Empathy List Archives

DF

Dr. Frank Stellmach

Sun, Sep 26, 2010 7:20 AM

Andreas,

I simply use products from Kontakt Chemie.
http://www.crcind.com/csp/web/home.csp

Kontakt LR = Kontakt PCC for chemical and mechanical cleaning (flux
residuals, water, dirt), afterwards Plastik 70 for sealing to avoid
corrosion, oxydation, leakage currents.

Good ventilation during application is important for all solvents, which
have a good cleaning effect.
They all are poisonous and evaporate easily.

To my experience, propyl alcohol is not strong enough, and acetone may
harm PCB and components.
The additional mechanical cleaning by a brusch helps a lot.

Frank

Andreas, I simply use products from Kontakt Chemie. http://www.crcind.com/csp/web/home.csp Kontakt LR = Kontakt PCC for chemical and mechanical cleaning (flux residuals, water, dirt), afterwards Plastik 70 for sealing to avoid corrosion, oxydation, leakage currents. Good ventilation during application is important for all solvents, which have a good cleaning effect. They all are poisonous and evaporate easily. To my experience, propyl alcohol is not strong enough, and acetone may harm PCB and components. The additional mechanical cleaning by a brusch helps a lot. Frank

BP

Bob Paddock

Sun, Sep 26, 2010 11:23 AM

On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach
drfrank.stellmach@freenet.de wrote:

sealing to avoid corrosion, oxydation, leakage currents.

A very common misconception is that Conformal Coating is a Hermetic
Seal. It is used a lot in the Coal Mines [Where I've done many
designs], and the Electronic Industry in general, to keep the caustic
dust off circuit boards.

As Conformal Coating is not a hermetic seal, what real happens is the
impurities in the water are kept away from the circuit, but the water
itself reaches the traces. Since the water is now fairly devoid of
contaminates the water acts more like a dielectric insulator. You
never notice it in a low impedance digital circuit, but unless
debugging is an obsession don't let it get near a RF tuning circuit or
a high impedance Sensor circuit.

The quality of the coating determines how long it will take the water
to reach the traces, it could be months, but it will reach the traces.

--
http://blog.softwaresafety.net/
http://www.designer-iii.com/
http://www.wearablesmartsensors.com/

On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach <drfrank.stellmach@freenet.de> wrote: > sealing to avoid corrosion, oxydation, leakage currents. A very common misconception is that Conformal Coating is a Hermetic Seal. It is used a lot in the Coal Mines [Where I've done many designs], and the Electronic Industry in general, to keep the caustic dust off circuit boards. As Conformal Coating is not a hermetic seal, what real happens is the impurities in the water are kept away from the circuit, but the water itself reaches the traces. Since the water is now fairly devoid of contaminates the water acts more like a dielectric insulator. You never notice it in a low impedance digital circuit, but unless debugging is an obsession don't let it get near a RF tuning circuit or a high impedance Sensor circuit. The quality of the coating determines how long it will take the water to reach the traces, it could be months, but it will reach the traces. -- http://blog.softwaresafety.net/ http://www.designer-iii.com/ http://www.wearablesmartsensors.com/

AS

Alan Scrimgeour

Sun, Sep 26, 2010 11:54 AM

I find isopropyl alcohol doesn't remove all visible traces of flux. I also
wonder if it's water content might cause the the same problems as water
based pcb cleaners that I mentioned in my last post.
Ordinarily I use cotton buds and acetone.

Alan

----- Original Message -----
From: "Dr. Frank Stellmach" drfrank.stellmach@freenet.de
To: volt-nuts@febo.com
Sent: Sunday, September 26, 2010 8:20 AM
Subject: [volt-nuts] PCB cleaning and sealing

Andreas,

I simply use products from Kontakt Chemie.
http://www.crcind.com/csp/web/home.csp

Kontakt LR = Kontakt PCC for chemical and mechanical cleaning (flux
residuals, water, dirt), afterwards Plastik 70 for sealing to avoid
corrosion, oxydation, leakage currents.

Good ventilation during application is important for all solvents, which
have a good cleaning effect.
They all are poisonous and evaporate easily.

To my experience, propyl alcohol is not strong enough, and acetone may
harm PCB and components.
The additional mechanical cleaning by a brusch helps a lot.

Frank

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

I find isopropyl alcohol doesn't remove all visible traces of flux. I also wonder if it's water content might cause the the same problems as water based pcb cleaners that I mentioned in my last post. Ordinarily I use cotton buds and acetone. Alan ----- Original Message ----- From: "Dr. Frank Stellmach" <drfrank.stellmach@freenet.de> To: <volt-nuts@febo.com> Sent: Sunday, September 26, 2010 8:20 AM Subject: [volt-nuts] PCB cleaning and sealing > Andreas, > > I simply use products from Kontakt Chemie. > http://www.crcind.com/csp/web/home.csp > > Kontakt LR = Kontakt PCC for chemical and mechanical cleaning (flux > residuals, water, dirt), afterwards Plastik 70 for sealing to avoid > corrosion, oxydation, leakage currents. > > Good ventilation during application is important for all solvents, which > have a good cleaning effect. > They all are poisonous and evaporate easily. > > To my experience, propyl alcohol is not strong enough, and acetone may > harm PCB and components. > The additional mechanical cleaning by a brusch helps a lot. > > Frank > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

AS

Alan Scrimgeour

Sun, Sep 26, 2010 12:00 PM

Do silicone based conformal coatings allow water in too?

Alan

----- Original Message -----
From: "Bob Paddock" bob.paddock@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Sunday, September 26, 2010 12:23 PM
Subject: Re: [volt-nuts] PCB cleaning and sealing

On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach
drfrank.stellmach@freenet.de wrote:

sealing to avoid corrosion, oxydation, leakage currents.

A very common misconception is that Conformal Coating is a Hermetic
Seal. It is used a lot in the Coal Mines [Where I've done many
designs], and the Electronic Industry in general, to keep the caustic
dust off circuit boards.

As Conformal Coating is not a hermetic seal, what real happens is the
impurities in the water are kept away from the circuit, but the water
itself reaches the traces. Since the water is now fairly devoid of
contaminates the water acts more like a dielectric insulator. You
never notice it in a low impedance digital circuit, but unless
debugging is an obsession don't let it get near a RF tuning circuit or
a high impedance Sensor circuit.

The quality of the coating determines how long it will take the water
to reach the traces, it could be months, but it will reach the traces.

--
http://blog.softwaresafety.net/
http://www.designer-iii.com/
http://www.wearablesmartsensors.com/

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Do silicone based conformal coatings allow water in too? Alan ----- Original Message ----- From: "Bob Paddock" <bob.paddock@gmail.com> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Sunday, September 26, 2010 12:23 PM Subject: Re: [volt-nuts] PCB cleaning and sealing > On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach > <drfrank.stellmach@freenet.de> wrote: > >> sealing to avoid corrosion, oxydation, leakage currents. > > A very common misconception is that Conformal Coating is a Hermetic > Seal. It is used a lot in the Coal Mines [Where I've done many > designs], and the Electronic Industry in general, to keep the caustic > dust off circuit boards. > > As Conformal Coating is not a hermetic seal, what real happens is the > impurities in the water are kept away from the circuit, but the water > itself reaches the traces. Since the water is now fairly devoid of > contaminates the water acts more like a dielectric insulator. You > never notice it in a low impedance digital circuit, but unless > debugging is an obsession don't let it get near a RF tuning circuit or > a high impedance Sensor circuit. > > The quality of the coating determines how long it will take the water > to reach the traces, it could be months, but it will reach the traces. > > -- > http://blog.softwaresafety.net/ > http://www.designer-iii.com/ > http://www.wearablesmartsensors.com/ > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

S

shalimr9@gmail.com

Sun, Sep 26, 2010 12:12 PM

Parylene is for all practical purposes an effective moisture barrier. However, it is very difficult to apply, and even harder to remove. We use it in extreme cases wen the environmental requirements are such that the normal urethane coating will not do.

Didier

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Bob Paddock bob.paddock@gmail.com
Sender: volt-nuts-bounces@febo.com
Date: Sun, 26 Sep 2010 07:23:24
To: Discussion of precise voltage measurementvolt-nuts@febo.com
Reply-To: Discussion of precise voltage measurement volt-nuts@febo.com
Subject: Re: [volt-nuts] PCB cleaning and sealing

On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach
drfrank.stellmach@freenet.de wrote:

sealing to avoid corrosion, oxydation, leakage currents.

A very common misconception is that Conformal Coating is a Hermetic
Seal. It is used a lot in the Coal Mines [Where I've done many
designs], and the Electronic Industry in general, to keep the caustic
dust off circuit boards.

As Conformal Coating is not a hermetic seal, what real happens is the
impurities in the water are kept away from the circuit, but the water
itself reaches the traces. Since the water is now fairly devoid of
contaminates the water acts more like a dielectric insulator. You
never notice it in a low impedance digital circuit, but unless
debugging is an obsession don't let it get near a RF tuning circuit or
a high impedance Sensor circuit.

The quality of the coating determines how long it will take the water
to reach the traces, it could be months, but it will reach the traces.

--
http://blog.softwaresafety.net/
http://www.designer-iii.com/
http://www.wearablesmartsensors.com/

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Parylene is for all practical purposes an effective moisture barrier. However, it is very difficult to apply, and even harder to remove. We use it in extreme cases wen the environmental requirements are such that the normal urethane coating will not do. Didier Sent from my Verizon Wireless BlackBerry -----Original Message----- From: Bob Paddock <bob.paddock@gmail.com> Sender: volt-nuts-bounces@febo.com Date: Sun, 26 Sep 2010 07:23:24 To: Discussion of precise voltage measurement<volt-nuts@febo.com> Reply-To: Discussion of precise voltage measurement <volt-nuts@febo.com> Subject: Re: [volt-nuts] PCB cleaning and sealing On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach <drfrank.stellmach@freenet.de> wrote: > sealing to avoid corrosion, oxydation, leakage currents. A very common misconception is that Conformal Coating is a Hermetic Seal. It is used a lot in the Coal Mines [Where I've done many designs], and the Electronic Industry in general, to keep the caustic dust off circuit boards. As Conformal Coating is not a hermetic seal, what real happens is the impurities in the water are kept away from the circuit, but the water itself reaches the traces. Since the water is now fairly devoid of contaminates the water acts more like a dielectric insulator. You never notice it in a low impedance digital circuit, but unless debugging is an obsession don't let it get near a RF tuning circuit or a high impedance Sensor circuit. The quality of the coating determines how long it will take the water to reach the traces, it could be months, but it will reach the traces. -- http://blog.softwaresafety.net/ http://www.designer-iii.com/ http://www.wearablesmartsensors.com/ _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

BP

Bob Paddock

Sun, Sep 26, 2010 12:14 PM

On Sun, Sep 26, 2010 at 8:00 AM, Alan Scrimgeour
scrimgap@blueyonder.co.uk wrote:

Do silicone based conformal coatings allow water in too?

To my knowledge all coatings will allow water to migrate to the board
level eventually.
It is only a mater of defining "eventually". The best coatings
setting under water may take months, in a normal room it could take
years.
It is one of those very slow drift mechanisms that is rarely accounted for.

If you read up Electrostatic Grade Op-Amps like the AD515 and friends,
they always tell you to "expose to air" the high impedance points.

While on the subject of water migration. Water can migrate up coaxial
cable. Took a shower from a cable on the second floor of a building
once, when the cable came down a tower, to ground level, and back up
to the second floor of the building. The connector had not been
removed in years.

On Sun, Sep 26, 2010 at 8:00 AM, Alan Scrimgeour <scrimgap@blueyonder.co.uk> wrote: > Do silicone based conformal coatings allow water in too? To my knowledge all coatings will allow water to migrate to the board level eventually. It is only a mater of defining "eventually". The best coatings setting under water may take months, in a normal room it could take years. It is one of those very slow drift mechanisms that is rarely accounted for. If you read up Electrostatic Grade Op-Amps like the AD515 and friends, they always tell you to "expose to air" the high impedance points. While on the subject of water migration. Water can migrate up coaxial cable. Took a shower from a cable on the second floor of a building once, when the cable came down a tower, to ground level, and back up to the second floor of the building. The connector had not been removed in years.

S

shalimr9@gmail.com

Sun, Sep 26, 2010 12:23 PM

Yes, many silicones are hygroscopic. We use a variety of silicone based potting compounds where I work that are slightly hygroscopic. Yet, they work well to contain water into a fish tank :)

I know silicone based conformal coatings are used in the automotive industry. I can tell you from experience that they are not moisture proof. I had a height sensor fail just for that in my Ford Expedition. The PWB was badly corroded under the conformal coating and traces were shorted. Once the coating was removed and the PWB cleaned, it worked again.

I understand that some silicone based oils are not.

Didier
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: "Alan Scrimgeour" scrimgap@blueyonder.co.uk
Sender: volt-nuts-bounces@febo.com
Date: Sun, 26 Sep 2010 13:00:03
To: Discussion of precise voltage measurementvolt-nuts@febo.com
Reply-To: Discussion of precise voltage measurement volt-nuts@febo.com
Subject: Re: [volt-nuts] PCB cleaning and sealing

Do silicone based conformal coatings allow water in too?

Alan

----- Original Message -----
From: "Bob Paddock" bob.paddock@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Sunday, September 26, 2010 12:23 PM
Subject: Re: [volt-nuts] PCB cleaning and sealing

On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach
drfrank.stellmach@freenet.de wrote:

sealing to avoid corrosion, oxydation, leakage currents.

A very common misconception is that Conformal Coating is a Hermetic
Seal. It is used a lot in the Coal Mines [Where I've done many
designs], and the Electronic Industry in general, to keep the caustic
dust off circuit boards.

As Conformal Coating is not a hermetic seal, what real happens is the
impurities in the water are kept away from the circuit, but the water
itself reaches the traces. Since the water is now fairly devoid of
contaminates the water acts more like a dielectric insulator. You
never notice it in a low impedance digital circuit, but unless
debugging is an obsession don't let it get near a RF tuning circuit or
a high impedance Sensor circuit.

The quality of the coating determines how long it will take the water
to reach the traces, it could be months, but it will reach the traces.

--
http://blog.softwaresafety.net/
http://www.designer-iii.com/
http://www.wearablesmartsensors.com/

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Yes, many silicones are hygroscopic. We use a variety of silicone based potting compounds where I work that are slightly hygroscopic. Yet, they work well to contain water into a fish tank :) I know silicone based conformal coatings are used in the automotive industry. I can tell you from experience that they are not moisture proof. I had a height sensor fail just for that in my Ford Expedition. The PWB was badly corroded under the conformal coating and traces were shorted. Once the coating was removed and the PWB cleaned, it worked again. I understand that some silicone based oils are not. Didier Sent from my Verizon Wireless BlackBerry -----Original Message----- From: "Alan Scrimgeour" <scrimgap@blueyonder.co.uk> Sender: volt-nuts-bounces@febo.com Date: Sun, 26 Sep 2010 13:00:03 To: Discussion of precise voltage measurement<volt-nuts@febo.com> Reply-To: Discussion of precise voltage measurement <volt-nuts@febo.com> Subject: Re: [volt-nuts] PCB cleaning and sealing Do silicone based conformal coatings allow water in too? Alan ----- Original Message ----- From: "Bob Paddock" <bob.paddock@gmail.com> To: "Discussion of precise voltage measurement" <volt-nuts@febo.com> Sent: Sunday, September 26, 2010 12:23 PM Subject: Re: [volt-nuts] PCB cleaning and sealing > On Sun, Sep 26, 2010 at 3:20 AM, Dr. Frank Stellmach > <drfrank.stellmach@freenet.de> wrote: > >> sealing to avoid corrosion, oxydation, leakage currents. > > A very common misconception is that Conformal Coating is a Hermetic > Seal. It is used a lot in the Coal Mines [Where I've done many > designs], and the Electronic Industry in general, to keep the caustic > dust off circuit boards. > > As Conformal Coating is not a hermetic seal, what real happens is the > impurities in the water are kept away from the circuit, but the water > itself reaches the traces. Since the water is now fairly devoid of > contaminates the water acts more like a dielectric insulator. You > never notice it in a low impedance digital circuit, but unless > debugging is an obsession don't let it get near a RF tuning circuit or > a high impedance Sensor circuit. > > The quality of the coating determines how long it will take the water > to reach the traces, it could be months, but it will reach the traces. > > -- > http://blog.softwaresafety.net/ > http://www.designer-iii.com/ > http://www.wearablesmartsensors.com/ > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

volt-nuts@lists.febo.com

PCB cleaning and sealing