The bristles don't need to be grounded, just be non-static generating, like
the metal handled, natural horsehair acid brushes we have been using. And,
yes, our operators are grounded to the workstation. With regard to the test
with ionizer, a lot of charge could be generated by a brush with, say nylon
bristles, but the ionizer would immediately mask/dissipate the charge
surrounding the action and make any possible measurement erroneous. The
field measuring equipment would only see the ionized blanket and not the
generated charge, no? The first test you suggest I believe, without
ionizer, is all you need to determine a safe process. You'll also find that
the presence of solvent, as opposed to a dry brush, prevents the
accumulation of charge and makes it safe for even the most sensitive
components.
R. G. Blomberg
Staff Production Engineer
-----Original Message-----
From: Cash, Alan [mailto:[log in to unmask]]
Sent: Wednesday, February 23, 2000 12:26 PM
To: [log in to unmask]
Subject: Re: [TN] Anti static brushes
You cannot ground insulative bristles, even if the handle of the brush is
conductive.
The operator must be grounded to the common ground of the work station.
Use of an ionizer would be a help.
Measure the static field generated by brushing a bare board with your
cleaning solvent without the ionizer and then with the ionizer. You may
find that the charge generated is not damaging to your most sensitive part
on the board using the ionizer. Please refer to the newly released
ANSI/ESD S20.20-1999 for more details.
Al Cash
-----Original Message-----
From: Lee Whiteman [mailto:[log in to unmask]]
Sent: Wednesday, February 23, 2000 7:39 AM
To: [log in to unmask]
Subject: Re: [TN] Anti static brushes
If you are going to use a non static dissipative brush, we strongly
recommend that your operators be grounded to earth ground and that an
ionizer be present and in use at the workstation. Suggest you get a copy of
ANSI / EIA-625: Requirements for Handling Electrostatic Discharge Sensitive
(ESDS) Devices for your review. We also recommend that you know the
sensitivity of your devices. For example, Class 0 devices are sensitive to
200 Volts or less.
Bob Lawler
Senior Design Engineer
ACI / EMPF
Telephone: (610) 362-1200; Ext. 222
FAX: (610) 362-1290
E-Mail: [log in to unmask]
Lee Whiteman
Senior Manufacturing Engineer
ACI / EMPF
Telephone: (610) 362-1200; Ext. 208
FAX: (610) 362-1290
E-Mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Michael D. Doty
Sent: Tuesday, February 22, 2000 3:25 PM
To: [log in to unmask]
Subject: Re: [TN] Anti static brushes
These are commonly refered to as solder brushes. They are putting on
the flux paste prior to sweating pipes.
Mike Doty
______________________________ Reply Separator
_________________________________
Subject: Re: [TN] Anti static brushes
Author: "Blomberg; Rainer (FL51)" <[log in to unmask]> at
smtplink-hadco
Date: 2/22/00 3:09 PM
Chris,
We use very inexpensive metal-handled acid brushes with bristles
cut down to
approx. 3/8 inch. We have been using them for years. Nearly any
production
tool supply house has them.
R. G. Blomberg
Honeywell - Space Systems
Staff Production Engineer
-----Original Message-----
From: Christopher Murphy [mailto:[log in to unmask]]
Sent: Tuesday, February 22, 2000 2:51 PM
To: [log in to unmask]
Subject: [TN] Anti static brushes
Dear All,
we currently use static dissipative brushes for cleaning wasted chips
off our placement machine feeder bases, and we also use them with a
solvent for cleaning localised areas of boards when rework has been
carried out.
The problem is that they are very expensive, so does anyone know of any
sources of reasonably inexpensive brushes?
I have seen other companies use wooden handled paint brushes with the
bristles cut down for these purposes - I assume this is not a good thing
due to the bristles not being ESD safe ?
Thanks in advance for any replies.
Chris Murphy,
Tait Electronics,
New Zealand
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