Producing nanorelief in machining hard brittle surfaces

Autor: T. B. Teplova
Rok vydání: 2009
Předmět:
Zdroj: Russian Engineering Research. 29:853-857
ISSN: 1934-8088
1068-798X
DOI: 10.3103/s1068798x09080243
Popis: The growth of the Russian electronics industry creates additional demand for hard crystalline materials. The high requirements on the machined surfaces used to manufacture substrates (the most massive electronic product) necessitate minimization of the imprinted microcircuits. One of the main problems in producing high-quality surfaces is to avoid defects due to brittle failure in surface treatment. This is especially important in producing surfaces with nanorelief, whose roughness (0.3‐1 nm) is comparable with the lattice parameters of the machined material. Traditionally, hard brittle materials and crystals are machined by grinding using free and bound abrasive. This produces a surface with roughness of around 200 nm and a disrupted subsurface layer. To achieve the required roughness (0.2‐10 nm, depending on the application), the blank is polished in aggressive media; this is a slow and laborious process. A promising alternative is quasi-plastic grinding [1]. Quasi-plasticity denotes the appearance of plastic properties in the surface layer of hard brittle materials in certain conditions. This technology is based on mechanical treatment of the surface with a tool supply amounting to fractions of a micron. Reducing the intensity of treatment in the surface layers of hard materials reduces the degree of brittle failure. In quasi-plastic machining, the rigidity of the structure is ensured by means of an elastic machining system, with relative insulation from external perturbations. As a result, brittle blanks may be machined in controllable conditions with the production of nanorelief at the surface. Investigation of quasi-plastic machining on Pegasus apparatus, for many amorphous glasses, single crystals, and ceramics, leads to the hypothesis that all materials (regardless of their hardness and brittleness) pass from brittle to quasi-plastic failure in surface machining if the supply is sufficiently small [2]. Thus, in grinding, when the transverse supply per wheel rotation is reduced from 75 to 2 nm/min on the Pegasus apparatus, the proportion of the surface that disintegrates is reduced from 99% to 5%. The flaw of the Pegasus apparatus is the lack of a diagnostic model for the machining parameters, which prevents automation of surface treatment. To eliminate this problem, a numerically controlled AN12F4 machine-tool module with sufficient rigidity in incision has been created on the basis of fundamental research at OAO ENIMS. This module permits quasiplastic grinding of hard brittle materials. The table presents the main parameters of the AN12F4 module, which ensures dynamic pulsed action of grains of the rotating tool on the crystal’s surface, as a result of the summation of two vectors: 1) the compressive-stress vector, determined by the potential energy of compression; 2) the tangential-stress vector, determined by the kinetic energy. Tests of an AN12F4 mockup are based on the principles of dimensionally controlled grinding of anisotropic materials, ensuring an absence of induced defects [3]. The test results are positive in machining ceramic
Databáze: OpenAIRE
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