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October 2005

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Subject:
From:
"Stadem, Richard" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard
Date:
Thu, 6 Oct 2005 14:54:39 -0500
Content-Type:
text/plain
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text/plain (94 lines)
Not solder paste. Paste flux, aka tacky flux. Not a problem on a warm or
hot board. This is a leaded part.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blomberg, Rainer
(FL51)
Sent: Thursday, October 06, 2005 11:47 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Protrusions

 Phil,

How does one apply solder paste to a board before it has cooled down?

Rainer Blomberg



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: Tuesday, October 04, 2005 11:22 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Protrusions

Hi Mary Jane,

My question is if you are using hot air to remove the flat pack, why
aren't you using the same hot air to resolder the replacement part?

If it were me, I would have the replacement part put back on the board
immediately, before it has cooled down, and thereby reduce the number of
temperature cycles the board has to go through.

The hot air will not give you any peaks to worry about as long as you
use a paste flux to facilitate the wetting of the solder.

You may not have the luxury of doing both operations at the same time,
but I would still opt to use the hot air on a flatpack.  Just make sure
you bump the flatpack pads before putting down the part.

Hope this helps....

Phil
Mary Jane Chism <[log in to unmask]> wrote:
We are experiencing icicles (solder protrusions) as the results of
rework being performed on a flatpak. The process is hot air removal of
the flat pak and hand soldering for replacement. In the process of hand
soldering, the operators are touching some of the surface mount
capacitors around the flat pak causing solder protrusions off of the
solder fillet of the capacitors.

In IPC-A-610, it states as long as the solder protrusions do not violate
height requirement and electrical clearance, they would be acceptable.
However, I feel the objective of performing rework is that you only
perform the operation of soldering without putting any thermal stress on
the rest of the components.

I realize this is hard for anyone to actually answer this, but my
question is, if you can answer this, would you:

1. Re-address your rework process and also get rid of the icicles?
2. Re-address your rework process but let the icicles go?
3. Don't do the rework?
4. Get different rework operators to perform the rework?

Your comments will be very much appreciated.

Thanks.

Mary Jane Chism

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