Effect of Abrasive Grain Concession on Micromechanical Behavior of Lapping Sapphire by FAP

At a Glance

Metadata	Details
Publication Date	2022-08-16
Journal	Micromachines
Authors	Huimin Xu, Jianbin Wang, Yiliang Xu, Qing’an Li, Benchi Jiang
Institutions	Anhui Polytechnic University
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Abrasive Behavior in Sapphire Lapping

This document analyzes the research paper “Effect of Abrasive Grain Concession on Micromechanical Behavior of Lapping Sapphire by FAP” and connects the findings to the advanced MPCVD diamond solutions offered by 6ccvd.com.

Executive Summary

This study successfully combined Molecular Dynamics (MD) simulation and experimental validation to analyze the material removal mechanism of single-crystal sapphire (c-plane) during Fixed Abrasive Pad (FAP) lapping using diamond grains.

Core Mechanism: The research modeled the microscopic yield behavior of diamond abrasive grains pressed into a sapphire workpiece, focusing on the transition to ductile-mode removal.
Key Simulation Finding: Increasing the diamond abrasive radius from 8 Å to 12 Å resulted in a significant increase in peak micro-cutting force, rising from 1000 nN to over 3500 nN, and raising the Newtonian zone temperature to 380 K.
Material Removal Rate (MRR): Experimental results confirmed that MRR increases non-linearly with diamond abrasive particle size (15 µm to 65 µm).
Surface Quality (Ra): Surface roughness (Ra) increased approximately linearly with abrasive particle size, highlighting the trade-off between removal efficiency and surface finish quality.
Ductile Regime Control: The findings emphasize that controlling the effective cutting depth of the diamond abrasive is critical for maintaining ductile removal mode and achieving high-quality surface processing (low Ra).
6CCVD Relevance: The need for highly uniform, high-strength diamond material for FAP manufacturing and precision micro-tooling directly aligns with 6CCVD’s expertise in custom MPCVD Single Crystal (SCD) and Polycrystalline Diamond (PCD).

Technical Specifications

The following hard data points were extracted from the molecular dynamics simulation and experimental validation sections of the paper.

Parameter	Value	Unit	Context
Workpiece Material	Single Crystal Sapphire	$\alpha$-Al₂O₃	c-plane (0001) orientation
MD Workpiece Dimensions	90 x 30 x 40	Å	Simulation Model Size
MD Abrasive Radii Tested	8; 10; 12	Å	Hemispherical Diamond Grain
MD Micro-Cutting Depth	5	Å	Fixed Simulation Parameter
MD Cutting Speed	150	m/s	Simulation Parameter
Max Peak Cutting Force (12 Å)	~4000	nN	Newtonian Zone (MD)
Steady-State Cutting Force (12 Å)	1250	nN	Newtonian Zone (MD)
Max Temperature (12 Å)	380	K	Newtonian Zone (MD)
Experimental Wafer Diameter	50.8	mm	Sapphire Slice
Experimental Abrasive Size Range	15 to 65	µm	Fixed Abrasive Pad (FAP)
Experimental Pressure	34.5	kPa	Grinding Process Parameter
Experimental Surface Roughness (Max)	~0.8	µm	Achieved with largest abrasive size

Key Methodologies

The study utilized a combined approach of Molecular Dynamics (MD) simulation and physical lapping experiments to analyze the micromechanical behavior.

Molecular Dynamics (MD) Simulation Setup

Model Construction: A rigid diamond abrasive grain (2374 atoms, hemispherical) was modeled cutting into a single-crystal sapphire workpiece (22,004 atoms, c-plane orientation).
Potential Function: The Matsui potential function was selected for its accuracy in modeling the lattice constant, elastic constant, and surface energy of $\alpha$-Al₂O₃.
Workpiece Zoning: The sapphire workpiece was divided into three zones:
- Boundary Zone: Atoms fixed in space to reduce boundary effects.
- Constant Temperature Zone: Controlled at 300 K for heat dissipation and temperature stabilization.
- Newtonian Zone: The processing area where atomic motion obeys Newton’s second law.
Cutting Parameters: Simulation utilized a 1 fs time step, 150 m/s cutting velocity, and a fixed micro-cutting depth of 5 Å.
Analysis: Focused on the evolution of cutting force, potential energy, and temperature in the Newtonian zone across three different abrasive radii (8 Å, 10 Å, 12 Å).

Experimental Validation (FAP Grinding)

Workpiece: Single crystal sapphire slices (50.8 mm diameter, 0.5 mm thickness, c-direction (0001)).
Equipment: Intelligent nano-polishing machine system (Nanopoli-100).
Abrasive Pad: Hydrophilic fixed abrasive polishing pad containing diamond abrasive particles with average sizes ranging from 15 µm to 65 µm.
Process Parameters: Grinding was performed at 80 rpm table rotation, 34.5 kPa pressure, and 100 mL/min fluid flow for 40 minutes.
Measurement: Material Removal Rate (MRR) was calculated from mass loss, and Surface Roughness (Ra) was measured using a Nano Map500LS 5 over a 1500 µm sampling length.

6CCVD Solutions & Capabilities

This research underscores the critical role of diamond material quality and precise dimensional control in achieving optimal material removal and surface finish for hard, brittle materials like sapphire. 6CCVD’s advanced MPCVD diamond capabilities are perfectly suited to support and extend this research, both in tool manufacturing and fundamental material science studies.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage
High-Purity Diamond Abrasive Source	High-Purity Polycrystalline Diamond (PCD) Plates	We supply large-area PCD plates (up to 125 mm diameter) with exceptional uniformity and mechanical stability, ideal for manufacturing next-generation Fixed Abrasive Pads (FAPs) that require consistent diamond distribution and yield behavior.
Precision Micro-Tooling & Edge Control	Optical Grade Single Crystal Diamond (SCD) Wafers	For studies requiring ultimate control over abrasive geometry (relevant to the 8 Å to 12 Å MD radii), our SCD wafers (thickness 0.1 µm - 500 µm) provide the highest crystallographic quality for fabricating ultra-sharp, durable micro-tools necessary for achieving and maintaining the ductile removal regime.
Custom Substrate Dimensions	Custom Dimensions and Substrate Thickness	We offer custom diamond substrates up to 10 mm thick and plates up to 125 mm in diameter, allowing researchers to scale up FAP designs or test novel diamond-based tooling inserts beyond standard commercial sizes.
Ultra-Low Surface Roughness	Advanced Polishing Services (Ra < 1 nm)	The paper targets low Ra for high-quality sapphire surfaces. 6CCVD provides SCD polishing to Ra < 1 nm and inch-size PCD polishing to Ra < 5 nm, crucial for creating reference surfaces or precision diamond tools where surface defects must be minimized.
Integration of Functional Layers	Custom Metalization Capabilities	If future FAP designs require integrated heating elements or electrical contacts (e.g., for chemo-mechanical effects or temperature control, as temperature reached 380 K in the MD study), 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) on both SCD and PCD.
Theoretical Model Extension	Engineering Support for Material Selection	6CCVD’s in-house PhD team can assist researchers in selecting the optimal diamond material (SCD vs. PCD, specific crystallographic orientation, or Boron-Doped Diamond (BDD) for conductive applications) to replicate or extend this Sapphire Lapping research, ensuring material properties align with advanced MD simulation inputs.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Aiming at exploring the material removal mechanism for sapphire using diamond abrasive grains at the microscopic level, this paper modeled and analyzed the microscopic yield behavior of diamond abrasive grains in the FAP grinding process of sapphire. Molecular dynamics were used to simulate the effects of abrasive particle size on the cutting force, potential energy, and temperature in the Newtonian zone during micro-cutting. The effect of different abrasive particle sizes on material removal was analyzed through experiments. The simulation results show that the abrasive particle radius was 12 Å, the micro-cutting force reached more than 3500 nN, while the cutting force with an abrasive particle radius of 8 Å only reached 1000 nN. Moreover, the potential energy, cutting force, and temperature in the Newtonian zone between the sapphire crystal atoms also increased. The results showed that the material removal rate saw a nonlinear increasing trend with the increase in particle sizes, while the surface roughness showed an approximately linear increase. Both of them showed a similar trend. The experimental results lay a theoretical basis for the selection of the lapping process parameters in sapphire.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi13081322

References

2016 - Process Optimization of Lapping Sapphire Substrate with Fixed Diamond Abrasive Pad
2021 - Chemo-mechanical grinding by applying grain boundary cohesion fixed abrasive for monocrystal sapphire [Crossref]
2013 - Evaluation of double sided lapping using a fixed abrasive pad for sapphire substrates [Crossref]
2020 - Machining characteristics and mechanism of GO/SiO2 nanoslurries in fixed abrasive lapping [Crossref]
2019 - Subsurface damage and material removal of Al-Si bilayers under high-speed grinding using molecular dynamics (MD) simulation [Crossref]
2020 - Effect of Cutting Depth on Mechanical Properties of Single Crystal gamma-TiAl Alloy
2019 - Molecular dynamics simulation of SiC removal mechanism in a fixed abrasive polishing process [Crossref]
2022 - Sharpening Mechanism of Extremely Sharp Edges for Diamond Micro Mills [Crossref]
2021 - Advances in micro milling: From tool fabrication to process outcomes [Crossref]