TECHNET Archives

March 2007

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Barmuta, Michael" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Barmuta, Michael
Date:
Wed, 21 Mar 2007 15:13:36 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (155 lines)
Jack: In answer to your responses below.  

	
Regards
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett WA
	
425-446-6076

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Evans
Sent: Wednesday, March 21, 2007 12:04 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. 
Based on your earlier input you are dumping this every month after
tinning @ 500 parts. This does not seem like a high loading factor. So I
wouldn't suspect high contamination levels from the parts your are
pretinning but it would be worthwhile to have Kester analyze the pot for
impunities when the problem is occurring. Among other things you could
be getting high gold or copper impurities.

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.
This is a RMA medium solids flux so I don't believe this is causing any
reaction problems. Is this flux really old? 

As a test you might try a flux from a different supplier, possibly an
RA.

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.
Next time you change out the pot thoroughly inspect it for breakdown,
deterioration, pitting, etc.

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.
It's possible your are getting contamination from the leads. It could be
oxides, organics, plating salts, mold release, etc. 

Are you doing any wire tinning, where sleeving or wire fines could be
getting in the pot?


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 
sometimes not. We use metcal tips.
See item 4 above

Also are you cleaning/de-drossing the pot regularly i.e. before every
use?

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.
 I don't think it's the actual feeder stock solder causing the problem.

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???
If you are doing a good job of cleaning out the pot during change out
this shouldn't be an issue. However this would probably show up during
the analytical analysis of
the solder in item 1 above.

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
-----------------------------------------------------


This message (including any attachments) contains confidential 
and/or proprietary information intended only for the addressee.  
Any unauthorized disclosure, copying, distribution or reliance on 
the contents of this information is strictly prohibited and may 
constitute a violation of law.  If you are not the intended 
recipient, please notify the sender immediately by responding to 
this e-mail, and delete the message from your system.  If you 
have any questions about this e-mail please notify the sender 
immediately. 

---------------------------------------------------
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
-----------------------------------------------------

ATOM RSS1 RSS2