The standard CO2 cleaning setup consists of:
- CO2 cylinder
- Fittings & PTFE lined hose
- Gun mechanism
- Venturinozzle
- Extras include pressure gauge, filter (recommended)
CO2 Snow Cleaner - Standard Unit
Carbon Dioxide (CO2) Snow Cleaning systems are for the most part straightforward, they consist of a CO2 source, cylinder fitting, a nozzle with an internal orifice, an on/off valve, and the means to transport the CO2 from the source to the nozzle. The products are made with a PTFE lined flexible stainless steel hosing and available on/off controls include solenoid, pneumatic, or manual valves, or hand guns. These products are designed for precision cleaning.
The standard unit is supplied with two nozzles - one asymmetric venturi stainless steel on the unit and a second low velocity nozzle, an on/off gun, a 10 foot flexible PTFE lined stainless steel hose, and a cylinder fitting. Optional submicron sintered stainless steel filter,s and an 0 - 2000 psi pressure gauge can be added.
CO2 cylinder fittings are available for British (BS-8), North American (CGA320 or CGA716), Europe (DIN-6) and Japan (JIS22R) style cylinders. The DIN-6 is the ISO international standard and works in many other countries. If these fittings don't match your requirments, please contact us to discuss further.
How does it work?
- CO2 is expanded through an orifice to create dry ice particles in a high velocity gas stream.
- Momentum transfer of the dry ice removes particles from the dirty sample.
- Hydrocarbons are removed by an transient solvent or freeze fracture mechanism.
- Gas stream blows away contaminants.
- CO2 snow stream cleaning can remove submicron particulates
Nozzle Design
Nozzle design is the most important factor for effective CO2 snow cleaning, with the Venturi orifice angle and length determine velocity of gas and size of CO2 snow. Constant enthalpy expansion within the nozzle ensures snow stream is kept as uniform as possible for reliable, repeatable cleaning.
Using the equipment
- Both liquid and gas CO2 cylinders can be used for cleaning each having their own attributes.
- Gas is generally a cleaner method as the source contains less contaminants. It is suited for smaller samples and does not last as long.
- Liquid CO2 generates more dry ice however has shown to contain more contaminants which could result in recontamination.
- Liquid CO2 is effective for larger areas and the source will last longer; a benefit for production applications.
- It is recommended to experiment with CO2 purity to determine cleaning effectiveness. HP CO2 can result in very high cleaning costs.
- A general start place would be 99.99% for most applications.
Applications
- contamination removal from metals, ceramics, polymers, and glasses
- particle and stain removal from Si, InP, and GaAs wafers
- cleaning optics, i.e., coated lenses, laser, IR and UV optics, diamond turned optics
- sample preparation before surface analysis (Auger, XPS, SIMS) and AFM
- basic surface science studies
- general laboratory, production, and cleanroom cleaning
- substrate preparation
- manufacturing of many metal and ceramic parts and assemblies
- cleaning vacuum systems components, bellows, electron and ion optics
- removing particles from microelectronic and hybrid circuits
- art cleaning
- cleaning telescope mirrors
Safety
Cryogenic Exposure is a risk. The stream is cold, -80C. Exposure of the stream to your skin will freeze it, though not instantaneously. We have tested short exposures here and found no problems. Running the stream over your fingers poses no safety issues (we tested this on ourselves); while holding the stream on yourself at one spot will cause a problem after a few seconds. Exposure is similar to liquid nitrogen. The user will be instantly aware of exposure and will withdraw hand. Never aim the stream at another person. Please wear safety glasses when using this equipment. And follow all safety rules for using compressed gases. See your safety officer or call if you have questions.
Carbon Dioxide Exposure and Oxygen Depletion - If too much carbon dioxide enters your work area, your available oxygen decreases. But far more serious, is excessive carbon dioxide exposure. If you recall the movie Apollo 13, the CO2 buildup was a greater risk than the oxygen consumption. The same applies here. Workplace exposure should be maintained below 0.1% for the entire workday and short term exposures limited to 0.5% for short term exposures. The air we breathe normally contains about 0.04 percent carbon dioxide. Building codes may require sensors and air exchanges if the room carbon dioxide level exceeds 1000 ppm.