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John Herminghaus
Joined: 09 Jan 2006
Posts: 6
Location: Siena Italy
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 Posted: Thu Aug 21, 2008 8:23 pm Post subject: Printed circuits |
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Bob,
I know that this subject has been discussed before, but can't find it.
In short, what do you recommend to clean printed circuit boards after
assembly?
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_________________
John Herminghaus
Lancair IV-P
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echristley(at)nc.rr.com
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| Posted: Fri Aug 22, 2008 7:10 pm Post subject: Printed circuits |
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John F. Herminghaus wrote:
| Quote: |
<catignano(at)tele2.it>
Bob,
I know that this subject has been discussed before, but can't find
it. In short, what do you recommend to clean printed circuit boards
after assembly?
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Depends on the flux you use. Some are water soluble. Depending on the
components added, these can go in the dishwasher as long as you don't
add any of the detergent.
RadioShack flux comes off with alcohol, but MEK is faster.
--
http://www.ernest.isa-geek.org
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nuckolls.bob(at)cox.net
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| Posted: Sat Aug 23, 2008 10:51 am Post subject: Printed circuits |
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At 06:20 AM 8/22/2008 +0200, you wrote:
| Quote: |
<catignano(at)tele2.it>
Bob,
I know that this subject has been discussed before, but can't find it.
In short, what do you recommend to clean printed circuit boards after
assembly?
|
There are some solders that offer water soluble fluxes but
unless you went to special effort to acquire this product,
you're not going to be able to simply run your boards through
the dishwasher.
I've removed "plastic" fluxes with carburetor cleaner in
spray cans from Wally World. I've bought it by the case
for under $1 a can. This is essentially strong but not
terribly aggressive solvent like lacquer thinner. You can
also try mild solvents like brush cleaners that are not
unlike starter fluid for charcoal. Denatured alcohol used
in shellacs is a good mild solvent that may work with your
flux.
Be cautious with aggressive solvents like acetone, mek
methyl chloride, etc. These can attack the binders in your
board's fiberglas as well as some finishes and plastics
used to fabricate the components. I use aggressive solvents
for spot cleaning . . . dampen a q-tip and rub locally.
You can use a brush dipped in solvent to dissolve flux
residue and flotsam it captures. Do a final rinse with
new, clean solvent and blow dry with your shop air or
a heat gun set on cold. After all acceptance tests are
complete, mask off connector pins and rotating parts.
Spray with a coat of Krylon Crystal Clear Glaze.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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rjquillin
Joined: 13 May 2007
Posts: 123
Location: KSEE
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| Posted: Sat Aug 23, 2008 8:02 pm Post subject: Printed circuits |
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At 11:48 8/23/2008, you wrote:
| Quote: | Be cautious with aggressive solvents like acetone, mek
methyl chloride, etc. These can attack the binders in your
board's fiberglas as well as some finishes and plastics
used to fabricate the components. I use aggressive solvents
for spot cleaning . . . dampen a q-tip and rub locally.
|
NASA really likes Isopropyl and Ethanol; both are spec'd in
NASA-STD-8739.4 for PWB fabrication and cleaning.
| Quote: | You can use a brush dipped in solvent to dissolve flux
residue and flotsam it captures. Do a final rinse with
new, clean solvent and blow dry with your shop air or
a heat gun set on cold. After all acceptance tests are
complete, mask off connector pins and rotating parts.
Spray with a coat of Krylon Crystal Clear Glaze.
|
Also consider HumiSeal 1B73 for an Acrylic MIL spec conformal. Used
it for years.
Chase also makes a newer Acrylic 1B31 that's easier to work with, and
a polyurethane 1A33.
All three are qualified to MIL-I-46058C.
http://www.humiseal.com/
Ron Q.
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steve(at)tomasara.com
Guest
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| Posted: Sun Aug 24, 2008 7:05 am Post subject: Printed circuits |
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Bob and group,
Questions follow my personal experiences below:
I've had good results with both 99% Rubbing Alcohol and commercial
spray-on flux remover on common rosin flux. Whenever I use a
traditional rosin flux solder (or solder wick for that matter) I clean
it off completely.
I've had bad experiences with water-soluble fluxes in the past and so
avoid them like the plague (except, obviously, where mandated by a
client's manufacturing operations). Although they may have gotten
better in the recent years (to be replaced with problems related to
RoHS, no doubt). In the past they were very demanding of very complete
cleaning and, if not cleaned completely, tended to enable the slow
"growth" (metallurgically speaking, not biologically speaking) of a
white fuzz the was conductive and which resulted in field failures one
or more years after ship (this is going back to the late eighties,
however, and may be irrelevant with todays products). I'm dreading the
re-appearance of this kind of problem with tin growth once our solder
and parts have been purged of the dreaded lead that was so helpful in
controlling this problem.
My current flux-of-choice is Kestor's No-Clean flux and, per Kestor, I
don't remove it. However, I have found if I try to remove it with the
same chemicals used for rosin flux, I can get white residue (which I
view with great suspicion). Last I looked (a couple of years ago)
Kestor's web-site had a white paper on this issue which (as I remember)
basically concluded by not recommending any flux remover for this flux
and by recommending re-fluxing and re-heating to get rid of the white stuff.
In conclusion, I pay great attention to which flux I wish was removed
before deciding on a course of action.
My questions:
How do other's in this group deal with "no-clean" fluxes?
How important is it to clear-coat boards (I assume this greatly helps
when in a condensing atmosphere but I don't have experience with this
process)?
Can you clear-coat over "no-clean" flux or must it be removed?
Thanks in advance for your thoughts,
Steve Stearns
Boulder/Longmont, Colorado
CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less)
Restoring (since 1/07): N45FC O235 Longeze Cothern/Friling CF1 (~1000 Hrs)
Flying (since 9/86): N43732 A65 Taylorcraft BC12D
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nuckolls.bob(at)cox.net
Guest
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| Posted: Sun Aug 24, 2008 8:54 am Post subject: Printed circuits |
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At 09:04 AM 8/24/2008 -0600, you wrote:
| Quote: |
Bob and group,
Questions follow my personal experiences below:
I've had good results with both 99% Rubbing Alcohol and commercial
spray-on flux remover on common rosin flux. Whenever I use a traditional
rosin flux solder (or solder wick for that matter) I clean it off completely.
|
Yes, those are what I've referred to as "plastic"
fluxes. Originally real tree-rosin, modern encarnations
are synthetic but no less messy when the hard work
(make it function) is done.
| Quote: | I've had bad experiences with water-soluble fluxes in the past and so
avoid them like the plague (except, obviously, where mandated by a
client's manufacturing operations). Although they may have gotten better
in the recent years (to be replaced with problems related to RoHS, no
doubt). In the past they were very demanding of very complete cleaning
and, if not cleaned completely, tended to enable the slow "growth"
(metallurgically speaking, not biologically speaking) of a white fuzz the
was conductive and which resulted in field failures one or more years
after ship (this is going back to the late eighties, however, and may be
irrelevant with todays products). I'm dreading the re-appearance of this
kind of problem with tin growth once our solder and parts have been purged
of the dreaded lead that was so helpful in controlling this problem.
|
Right on. My all time favorite solder is Kester Resin
44 that I've stockpiled to a lifetime supply. It flows
well, fluxes well, and yes . . . it demands some attention
to cleaning when you're all done.
| Quote: | My current flux-of-choice is Kestor's No-Clean flux and, per Kestor, I
don't remove it. However, I have found if I try to remove it with the
same chemicals used for rosin flux, I can get white residue (which I view
with great suspicion). Last I looked (a couple of years ago) Kestor's
web-site had a white paper on this issue which (as I remember) basically
concluded by not recommending any flux remover for this flux and by
recommending re-fluxing and re-heating to get rid of the white stuff.
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Interesting! I've not experienced this stuff first
hand. I think one of my clients uses it on their
hand-assembly line. I'll inquire as to their post-
assy processes. The flux used on their pick-n-place
line is water soluble. This stuff is removed by an
expensive "dish washer" with some kind of proprietary
surfactants (probably dish soap).
They DO come out very clean and read to conformal
coat.
| Quote: | In conclusion, I pay great attention to which flux I wish was removed
before deciding on a course of action.
|
Sounds like a folk who's been-there-done-that.
| Quote: | My questions: How do other's in this group deal with "no-clean" fluxes?
How important is it to clear-coat boards (I assume this greatly helps when
in a condensing atmosphere but I don't have experience with this process)?
|
I've never been tasked with crafting that process
but I'll ask around. I don't think anyone in production
uses a no-clean flux. There are just too many contaminant
and surface prep issues for coating that make post-solder
cleaning a really big issue. I was told by a Kester rep
many moons ago that the whole idea behind no-clean
flux was that it didn't leave reactive contaminants
behind . . . at least reactive at normal operating
temperatures and humidity. Obviously, to be a good
flux it had to be very reactive at solder temperatures.
| Quote: | Can you clear-coat over "no-clean" flux or must it be removed?
|
That's what they told me . . . but it still LOOKED
like (at)!#(at)(at)#(at)$. That's why I've never embraced these
materials personally. Good ol' "44" and some moderately
strong solvents have served me and my sense of
craftsmanship well for decades.
| Quote: | Thanks in advance for your thoughts,
|
You've raised some interesting questions. I'll see
what my friends in the industry can offer. In the
mean time, check out this resource at:
http://www.kester.com/en-us/datasheets/ds_dirdetail.aspx?location=Fluxes
This suite of products goes back at least 50 years
and includes the present offerings from Kester.
Bob . . .
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steve(at)tomasara.com
Guest
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| Posted: Mon Aug 25, 2008 7:06 am Post subject: Printed circuits |
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Since the interest level seems high, I'll add a little more info....
| Quote: | ** Right on. My all time favorite solder is Kester Resin
44 that I've stockpiled to a lifetime supply. It flows
well, fluxes well, and yes . . . it demands some attention
to cleaning when you're all done.
**
I also use and prefer Kester 44 for use in hand soldering. Most of my
|
work these days, however, is with surface mount parts which I reflow.
Here I use Kester R276 No-Clean solder paste. Invariably I end of with
a mix of both fluxes as, after re-flow, I'll have to hand-solder the
through-hole parts or do some rework (I haven't had good luck with
no-clean solder-wick so I stick to the rosin based fluxes on my solder
wick as well). This gets cleaned with Isopropyl (via cotton swabs) or
with a mixture from a flux-remover pen (I haven't checked the MDS but I
suspect it's Isopropyl with a little MEK, it's a bit more aggressive
than the Isopropyl alone). Which results in some white residue from the
no-clean flux. So then I add Kester #951 from a flux pen (which I
recommend - good stuff) and reheat with hot air.
This sounds more time-consuming than it is. In reality it goes pretty
fast and I don't have to get up from my bench. My lab does not have a
good facility for appropriate board-level cleaning operations so when I
have to clean a whole board I do it outside...
Steve Stearns
Boulder/Longmont, Colorado
CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less)
Restoring (since 1/07): N45FC O235 Longeze Cothern/Friling CF1 (~1000 Hrs)
Flying (since 9/86): N43732 A65 Taylorcraft BC12D
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