Inge:
I would suggest to place the board horizontally and spray from
the bottom, to wet the dust and pull it down. Flip board and repeat.
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Thursday, March 29, 2007 1:58 AM
To: [log in to unmask]
Subject: Re: [TN] ESD charges in conformal coatings (conclusion)
Don't know if we need bake...inside tent it's oftenly 50 Centigrades! If
we place the boards in free air, the coating will soften...
Will have a look at Reztore, never heard of before...
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: den 28 mars 2007 21:31
To: [log in to unmask]
Subject: Re: [TN] ESD charges in conformal coatings (conclusion)
Inge,
Sorry to comment so late but....
I have used ionized air to spray DI/IPA to clean conformal coated boards
in
the field. If you rinse in DI water, you will blow the moisture
further
into them when you "dry" them off (you might need to bake them
afterwards.)
I also have to wonder if your industrial ionized air blower was balanced
(it is a little tricky to measure ionized air streams). You have to use
a charged plate to check it. I was recently auditing a subcontractor
who had ESD ionizers which were charge generators instead of
neutralizing.
Out of Box thought:
I just wonder if Desco's topical "Reztore" would work well for such an
application. It dries rapidly, is not flammable, and if sprayed using
an ESD air ionizer, it could have enough force to "clean" the dust and
dirt right off of your boards. I haven't tested it for its
compatibility with conformal coatings but then again, I haven't had to
worry about cleaning conformal coated boards in the field for a very
long time.
I am a firm believer in Reztore and I suggest that anyone who has an
office white board (with traces of past scribbling on it) should try it.
At 07:08 PM 3/28/2007 +0200, Inge wrote:
>James,
>
>thanks for the response. We bought some ESD brushes and found a big and
>professional ionized air blower. We placed the coated board on a
grounded
>workbench and switched on the blower to stream ionized air across the
>board. And measured with a ESD instrument. Then we swept the ESD brush
a
>couple of times across the board. Guess what happened. The instrument
read
>3,000 Volts! I'm not going to try an explanation how this could happen.
>Got no time just now.
>
>Next experiment. We took the 'charged' boards and dipped them in DI
water
>for a couple of seconds, lifted them up and dried them rapidly with a
dry
>nitrogen pistol. New ESD readout gave 0 Volts.
>
>We skip all thoughts about ionizers and brushes and go for rinsing in
DI
>water.
>
>Thanks, you all that contributed with ideas.
>
>Inge
>
>
>
>----- Original Message ----- From: "James Verrette"
<[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, March 28, 2007 2:52 PM
>Subject: Re: [TN] ESD charges in conformal coatings
>
>
>Inge,
>
>
>
>Have you tried an Anti-Static Film Cleaner like "Film Kleen" from
>Anchor? There is a Film Kleen, Film Kleen II, Diazo Film Kleen, not
sure
>what the difference is. Circuit Check recommends the Diazo Film Kleen
>for cleaning their fixtures. I also stumbled across an Ionizer that
>fits on can of compressed air.
>
>
>
>http://www.kinetronics.com/cgi-local/SoftCart.100.exe/online-store/scst
o
>re/cai.html?L+scstore+zczg8040ff939793+1180305318
>
>
>
>Jim Verrette
>
>Electrical Engineer
>
>
>
>
>
>-----Original Message-----
>
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
>
>Sent: Tuesday, March 27, 2007 7:09 AM
>
>To: [log in to unmask]
>
>Subject: [TN] ESD charges in conformal coatings
>
>
>
>
>
>Hi all gnus and gurus,
>
>=20
>
>Sometimes, we need clean boards from dust and dirt. Field practise, no
>
>proffesional facilities. Not surprisingly, you move electrons from the
>
>conformal coating's surface. I have measured several kilovolts at a
>
>distance of one inch from the board. The highly insulating acrylic
>
>coating keeps the charges effectively for hours, quite expected too.
ESD
>
>brushes not much better. Not even grounded ESD brushes works. I get rid
>
>of the surface charges if I dip the board in water, quite natural,
>
>because of the large contact area and polarisation media. EE in the US,
>
>did an investigation during 8 years. They ranged the 23 most common
>
>electrical failures and their sources. Conformal coating charges came
as
>
>number 9.
>
>
>
>Question: anyone who can recommend a dust and dirt removal method, when
>
>dry brushes don't work and water is not allowed?
>
>
>
>Inge
>
>
>
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