www.intec.ugent.be
WAVEGUIDES IN BOARDS WAVEGUIDES IN BOARDS
BASED ONBASED ON ORMOCER ORMOCERs s [email protected]
INTEC - Department of Information Technology
OutlineOutline
Introduction ORMOCERs Laser ablation Waveguides Deflecting optics Coupling structure Conclusion
INTEC - Department of Information Technology
IntroductionIntroduction
Integration of optical interconnects on board level Approaches
Fiber based Waveguide based
glass sheet polymers
http://www.circuitree.comPrinted Optical Waveguides: The Next Interconnect (H.Holden)
INTEC - Department of Information Technology
ORMOCERORMOCERss
ORganic Modified CERamics Fraunhofer Institute - Germany Inorganic-Organic Hybrid Polymers Applications
microoptical elements (lenses, lens arrays, gratings, prisms) vertical integration: stacked optical waveguides (wafer scale) board level optical interconnects
General properties Compatibility with PCB manufacturing
lamination 180°C 200 Pascals assembly (solder reflow) up to 250°C
Good planarisation properties RMS roughness 2 - 4 nm Long-term stability under variable environmental conditions
(humidity, temperature) Low shrinkage
INTEC - Department of Information Technology
ORMOCERORMOCERss
Optical properties (www.microresist.de)
Refractive index @ 830 nm (adjustable) CORE 1.5475 CLADDING 1.5306
Attenuation
Waveguides Photolithography Laser ablation
INTEC - Department of Information Technology
ORMOCERORMOCERss
Application scheme
applicationspin-coating
softbake80-120 °C, <5 min
flood exposure
post exposure bake80-120 °C, <5 min
developmentcuring120-240 °C, up to 3 hrs
laser ablation
exposure
curing120-240 °C, up to 3 hrs
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Laser ablationLaser ablation Set-up
KrF Excimer Laser(can be tilted)248 nm
Frequency tripledNd-YAG Laser355 nm
CO2 Laser
9.6 m
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WaveguidesWaveguides UV-Defined
Cross section: 20 x 20 μm2 waveguides (250 μm pitch)
Laser-ablated Compatible with standard electrical PCB manufacturing (microvia’s) Adapt the pattern as a function of distortion in the substrate (FR4) Rapid prototyping Define microstructures and microoptics on a top surface of a
heterogeneous optoelectronic module in a very late phase of the assembly process
Entire optical interconnection using one technology
OPTICAL LAYERS
COPPER
FR4
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WaveguidesWaveguides Laser-ablated
Laser beam moves over surface Technology sequence
bottom cladding layer core layer laser ablation microstructuring upper cladding layer
Experimental results KrF Excimer laser (248 nm)
50 x 50 μm2
trapezoidal shape low ablation speed roughness to high
1st ablation
2nd ablation
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WaveguidesWaveguides Frequency tripled Nd-YAG laser (355 nm)
50 x 50 μm2
clean surfaces ablation speed: 1 mm/s
photo-dissociation photo-thermal ablation
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Deflecting opticsDeflecting optics
45 micromirrors micro machining techniques (90 V-shaped diamond blade)
excellent cut surface difficult to cut individual waveguides on the same substrate
(physical size of the machining tool)
remove waveguide film from substrate
cutting from back-side
diamond blade
claddingcorecladding
substrate
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Deflecting opticsDeflecting optics 45 micromirrors
reactive ion etching RIE (45 oblique etching) limited by directional freedom different process steps
temperature controlled RIE (90 RIE + heat treatment) not limited by directional freedom material dependent
laser ablation set-up: excimer laser beam can be tilted
– Total Internal Reflection (TIR) negative facet
– coated mirror (Al, Au)positive facet
RIE
Al maskcladdingcorecladding
substrate
TIR condition crucial glue (mounting lens plate) humidity
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Deflecting opticsDeflecting optics Total Internal Reflection
Smooth surface Tapering compensated Flatness of the mirror at core layer
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Coupling structureCoupling structure Example: MT-compatible coupling
Microlenses and 700 m holes ablated in a polycarbonate (PC) plate (Kris Naessens, Ph.D. thesis Ghent University)
Alignment: ribbon - lenses: 700 m pins match holes in PC plate
Alignment: micromirror - lenses: flip chip set-up (alignment marks)
Lenses ablated in upper-cladding layer Visual alignment under ablation set-up
with respect to 45 micromirror
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ConclusionConclusion
Integration of optical interconnects on board level polymer waveguides
Compatibility with the manufacturing and assembly processes of the conventional electrical board technology ORMOCERs Laser ablation
Entire optical interconnection using one technology Waveguides Micromirrors Microlenses Alignment features
SEM pictures show very smooth surfaces
