井冈山What influence does the particle size of diamond micro-powder have on the polishing effect?

The particle size of diamond micro-powder has a decisive influence on the polishing effect. Its core mechanism of action is reflected in the matching of particle size distribution, particle morphology and processing target. The specific influences are as follows:

I. Quantitative Relationship between Particle Size and Surface Roughness

Fine particle size (0.5-3μm)

Surface quality: In the polishing of copper materials, micro-powder with a particle size of 1μm can increase the surface microhardness to HV85 (25% higher than the original surface), with a Ra value of ≤0.02μm, achieving a mirror-like effect. Scanning electron microscopy shows that the oxide layer can be peeled off within 15 seconds, and the exposed area of the base metal reaches 92%.

Processing efficiency: With a particle size of 1.5μm and a polyurethane polishing pad, the material removal rate remains stable at 0.15-0.2mm³/min within 30 minutes, and the standard deviation of surface roughness is ±0.003μm.

Process stability: By adopting a three-stage particle size transition system (3μm coarse polishing →1μm fine polishing →0.5μm final polishing), the scattering loss of the optical device's reflecting mirror surface can be reduced to 0.15dB/km, meeting the fiber coupling standard.

Coarse particle size (>5μm)

Surface damage: During the polishing of SiC wafers, large-sized particles tend to embed into the wafer surface, causing microcrack damage. For instance, the use of micro-powder with uneven morphology can cause the surface of the wafer to be sandy and the number of scratches to be countless.

The contradiction between efficiency and cost: Coarse particle size can enhance the material removal rate (for instance, the efficiency of diamond micro-powder is 40% higher than that of alumina polishing agent), but the surface quality needs to be balanced. Experiments show that if the particle size is too large (such as >3μm), it will cause the depth of the polishing scratch on copper materials to exceed 2μm, and subsequent fine polishing correction is required.

Ii. The Synergistic Effect of particle size distribution parameters (D5/D50/D95)

The influence of the D5 value

D5 represents the proportion of fine-end particles. Reducing it can enhance the surface finish. For instance, in the manufacturing of semiconductor chips, micro-powders with a smaller D5 value can fill the gaps between large particles, reduce surface scratches, and increase the qualified rate of copper material polishing from 78% to 95%.

However, a D5 value that is too small will reduce grinding efficiency and needs to be compensated for through process optimization (such as ultrasonic assistance). 40kHz ultrasonic waves can make the movement trajectory of micro-powder more regular, reducing the surface waviness to one third of that in conventional processes.

The stability of the D50 value

D50 is the average particle size, and its fluctuation directly affects the processing accuracy. In the polishing of optical glass, the micro-powder with precisely controlled D50 value can ensure surface flatness, reducing the corrosion area to only 0.3% after the salt spray test (8.7% for non-compliant parts).

The deviation of the D50 value can be ensured to be less than 5% through laser diffraction detection, meeting the requirements of high-precision processing.

Upper limit control of the D95 value

D95 reflects the content of coarse particles, and its increase may lead to an increase in surface roughness. For instance, in the polishing of copper materials, micro-powders with a relatively high D95 value need to be accompanied by a coolant flow rate of ≥5L/min to prevent secondary adhesion of copper shavings. Otherwise, if the contact point temperature exceeds 80℃, it will cause passivation of the micro-powders.

Iii. Adaptability of particle size to processing scenarios

Precision polishing (such as semiconductors, optical devices)

Give priority to using micro-powders ranging from 0-0.5μm to 6-12μm, in combination with polyurethane or nano-diamond suspensions. For instance, by adopting this solution, a certain enterprise has increased the utilization rate of copper materials from 82% to 94%, saving over 1.2 million yuan in raw material costs annually.

The humidity of the working environment should be controlled (45-55%RH) to prevent the agglomeration of fine powder, which may affect the uniformity of dispersion.

Rough grinding processing (such as metal cutting, geological drill bits)

Micro-powders ranging from 5-10μm to 12-22μm can be selected, taking into account both efficiency and surface quality. For instance, in the surface grinding of single diamond crystals, the surface roughness can be gradually reduced step by step through a multi-step process (gradually decreasing the particle size), eventually reaching Ra=50nm.

Optimization of Special scenarios

Electromagnetic field assistance: Applying a 0.5T magnetic field can Orient and align the micro-powder, increasing the cutting efficiency by 15%, but the cost of equipment renovation increases by 30%.

Temperature control: A constant temperature circulation system is adopted to stabilize the temperature at 50±5℃, which can prevent the passivation of fine powder and extend the service life of the polishing liquid.

Iv. Suggestions for Economic Efficiency and Process Optimization

Cost balance

Although the unit price of diamond micro-powder is 8 times higher than that of alumina, the overall efficiency is improved (material removal rate +40%) and the scrap rate is reduced (pass rate +17%), and the overall cost can be saved by 18-25%.

Each kilogram of micro-powder can process copper materials covering an area of up to 15 square meters, and the cost is reduced by 22% compared with traditional processes.

Equipment and process selection

Medium and small batch production: Use particle size adjustable equipment to flexibly adapt to the needs of different processing stages.

Mass production: Configure multi-station automatic lines to achieve the best cost performance. For instance, a dual-axis self-rotating polishing machine is 60% more efficient than a single-axis device.

Key points of quality control

Particle size detection: mainly laser diffraction method, supplemented by sieving method (only applicable to particles >40μm).

Impurity control: The purity of the diamond should be over 99%, and magnetic impurities should be low to avoid agglomeration that may affect the precision polishing effect.

Batch stability: Each batch is sampled for energy spectrum analysis to ensure that the oxygen content on the copper surface is ≤1.5at%.