For fabricators to produce quality optical components that deliver the fast, reliable performance as intended, they must meet exacting quality standards. That means fabricators must take extreme care with each stage of the production process. This includes the important step of cleaning the lenses, prisms, diffraction gratings, optical filters and mirrors that make up the photonic devices. Finished optical substrates must not only be flawless, they must also be perfectly clean.
Optical elements are typically exposed to dust particles, fingerprint smudges, gasified fumes and other production debris during manufacture. Even the slightest bit of contamination is detrimental to an optical substrate’s performance. Without proper cleaning before final coating, packaging and shipping, they run the risk of poor performance. Or even permanent damage if used dirty.
There are different ways to clean optical elements. Many lenses, optical filters and other optical elements are made from more robust glass materials and are safely cleaned with automated procedures and tools. Vapor degreasing is a long-term batch cleaning process which effectively cleans substrates while also addressing other burdens like sustainability and cost-effectiveness. Some companies are renewing their interest in vapor degreasing over other cleaning methods because it is a highly-effective way to clean optical elements and addresses associated production concerns.
How It Works
A vapor degreasing machine is a closed-loop system. Used within it, is a specialized low-boiling, non-flammable fluid as the cleaning agent. The cleaning fluid constantly re-purifies and recycles for hundreds of cycles before it needs refreshing. This limits fluid use, reduces waste generation and lowers disposal costs.
The machine contains two chambers: the boil sump and the rinse sump. In the boil sump, the cleaning fluid heats the fluid into vapors. The warm vapors rise upwards in the machine and are then trapped by a layer of refrigeration which creates a temperature inversion. The vapors then condense back into liquid form and return into the cleaning machine to be re-used.
Once cleaned, a batch of optical devices is mechanically transferred to the internal rinse sump for final rinsing in a pure, uncontaminated fluid. The devices come out clean, dry, spot-free and immediately ready for the next step in the process.
Sensitive optical components are typically damaged if inappropriate cleaning fluids are used. For instance, plastic optics are easily softened by acetone and some hygroscopic crystal materials may be dissolved through contact with water. Many vapor degreasing fluids have excellent materials compatibility and can be used on glass, fused silica, crystals, plastics and metals.