Department of Mechanical and Industrial Engineering DESIGN OF A FATIGUE MACHINE FOR THIN MEMBRANES E. ALACA, M. T. A. SAIF, H. SEHITOGLU FRACTURE CONTROL PROGRAM October 9, 2001 University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering BIAXIAL TESTING • NEW TESTING APPARATUS – MONOTONIC and – FATIGUE TESTING OF THIN FILMS displacement data monitor laser sensor and camera thin film piezo actuator wafer output input piston pressure transducer fluid chamber amplifier pressure data Feedback control drives piezo. University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering TESTING APPARATUS A: B Laser Sensor A B: Specimen C: G Piezo Actuator D: C Fluid Chamber E: D Multi-axis Stage F: Pressure Transducer F E University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering SPECIMEN FABRICATION 25 mm specimen specimen holder University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering MONOTONIC RESPONSE 4.6 µ m -thick polyimide film 1.8 1.72439 ( ν =0.3) 1.6 1.4 2/3 k=(E/4)(pa/Eh) 1.2 1.0 σ /k 0.8 0.6 ν =0.3 ν =0.4 0.4 ν =0.2 0.2 0.0 0 2 4 6 8 10 12 σ 0 /k University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering FATIGUE RESPONSE 4.6 µ m -thick polyimide film mid-point deflection 0.30 0.20 Diameter = 2 mm 140 maximum pressure 0.25 130 0.15 mid-point deflection [ µ m ] 0.20 pressure [ MPa ] pressure [ MPa ] 0.15 0.10 cycle 301 cycle 701 0.10 0.05 minimum pressure 0.05 90 15.7 µ m pressure 0.00 80 0.00 0 60 120 180 125 130 135 140 145 time [ s ] mid-point deflection [ µ m ] University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering FRACTURE OF 150 nm -THICK Al FILM ON 4.6 µ m -THICK POLYIMIDE SUBSTRATE Vibration isolation and remote focusing make in-situ microscopy possible. “Mud cracking” commonly observed in ceramic coatings, drying coffee-water mixtures, starch-water mixtures,volcanic rocks, desiccating mud and clays. University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering DETERMINATION OF THE CRITICAL STRESS INTENSITY FACTOR FOR 150 nm -THICK Al ( ) 1 − ν f h σ 2 2 G = 1 π g( α , β ) 1. 2 E f Beuth, Int. J. Solids Structures , 1992 2. Steady-state channeling of isolated, straight cracks takes place at p = 0.235 MPa. c = 1 . 670 MPa m K I University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering CONCLUSION • New apparatus to conduct fatigue testing on thin films. • Elastic properties are extracted from monotonic tests. • Critical stress intensity factors can be determined for thin films using in-situ microscopy. University of Illinois at Urbana-Champaign
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