Did you see this before you started tinning lead-free components?


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Evans
Sent: Wednesday, March 21, 2007 2:04 PM
To: [log in to unmask]
Subject: Re: [TN] Whisker contamination is solder pot

Michael,
thanks for your reply and here are the answers, best I know:


1. What is the capacity of the solderpot?
This solder pot holds about 12 lbs.

2. What is the flux being used?
Almost exclusive to Kester 186-25, but a few drops of a kester OA might
be 
used in extreme circumstances. The exceptional use of OA is so
infrequent 
that I would rule it out all together, being used maybe once or twice
every six 
months.

3. What is the material the pot is made of? 
I am almost completely sure that this is milled out of stainless, but
the photo 
copied manual that I have for this doesn't specify.  It does not appear
to be 
magnetic.

4. Does the problem show up on a new pot charge or does it require time
to develop if so how long?
I have this problem today and it has been two weeks since I changed the 
solder. We had a HUGE batch (for us) of parts go through this this week,

about six hundred soic's.  These particular components were lead free
and we 
were having a difficult time getting them to reflow in the smt process
without 
pre tinning them.

5. What is your definition of "polarized metal stuff"? Are you saying
magnetic or are we getting into dipole moments and ligand field theory?

Well, often when we see this fine hairlike strand, we have to heat the
lead and 
scrape it off with an iron. It doesn't become molten in normal soldering

temperatures and it doesn't want to let go of the lead that it is
attached to. If 
we use braid, we often find ourselves chasing it up and down the lead. 
Sometimes it seems to attracted to the soldering iron tip, as if
magnetic and 
somtimes not. We use metcal tips.

I changed this solder pot today and used a new lot/date code of solder.
So, I 
expect that this problem will appear to go away and I will assume that I
have 
solved the problem.  Then, sometime in the future, I will rear it's ugly
head 
again.   We had this problem in our Corfin tinning system and we blamed
the 
solder for several months.  Finally, they removed the solder pot and
replaced it 
with a brand new lot of solder and the problem went away.  The lot date 
codes of solder that I am using have nothing to do with that story, but
I 
wonder if in the past, this pot could have been contaminated and there
are 
gremlins floating around in there that only show up on occasion???

Jack Evans,
Aeroflex Colorado

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------