Application · Sapphire CMP
Colloidal silica for sapphire polishing
Potassium-stabilized colloidal silica of 41 to 137 nm for chemical mechanical polishing of sapphire substrates, watch covers and optical windows. Supplied as concentrate to slurry makers and polishing shops.
Why colloidal silica
Chemical mechanical polishing of a very hard crystal
Sapphire is one of the hardest materials to polish. In chemical mechanical polishing (CMP), alkaline colloidal silica reacts with the sapphire surface to form a softer layer, which the silica particles then wipe away. This gives a smooth, damage-free surface without the scratches left by harder abrasives.
- Sapphire wafers for LED and RF devices
- Watch covers, camera lens covers and optical windows
- Other hard crystals and ceramics, such as SiC substrates
For sapphire, larger particles and higher solids are usually chosen to keep the removal rate high, followed by finer grades where a better finish is needed.
Recommended grades
Grades for sapphire slurries
| Grade | Particle size (DLS) | SiO₂ | pH | Stabilizer | Best for |
|---|---|---|---|---|---|
| CS-HP 74K | 74 nm | ≈41% | 9–11 | Potassium | Main polishing of sapphire substrates and windows |
| CS-UP 135K | 137 nm | ≈40% | 9.5–10.5 | Potassium | High-removal polishing; ultra-high purity, supplied by project |
| CS-HP 41K | 41 nm | ≈40% | 9–11 | Potassium | Finer finish after main polishing |
Particle size and SiO₂ are typical values from production batches; pH is the specification range. Full TDS, SDS and trace-metal data on request.
What matters in a sapphire slurry
What we control for you
Particle size and distribution
Average particle size is measured on every batch by dynamic light scattering. Size distribution reports are available on request.
Stability at high pH
Potassium-stabilized grades stay dispersed at the alkaline pH used in sapphire CMP.
Low trace metals
High-purity grades keep metal contamination low. Ultra-high-purity grades have sodium below 3 ppm by ICP-MS.
Grades for slurry makers
Supplied as concentrate in drums or IBC totes for slurry makers and polishing shops. Particle size and solids can be adjusted.
FAQ
Common questions
Which particle size is best for sapphire polishing?
Sapphire slurries usually use larger particles, typically about 50 to 120 nm, to keep the removal rate high. CS-HP 74K is our main grade; CS-UP 135K is available by project for high-removal steps.
Can you match the colloidal silica we use now?
Yes. Send us the datasheet or a sample of your current product, and we will propose a matching grade or adjust particle size, solids and pH.
Do you supply finished slurry?
We supply colloidal silica concentrate for slurry makers and polishing shops. Additives such as pH adjusters are usually added by the user.
Is colloidal silica hazardous for shipping?
Colloidal silica is generally not classified as dangerous goods for transport. Please check the SDS for each grade.
Test it on your own samples
Tell us your material, current polishing product and target finish. We will suggest a grade and send a free sample with its COA. Freight is paid by the customer, by courier account or in advance.
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