Page 1
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
High-Reliability Accelerometer and Pressure Sensor Design and Test (invited paper)
Presentation at the 4th Annual Conference on MEMS Testing and Reliability
by Tom Kwa, Meggitt Sensing Systems October 18th, 2012
The information contained in this document is considered non-technical data defined under section 120.10 of the International Traffic in Arms Regulations (ITAR) and is approved for public distribution.
Page 2
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Meggitt organization and capabilities
Page 3
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Company history and achievements in MEMS
; Endevco Laboratories founded in Los Altos, CA
First MEMS sculptured silicon diaphragm (1976)
First optimally-damped MEMS crash-test accelerometer (2007) Smallest single-chip triaxial PR accelerometer (2008)
Most survivable accelerometer (2008)
First wafer-level packaged, surface-mountable accelerometer (2004)
First and only 200,000g MEMS accelerometer (1982) First MEMS VC accelerometer with internal electronics (1984) First monolithic MEMS accelerometer for crash testing (1987)
Page 4
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Meggitt’s markets
Page 5
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Meggitt’s MEMS fab
SAN FRANCISCO
Sunnyvale, CA MEMS facility
Silicon Valley
Page 6
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Meggitt MEMS facility
! 20,000 square feet ! 3,500 square feet of Class 10,000 or better clean room
! Wafer Fabrication ! Wafer Bonding and Dicing ! Assembly & Test
Assembly & Test
Diffusion
Etch
Photo
Thin films
Page 7
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Features differentiating Meggitt’s MEMS designs
! Small die size (1-3 mm2 footprint, 0.2-1 mm height)
! Robust and reliable designs (used in mission-critical applications, e.g., fuzes and pacemakers)
! High performance (high sensitivity, resonance, over-range)
Meggitt Sensing Systems US Patented
Page 8
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Origins of device unreliability
! Mechanical − Fracture (over-load, stress concentration) − Stiction (humidity, particles) − Stress (base strain, conditioning)
! Electrical − Shorts (ESD, metal diffusion) − Opens (ESD, metal corrosion) − Drift (mobile ions, contact surface, stress relief)
Page 9
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Example 1: Pacemaker accelerometer
Page 10
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Requirements for implantable accelerometers
Critical: ! Reliability ! Low power consumption ! Small size Important: ! Sensitivity ! Transverse sensitivity ! Dynamic range ! Linearity ! Noise ! Frequency response
Page 11
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 29950 accelerometer
! Used for over 15 years in implantable heart devices without field returns ! Variable Capacitance Accelerometer ! 2.1 x 2.9 x 0.8 mm3
Page 12
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 29950 accelerometer in surface-mount package
Page 13
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 40366 wafer-level packaged, surface-mount accelerometer
Covered by US Patents 4,999,735 and
7,696,083
Page 14
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Page 15
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Over-range and anti-stiction features in Endevco® model 40366
Meggitt Sensing Systems
Meggitt Sensing Systems
Page 16
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Acceleration test 1400g (x, y and z)
Meggitt Sensing Systems
Meggitt Sensing Systems
Mechanical Fracture (over-load, stress concentration) Stiction (humidity, particles) Stress (base strain, conditioning)
Electrical Shorts (ESD, metal diffusion) Opens (ESD, metal corrosion) Drift (mobile ions, contact surface, stress relief)
Page 17
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Shock test (2300g)
Mechanical Fracture (over-load, stress concentration) Stiction (humidity, particles) Stress (base strain, conditioning)
Electrical Shorts (ESD, metal diffusion) Opens (ESD, metal corrosion) Drift (mobile ions, contact surface, stress relief)
Page 18
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Temperature cycling test (-55 to 125ºC)
Mechanical Fracture (over-load, stress concentration) Stiction (humidity, particles) Stress (base strain, conditioning)
Electrical Shorts (ESD, metal diffusion) Opens (ESD, metal corrosion) Drift (mobile ions, contact surface, stress relief)
Page 19
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Hermeticity test
Mechanical Fracture (over-load, stress concentration) Stiction (humidity, particles) Stress (base strain, conditioning)
Electrical Shorts (ESD, metal diffusion) Opens (ESD, metal corrosion) Drift (mobile ions, contact surface, stress relief)
Page 20
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Ball shear test
Page 21
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 40366 performance and physical specifications
Parameter Value
Nominal range +/-2 g
Shock limit 10,000 g
Dimensions [mm] 2.1 (W) x 2.9 (L) x 0.8 (H)
Nominal sensitivity 0.15-0.35 pF/g
Transverse sensitivity 0.5%
Frequency response -20 dB @ 1 kHz
Hermeticity <5E-8 cc/s (MIL-STD-883)
Non-destructive shear 2,000 gram
Electrical isolation >10 GΩ
Storage temperature -55 to 125ºC (minimum)
Page 22
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Example 2: Bunker-buster accelerometer
Page 23
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Requirements for accelerometers in high-shock applications
Critical: ! Reliability ! Survivability ! Minimal zero-shift after shock Important: ! Small size ! Sensitivity ! Transverse sensitivity ! Dynamic range ! Resonance modes ! Frequency response
Page 24
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® bunker-buster accelerometer
US Patented
Page 25
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Survivability enhancements in Endevco® model 72 accelerometer
! Mechanical stops prevent damage to die from high-g over-range inputs − Base and lid serve as stops (z-axis) – walls for x, y − Approximately 3 times full-scale range
! Light damping attenuates resonance to prevent damage due to ‘ringing’ − Mechanism is squeeze-film gas damping − 5% nominal (can be adjusted) − Additional benefit is preventing saturation of signal conditioning circuitry
Page 26
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 2925 Comparison Shock Calibrator for low-g shock testing
Page 27
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Shock survivability test set-up
! Testing on Hopkinson Bar ! Tested over temperature (hot and cold) ! 20,000g range unit survived to 240,000g in sensitive and cross axes
Page 28
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Endevco® model 2973A Hopkinson bar for high-g shock testing
Page 29
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Survivability test data
Page 30
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Zero-shift-after-shock results
! 20,000g (1x) sensitive axis < 30g ! 80,000g (4x) sensitive axis < 40g ! 80,000g (4x) cross axis < 40g
Page 31
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Base strain test results
Page 32
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Very-High G shock machine
Page 33
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Cannon and sled tests
http://www.youtube.com/watch?v=2_JTT3OsDJQ
Page 34
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Flight test
Page 35
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Example 3: Aircraft tire pressure sensor
Page 36
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Requirements for pressure sensors on aircraft tires
Critical: ! Reliability ! Output stability ! High-temperature survivability Important: ! Pressure over-range ! Acceleration sensitivity ! Breakdown voltage
Page 37
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
General factors affecting die stability
! Materials − E.g., Impurities, metal stack
! Design – Layout − Geometry
! Design – Process − E.g., Bonding
! Facility – Equipment − E.g., Uniformity in Photo, Diffusion, Etch
! Facility – Environment − Particle count, contaminants
Page 38
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
General factors affecting pressure transducer stability
! Materials − E.g., Substrate, adhesives
! Design − E.g., Package build-up, mounting technique
! Post-assembly treatment − E.g., Burn-in scheme
Page 39
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Design features of Endevco® model 30225 high-temperature pressure sensor
! Silicon-On-Insulator starting material ! High-temperature capable metal stack
Meggitt Sensing Systems Meggitt Sensing Systems
Page 40
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Thermal cycling profile (-55 to 260ºC)
Time
Time
Page 41
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Summary
! Parameters measured to evaluate device reliability include zero-measurand output (zero offset), sensitivity, and resistance, before, during and after subjecting the devices to their full-scale operating measurement range while also subjecting the devices to elevated temperatures, humidity and vibration levels to screen for or induce early mechanical or electrical failure
! Design features required to ensure high reliability are driven by the application
! Despite careful design and various qualifications, extensive in-production testing is unavoidable to guarantee high reliability …which comes at a cost
Page 42
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Further reading
[1] “Practical Understanding of Key Accelerometer Specifications,” Technical Paper No. 328, Meggitt (San Juan Capistrano), Inc.
[2] T. Kwa, “Wafer-level packaged accelerometer with solderable SMT terminals”, IEEE Sensors 2006, Daegu, Korea, Oct 22-25, 2006.
[3] T. Kwa, G. Pender, J. Letterneau, K. Easler, R. Martin, “A new generation of high-shock accelerometers with extreme survivability performance”, 53rd NDIA Fuze Conference, Orlando, FL, May 19-21, 2009.
[4] T. Kwa, G. Pender, J. Letterneau, “Triaxial accelerometer for placement in the ear canal”, Nanotech 2010, Anaheim, CA, June 21-24, 2010.
[5] “Model 2925 AACS Comparison Shock Calibrator (POP)”, Datasheet No. 2925, Meggitt (San Juan Capistrano), Inc.
Page 43
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release.
Contact info
Tom Kwa, PhD, Design and Development Manager Meggitt Sensing Systems 355 N. Pastoria Ave Sunnyvale, CA 94085 Tel: +1 (408) 739-3533 [email protected]
Page 44
© Meggitt Sensing Systems. 120.10 NON-TECHNICAL DATA DEFINED UNDER THE ITAR Distribution Statement: Public Release. 44
Thank you