Miniaturised Hermetic Packages in Glass and Sapphire Mark Fretz Swissphotonics Workshop Alpnach, 16.05.2017 OutlineWhat’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 1 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 2 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 3 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 4 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 5 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 6 CSEM Approach: Laser Assisted Diffusion Bonding Transparent lid Proper metallisation Good surface roughness Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 7 CSEM Approach: Laser Assisted Bonding: Examples Cochlear Implant Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 8 CSEM Approach: Laser Assisted Bonding: Examples Implantable pressure sensor Sapphire package Commercial pressure sensor LADB seal 4 mm Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 9 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 10 CSEM Approach: Non Destructive FTIR Leak Testing 1E-11 • Detection depends mainly on 2 bar bombing pressure ) 1 - s 3 3.6 mm3 1E-12 • Concentration of N2O 1.4 mm3 (atm cm (atm • Duration of bombing limit Detection 1E-13 0 20 40 60 • Bombing pressure Bombing time (day) • Length of light path through the package 3 min 1E-4 ) 1 - s 10 min • Detector sensitivity/resolution 3 30 min 1E-5 (atm cm (atm Largest leak rate Largest 1E-6 0 1 2 3 4 5 6 7 8 Cell volume (mm3) Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 11 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 Copyright 2017 CSEM | Miniaturized Hermetic Packages in Glass and Sapphire | Mark Fretz | Page 12 .