English abstract…………………………………………………………………..i Chinese abstract………………………………………………………………….ii Acknowledgement………………………………………………………………iii Contents……………………………………………………………………...….iv Index of diagram…………………………………………………………….….vi Index of table……………………………………………………………………x Chapter 1 Introduction…………………………….………………………….….1 Chapter 2 Literature review………………………………………………….…..2 2.1Kovar……………………………………………………………….2 2.1.1 Property of Kovar alloy………………………………………2 2.1.2 Application of Kovar alloy……………….……………..……4 2.1.3 Sealing of Kovar alloy…………………….…………….……4 2.2 7056 glass………………………………………………………….5 2.2.1 Properties of 7056 glass………………………………………5 2.2.2 Applications of 7056 glass……………………………………5 2.2.3 Sealing of 7056 glass…………………………………………6 2.3 Glass-to-metal sealing…………………………………………….7 2.3.1 Glass-to-metal sealing technology……………………...……7 2.3.2 Glass-to-metal sealing mechanism－Wetting……………….10 2.3.3 Glass-to-metal sealing mechanism—Preoxidization………..12 2.3.4 Effects of the oxygen content on wettability of glass……….15 2.4 Dealing with glass -metal seals………………………………….16 2.4.1 Effects of the oxides and parameters on the thermal treatment ………………………………………………………………..17 2.4.2 Effect of the used atmosphere………..……………………..21 2.4.3 Reactions of the interface and mechanism of bonding…..…22 2.4.4 Stresses in glass-to-metal seals……………..………..……..26 2.5 Field assisted glass-Metal sealing anodically……………………29 2.5.1 Parameters in the anodiclly bonding process.…….…….…..30 2.5.2 Effect of the operational parameters for the anodic bonding …………………………………………………...…………..33 Chapter 3 Experimental procedure………………………….………………….35 3.1 Experimental procedure……...………..…………………………35 3.2 Wetting experiment………………………………………………36 3.3 Sealing experiment………………………………………………37 3.4 Re-oxidization…………………………………………………...38 3.5 Shear stress Test…………………………………………………39 3.6 Observation by the OM……………………..…………………...40 3.7 Analysis by the SEM…………………………………………….40 Chapter 4 Results and discussion………………………………………………41 4.1 Wetting…………………………………………………………..41 4.2 Glass-to-Kovar sealing interfacial structural……………………44 4.2.1 Observation by optical microscope…………………………44 4.2.2 Analysis by the SEM………………………………………..51 4.2.3 Analysis by the EDX………………………………………..60 4.3 Sealing strength of the shear stress test………………………….61 Chapter 5 Conclusion……………………………………….………………….70 Reference……………………………………………………………………….71 Appendix……………………………………………………………………….75 Index of diagram Fig.2.1 Thermal expansion of metals[2]……….……………………………....…3 Fig.2.2 Expansion-Temperature diagram of Kovar-to-glass sealing[3]….…….....4 Fig 2.3 Classification of glass-to-metal sealing [4]………………….……………7 Fig.2.4 Typical design of matched glass-metal seal[5]…………….………….….8 Fig. 2.5 Typical design of compression glass-metal seal[5]………………….…10 Fig 2.6 Typical design of ductile metal[5]……………………………………....10 Fig.2.7 Interfacial energy for wetting [6]………………………………………..11 Fig.2.8 Effect of the oxygen content for wettability of glass in air [8]………….15 Fig. 2.9 Dilatometric profile of the interfacial zone[13]……………………..…..19 Fig.2.10 Evolution of profiles of concentration of iron, nickel and cobalt by EDAX[14]………………………………………………………….20 Fig.2.11 Metal-glass interfaces that might promote mechanical bonding[8]…....23 Fig.2.12 Schematic representation of glass-iron interface[8]…….……………...24 Fig.2.13. Schematic presentation of interfacial reaction and galvanic corrosion[8]………………………………………………………....…25 Fig.2.14. Stress development in seals[2]………………………………………...27 Fig.2.15 Graphic sketches of expansion (ΔL/Δ0)-temperature[2]……………..28 Fig.2.16 Schematic diagram of the assembly of anodic bonding apparatus [26]...29 Fig.2.17 Fracture modes of tensile tested specimens [26] ……………………....31 Fig.2.18 Graphic sketches of the stress, strength and tightness to liquid- bonding temperature[27]……………………………………………..….32 Fig.2.19 Flow lines of cations towards the cathode[26]…………………………33 Fig. 3.1 The diagram of experimental procedure………………………………35 Fig.3.2 The diagram of sample of wetting……………………………………..36 Fig.3.3 The diagram of sample of shear stress test……………………………..37 Fig.3.4 The diagrams of the shear stress test………………………………...…39 Fig.4.1 The diagrams of wetting experiment…………………….……………..42 Fig.4.2 The OM diagram of Kovar……………………………………………..45 Fig.4.3 The diagram of the interfacial structures at 850℃sealing for 15 min without preoxidization……………………………………………..46 Fig.4.4 The diagram of the interfacial structures at 850℃sealing for 15min with preoxidization at 700℃ for 10min……………………………..…46 Fig.4.5 The diagram of the interfacial structures at 900℃sealing for 15min with preoxidization at 700℃ for 10min……………………………..…47 Fig.4.6 The diagram of the interfacial structures at 900℃sealing for 15 min without preoxidization…………………………………………….47 Fig.4.7 The diagram of the interfacial structures reoxidized at 700℃ for 10 min with #600 abrasive paper(Ra＝6.81μm)and sealing at 920℃for 15min………………………………………………………………...…48 Fig.4.8 The diagram of the interfacial structures reoxidized at 700℃ for 10 min with #800 abrasive paper(Ra＝5.76μm) and sealing at 920℃for 15min………..…………………………………………………………49 Fig.4.9 The diagram of the interfacial structures reoxidized at 700℃ for 10 min with #1000 abrasive paper(Ra＝4.71μm) and sealing at 920℃for 15min….……………………………………………………………….49 Fig.4.10 The diagram of the interfacial structures reoxidized at 700℃ for 10 min with #1200 abrasive paper(Ra＝3.67μm) and sealing at 920℃for 15min…………………………………………………………….…….50 Fig.4.11 The diagram of the interfacial structures reoxidized at 700℃ for 10 min with #1500 abrasive paper(Ra＝3.14μm) and sealing at 920℃for 15min…………………………………………………………..……….50 Fig.4.12 The signal diagram of the interfacial structure between the glass and Kovar alloy……………………………...…………………………52 Fig.4.13 The quantitative analytic diagram of the interfacial structures of glass-preoxidized Kovar sealing at 950℃for 15min[29]……….……….53 Fig.4.14 The analysis of the sealing interfacial structures and the quantitative element of Fe, Ni, Co, and Si at 950℃responding to the Fig.4.13[29]….53 Fig.15 The signal graph of the interfacial structure between the glass and Kovar alloy………………………………………………………………….…54 Fig.16 The line scan and the elements distribution diagrams of #600 and the interface at 23μm……………………………..……..…………...……55 Fig.17 The line scan and the elements distribution diagrams of #800 and the interface at 22μm………………………………..…………….………56 Fig.18 The line scan and the elements distribution diagrams of #1000 and the interface at 17μm…………………………………………..………….57 Fig.19 The line scan and the elements distribution diagrams of #1200 and the interface at 19μm……………………………………………..……….58 Fig.20 The line scan and the elements distribution diagrams of #1500 and the interface at 15μm……………………………………………...………59 Fig.4.21 The EDX of the dendritic structures……………………….…..……..60 Fig.4.22 The sample (code 11 and 12)of shear stress test is preoxidized at 700℃ holding for 10 min and sealing at 900℃ holding for 15min…..….…...62 Fig. 4.23 The diagram of the shear stress strength for glass-to-Kovar sealing (oxidization)…………………………………….………………...……63 Fig. 4.23 The diagram of the shear stress strength for glass-to-Kovar sealing (reoxidization)……………………………….…………………………66 Index of table Table 2.1 Chemical properties of Kovar [1]…………………………………..….2 Table 2.2 Average linear coefficient of thermal expansion of Kovar [1]….……...2 Table 2.3 Values of mechanical properties for some sealing metals and alloys [2]3 Table 2.4 Compositions of 7056 glass………………..…………………………5 Table 2.5 Properties of 7056 glass………………………………………………5 Table 2.6 The value of viscosity for glass……………………………………….6 Table 2.7 Choices of glass materials…………………………………………….8 Table 2.8 Sealing condition and results of glass-Kovar sealing[14]……………..21 Table 2.9 Results of tensile tests[26]……………………………….……...…….31 Table 4.1 The results of the wetting experiment…………………….…………43 Table 4.2 Results of the preoxidization in the glass-Kovar sealing by the shear stress test………………………………………………………64 Table 4.3 Results of the reoxidization in the glass-Kovar sealing by the shear stress test………………………………………………………67