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August 2008

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Subject:
From:
"Creswick, Steven" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Creswick, Steven
Date:
Mon, 11 Aug 2008 07:54:00 -0400
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Whoa Ingemar,

Are you just coming out of hibernation??  Kinda behind in your e-mails
maybe???   :-)

Let me check with March to see if they have some concise learning tools
out there.  Their site http://www.marchplasma.com/index.html   did not
have anything that just jumped out and grabbed me with a wealth of
obvious info in the Support section, but there were multiple topics that
had internal links to published papers, etc.  Will just take a bit of
time to muddle through them.

For the most part, it is all relatively straight forward.  You have
Time, RF Power, Gas species, and Chamber pressure [vacuum] to play with.
My simple way of thinking of it is that greater pressure means more gas
atoms, therefore, with the correct amount of RF energy, I could be
cleaning more aggressively - or I could be re-depositing it just as
quickly.....  Doing a wetting angle test on the specimen is the best
litmus test one can do.  Even just putting a drop of water on a part
[with a control] can provide insight if a wetting angle tester is not
convenient.

We have multiple AP-1000's and Flextraks.  Have been in communications
with March of late anyway.  Let me check with them to see if they have
any Plasma Cleaning for Beginners documents out there.

If they come back with some papers, maybe we can get Steve to put them
on his 'wall' for all to see.

Steve - still flying

-----Original Message-----
From: Hernefjord Ingemar [mailto:[log in to unmask]] 
Sent: Monday, August 11, 2008 7:05 AM
To: TechNet E-Mail Forum; Creswick, Steven
Subject: RE: [TN] Plasma Surface Treatment For Conformal Coat

Trikeman,

late reaction...I agree with Watt you say. One problem here: most of us
know too little about running these machines. Do you know about any good
books to place in the hands of our technischzans?

Inge




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven
Sent: den 6 februari 2007 20:37
To: [log in to unmask]
Subject: Re: [TN] Plasma Surface Treatment For Conformal Coat

Joe,

From a microelectronics standpoint [hermetic type of stuff] I have
always been under the impression that removal of silicone residue with
standard gases such as Argon, Oxygen, Nitrogen, or Argon+Hydrogen mixes
was not reasonably possible - talking RF plasmas in a partially
evacuated chamber, here.  Our best plan, was not to have it [silicone]
there in the first place - silicones have a really nasty tendency to
migrate all over the place, on occasion.

The greatest part of my fear of placing a silicone containing part
within the chamber is that some of what gets dislodged from the piece in
question may deposit on the chamber walls [instead of getting sucked out
the vacuum].  This can mean that the next part to go into the chamber
may get a smattering of this as it becomes knocked from the chamber
walls.  This would not be good for a part which was going to be wire
bonded, for example.

At our power levels, angstoms, or atomic layers, of contaminates are
removed.  I don't normally attempt to remove visibly thick layers of
contaminates with the plasma because doing so usually either takes a
long, long, time and/or the parts become hot and/or discolored [eg O2
will turn silver black.  Go long enough and SnPb solder will get dark
and dull looking, etc.].

A 'quicky' O2 plasma - say 5 minutes, at 150W, at about 150-200 mT will
do a nice job of activating the surface of many plastics for promotion
of adhesive adhesion though.  I have little doubt that it would also
improve the wetting characteristics of your bare laminate and/or solder
mask, but I would not necessarily lay claim that it would remove gobs of
organics [within a reasonable time frame, that is].

I'm interested in hearing what Yoda Ingemar and D Hillman have to say on
the matter.

PS - Ingemar, I had -16F, outside air temp this morning [-14F
yesterday].  Getting more like your neck of the woods each day!  Have
had enough, thank-you.

Steve



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US
SSA)
Sent: Tuesday, February 06, 2007 11:23 AM
To: [log in to unmask]
Subject: [TN] Plasma Surface Treatment For Conformal Coat

While we're on the subject of CC, does anybody use plasma to remove
stubborn organic residues (e.g. silicones) from board surfaces, or
otherwise change the surface energy to promote coating adhesion?

We're not talking about long or aggressive exposure here, just enough to
remove a thin layer of contaminant, or roughen the surface of a glossy
soldermask.  So I'm not much concerned about removing markings or
anything, but are there any other potential pitfalls?

Joe Kane
BAE Systems
Johnson City, NY

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