Excellent summary of lead-free soldering. I've noticed some of the same effects when I hand solder with lead-free.
Mark Mayer, PE
Senior RF Engineer
Centurion Wireless Technologies
3425 N. 44th St.
Lincoln NE 68504
(402) 325-3262 (direct)
(402) 325-3200 (main)
www.centurion.com
-----Original Message-----
From: Lee Whiteman [mailto:[log in to unmask]]
Sent: Thursday, December 01, 2005 6:12 PM
To: [log in to unmask]
Subject: Re: [LF] Lead-free Hand Soldering Implementation
Ken,
Here are a few things that we found when performing Lead Free Hand
Soldering:
1. Because of the higher soldering temperatures, the solder tip temperature
has to be set higher. For example, with the solder alloys soldered, ACI
found that the solder tip temperature had to be set at 343oC for Lead Free
solders, as opposed for 315oC for SnPb.
2. Selecting the solder tip becomes more important for Lead Free soldering.
Too small a solder tip will not provide sufficient heat transfer during the
soldering process.
3. It was discovered that a longer dwell time - the time the soldering iron
was in contact with the hardware - was required to promote adequate heat
transfer during the soldering process.
4. The higher soldering temperature requires that the soldering iron must
remain clean and coated with the solder alloy. The higher soldering
temperatures can result in the soldering iron tip becoming oxidized if not
cleaned and coated. Lead Free solders are more sensitive to the effects of a
dirty soldering iron.
5. Solder tips used to solder with Lead Free solders must be separated from
solder tips used with SnPb solders. Using a SnPb coated solder tip to solder
with Lead Free solders can result in a solder joint contaminated with Lead
(Pb). There is some evidence that Lead Free solders joints, contaminated
with Pb, are not as reliable as uncontaminated Lead Free solder joints.
6. Lead Free solders do not wet as well as SnPb solders. To improve wetting,
a more active solder flux may be considered. However, if a more active flux
is used, more aggressive cleaning processes will be required. Active fluxes
leave residues on hardware, which will promote dendritic growth and poor
conformal coat adhesion.
7. Due to the higher soldering temperatures, the soldering iron had to be
removed faster for Lead Free than for SnPb. Lead Free solders and SnPb
solders have different cooling rates and cooling characteristics. Quick
solder iron removal prevents the soldering process from disturbing the
solder joint and the board pads. Lifted pads and lifted fillets are more
prominent with Lead Free Solders.
8. Recommend preheating the PWA between 100C to 120C. These temperatures
will be dependent upon the board material, board thickness, and
configuration. Preheating the boards before soldering offers several
advantages:
- Prevent board and component thermal shock
- Reduces the amount of thermal gradients in the board
- Prevent pad lifting by reducing the solder tip contact time
- Reduces soldering dwell time
- Improve wetting during the soldering process by having the board at an
elevated temperature during the soldering process
- Reduces the effect of Coefficient of Thermal Expansion (CTE) mismatch
between components and boards
9. Use a hot plate during hand soldering. We recently did a Lead Free audit
at a customer's place and found the operator had a difficult time performing
hand soldering with Lead Free solders (SAC-305). A hot plate was provided to
the operator - the operator was able to perform hand soldering much easier
than before.
If you have any questions, give me a call off-line.
Hope this helps.
Good Luck.
Lee Whiteman
Senior Manufacturing Engineer
American Competitiveness Institute
E-Mail: [log in to unmask]
Ph: (610) 362-1200 x208
Fax: (610) 362-1290
This message is for informational purposes only and does not supersede,
modify, or create any agreements with ACI. Information contained in this
message does not bind ACI or its affiliates to any commitment, either
express or implied, unless ratified in writing by an authorized
representative.
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Kanaiyalal Patel
Sent: Wednesday, November 30, 2005 1:10 PM
To: [log in to unmask]
Subject: [LF] Lead-free Hand Soldering Implementation
Lead-free Implementers,
I have been assigned to implement Lead-free Hand Soldering on our
manufacturing floor. I believe many of us have already implemented similar
activities on their floor. I really appreciate if someone can share their
experience to make it foolproof and also provide signs/warning/alert
documents prepared for the area to warn everyone including operators.
Any help will be highly appreciated.
Re,
Ken Patel
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To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
To temporarily stop/(start) delivery of Leadree for vacation breaks send: SET Leadfree NOMAIL/(MAIL)
Search previous postings 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
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