Theoretical and Experimental Investigations on Thickness Uniformity in Double-sided Lapping

Abstract The double-sided lapping process is extensively employed in the manufacturing of wafers, optical windows, and seal rings due to its high efficiency and ability to achieve precise flatness. However, limited research has explored the thickness uniformity among different workpieces after double-sided lapping, and the underlying mechanism remains unclear. To address the demand for higher precision, this paper first analyzed the relative kinematic model between the workpiece and the lapping plate to clarify the causes of thickness variations among workpieces after double-sided lapping. Subsequently, a finite element method (FEM) model was developed to account for the pressure distribution on the workpiece surfaces at the initial stage of the process. The results indicate that the number of workpieces influences the final thickness variation. Then, various sets of thin copper plates with different thicknesses were lapped, and the findings revealed that five copper plates processed simultaneously exhibited more uniform thickness compared to the three plates. The experimental results align well with the theoretical analysis. Ultimately, a thickness variation of less than 6 μm was achieved on five copper plates measuring Φ100 × 2.9 mm. This study presents a comprehensive analysis of the mechanisms influencing thickness uniformity in the double-sided lapping process and provides practical guidelines for optimizing the process to achieve stringent precision standards in industrial applications.