Machinery's Handbook, 31st Edition
DUCTILE REGIME MICROMACHINING 1175 angle, side relief angle, side clearance angle, end cutting edge angle, side cutting edge angle, nose radius) with the addition of edge sharpness as (5°, 0°, 0°, 5°, 5°, 30°, 0°, 0.51– 2.00 mm, 10–40 nm). The ultraprecision machining process was performed on a rigid system that has 9 nm positioning accuracy. Compressed air was used to blow chips away from the finish machined area. Surface finish of a machined wafer was measured with an atomic force microscope (AFM) and a phase-shift interferometer (PSI). Surface finish measurements indicated ductile or brittle chip fracture on machined sur faces. As depth of cut reduced below 1 m m, the surface finish was also diminished due to a higher percentage of ductile machined surfaces. Perfect ductile regime machining was achieved when depth of cut was between 0.1–0.5 m m. A smaller depth of cut in the neigh borhood of 0.05 m m (50 nm), however, worsened the surface finish because machining at such shallow depth of cut (close to the cutting tool edge radius of 40 nm) would plow and fracture the material surface. At the same cutting parameters, micromachining along the silicon <110> directions gave better surface finish while brittle chipping was seen when cutting along the silicon <100> directions (Fig. 15, Fig. 16a, and Fig. 16b). [100]
200 150 100 50
PSI in <110> PSI in <100>
0.0 0.2 0.4 0.6 0.8 1.0 Maximum Chip Thickness ( m) µ 0
[110] Fig. 14. Machining plan on (001) wafers. A wafer was faced at a constant depth in different zones (left) or changing cutting depth in a taper cut (right).
Fig. 15. Surface finish as a function of the maximum chip thickness (depth of cut) and crystalline direction of the silicon wafer. The minimum surface finish is with ductile machined surface.
400 nm 200
400 nm 200
nm
nm
6
15
4
10
2
5
Fig. 16a. Perfect ductile regime machining of (001) silicon along [110]. Fig. 16b. Mixed mode of ductile regime and pitting along [100]. Speed 75 m/min, feed 2.5 m m/rev; depth 0.5 m m; SCD tool (5°,0°,0°,5°,5°,30°, 0°, 0.5mm,10–40nm). Cutting Fluids in Micromachining Micromilling and microdrilling, among the most versatile manufacturing processes, can be leveraged from existing technology to produce 3D microparts or microcavities in molds and dies for mass-replication. Although macro-scale milling and drilling tech- nology is mature, micro-scale milling/drilling technology is yet to be fully developed. Extending common practices in macromachining to micromachining often ends up with failure. Very short tool life is experienced with micromachining, and flood cooling is
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online