Papers by Author: Li Jie Ma

Abstract: The ultra-thin 304 stainless steel sheet will be used in flexible displays for substrate material. In chemical mechanical polishing of ultra-thin stainless steel, the pH value of polishing slurry has an important influence on the material removal rate (MRR). In this paper, the influences of pH regulator in slurry on MRR had been studied in CMP of ultra-thin 304 stainless steel based on alumina (Al₂O₃) abrasive in acidic polishing slurry. The research results show that, in the same conditions, different pH value had a different chemical action mechanism and a different MRR. And also, different oxidant with pH regulator had a different chemical action mechanism and a different MRR. The research results can provide the reference for studying the slurry in CMP of ultra-thin stainless steel.

Abstract: Chemical mechanical polishing (CMP) is the most effective technology to achieve ultra-smooth without damage surface in ultra-precision machining of stainless steel substrate. In this paper, according to the slurry ingredients obtained by former research, the influences of the CMP process parameters, such as the rotational velocity of the platen and the carrier, the polishing pressure and the abrasive size on the material removal rate (MRR), have been studied in CMP stainless steel substrate based on the alumina (Al₂O₃) abrasive. The research results show that the material removal rate increases with the increase of the abrasive size, the rotational velocity of the platen and the polishing pressure significantly and the surface roughness increases with the increase of the abrasive size. This study results will provide the reference for optimizing the process parameters and researching the material removal mechanism in CMP stainless steel sheet.

Abstract: Chemical mechanical polishing (CMP) had been considered as the most practical and effective method of achieving an ultra-smooth and non-damage surface in manufacturing SiC crystal substrate. CMP slurry was one of the key factors of CMP technology. In this paper, through investigating the changes of several core factors to evaluate the performance of CMP, such as the material removal rate (MRR), surface roughness Ra, 3D surface profiler, etc., the influence of various slurry and its content on the polishing efficiency and surface finish quality had been studied. The research results showed that different oxidant had different chemical action mechanism, also affecting the stability of CMP slurry and surface quality of specimen; adding suitable an oxidant to slurry could effectively improve the CMP performance.

Abstract: Ultra-thin stainless steel sheet is likely to be the ideal substrate materials used for flexible display. In order to obtain ultra-thin stainless steel substrate with high accuracy, low surface roughness and without damage, the ultra-precision lapping and chemical mechanical polishing technology must be used. In this paper, the lapping paste for stainless steel has been designed using the orthogonal experiment method. According to the range analysis method, an optimal lapping paste had been obtained. Tests lapping the 304 stainless steel sheet with the optimal lapping paste have been done. The test results show that the MRR is about 240nm/min and the surface rough Ra is about 128 nm. This research results can provide theory support for ultra precision machining the stainless steel.

Abstract: Flexible displays will become the mainstream display of next generation, so the manufacturing technology of the flexible display substrate is one of very important technologies. In this paper, according to orthogonal design, the composition selection and optimization of chemical mechanical polishing (CMP) slurry based on alumina abrasive had been done in CMP ultra-thin stainless steel surface by a lot of tests. The CMP slurry based on alumina abrasive for ultra-thin stainless steel surface had been obtained. According to the test results, the material removal rate (MRR) is about 177 nm/min and the surface roughness (Ra) is about 0.018μm.

Abstract: In this study, according to physic-chemical characteristic of the SiC crystals, we analyzed and researched the role of pH modifier in SiC crystal substrate chemical mechanical polishing and the surface after polishing. We used different polish agents which was made up with inorganic and organic bases to experiment, and then analyzed the results. The parameters of the polishing specimen, such as the removal rate of material, surface scanning and the roughness, were analyzed and used to determine the different pH modifiers played different roles in the stability of polish agents and surface quality of the specimen.

Abstract: This paper investigates the effect of spindle clamping force on the static and dynamic characteristics of the spindle-tooling system through measuring the frequency response function of the tool end point in variable spindle clamping force. The research shows that the limited static stiffness increases accordingly and normal static stiffness changes little as the spindle champing force increases. The high spindle clamping force leads to reduce the modal damping of the spindle-tooling system while the natural frequency varies slight. The analyses of process stability indicates that the low spindle clamping force can improves the process stability because of the higher damping in some clamping force range.

Abstract: Based on the metal cutting experiments, the forming model of feed direction burr is proposed in the paper, a physical parameter of determining the generating of typeⅠ feed direction burr — critical tool edge angle rI χ is given. And the main factors which influence rI χ are studied by the experiment, and related theory analysis is made. Furthermore, some new controlling methods and technology to restrain or decrease the feed direction burr in machining are developed.

Abstract: We had done the two-pass grind-hardening experiment on 40Cr steel using the conventional aluminum grinding wheel on a surface grinder, compared the structure and performance of the hardened layer of one-pass grinding with those of two-pass grinding and analyzed the forming mechanism of two-pass grinding hardened layers. The results show that there are a similar martensite structure and change rules of hardened layer of one-pass grinding and two-pass grinding in spite of the different of initial structures, for martensite has tempered by the action of the creep feed grinding temperature field. The depths of hardened layer, microhardness and wear resistance have further improved, but the maximal compressive residual stress and its influencing depth of hardened layer have decreased. The forming mechanism of the two-pass grinding hardened layer is the same as that of the grinding hardened layer of quenched steel.

Abstract: As the common materials of making cutting tool, the cemented carbide has been widelyused in all kinds of mechanical machining. Based on the manufacturing craft of the brazing welded cemented carbide cutting tools, according to the theory of engineering mechanics and fracture mechanics, the main factors are analyzed and studied which influence surface cracks of cutting tool from prefabricated stress σc, brazing stress σq, removable stress σw at heat preservation and extra stress σf several aspects in this paper. Then the author founded the math-mechanics model of forming the surface cracks and deduced the critical condition generated surface cracks in brazing welded cemented carbide cutting tools and puts forward several kinds of technology, crafts and methods restraining or minishing surface cracks of the cemented carbide cutting tools.