Ofer,
Following up on what Ioan said, there is a plethora of lead free
component finishes that are being marketed right now. Basically,
component manufacturers are selecting finishes which are being defined
by the market. I've seen Ni, Pd, NiPd, SnAg, SnAgCu, Sn being marketed.
In my experience, we have not found any material compatibility issues
with using them with SnPb solder or lead free solders (SnAgCu, SnAg,
SnCu, SnAgCuSb are the ones we tested). There has been a few papers
concerning lead contamination with lead free solders, but we have not
seen any negative effects.
Ioan is correct about the soldering temperatures. For example, SnPb
reflow soldering is performed at around 220C. Depending upon the alloy
used, lead free soldering can range from 240C to 260C. The resulting
solder joint will have a dull grainy appearance. Lead free solders do
not wet as well as SnPb so you may have to use a more aggressive
(active) solder flux and / or nitrogen in you soldering process to
improve wetting. However, using a more aggressive (active) solder flux
may require you using a more aggressive cleaning process to remove the
residues left from the soldering process which are baked on due to the
higher soldering temperatures.
Suggest that you consider monitoring the IPC's Lead Free forum for
additional details.
Give me a call off line if you want to discuss lead free soldering in
more detail.
Hope this helps.
Good Luck
Lee Whiteman
Senior Manufacturing Engineer
ACI
E-Mail: [log in to unmask] <mailto:[log in to unmask]>
Ph: (610) 362-1200 x208
Fax: (610) 362-1290
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ofer Cohen
Sent: Thursday, May 29, 2003 11:06 AM
To: [log in to unmask]
Subject: [TN] Combination Leadless and SnPb
Hi all,
Lately I receive messages from components manufacturers, stating they
are moving from Tin-Lead finish to lead-less finish (not specified which
one - my regular question that regularly is not being answered). Most of
the components are still with the SnPb finish, the PCBs Tg are 145 deg
C, unless I had a specific need (extra depth, for instance to move to
what is currently called high Tg (and in the future will probably be the
standard
boards) and the pastes are, of course, SnPb, hence would not survive the
higher soldering temperature needed to tickle the lead-less finish.
Should I modify the work processes? Should I wait? Are there any
workmanship/ reliability effects to these changes? Helppppppppppp...
Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.
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