From: NAME: WILLIAM G KENYON
FUNC: Chemicals/Electronics
TEL: 302-652-4272 <KENYONWG@A1@ESVAX>
To: NAME: [log in to unmask] <"[log in to unmask]"@ESDS01@MRGATE@ESVAX>
There are many acceptable cleaners for RMA flux available today
that have documented use success.
By class by time of introduction:
HCFC:
The only member of this class that is approved by SNAP is
HCFC-225. The blends and azeotropes are also accepted. These are
in use for RMA flux removal in high rel. (military) applications.
Since the allowed workplace levels are much lower than CFC-113 or
TCA type products, retrofitted equipment is highly recommended.
Such equipment is extremely efficient.
HFC:
The first approved member of this class was 43-10. Similarly,
blends and azeotropes are also accepted.
New members of this class are benzotrifluoride and
octafluorocyclopentane (see proceedings of Oct. CFC Conf.).
HFE:
The first approved member of this class was 7100. Similarly,
blends and azeotropes are also accepted. In addition, a
co-solvent process using HFE and high boiling organic solvent in
the first tank of a vapor defluxer was described at Nepcon West
Feb. 96 for the replacement of HCFC-141b for RMA flux removal in
a high reliability application. The workplace exposure level of
HFEs tend to be high enough (about 2x TCA) so they can be used in
modern vapor defluxers without retrofitting. This is a great
advantage to small to medium size companies.
Alcohol:
2-propanol (IPA) with a cyclohexane/IPA first wash has been
effective for RMA flux removal. Explosion/flame proof equipment,
while required, is readily available from several sources in a
variety of sizes.
n-Propyl Bromide:
This is a new material, not yet formally SNAP approved, which has
the potential to be an effective TCA replacement. Available from
several sources, a comprehensive paper was presented at the CFC
Conf., Oct.96.
Aqueous/Saponifier:
Effective removal of RMA flux by saponifier has been around since
1974. Now both the traditional organic and the new inorganic
saponifiers are available. However, if solvent was the previous
process, then new equipment will be needed, as well as training
in handling an aqueous waste stream properly.
Semi-Aqueous:
This was the break-through technology that showed that surface
mount could be cleaned without CFC-113. Both terpene-based and
hydrocarbon-based versions are available. New equipment was
needed to implement this process, which is used world wide.
A new variant of the process is to use a 5% water emulsion of the
semi-aqueous cleaning agent as the wash step, followed by a water
rinse and dry. This simplified the machine design, eliminated
any flammability concern with the organic solvent, greatly
minimized the waste stream and thus dramatically cut operating
costs.
In addition, there are many niche products, but this summarizes
the mainstream product classes that are represented in the United
Nations Environment Programme (UNEP) Solvents and Cleaning Agents
Technical Options Committee (TOC) report.
--Bill Kenyon
Global Centre for Process Change, Inc.
302-652-4272/-5701 Tel/Fax
US Member, UNEP TOC.
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