Silicon oil leakage on PCB - how to remove?

Any residue/dirt that the oil dissolves will increase its conductivity. Unless you've got really high impedance stuff I'd be surprised if this was a problem.

You seem worried about the board and conductivity of the oil, but I'd be more worried about any sockets/plugs connecting to and from the board and the oil making an insulating layer. Any socketed chips?

Tim.

Reply to
Tim Shoppa
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OK, before you said video and codecs, which is rather low impedance stuff, but a mike amp will be very sensitive to megohm level impedances.

As Spehro asked, any CMOS crystal oscillators?

Tim.

Reply to
Tim Shoppa

The stuff may be penetrating the epoxy of IC packages and causing swelling, stressing chips and maybe breaking wire bonds. You might try some side experiments to see if this is what's happening.

John

Reply to
John Larkin

We were using the stuff for compass fluid and had a similar problem. Put it in the dishwasher on "hot" and use LIQUID dishwasher detergent, not the granulated stuff that has an abrasive in it. After a couple of trips through the dishwasher, rinse in 98% isopropyl alcohol and let it dry, dry, dry. A warm location (NOT THE OVEN) of about 90°F helps it dry faster. A small 5 watt bulb inside of a shoebox will get you into the general area.

Jim

Reply to
RST Engineering (jw)

We've put silicone oil on contacts to improve the reliability. ;-) How do you know that it's silicone oil?

Any 32.768kHz etc. crystals?

I think the oil can "attract" a thin layer of moisture on the surface, perhaps leading to subtle problems if the circuitry is really finicky.

It's probably really, really, hard to get rid of that stuff, BTW.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
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Reply to
Spehro Pefhany

In my chem lab days there were several methods which were the most effective at removing silicone based lubes and vacuum grease:

Quick method:

  1. diethyl ether - this might be suitable for washing a PCB. Trouble is with silicone grease it would leave a trace of whitish residue, which could then be further removed by some acetone or methanol. But it was the only solvent that after wiping a silicone grease soaked ground glass joint, would leave the joint looking "dry". Might not have a residue problem if used to wash off an oil rather than a grease.

More time consuming but superior:

  1. potassium hydroxide in methanol - really effective at stripping grease off glass, and leaving a surface completely free of foreign material. Needs a good 24-48 hour soaking. So effective that water wets the surface after this treatment completely like a sheet, with no beading. This also dissolves just a tiny bit of the glass itself. Sodium or potassium hydroxide saturated in water is also effective, just takes a longer time to soak through the crud.

Obviously this treatment might not be idea for PCBs.

My favorite:

  1. Boiling perchloric acid - oh, this stuff was just way too much fun. Used to clean trace residues of metals and metal oxides/hydroxides off glassware used for trace analysis. Good for cleaning out the frits of sintered glass crucibles. Don't treat anything organic or boil it to anhydrous, or else KA-BOOM!

  1. Hydrofluoric acid - also good at restoring wetability to glass. But even more scary than HCl04.

I'd suggest attempting a rinse with diethyl ether.

Good day!

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_______________________________________________________________________
Christopher R. Carlen
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Reply to
Chris Carlen

Personally, I recommend against baking anything dry after washing and rinsing - before baking it, blow it dry with clean, dry, NON-oiled shop air, then go ahead and warm it up if needed - I'd even recommend something like a hair dryer - NOT a heat gun!

Cheers! Rich

Reply to
Rich Grise

....

.... One of my projects has circuit boards immersed in high voltage oil. The oil induced failure I get is when I have a radial electrolytic capacitor mounted standing up on the circuit board. The rubber plug where the leads come out soaks up oil, swells, and pulls the leads right out of the circuit board. It is pretty much an irresistible force. Anything that has rubber in it is going to have trouble.

Also on these boards we have fiber optic cables. At first we tried the common orange kind, but that orange stuff, whatever it is, soaked up the oil and became very stiff. It also expanded enough to yank the fibers out of the connectors.

Paul Probert University of Wisconsin

Reply to
Paul Probert

Silicone oil used to be used in Xerox copiers when I worked for Rank-Xerox many years ago; we had a lot of trouble removing traces of it from panels before repainting them (it stopped the paint adhering properly). We used a special detergent from these people:

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to remove it.

Don't get the stuff in your eyes, even a very small amount transferred from the fingers can make them sore for hours. No permanent damage, though.

Reply to
Leon Heller

I read in sci.electronics.design that Tim Shoppa wrote (in ) about 'Silicon oil leakage on PCB - how to remove?', on Wed, 27 Apr 2005:

Some of these oils have high penetrating power and a high dielectric constant, so some capacitor values may have changed.

You can't wipe the stuff off because of its surface tension and viscosity. You may be able to get a 'removing fluid' from the oil suppliers. It may be costly.

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Reply to
John Woodgate

Hi All,

We have a product containing a PCB filled with high-speed DSP's and such (Video conference Codec). Above this PCB a mechanical damper is placed to dampen the motion of a lid that can flip open.

We are now faced with malfunctioning dampers, causing Silicone Oil to leak on the PCB. Although the stuff seems non-conductive, the PCB's affected faithfully stop working.

Questions:

  1. How does Silicone Oil affect the electronics? (my meter can measure up to 40 MOhm, but registers nothing - does the presence of other materials / voltages etc. cause some reaction?)

  1. Is there a way to get rid of the stuff and get the expensive PCB working again? Wiping off does not seem to cut it - I fear some irreversible chemical transformation took place.

I like to learn more about these phenomena - input welcome!

--
 - René
Reply to
René

I read in sci.electronics.design that René wrote (in ) about 'Silicon oil leakage on PCB - how to remove?', on Wed, 27 Apr 2005:

Clean off with special cleaner and then conformally-coat the boards affected.

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Regards, John Woodgate, OOO - Own Opinions Only.
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Reply to
John Woodgate

Perhaps your PCB or some device packages are absorbing the oil, swelling, and the resulting mechanical distortion is causing BGA ball failure or some other mechanical failure. I would expect board swelling to be visible as warpage, but package swelling could be hard to see. If it is occurring, oil absorption should be measurable as weight gain in a test which should be done at least at the peak temperatures seen in service or accelerated by slightly higher temperatures.

If the damage is from swelling it is irreversible.

And Sphero is right, the stuff is just about impossible to completely remove even if only adsorbed (surface coating) vs absorbed (into volume). I once knew someone who tried hundreds of methods to remove silicone mold release from polycarbonate aircraft windshields prior to CVD coating, without complete success. They had to make the process tolerate some residual silicone. Acetone and some other solvents will reduce it to a thin layer, however.

It is also possible that the damper oil is not pure silicone oil but has some additive(s) which attack some polymers - such as the seal on the damper, and your board or packages.

Reply to
Glen Walpert

Hi Tim, Thanks for fast response! I would not be worried - if not the affected boards would fail operation as soon as leakage occurs.

The PCB has several sub-functions, and the malfunction is clearly tracable to the location of the "puddle".

If e.g. a drop of the stuff lands on the balanced mike amplifier - the whole goes out of bias and the mike input is effectively dead. So obviously it "does" something "conductive" with the circuit, though directly measured (2 probes in a drop of the oil) does not reveal any substantial conductivity. The circuits are not super-high impedant, but on e.g. some amp circuits a ~1 MOhm phenomena would spoil the function. Also some Audio / Video DA's were observed to stop.

Wiping the oil off sometimes clear the problem, but it may come back later. A reliable repair method would probably involve more than just wiping it off - but how?

--
 - René
Reply to
René

The design (A Tandberg H323 Codec board) contains several dedicated clock oscillators (complete Xtal+osc assemblies in a metal can) on various frequencies. All work. (no oscillators on a "leftover" CMOS gate)

Video parts also contain DA's / amps, that at some level run impedances substantially higher than 75 Ohms.

The design has several separate operational parts that communicate with each other - if one partial function does not chime in, the rest may also not initialise. This makes cause / effect hunting a little tricky. The balanced amp example is a nice "stand alone' function I observed to fail when exposed to the oil.

Am I sure it's Silicone oil? Well - that is what the damper datasheet tells me, but whatever special dopes are present I do not know.

Suppose "megaOhm" circuits were involved - would this be normal behaviour for silicone oil?

I am now toying with Fluxclene - see what good that does...

Thanks for all suggestions mentioned so far by many. I will try the Decon lead.

--
 - René
Reply to
René

I read in sci.electronics.design that René wrote (in ) about 'Silicon oil leakage on PCB - how to remove?', on Wed, 27 Apr 2005:

You won't have such high-impedance circuits in a mic amp. It's really very surprising that that fails, unless some component is damaged by oil penetration.

--
Regards, John Woodgate, OOO - Own Opinions Only.
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Reply to
John Woodgate

no. no. no. no.

Reply to
Aubrey McIntosh, Ph.D.

On Wed, 27 Apr 2005 10:28:55 -0700, Chris Carlen wrote in Msg.

This is interesting. What concentration? Does the KOH just dissolve in methanol, or does one add some water? Does NaOH work as well?

I work in the UHV field, and somethimes we have to get small traces of stuff off of surfaces.

Are you talking about smoking, concentarted, boiling HCl? Your post doesn't sound like you believed in diluting anything ;-)

--Daniel

Reply to
Daniel Haude

On Wed, 27 Apr 2005 16:08:15 GMT, Glen Walpert wrote in Msg.

This can probably be excluded if the damage occurs immediately after exposure to oil because I guess the swelling/soaking would take some time.

--D.

Reply to
Daniel Haude

I am assuming that the problem oil is something like a polydimethylsiloxane (

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)

I would worry that the KOH / Methanol will "clean" the polymers off of the pcb silkscreen, chips, and even the PCB substrate. I have seen 250 mL beakers that I used as a KOH/Methanol bath display significant etching. It dissolves skin. Use gloves. It dissolves corneas faster. Use goggles. Spatter is invisible on clothing, and transfers to unprotected skin. Change clothes and shower after handling. NaOH/Methanol forms insoluable crud, so KOH is preferred.

A couple of web sites mention benzene. You can't (or shouldn't) get that now, but toluene or xylene may substitute. I'm a little surprised that they work, and don't remember trying them directly. I suspect that you can get mixed xylenes at an art supply house as some or other paint thinner or brush cleaner. They burn easily -- act as if you are handling gasoline.

Someone else mentioned diethyl ether. The flammability of (this) ether makes gasoline look safe. More problematic is that you will be tempted to keep the left over material. On exposure to oxygen, even in a "closed" container, it forms explosive material with LEGENDARY sensitivity.

Another web site did not offer any information specifically relevant to this newsgroup at all:

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Despite the general acceptance of opinion over lab work in most newsgroups, I do mention the entry from the paper mill. Use your browser to search for "Table 1" about a third of the way down the article. My gut sense was ethyl acetate would be a good solvent, and their finding of methyl ethyl ketone fits in nicely with that. Their finding of hexane surprises me some, but hey, they went to the lab and I didn't.

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Reply to
Aubrey McIntosh, Ph.D.

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