• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.44-50
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• 2019

CMP is the most critical process in the manufacture of silicon wafers, and the use of retaining rings, which are consumable parts used in CMP equipment, is increasingly important. Since the retaining ring is made of plastic, it is not only weak in strength but also has the problem of taking a long time for the flattening operation of the ring itself performed before the CMP process, and of the imbalance of force due to bolt tightening causing uneven wear. In order to solve this problem, the retaining ring and the insert ring are integrally used, and the flatness of the retaining ring may be affected depending on the material of the insert ring. Also, the residual stress generated in the manufacturing process of the insert ring may cause distortion of the ring, which may adversely affect the precision polishing. In this study, when the insert ring is made of Zn or STS304, the thickness variation and the flatness of the retaining ring are compared and, finally, the material removal rate is analyzed by polishing the wafer by the oxide CMP process. Through these experiments, the effects of the insert ring material on the polishing accuracy of the wafers were investigated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.22-28
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• 2020

This paper investigates the effects of retaining ring materials, particularly PPS and PEEK, used in the CMP process, on wafer polishing and ring wear. CMP can be performed using bonded type retaining rings made with PPS or injection molding type retaining rings made with PEEK. In this study, after polishing a wafer with a PPS retaining ring, the average profile height of the wafer was 0.098 ㎛ less than that of the wafer polished with a PEEK retaining ring, implying that PPS retaining rings achieve a higher polishing rate. In addition, the center area of the wafer profile had less deviation and improved flatness after polishing with the PPS ring. These results indicate that a higher polishing rate and smaller profile height deviation can be achieved using retaining rings made with PPS compared to retaining rings made with PEEK. Therefore, with semiconductor circuit patterns becoming finer and wafer sizes becoming larger, the use of PPS in CMP retaining rings can obtain more stable wafer polishing results compared to that of PEEK.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.148-153
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• 2004

This paper represents that parts of a large generator operating in 1000 MW are affected by centrifugal forces due to high-speed rotation in 3600 rpm and 3D FEM Analyses are required to obtained the structural reliability of the generator. From these results, one would know the weakest locations and the stress distributions. The fatigue life is calculated in order to grasp the remaining life of generator. 2D and 3D analyses are performed to calculate stresses of the generator rotor and the retaining ring. From 2D results, we find the SCF at the slot and sub-slot of the rotor. 3D analysis is applied at the end part of generator rotor, which represents complex geometry, and rotor and retaining ring shrink thermally. With these results, designers of rotor and retaining ring can compare with the results of design code and verify the stress distributions of generator rotor and retaining ring, and then calculate the remaining life from the low-cycle fatigue data.

• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.13-16
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• 2011

This paper describes the reduction method of eddy current loss generated into a retaining ring installed in wound-field superconducting machine. In order to suggest the reduction method of eddy current loss of the retaining ring, this paper is divided into three parts. Firstly, eddy current loss of prototype model is calculated. Secondly, eddy current loss versus material and shape of the retaining ring is compared. Finally, the material and the shape of the retaining ring to reduce coupling loss generated by a time-varying magnetic field are proposed. In this paper, eddy current loss is calculated by 3-dimensional transient analysis.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.848-853
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• 2001

A study about the shrink fits of rotor and retaining ring in generator was performed for the cases of three radial interference. The shrink-fitted retaining ring used to restrain the end turns of the winded coils in the rotor against centrifugal force requires very careful attention during design and manufacture because it has traditionally been the highest-stressed component of the generator. The contact pressures and residual stresses were obtained by the finite element analysis for each radial interference at zero, 100% rated, and 120% rated speeds, respectively. The results of analysis show that the radial interference in use needs to be increased carefully.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.65-70
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• 2010

Retaining rings are used to support the field winding end turns from the centrifugal force by the high speed of the field and these are the overstressed parts among the generator parts. There have been several retaining failures in Europe and America, all attributable to stress corrosion cracking in 18Mn-5Cr steel. Since then, each manufacture companies have developed a good 18Mn-5Cr steel in temperature, strength characteristic and it is used in many field now. From many findings and test results, we could conformed that the failure might be grown in the overstressed condition unrelated to the moisture particle.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.107-109
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• 1998

This paper presents mechanical analysis of gas turbine generator (113MVA, $3{\phi}$, 2P, 0.9PF, F class, 3600rpm, 60Hz, 13.8kV, 4.72kA, Air-Cooling) field coil deformation. Rotor end coil deformation is only appeared on turbine end but collector end coil is normal. Expansion direction of end coil is tangential not axial. Deformation appears more severe at top turn. Retaining ling is expanded by centrifugal force of coil and itself. In case friction coefficient between coil top surface and retaining ring insulation inner surface is small, coil end length ${\ell}$ does not change. However, in case friction coefficient big condition, coil end is expanded ${\Delta}{\ell}$ due to start and stop. Deformation is assumed about 30mm by watching photograph inner surface of retaining ring is coated by Teflon at manufacturing condition. Usually Teflon coating insulation surface is small friction coefficient. It's value 0.08${\sim}$0.15. However it's value exceeds more than 0.297. Since top turn deformation appears. The distortion and subsequent failure have occurred because of the lack of a sufficient slip-plane between the top field coil conductors and the inside surface of the retaining ring insulation on the turbine end of the field-winding.

• Korean Journal of Materials Research
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• v.23 no.9
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• pp.483-488
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• 2013

Over the past few decades, high-nitrogen austenitic steels have steadily received greater attention since they provide a unique combination of high strength and ductility, good corrosion resistance, and non-magnetic properties. Recently, highnitrogen 18Mn-18Cr austenitic steels with enhanced strength have been developed and widely used for generator retaining rings in order to prevent the copper wiring from being displaced by the centrifugal forces occurring during high-speed rotation. The high-nitrogen austenitic steels for generator retaining ring should be expanded at room temperature and then stress relief annealed at around $400^{\circ}C$ to achieve the required mechanical properties. In this study, four kinds of high-nitrogen 18Mn-18Cr austenitic steels with different nitrogen content were fabricated by using a pressurized vacuum induction melting furnace, and then the effects of nitrogen content, cold working, and stress relieving on tensile properties were investigated. The yield and tensile strengths increased proportionally with increasing nitrogen content and cold working, and they further increased after stress relieving treatment. Based on these results, a semi-empirical equation was proposed to predict the tensile strength of highnitrogen 18Mn-18Cr austenitic steels for generator retaining rings. It will be a useful for the effective fabrication of high-nitrogen 18Mn-18Cr austenitic steels for generator retaining rings with the required tensile properties.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.849-853
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• 2000

The retaining rings used to restrain the end turns of the rotor winding against centrifugal force require very careful attention during design and manufacture because they have traditionally been the highest-stressed components of the generator. In other words, the rings maintain their shrink fits during their entire service life. In this study, using finite element method, the part of shrink fits in generator was analyzed to obtain residual stresses in retaining ring and contact Pressures between contact surfaces at zero, rated, and 120 rated speeds, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.843-844
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• 2012