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Micromechanics of macroelectronics. Zhigang Suo Harvard University. Work with Teng Li, Yong Xiang, Joost Vlassak (Harvard University) Sigurd Wagner, Stephanie Lacour (Princeton University). Displays. Sony e-Reader. Roll-to-roll printing Low cost, large area. defect. - PowerPoint PPT Presentation

Text of Micromechanics of macroelectronics

  • Micromechanics of macroelectronicsZhigang SuoHarvard UniversityWork with

    Teng Li, Yong Xiang, Joost Vlassak (Harvard University)Sigurd Wagner, Stephanie Lacour (Princeton University)

  • Displays

  • Roll-to-roll printing Low cost, large area

  • Challenges to the mechanics of materials and structuresLarge structuresHybrid materials (organic/inorganic)Small features

  • How to make brittle materials flexible?Thin substrateStrain caused by bendingRNeutral planectopSuo, Ma, Gleskova, Wagner Appl. Phys. Lett. 74, 1177-1179 (1999).

  • High strain and fractureGleskova, Wagner, Suo Applied Physics Letters, 75, 3011 (1999)

  • How to make stretchable circuits?Islands, linked by interconnectsFracture at crossoversFatigue of metalsSmall island sizeMost microelectronic materials fracture at small strains (less than about 1%)Polymer substrateHsu, Bhattacharya, Gleskova, Huang, Xi, Suo, Wagner, Sturm, APL 81, 1723 (2002).

  • Debonding and crackingGleskova, Wagner, Suo Applied Physics Letters, 75, 3011 (1999) SiN island on Kapton substrateBhattacharya, Salomon, WagnerJ. Electrochm. Soc. 153, G259 (2006)

  • Metal on polymerAl, Cu, AuMetal film deforms plastically (Ho, Kraft, Arzt, Spaepen)What is the rupture strain of the metal film?Kapton, Silicone

  • Ductile vs. brittle filmRupture by neckingRupture by breaking atomic bonds

  • FEM: large-amplitude perturbationFree-standingSubstrate-bondedLong-wave perturbationConclusion from nonlinear analysis:Substrate retards perturbation of ALL wavelengths.Substrate-bondedshort-wave purturbatione=0.8Li, Huang, Suo, Lacour, Wagner, Mechanics of Materials 37, 261 (2005)

  • Al film on Kepton substrate5000 Al film, 7 % Strain5000 Al film, 10 % StrainGage, Phanitsiri (2001)Chiu, Leu, Ho, (1994)Alaca, Saif, Sehitoglu (2002)Channel cracks start at ~2% strain

  • Possible causes for small rupture strains of metal on polymerThe film is brittle.

    The film debonds from the substrate.

    The substrate is too compliant.

  • Co-evolution: necking and debonding

    Coupled rupture and debondEE10.4 Thursday 2:30pm, Teng Li Ductility of thin metal films on polymer substrates modulated by interfacial adhesion.

  • T2235%37.3%38%38.5%T1235%37.3%38%38.5%Li, Suo, IJSS (2006)

  • Effect of adhesionXiang, Li, Suo, Vlassak, APL 87, 161910 (2005) 100nm Cu /10nm Ti/Kapton, strained to 10%100nm Cu /20nm C/ Kapton, strained to 6%

  • 170nm Cu /10nm Ti/ Kapton strained to 30%Xiang, Li, Suo, Vlassak, APL 87, 161910 (2005)

  • The effect of substrate stiffnessEsub = 2 MPa, = 2.8%

    Esub = 300 MPa, = 47%Esub = 150 MPa, = 37%Li, Huang, Suo, Lacour, Wagner, Appl. Phys. Lett. 85, 3435 (2004)

  • Au film on PDMS substrate survives large elongation electron-beam evaporation101 cycles of elongation by 35%PDMS (1mm)Cr (5 nm)Au (25 nm)Lacour, Wagner, Huang, Suo,, APL 82, 2404 (2003).

  • Au film is cracked from the beginning, but1st cycle to 35% strain101st cycle to 35% strainLacour, Li, Chen, Wagner, Suo, APL 88, 204103 (2006).

  • Other Compliant PatternsWhen pulled, the sheet elongates by bucklingY-shaped cracks

  • The importance of being compliant

  • Serpentine:a compliant pattern of a stiff materialTop surfaceBottom surface Li, Suo, Lacour, Wagner, JMR 20, 3274 (2005) Large elongation, small strainA platform for devices

  • SummaryA stiff polymer substrate can retard necking in a metal film.

    A compliant polymer substrate can accommodate large displacement of a patterned film.