Hello,
I work for a company and we process silicon wafers. We do lapping and I have a question regarding our slurry.
We use water as the vehicle and aluminum oxide for the abrasive. I believe we use Aqualap for the suspension treatment. Can you guys explain to me what exactly the suspension treatment does? I think I know but I'm not 100% sure.
When you deal with very fine particles interesting things start to happen, that do not happen at larger scale.
1. Very fine particles can coagulate together to form larger structures
2. very fine particles take a very long time to settle to the bottom of the solution. Extreme case of this is a colloidal suspension when particles do not settle at all.
As the result you end up with misc additives to abrasive slurries that enhance or eliminate these side effects.
Sodium silicate is often used to "thicken" the liquid and enhance its ability to hold patricles in suspension.
Coagulating agents are used to cause particles to stick together and drop out of solution (pool water "polishers" basically do this).
Soap is often used to break water surface tension to allow very fine abrasive particles to stay in suspension and to get closer to object being polished, vs just gliding on a layer of water just above the surface being polished.
These effects usually have larger effect at sub micron polish level and are rarely even thought of if you are polishing with like a 200 grit compound or bigger particle size.
Do you have msds for your suspension treatment. I cant find it online.
