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Research Papers

Experimental Study and Modeling of Lapping Using Abrasive Grits with Mixed Sizes

[+] Author and Article Information
Chunhui Chung

Research Fellow  Department of Mechanical Engineering, National Chiao Tung University, Hsinchu, Taiwan 30010

Chad S. Korach

 Department of Mechanical Engineering, Stony Brook University, Stony Brook, NY 11794-2300

Imin Kao1

 Department of Mechanical Engineering, Stony Brook University, Stony Brook, NY 11794-2300kao@mal.eng.sunysb.edu

According to different measurement, there are different results for the distribution of abrasive grits [29]. In this paper, we follow the FEPA grading chart.

1

Corresponding author.

J. Manuf. Sci. Eng 133(3), 031006 (Jun 08, 2011) (8 pages) doi:10.1115/1.4004137 History: Received May 01, 2010; Revised April 25, 2011; Published June 08, 2011; Online June 08, 2011

In this paper, the lapping process of wafer surfaces is studied with experiments and contact modeling of surface roughness. In order to improve the performance of the lapping processes, effects of mixed abrasive grits in the slurry of the free abrasive machining (FAM) process are studied using a single-sided wafer-lapping machine. Under the same slurry density, a parametric experimental study employing different mixing ratios of large and small abrasive grits and various normal loadings on the wafer surface applied through a jig is conducted. Observations and measurements of the total amount of material removed, material removal rate, surface roughness, and relative angular velocity are presented as a function of various mixing ratios and loadings and discussed in the paper. The experiments show that the 1:1 mixing ratio of abrasives removes more material than other mixing ratios under the same conditions, with a slightly higher surface roughness. Modeling of the mixed abrasive particle distributions correspondingly indicates that the roughness trend is due to the abrasive size distribution and the particle contact mechanics. The results of this study can provide a good reference to the FAM processes that practitioners use today by exploiting different abrasive mixing ratios in slurry and normal loadings in the manufacturing processes.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Logitech PM5 lapping machine, employed to conduct experiments in this paper

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Figure 2

Depth of the material removal with (a) 2.3-kg and (b) 4.1-kg loadings in lapping

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Figure 3

Angular velocity of jig with the (a) 2.3-kg and (b) 4.1-kg loadings during lapping

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Figure 4

Average rms surface roughness after lapping. The unit is in micron.

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Figure 5

Typical surface morphology of lapped wafer surface. The scale bar is 50 μm.

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Figure 6

Normalized linear distributions for FEPA F-400 and F-600 SiC powders, based on data in Table 2. The slope of the F-600 powder from the mean size to the maximum size is calculated as −0.1%/ μm. The tail portion of the F-600 distribution from 15.8 μm to the maximum is 7.3% of the total distribution volume.

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Figure 7

Plot of individual roughness contributions from the F-400 and F-600 roughness models, as a function of the concentration factor k. For Rs400, k is defined by k400 , though for Rs600, k is defined by (kmax  – k600 ) to plot on the same axis. As abrasive concentration decreases (decrease in k) the roughness decreases for the models of both powders. F-400 is affected by the interaction of the F-600 abrasives beginning at a critical concentration k* = 0.4 kmax , and is the reason for the change in slope of the F-400 roughness curve at k=0.64×10-6.

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Figure 8

Comparison of material removal rate and rms surface roughness at (a) 2.3-kg and (b) 4.1-kg loadings

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Figure 9

Plot of the mixed abrasive model and the experimentally measured roughness as a function of F-400 particle concentration for (a) 2.3-kg and (b) 4.1-kg cases

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