TECHNET Archives

August 2000

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 26 Aug 2000 11:18:00 +0300
Content-Type:
text/plain
Parts/Attachments:
text/plain (118 lines)
Phil

There are hundreds of products, some of which will work better with the flux you are
using than others. It is therefore impossible to recommend one which is universal for
all fluxes and conditions of use. I must admit I'm very surprised that you are still
using a 1,1,1-TCA-based material as this material has been banned from manufacture in
developed nations since 1996 under the Montreal Protocol. Your supply must therefore
come from either stockpiled or recycled material. The shelf life of stabilised
1,1,1-TCA is considered to be 18 - 24 months after which free hydrogen chloride may
start to form and remain dissolved in it. Most recycled material also contains
uncontrolled hydrogen chloride. You may therefore be currently spraying your boards
with a free acid, which would probably do more harm than not cleaning them at all. I
should also like to point out that aerosol spraying this solvent is 100% emissive and
you are not helping the ozone layer any. Just to give you a picture of what is
happening, releasing the contents of just one can is approximately equivalent to
removing ALL the ozone between 15 and 50 km altitude in a column of about 1,000 m2 (1/4
acre) base for 8 years (of course, it does not work like that, but this is more
pictorial).

I therefore entreat everyone who still has 1,1,1-TCA or CFC-113 (Freon, Arklone etc.)
solvents in any form or package to have them destroyed immediately by an approved means
or facility: please contact your local environmental authorities for details how to do
it.

Now, to return to your problem. As stated above, I cannot recommend a product for your
specific application but I can recommend a substance NOT to use, especially in an
aerosol. That is any product containing n-propyl bromide (aka 1-bromopropane or nPB).
This is a solvent with characteristics similar to 1,1,1-TCA. It has a short atmospheric
residence time, compared with many other solvents, because it is easily hydrolysed.
This may make it potentially quite toxic (acute toxicity is moderate, chronic toxicity
is totally unknown and sub-chronic toxicity is very doubtful with some reports of
reduced sperm counts and mobility and neurotoxicity in rats at fairly low exposure
levels - contact me privately for references). Worse than its toxicity is that it is
ozone-depleting, but not yet regulated by the Montreal Protocol. A sub-committee is
currently evaluating potential use of nPB with a view to eventual regulation by the
Parties to the Protocol, if deemed necessary. The reason that it has not yet been
regulated is because of its short residence time, which the traditional methods of
modelling ozone depletion foxes, so there is still some doubt about the mechanisms.
What is certain is that the ozone-depleting effect, unlike other solvents, depends
largely on the latitude of emission (also, to a lesser extent, the longitude) and even
the season and weather. These two factors should be sufficient discouragement, combined
with the possibility of it being phased out rapidly should the Parties to the Protocol
so decide. In the USA, there is an anomalous regulatory position. The US EPA has not
given it SNAP approval as a suitable replacement for regulated OD solvents and is
unlikely to do so this year. This means that it can be freely used for all applications
until any restrictions imposed by a later SNAP decision are known. Furthermore, OSHA
has not declared an OEL/PEL, but has requested the National Toxicology Program to
evaluate it (a process unlikely to be completed before 2003 or 2004). The manufacturers
give a recommended, but unofficial, OEL of 100 ppm, but from what little data is known,
this may seem to be very generous and 20 - 25 ppm more prudent, possibly even less. No
reporting is required to the Toxics Release Inventory, RCRA, Safe Drinking Water Act or
Clean Water Act, so use of the solvent is very liberal with no bureaucratic hindrances,
as with the traditional chlorinated solvents. In other words, the use of new solvents,
like nPB, is totally devoid of restrictions until such time as they are shown to be
dangerous to health, safety and the environment. Compare this with new pharmaceutical
products which are unavailable until they have been proved safe. At this moment, there
is an estimated 5000 tonnes of nPB being used in the US, annually, but there is a
potential market of about 100,000 tonnes with more than as much again in other
countries (this figure assumes no regulatory hindrances, but OSHA place it
pessimistically at 300,000 tonnes which, in my opinion, is not realistic). If it should
prove, in a few years, to have serious chronic effects, I can foresee that there may be
some class action suits.

Hope this helps.

Brian

Phil Nutting wrote:

> Hi TechNetters
>
> For hand spot cleaning of PWBs we currently use a Miler-Stephenson product
> MS-195/CO2 which contains 1,1,1 Trichloroethane.  I'm considering changing
> to a newer Ozone friendly material.  Are there any recommendations for an
> aerosol package of board cleaner (using rosin flux at the moment)?  Or
> recommendations of what NOT to buy?  The stuff we use works very well but
> I'm trying to come into the new millinneum with many of our processies.
> Yikes... change!
>
> Reagrds,
>
> Phil Nutting
> Manufacturing Engineer
> Kaiser Systems, Inc.
> 126 Sohier Road
> Beverly, MA 01915
> ph: 978-922-9300
> fx: 978-922-8374
> [log in to unmask]
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
> the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
> information.
> If you need assistance - contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> ##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################

ATOM RSS1 RSS2