Ken, Christian, Alejandro,
the thing with Pb vapour is just sitting in some corners of my memory, heard
many many years ago from (I canīt even remember who) one "soldering
expert". Not something scientifically.
It sticks there maybe as a reminder that temperatures that high are not good
at all for soldering and people.
For Alejandro: Just turning down the temperatures might not be the help
cause perhaps your equipment doesnīt allow for good soldering anymore or
your operators will not be able to produce good joints anymore.
The advice from Moffid seems the most suitable, aquiring external advice on
equipment and the correct use of it with additional training of your
operators where they learn that itīs gonna work that way might be the right
thing to do if you encounter problems with certain rearrangements regarding
temperatures.
Itīs of no help if you change the settings by order and your soldering
doesnīt work anymore
I noticed that after training the operators stopped arguing about
"limitations" instead they asked for the proper equipment.
best regards
Wolfgang
-----Ursprüngliche Nachricht-----
Von: Ken Mc Gowan [mailto:[log in to unmask]]
Gesendet am: Freitag, 23. Februar 2001 02:02
An: [log in to unmask]
Betreff: Re: [TN] AW: [TN] Temperatures for Rework operation
Wolfgang,
Fundemental problem with Pb vapour pressure. Look up why 63:37 melts at
lower than either of the elemental components. God rest GW FRS d Sept 26
1996.
Best Regards,
Ken
----- Original Message -----
From: Bev <mailto:[log in to unmask]> Christian
To: [log in to unmask] <mailto:[log in to unmask]>
Sent: Thursday, February 22, 2001 2:36 PM
Subject: Re: [TN] AW: [TN] Temperatures for Rework operation
Wolfgang,
The health problem with lead from hand soldering at normal temperatures is
NOT due to vapor ingestion by the workers. If you go to the web site of
Vulcan Lead Inc.
http://www.vulcanlead.com/newfiles/techgendata2.html#Anchor#6
<http://www.vulcanlead.com/newfiles/techgendata2.html#Anchor#6> they list
the vapor pressures for molten lead from 808C and higher. Using a plot of
log P as a function of 1/T (T in Kelvin), I have calculated that at 400C the
vapor pressure of lead is only going to be in the range of 1.2 x 10-7 torr.
In Cotton and Wilkinson's "Advanced Inorganic Chemistry", 3rd edition, page
506 they state that at 20C the vapor pressure of mercury is 1.3 x 10-3 torr
and that this value is "appreciable". So I think we can say that a vapor
pressure of 1.2 x 10-7 torr for lead at four hundred C is pretty low. Since
most people (I hope) do not solder above 752F, then the workers should be
safe from lead vapor.
Some companies state that soldering should not be done above 600F, but I
would like to see someone do that on some of the nastier components.
Now if one is talking about flying metal fragments from cutting leads when
not wearing safety glasses or not washing ones hands before eating, smoking
or using the bathroom, then we have a different situation.
regards,
Bev Christian
Research in Motion
-----Original Message-----
From: Busko, Wolfgang [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: February 22, 2001 4:45 AM
To: [log in to unmask]
Subject: [TN] AW: [TN] Temperatures for Rework operation
Hi Alejandro,
if you have 400°C at the tip thatīs to much. The risk of damaging parts and
boards is quite high and if my memory is right the Pb starts to evaporate in
this temperature range with all the hazards for the operators.
Consider what you have for temperatures in your wave and your reflow.
I know itīs hard to maintain the temperature during the handsoldering with
certain equipment thatīs not capable of delivering enough energy in time to
the tip to encounter the loss that you have due to heating the joint and
itīs surrounding and itīs widely seen that operators work with higher temps
to get the job done.
A better way is to use different tips (soldering irons) for different
joints, using one small tip for everything just doesnīt work. We have at
least three different sets at the reworkplace with additional hot air device
for preheating the units so that thereīs no need to go to high in
temperature.
There are other systems available with faster energy transport to the tip
and easy change of tips ( in seconds ) for different tasks.
Keep things under control and you also might measure your temp. at the tip
and how it behaves during soldering to see what you need.
Preheating is often the answer to many problems.
Good luck
Wolfgang
-----Ursprüngliche Nachricht-----
Von: Becerra Alejandro [ mailto:[log in to unmask] <mailto:[log in to unmask]> ]
Gesendet am: Donnerstag, 22. Februar 2001 00:11
An: [log in to unmask]
Betreff: [TN] Temperatures for Rework operation
Hello to All,
I am interested in the optimum temperature for the soldering iron used in
rework operations.
At this moment we use 750F (Aprox. 400C) in the soldering irons for the
touch up operation (Rework operation in line for wave soldering).
Is it correct this temperature or do we use a lower temperature?
Thanks in advance
Alejandro Becerra
Quality Assurance
Phone (915) 841-8439, Fax (915) 841-8401
[log in to unmask]
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