Handbook of Solvents - George Wypych - ChemTech - Ventech!

914 Martin Hanek, Norbert Löw, Andreas Mühlbauer
Figure 14.8.15. Scheme of a low-pressure batch cleaning system.
high-pressure cleaning unit is supplied with VIGON � A200 by a chemical dosing station.
Cleaning medium quality can be maintained by installing a flux absorber system. The
cleaned parts are blown-out with an air knife to minimize carry-over losses from the
high-pressure cleaning section. Pre-rinsing the parts with deionized water follows the
cleaning section. A fine rinse unit ensures minimum ionic contamination on the PCBs.
Finally, the cleaned parts are then blown off with hot air. Complete drying, particularly of
parts that retain a great deal of liquid, can be performed with an infrared dryer. 20,21
14.8.4.2 Flux removal from printed circuit boards - water-free cleaning
processes
In the European Community, the production and sales of chlorinated fluorocarbons (CFCs)
have been banned since 1995. Due to their ozone depletion potential (ODP)
hydrochlorinated fluorocarbons (HCFCs) are also subject to be phased-out. The revision of
EC Direction 3094/95 proposed in Article 5 the ban of HCFCs as solvents for parts cleaning.
HCFCs are not allowed in open solvent applications and their use in contained cleaning
systems, such as industrial equipment with ultrasonic agitation, will be banned by January
1, 2002. However, the aerospace and aeronautic industries are allowed to use HCFC until
January 1, 2002. Furthermore, in some countries, including Germany and Switzerland, national
ordinances have prohibited the use of HCFCs to replace CFC solvents for several
years. Consequently, the search for alternative solutions to avoid cleaning (no clean technology)
or to use environmentally acceptable solvents leads to new cleaning processes including
new cleaning agents and new cleaning equipment.
• Novec TM hydrofluoroether (HFE) in combination with a cosolvent, and
• High boiling cleaning agents that can be recycled continuously by vacuum
distillation.
These two new processes can permanently replace both 1,1,1-trichlorochlorethane
and CFC-113, as well as, chlorinated solvents such as dichloromethane, trichloroethylene
(TCE) , perchloroethylene and HCFC-141b.