Effect of initial deflection of diamond wire on thickness variation of sapphire wafer in multi-wire saw

At a Glance

Metadata	Details
Publication Date	2015-04-01
Journal	International Journal of Precision Engineering and Manufacturing-Green Technology
Authors	Doyeon Kim, Hyoungjae Kim, Sangjik Lee, Haedo Jeong
Institutions	Korea Institute of Industrial Technology, Pusan National University
Citations	47
Analysis	Full AI Review Included

TECHNICAL ANALYSIS & DOCUMENTATION: MPCVD DIAMOND FOR PRECISION WAFERING OPTIMIZATION

Executive Summary

This document analyzes the technical findings regarding the optimization of sapphire wafer slicing via Multi-Wire Sawing (MWS) using controlled initial wire deflection. The key conclusions directly inform the requirements for high-performance diamond tooling materials, a core offering of 6CCVD.

Process Optimization Focus: The study identifies initial wire deflection (D) as the primary control parameter governing the Total Thickness Variation (TTV) in sapphire wafering.
Accelerated Wear for Stability: Increasing the initial wire deflection (D2=2 mm, D4=4 mm) significantly increases the initial cutting load, which, according to Archard’s wear law, accelerates the wear rate of the diamond abrasives.
Improved Break-In: This accelerated wear results in a faster “break-in” time for the diamond wire, leading to quicker stabilization of the cutting force and cutting depth.
TTV Reduction: By achieving faster stabilization, the critical diameter variation of the diamond wire between the initial and final contact points is reduced, directly minimizing the overall TTV of the processed wafer.
Kerf Loss Minimization: Optimized deflection conditions (D2, D4) led to the smallest kerf loss (approx. 235 µm) compared to the zero-deflection condition (D0, approx. 260 µm).
Material Implication: The success of this optimization hinges entirely on the consistency and extreme hardness (H) of the diamond abrasive grit used in the electroplated wire tooling.

Technical Specifications

The following parameters define the experimental conditions used to determine the effect of initial wire deflection on cutting performance and diamond abrasive wear.

Parameter	Value	Unit	Context
Workpiece Material	C-plane Sapphire Ingot	N/A	50 mm x 50 mm square
Diamond Abrasive Diameter	30-40	µm	Commercial Ni-electroplated wire
Diamond Core Diameter	0.18	mm	Commercial Ni-electroplated wire
Wire Tension	40	N	Constant operational setting
Wire Speed	400	m/min	Constant operational setting
Ingot Feeding Speed	0.75	mm/min	Cutting feed rate
Initial Deflection Conditions	0, 2, 4	mm	Tested parameters (D0, D2, D4)
Cutting Depth Target	30	mm	Target feed depth for the experiment
Optimized Kerf Loss Range	235-240	µm	Achieved under D2/D4 conditions
Cutting Load (D2/D4 Stable)	~2.5	N	Load measured against feeding direction
Abrasive Extrusion Height (Initial)	25-30	µm	Measured on new wire (D0 condition)
Coolant Type	DKW-1P, 5 wt% diluted	N/A	Slurry solution

Key Methodologies

The experiments were conducted using a customized single-wire saw apparatus to isolate the effect of initial wire deflection (D) on cutting load and abrasive wear.

Workpiece Preparation: A 50 mm x 50 mm C-plane sapphire ingot was prepared for cutting.
Diamond Tooling: Commercial nickel-electroplated diamond wire (0.18 mm core, 30-40 µm grit) was utilized.
Experimental Setup: A single wire saw was equipped with two 5 kg capacity load cells to monitor:
- Cutting force (along the wire moving direction).
- Cutting load (against the ingot feeding direction).
Wire Deflection Control: Experiments were systematically run under three initial deflection conditions: D0 (0 mm), D2 (2 mm), and D4 (4 mm).
Wear Monitoring: A vision system (CCD camera, image processing) was used to measure the variation in the diameter and average extrusion height of the diamond abrasives after every 100 contacts between the ingot and the wire.
Performance Measurement: Kerf loss (cutting path width) was characterized using a digital microscope (VHX-2000X, Keyence) to assess the effectiveness of the deflection conditions on overall TTV reduction.

6CCVD Solutions & Capabilities

The research highlights that the key to optimizing MWS performance is controlling the wear rate (V) of the diamond abrasive, which is critically dependent on its intrinsic hardness (H). 6CCVD’s specialized expertise in high-purity, high-strength MPCVD diamond is essential for engineering superior wire saw tooling or providing the final precision substrates.

Requirement/Challenge from Paper	6CCVD Solution & Capability	Application & Sales Benefit
Need for extremely hard, consistent abrasive material (Maximizing H in Archard’s Wear Law).	Polycrystalline Diamond (PCD) Material: 6CCVD offers high-quality MPCVD PCD substrates which serve as the foundation for durable tooling. Our controlled-process PCD exhibits superior homogeneity and toughness, ideal for abrasive manufacturing.	Enhanced Tool Life: Providing diamond feedstock that minimizes variability in hardness and wear coefficient (K), leading to more predictable break-in and sustained cutting performance.
Need for precision substrates in wafering applications (Sapphire, SiC, GaN).	Custom Dimensions & Thickness Control: We supply MPCVD diamond wafers (SCD and PCD) up to 125mm in diameter. SCD thickness ranges from 0.1µm up to 500µm, and substrates up to 10mm.	Diverse Substrate Supply: Offering high-quality, thermally and electrically stable diamond substrates for advanced optics, heat sinks, and power electronics (GaN/SiC on Diamond).
Requirement for low surface damage and TTV mitigation in post-sawing processes.	Ultra-Precision Polishing Services: We offer superior polishing capabilities, achieving Ra < 1nm for SCD and Ra < 5nm for inch-size PCD plates.	Minimized Post-Processing: Reduces or eliminates the need for extensive post-sawing Chemical Mechanical Polishing (CMP), drastically cutting manufacturing time and cost.
Complex material interaction, friction, and tribological analysis support.	In-House PhD Engineering Support: Our material scientists specialize in the tribology and mechanics of diamond. We assist clients in modeling abrasive wear (Archard’s Law) and optimizing material selection for severe conditions like high-tension MWS.	Process Optimization Partnership: Leverage our expertise to design customized diamond materials for optimal hardness and geometry tailored to specific wire tension and feed rate recipes.
Integration of sawed wafers into devices requiring electrical contacts.	Advanced Metalization Capability: We offer custom internal metalization services (Au, Pt, Pd, Ti, W, Cu) on diamond substrates, readying wafers for subsequent thermal management or sensor applications.	Turnkey Manufacturing: Providing ready-to-use diamond components, simplifying the supply chain for advanced device integration.

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

Tech Support

Original Source

DOI: https://doi.org/10.1007/s40684-015-0015-x

References

2015 - Sapphire Substrate to Dominate LED Market in 2014
2013 - Proc. of the Asian Society for Precision Engineering and Nanotechnology
1996 - Friction, Wear, Lubrication: A Textbook in Tribology [Crossref]