1. Événement - date ICM conference 2015 Haithem Skima FEMTO-ST Institute December 21 st, 2015 Accelerated Lifetime Tests and Failure Analysis of an Electro-thermally Actuated MEMS valve firstname.lastname@femto-st.fr FEMTO-ST Institute, Besançon – France Haithem Skima, Kamal Medjaher, Noureddine Zerhouni, Christophe Varnier, Eugen Dedu and Julien Bourgeois

2. 2/ 18 Outline H. Skima, K. Medjaher, N. Zerhouni, C. Varnier, E. Dedu, J. Bourgeois, ICM Conference, December 20-23, 2015 oIoI ntroduction oMoM otivation oAoA ccelerated lifetime tests oRoR esults oCoC onclusion and future work

3. 3/ 18 o Micro-Electro-Mechanical Systems: MEMS A MEMS is a micro-system that integrates mechanical components using electricity as source of energy in order to perform measurement functions and / or operating in structure having micrometric dimensions. OthersMOEMSRF MEMS Micro actuators Micro sensors Bio MEMS Categories of MEMS o Applications Automotive Aerospace BiomedicalOptical FluidicCommunication technologies Introduction Introduction Motivation Accelerated lifetime tests Results Conclusion

4. 4/ 18 Introduction o Mechanical, electrical and material based failures mechanisms o Failure mechanisms related to manufacturing or to utilization Influence factors: temperature, humidity, vibration, noise, dust, shocks, overcharges … [H. R. Shea 2007, M. McMahon et al. 2012, J. Ruan et al. 2009, R. Mûller-Fiedler et al. 2002] [M. MATMAT 2010] Introduction Motivation Accelerated lifetime tests Results Conclusion

5. 5/ 18 Introduction  Stiction in electro-thermal actuator [M. Dardalhon 2003]  Micro-actuator finger fracture [ B. Charlot 2001]  Contamination in a comb-drive [Tanner et al. 2000 ]  Stiction of the finger on the substrate [Tanner et al. 2000] o Examples of failure mechanisms in MEMS Introduction Motivation Accelerated lifetime tests Results Conclusion

6. 6/ 18 Prognostics & Health Management: PHM Motivation MEMS Reliability issues Loss of performance Faults (Non achieved functions) Risk of accidents  Reliability  Availability  Security  cost Introduction Motivation Accelerated lifetime tests Results Conclusion Accelerated lifetime tests performing Health assessment and state estimation Time to failure prediction Decision making Degradation model definition MEMS

7. 7/ 18 Accelerated lifetime tests o Definition Accelerated lifetime test is an aging of a product that induces normal failures in a short amount of time by applying stress levels much higher than normal ones (stress, strain, temperatures, voltage, vibration rate, pressure, etc.). The main interest is to observe the evolution over time to predict the life span. Reliability results can then be obtained by analyzing the product’s response to such tests. o Difficulty in MEMS failure analysis ‒ Structures of interest are not exposed for direct observation ‒ Structures that provide the stimulus for motion or actuation are obscured from view Introduction Motivation Accelerated lifetime tests Results Conclusion

8. 8/ 18 Accelerated lifetime tests o System description Electrothermally actuated MEMS valve designed by DunAn Microstaq company to control flow rates or pressure with high precision at ultra-fast time response (<< 100 ms). It is currently being used in a number of applications in air conditioning and refrigeration, hydraulic control and air pressure control Electrical connections Movable membrane Fluid connection ports Common port Normally closedNormally open Common portNormally closed Scanning Electron Microscope (SEM) pictures (FEMTO-ST) Anchorage ᶿ l Hot arms Shuttle Direction of movement ‒ Maximum actuation voltage: 12V ‒ Current consumption can reach 1A Introduction Motivation Accelerated lifetime tests Results Conclusion

9. 9/ 18 Computer Arduino Voltage suppliers NI card Camera Light source MEMS Experimental platform - (FEMTO-ST) Accelerated lifetime tests o Experimental setup PT100 RTD Input and output of air Metal plate Electronic card MEMSPins Support 1- Experimental platform Introduction Motivation Accelerated lifetime tests Results Conclusion 2- Setup in the SEM

10. 10/ 18 Accelerated lifetime tests NI card Camera Arduino card Voltage supplier Light source Pressure regulatorAir filter MEMSPT100 Air supply Temperature measurement Supply Image acquisition Air flow Electronic card Global synoptic of the experimental platform Processing and storage of data o Experimental setup Introduction Motivation Accelerated lifetime tests Results Conclusion 1- Experimental platform

11. 11/ 18 Accelerated lifetime tests Direction of motion Movable Membrane Direction of motion Guppy Pro F-031 with 100 fps Matlab Image- processing algorithm Time response – parameters identification MEMS are supplied with a square signal of 8V magnitude and a frequency equal to 1Hz. This voltage is not too high to not bring up prematurely degradation and not to low to obtain enough displacement The current consumption of a new MEMS at 8V is about 0.55A and the displacement is about 65µm Introduction Motivation Accelerated lifetime tests Results Conclusion

12. 12/ 18 Accelerated lifetime tests Movable membrane o Experimental setup Introduction Motivation Accelerated lifetime tests Results Conclusion 2- Setup in the SEM Electrical connections MEMS

13. 13/ 18 Accelerated lifetime tests o Tests Tests consist in cycling MEMS valves and changing at each time the operating condition: a)Unfiltered air – Experimental platform b)Without air – in the SEM c)Filtered air – Experimental platform Unfiltered airWithout airFiltered air Cycling four MEMS valves with an unfiltered air Experiments remained running for more than one month Measurements were collected every day, after 25000 cycles, and at each measurement the displacement of the membrane is calculated. Cycling one MEMS valve inside the SEM without air The displacement of the membrane is calculated by using the SEM images. Cycling four MEMS valves with filtered air Experiments remained running for more than three months Measurements were collected after approximately 90000 cycles. Introduction Motivation Accelerated lifetime tests Results Conclusion

14. 14/ 18 Results o Unfiltered air SEM image showing contamination at the normally closed fluid port Image taking by the camera showing a damaged membrane Video showing the degraded state of the membrane and its small displacement TestInitial displacement Performed cycles Displacement at the end of the test Membrane state Unfiltered air65 µm1 million10 µmdegraded o Without air TestInitial displacement Performed cycles Displacement at the end of the test Membrane state Without air65 µm80000050 µmgood This test has been stopped since we can not use the SEM for long Introduction Motivation Accelerated lifetime tests Results Conclusion

15. 15/ 18 ‒ Good surface state of the membrane ‒ For the electrothermally actuators, a failure is defined as the point at which the displacement decreases by 20% [Conant et al 1998] Results o Filtered air ‒ 8 million cycles (guaranteed by the manufacturer) performed without a significant decrease of the displacement (less than 10% of displacement decrease) or membrane degradation Faulty MEMS Degradation at the actuator New MEMSMEMS at the end cycling Introduction Motivation Accelerated lifetime tests Results Conclusion ‒ After 12 million cycles, the displacement is about 15 µm (23% of the initial displacement)

16. 16/ 18 Results TestInitial displacement Performed cycles Displacement at the end of the test Membrane state Unfiltered air65 µm1 million10 µmdegraded Without air65 µm80000050 µmgood filtered air65 µm12 million15 µmgood The variation of the displacement depends on the degradation Introduction Motivation Accelerated lifetime tests Results Conclusion

17. 17/ 18 Conclusion ‒ Two experimental setup designed to perform accelerated lifetime tests to an electro- thermally actuated MEMS valve ‒ Three accelerated lifetime tests performed ‒ Unfiltered air can cause the contamination at the actuator and the membrane, early failure ‒ Very small displacement of the membrane after 12 million cycles with good surface state degradation at the actuator which is obscured from view ‒ Perform new tests by changing input parameters such as supply voltage and operating frequency to see their impact on the MEMS degradation ‒ Analyze data collected during tests in order to define a degradation model of the MEMS ‒ Implement Prognostics and Health Management approach to estimate MEMS health states and predict their time to failure o Conclusion o Future works Introduction Motivation Accelerated lifetime tests Results Conclusion

18. 18/ 18 Thank you for your attention H. Skima, K. Medjaher, N. Zerhouni, C. Varnier, E. Dedu, J. Bourgeois, ICM Conference, December 20-23, 2015