Precision cleaning requires CO2 technology that provides improved performance, productivity, environmental quality and economics, all while adapting to rapidly evolving device manufacturing technology. CO2 technology has been used primarily as a means for increasing the cleanliness of components, assemblies, tools and fixtures to increase both capacity and quality. However, arguably more significant, CO2 technology has proven itself to be a means for reducing the cost and improving the productivity of manufacturing high volume and high reliability products. In response to new manufacturing pressures, solvent-based cleaning processes have re-emerged to prevent malfunctions in high-reliability or high-power applications, necessitating a green process solution.
A precision cleaning technology called centrifugal CO2 cleaning combines unique centrifugal dry washing and rinsing processes using specially formulated high-boiling solvents such as citrus terpenes and paraffins with recycled carbon dioxide in a tunable cleaning solvent system.
Let's look at the 3 ways CO2 immersion is used and tested.
1. Precision Cleaning
Precision cleaning trends caused a change in solvent cleaning practices in the 1990's. New environmental concerns and legislative agendas regarding climate change, water and energy conservation shaped the new precision cleaning imperatives for the future. Complex devices such as flip-chip assemblies, disk drives, parts with micro-machined features, composite materials, bioabsorbable polymers, and partially assembled devices had a cleaning need that could not be solved with traditional methods.
In the early 1990s, the first generation Centrifugal CO2 cleaning systems were introduced as an alternative to ozone-depleting substances. This process was adopted faster for high-tech industrial applications. This new process proved to be as good or better than comparable cleaning processes and overcame weak solvent power. Centrifugal CO2 cleaning technology provided significant improvements in productivity, environmental quality, and cost of ownership of their precision cleaning operations.
Liquid CO2 is more suited as a solvent for less complex contamination but very effective for penetrating complex substrate geometries. CO2 is also an excellent drying or rinsing agent (as a solvent) for more powerful washing agents such as a high-boiling solvent (HBS). Using this unique solvent scheme, a range of wash-rinse cohesion energies, solvent powers, viscosities and surface tensions can be employed to address many different types of challenging (and more general) device cleaning applications. CO2 technology offers manufacturers, component suppliers and assembly equipment OEMs new techniques to retool their factories and equipment for clean production.
2. Outgassing - Extraction
For outgas cleaning involving certain polymers and applications, an optimal vacuum degas step is employed to remove residual adsorbed CO2 gas. All CO2 process fluids are automatically transferred and recovered using an integrated fluids management and recycling subsystem.
Centrifugal CO2 systems combine centrifugation, ultrasonics, exclusive CO2-expanded and/or optional O3-loaded prewash agents, liquid carbon dioxide, and optional downstream plasma post-processing with energy-efficient fluids recycling and reuse in a single system. This system is the most capable precision cleaning platform available today and uses only environmentally safe and non-toxic cleaning agents. The parts washing chamber is a top-loading basket centrifuge with a manual or automatic closure. The system includes fluids distillation, re-circulating spray-under-immersion, and clean fluid storage.
3. Reusable CO2
The CO2 expanded HBS wash system separates, cleans and recovers carbon dioxide, HBS and contaminants using phase separation and microfiltration. The recovered CO2 is transferred into both the gross rinse tank and final rinse tank for reuse. The system is capable of recovering more than 95% of the CO2 for reuse. Centrifugal CO2 cleaning is a great substitute for traditional solvent and aqueous processes with bio-based agents reduces pollution, conserves energy and eliminates manufacturing wastes.
Why Centrifugal CO2 Immersion Cleaning?
1. Fully developed cleaning technology that provides a number of unique process benefits.
2. 100% dry cleaning (and rinsing).
3. Bio-based cleaning chemistries.
4. Extremely low surface tensions and viscosities.
5. Solvent cleaning power control.
6. Reduces waste generation and operational costs by eliminating the need for water, waste-water treatment, water recycling and drying with a smaller footprint.
7. Environmental safety and lower energy demand.
8. Develops unique cleaning solutions for the most demanding substrate-contaminant combinations.