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Miniaturised Hermetic Packages in Glass and Sapphire Mark Fretz
Swissphotonics Workshop
Alpnach, 16.05.2017
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 1
Outline What’s in the package?
• Challenges in miniaturized packaging
• State-of-the-art package sealing
• CSEM approach
• Laser assisted bonding
• Examples
• Hermeticity testing
• Volume production
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 2
Challenges in Miniaturized Packaging
• Transparency for RF and visible light and Laser assisted
bonding
• Limited number of materials which comply with
above requirements and are suitable for harsh
environments (e.g. space or implants)
• Solution
• Sapphire & glasses
• Laser assisted diffusion bonding
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 3
Challenges in Miniaturized Packaging
• Bonding of miniaturised packages
• New bonding materials for harsh environments
and medical applications have high melting
points (Pt, Ti, Pd, Au)
• Lid brazing or soldering of these materials
generates excessive heat
• Solution
• (Localised heat) + (bonding below melting point)
• (Laser assisted) (diffusion bonding)
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 4
Challenges in Miniaturized Packaging
• Stresses
• High temperature brazing or soldering lead to
stresses in the package
• Solution
• Localised heat keeps the package cool
• Diffusion bonding generates lower stresses at the
interface)
(Laser assisted) (diffusion bonding)
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 5
Challenges in Miniaturized Packaging
• Hermeticity Testing
• Small packages require lower leak rates down to 6*10-15 atm.cc/s(1)
• Current best helium leak rate detection: 5*10-12 atm.cc/s(1)
• New Approach
• Fourier transform infrared spectroscopy (FTIR)
(1)G. Jiang, D.D. Zhou, Implantable Neural Prostheses 2, Chapter 2: Technology Advances and Challenges in Hermetic Packaging for
Implantable Medical Devices, Springer, 1st Edition
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 6
State-of-the-Art Package Sealing
• Glass frit bonding
• High temperature bonding, not biocompatible
• Laser assisted soldering
• High temperature, not biocompatible
• Laser welding /Resistance welding
• Very high temperatures, not biocompatible
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 7
CSEM Approach: Laser Assisted Diffusion Bonding
Proper metallisation
Good surface roughness
Transparent lid
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 8
CSEM Approach: Laser Assisted Bonding: Examples
Cochlear Implant
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 9
CSEM Approach: Laser Assisted Bonding: Examples
Implantable pressure sensor
4 mm
Sapphire package
Commercial pressure sensor
LADB seal
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 10
CSEM Approach: Non Destructive FTIR Leak Testing
• Bombing with N2O high pressure
• 2 to 5 bars
• Not present in ambient
atmosphere (low background)
• Peaks at wavenumber 2237 & 2212
cm-1
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 11
CSEM Approach: Non Destructive FTIR Leak Testing
• Detection depends mainly on
• Concentration of N2O
• Duration of bombing
• Bombing pressure
• Length of light path through the package
• Detector sensitivity/resolution
1E-13
1E-12
1E-11
0 20 40 60
Det
ecti
on
lim
it
(atm
cm
3s-1
)
Bombing time (day)
3.6 mm3
1.4 mm3
1E-6
1E-5
1E-4
0 1 2 3 4 5 6 7 8
Larg
est
le
ak
ra
te(a
tm c
m3
s-1)
Cell volume (mm3)
30 min
10 min
3 min
2 bar bombing pressure
Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 12
CSEM Approach: Volume Production
• Array level tested successfully
• Glass on silicon
• Chip size: 3.350 x 2.0 mm
• Array size : 13.4mm x 8.0mm
• Overall time for the array is 48 seconds
• Estimated on 200mm wafer: 75mins (~4’000 parts 1 sec/part)
• Estimated for 100mm wafer: 15 minutes (~1’000 parts)
• Further reduction by a factor of 4 seems feasible with further optimisation