# Best chemical for removing flux residue?

T

#### [email protected]

Jan 1, 1970
0
When repairing circuitry, its often tricky to remove flux residues
from the PCB after rework.
The flux remover spray I find locally in my area doesnt seem to be
very effective.
From what I understand years ago, they banned the really good stuff
for this (some type of CFC). Can anyone recommend an effective flux-
remover spray (brand) that perhaps I can order online?
Thanks

R

#### Ron(UK)

Jan 1, 1970
0
When repairing circuitry, its often tricky to remove flux residues
from the PCB after rework.
The flux remover spray I find locally in my area doesnt seem to be
very effective.
for this (some type of CFC). Can anyone recommend an effective flux-
remover spray (brand) that perhaps I can order online?
Thanks

A trick I used to do when I repaired boards for a commercial company,
was to lightly brush over the newly soldered joints with a brass wire
brush, then mop over the area with isopropanol. This smooths out the
coating on the board and makes it virtually impossible to see which
components have been changed.

Ron(UK)

D

#### Dave Plowman (News)

Jan 1, 1970
0
When repairing circuitry, its often tricky to remove flux residues
from the PCB after rework.

I've never bothered in many many years of DIY building stuff and never had
problems. Might make a difference with densely packed SM technology,
though.

S

#### Smitty Two

Jan 1, 1970
0
When repairing circuitry, its often tricky to remove flux residues
from the PCB after rework.
The flux remover spray I find locally in my area doesnt seem to be
very effective.
for this (some type of CFC). Can anyone recommend an effective flux-
remover spray (brand) that perhaps I can order online?
Thanks

Isopropyl alcohol works quite well, as long as it's 99% or so. Don't use
the watered-down drugstore kind. Commercial flux thinner is mostly ethyl
alcohol and that works, too, but it's usually more difficult to obtain
and quite a bit more expensive. Isopropyl runs in the neighborhood of
$25 for a five gallon can from an industrial chemical supply house. I don't use a spray bottle because it distributes the dissolved flux all over the place rather than picking it up. I buy 6" cotton swabs by the case (10,000 pieces) for less than$50. A Menda dispenser is handy for
dampening the swab prior to working the flux residue. Several swabs will
be needed and patience is more important than furious pressure and
speed. Still it only takes a minute or two to clean up after a typical
component replacement.

J

#### James Beck

Jan 1, 1970
0
Isopropyl alcohol works quite well, as long as it's 99% or so. Don't use
the watered-down drugstore kind. Commercial flux thinner is mostly ethyl
alcohol and that works, too, but it's usually more difficult to obtain
and quite a bit more expensive. Isopropyl runs in the neighborhood of
$25 for a five gallon can from an industrial chemical supply house. I don't use a spray bottle because it distributes the dissolved flux all over the place rather than picking it up. I buy 6" cotton swabs by the case (10,000 pieces) for less than$50. A Menda dispenser is handy for
dampening the swab prior to working the flux residue. Several swabs will
be needed and patience is more important than furious pressure and
speed. Still it only takes a minute or two to clean up after a typical
component replacement.
Why not use the watered down stuff?
Some of the fluxes out there are water soluble and between the alcohol
and the water I think you would have the bases covered.
We have been using 90% for 20+ years. Seems to have worked just fine
for us. In fact, until they changed their formula, we used a local
industrial chemical manufacturer's "Window Cleaner" that was just
isopropyl, water, some surfactants, and a little blue dye. 55 gallons
drums of the stuff was pretty reasonable.

Jim

S

#### Smitty Two

Jan 1, 1970
0
James Beck said:
Why not use the watered down stuff?
Some of the fluxes out there are water soluble and between the alcohol
and the water I think you would have the bases covered.
We have been using 90% for 20+ years. Seems to have worked just fine
for us. In fact, until they changed their formula, we used a local
industrial chemical manufacturer's "Window Cleaner" that was just
isopropyl, water, some surfactants, and a little blue dye. 55 gallons
drums of the stuff was pretty reasonable.

Jim

Good considerations, and I'm hardly in a position to disagree with your
experience. My thinking is that if it's water soluble flux, use water.
If not, the water just reduces drying time, reduces cleaning
effectiveness, and helps to exacerbate the spreading of flux residue
over an increasingly larger area of the board.

Of course, for most repair work, that's not an issue. Perfect cosmetic
cleanliness is demanded of me by my commercial customers, so a little
irregularly shaped stain of flux residue, however slight, just won't
fly. Your average consumer isn't going to notice or expect that.

It's good to remember that rosin flux is non-corrosive and
non-conductive and there's no real need (other than cosmetic) to clean
it up at all, while water soluble flux is definitely corrosive and
should be pretty thoroughly removed soon after use.

S

#### Smitty Two

Jan 1, 1970
0
If not, the water just reduces drying time,

Uh, I meant increase, of course.

A

#### Arfa Daily

Jan 1, 1970
0
When repairing circuitry, its often tricky to remove flux residues
from the PCB after rework.
The flux remover spray I find locally in my area doesnt seem to be
very effective.
for this (some type of CFC). Can anyone recommend an effective flux-
remover spray (brand) that perhaps I can order online?
Thanks

For many years I've used Servisol De-Flux 160. Just got a new can today in
fact. Cheap, well behaved and controlled aerosol, and very effective.

Arfa

J

#### Jim Yanik

Jan 1, 1970
0
Why not use the watered down stuff?
Some of the fluxes out there are water soluble and between the alcohol
and the water I think you would have the bases covered.
We have been using 90% for 20+ years. Seems to have worked just fine
for us. In fact, until they changed their formula, we used a local
industrial chemical manufacturer's "Window Cleaner" that was just
isopropyl, water, some surfactants, and a little blue dye. 55 gallons
drums of the stuff was pretty reasonable.

Jim

The usual "rubbing" alcohol found in US drugstores is 70% alk.

J

#### James Beck

Jan 1, 1970
0
The usual "rubbing" alcohol found in US drugstores is 70% alk.
Here, I have no problem finding 90% at our local national chain drug
store.
70% is the most common, but 90% is not that obscure.

Jim

J

#### JeffM

Jan 1, 1970
0
Dave said:
I've never bothered in many many years of DIY building stuff
Makes me think you don't live near a large body of water.
When working in a Southern climate near the Atlantic Ocean,
airborne moisture was the enemy.
Anything that would absorb it was equally depricated.

This report
says that putting PCBs in a vapor degreaser made things WORSE.
So much for intuition.

D

#### Dave Plowman (News)

Jan 1, 1970
0
Makes me think you don't live near a large body of water.

In the UK? You're never that far from a large body of water. Including the
sky...
When working in a Southern climate near the Atlantic Ocean,
airborne moisture was the enemy.
Anything that would absorb it was equally depricated.

If the sort of flux found in standard lead multicore solder was very
hydroscopic surely it would be easy to wash off with water?

I'm ignoring modern lead free solder and water based flux. For the rest of
my life. ;-)

D

#### DaveM

Jan 1, 1970
0
Smitty Two said:
Good considerations, and I'm hardly in a position to disagree with your
experience. My thinking is that if it's water soluble flux, use water.
If not, the water just reduces drying time, reduces cleaning
effectiveness, and helps to exacerbate the spreading of flux residue
over an increasingly larger area of the board.

Of course, for most repair work, that's not an issue. Perfect cosmetic
cleanliness is demanded of me by my commercial customers, so a little
irregularly shaped stain of flux residue, however slight, just won't
fly. Your average consumer isn't going to notice or expect that.

It's good to remember that rosin flux is non-corrosive and
non-conductive and there's no real need (other than cosmetic) to clean
it up at all, while water soluble flux is definitely corrosive and
should be pretty thoroughly removed soon after use.

Rosin-based flux comes in several levels of activity. Type R (rosin) flux
contains rosin only, with no cleaning agents. RMA flux (rosin-mildly activated)
contains a nominal amount of cleaning agents, and RA (rosin-activated) flux
contains a fair amount of cleaning agents. The cleaning agents act on the
metals being soldered to remove surface contaminants and float them away so the
metals are adequately wetted by the solder.
The RMA and RA fluxes are corrosive if insufficient heat is applied to the
fluxed area during solder to neutralize the cleaning agents, and over time will
definitely cause problems if not properly cleaned after soldering.

Water soluble fluxes are more active than any of the rosin-based fluxes.
Organic flux is more active than RA flux and inorganic flux is the most active.
Obviously, all fluxes need to be cleaned after soldering to avoid any
possibility of contamination or corrosion. Mil-spec soldering requires that all
flux residue be removed after soldering is complete.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

Life is like a roll of toilet paper; the closer to the end, the faster it goes.

S

#### Smitty Two

Jan 1, 1970
0
The RMA and RA fluxes are corrosive if insufficient heat is applied to the
fluxed area during solder to neutralize the cleaning agents, and over time
will
definitely cause problems if not properly cleaned after soldering.

Kester disagrees.

D

#### Dave Plowman (News)

Jan 1, 1970
0
Rosin-based flux comes in several levels of activity. Type R (rosin)
flux contains rosin only, with no cleaning agents. RMA flux
(rosin-mildly activated) contains a nominal amount of cleaning agents,
and RA (rosin-activated) flux contains a fair amount of cleaning
agents. The cleaning agents act on the metals being soldered to remove
surface contaminants and float them away so the metals are adequately
wetted by the solder. The RMA and RA fluxes are corrosive if
insufficient heat is applied to the fluxed area during solder to
neutralize the cleaning agents, and over time will definitely cause
problems if not properly cleaned after soldering.

I've never noticed being given a choice when buying lead multicore. And I
buy it from a large supplier, and keep four reels of different sizes on a
dispenser. Perhaps I've simply never looked. Of course what industry uses
for mass production can well be different from that used for one off
construction, repair and servicing.

The earliest PCB I have and assembled is well over 40 years old. Still
works fine. ;-)

G

#### GregS

Jan 1, 1970
0
Isopropyl alcohol works quite well, as long as it's 99% or so. Don't use
the watered-down drugstore kind. Commercial flux thinner is mostly ethyl
alcohol and that works, too, but it's usually more difficult to obtain
and quite a bit more expensive. Isopropyl runs in the neighborhood of
\$25 for a five gallon can from an industrial chemical supply house.

I use ethanol when I get it for free. You can even take a drink if you need it.
95% is the common variety, and the higher % stuff has some nasties.

Electronic supply houses sell the isopropal, allthough shipping can be a problem
fo rthe high % stuff. I have also used some harsh spray cleaners, but they
can damage components.

We used to use Tri back in the 60's to clean boards. used to have a spigot
at DEC for cleaning boards. Worked the best.

greg

T

#### Tim

Jan 1, 1970
0
I use laquer thinner on a q-tip. Wrks well for me. It does leave a
slight whit residue sometimes, but that is easy to wipe off.

- Tim -

M

#### me

Jan 1, 1970
0
Electronic supply houses sell the isopropal, allthough shipping can be
a problem fo rthe high % stuff. I have also used some harsh spray
cleaners, but they can damage components.

We used to use Tri back in the 60's to clean boards. used to have a
spigot at DEC for cleaning boards. Worked the best.

greg

Acetone and a small brush works nicely.

M

#### Mark D. Zacharias

Jan 1, 1970
0
me said:
Acetone and a small brush works nicely.

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I use MEK (methyl ethyl ketone). I can pick it up in gallon sized cans at a
paint store. Does a wonderful job with flux, just don't get it on plastic...

Mark Z.

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