Classification of diamond powder quality levels: What are the differences among different levels?

Diamond powder, as the core raw material in the field of super-hard materials, is widely used in precision processing, optical manufacturing, semiconductor industries, etc. The quality grade of diamond powder directly affects the processing effect and cost-effectiveness. However, the market standards vary and the classification is ambiguous, often confusing the purchasers. This article analyzes the quality grade classification of diamond powder from three dimensions: core indicators, application scenarios, and detection methods, to help you make precise selections. 

I. Core Classification Criteria for Quality Grades

The quality grades of diamond micro-powder are mainly divided based on four core indicators: particle size distribution, impurity content, crystal morphology, and thermal stability. Generally, they are classified into three grades: industrial grade, precision grade, and ultra-precision grade.

Particle size distribution

Particle size distribution is a key indicator for measuring the uniformity of micro-powder. For the industrial grade, the deviation of D50 should not exceed the nominal value by ±15%, and the span coefficient ((D90 - D10) / D50) should be ≤ 2.0; for the precision grade, the deviation is narrowed to ±10%, and the span coefficient ≤ 1.5; for the ultra-precision grade, the deviation of D50 should be ≤ ±5%, and the span coefficient ≤ 1.2. For example, if the particle size deviation of the micro-powder used for semiconductor wafer polishing exceeds the standard, it will cause scratches or waves on the processing surface.

Impurity content

Impurity content directly affects the chemical stability and processing life of the micro-powder. For the industrial grade, the total amount of metallic impurities (Fe, Ni, Co, etc.) is ≤ 3%, and the total amount of non-metallic impurities (S, Cl) is ≤ 0.5%; for the precision grade, the total amount of metallic impurities is controlled at ≤ 1.5%, and a single element is ≤ 0.8%; for the ultra-precision grade, the total amount of metallic impurities should be ≤ 0.5%, and harmful element residues must be confirmed through ICP-OES testing.

Crystal morphology

Crystal morphology determines the cutting force and surface quality of the micro-powder. For the industrial grade, up to 15% of irregular particles are allowed; for the precision grade, the proportion of regular particles should be ≥ 85%, and there should be no obvious agglomeration; for the ultra-precision grade, the particles must be confirmed to have a complete hexagonal or octagonal shape through SEM observation, with clear edges and no defects.

Thermal stability

Thermal stability reflects the performance retention ability of the micro-powder in a high-temperature processing environment. For the industrial grade, the quality loss at 800°C should be ≤ 5%; for the precision grade, the standard is raised to ≤ 2%; for the ultra-precision grade, the quality loss at 1000°C should be ≤ 0.5%, and there should be no graphitization phenomenon through TGA testing. 

II. Differences in application scenarios of different levels

Industrial grade: Suitable for common grinding and rough polishing scenarios, such as stone processing and ordinary metal cutting. It has a lower cost but lower processing efficiency and higher surface roughness.

Precision grade: Used for precise polishing of optical glass, hard alloys, etc., such as camera lenses for mobile phones and mold steel processing. It has high processing efficiency and surface roughness can reach Ra0.01μm or below.

Ultra-precision grade: Specifically designed for ultra-hard materials such as semiconductor wafers and sapphire substrates, such as 5G chip manufacturing and LED substrate processing. Its processed surface roughness can reach Ra0.001μm level, and there is no sub-surface damage. 

III. Detection Methods for Quality Grades

Particle size detection: Use a laser particle size analyzer (such as Malvern Mastersizer 3000) for wet dispersion testing. Three measurements are required and the average value is taken.

Impurity analysis: Detect metal impurities using ICP-OES and non-metal impurities using ion chromatography. Compliance with relevant national standards is necessary.

Morphological observation: Use SEM to take representative images at a magnification of 5000 times to assess the regularity of the particles.

Thermal stability test: Heat at a rate of 10°C/min in nitrogen protection to 1000°C. Record the mass loss curve using TGA. 

Conclusion

The classification of the quality grades of diamond powder is a comprehensive balance of technology, cost and application. When purchasing, one needs to select the corresponding grade of product based on factors such as processing materials, surface roughness requirements, and equipment parameters. For example, the semiconductor industry should prefer ultra-precision grade powder, while for ordinary stone processing, industrial grade can be chosen to reduce costs. By understanding the grade differences, one can avoid the risks of "over-provisioning" or "insufficient performance", and achieve the maximization of cost-effectiveness.