Chris,
Wow! Lots of questions.
Yes SAC 305 is becoming the industry standard. See the IPC Solder Value
Council Abstract or the report if you have $.
Dr. Lee of Indium and his co-workers have shown that the amount of
silver affects tombstoning and voiding and the results go in opposite
directions!
Safest bet? There are no guarantees, since we are going into this half
blind.
You could mix 405 and 305, just like we have been mixing 53/37, 60/40
and 62/36/2, but do you really want yet another variable in the mix?
This is NOT a Materials Dec. issue (assuming you are lead, cadmium and
Hg free).
No, I do not know of a better alloy. No, we are not using anything
else. Fortunately we do not wave solder.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Schaefer
Sent: September 21, 2005 1:40 PM
To: [log in to unmask]
Subject: [TN] Lead Free pastes, wave solder, and core solders
Hello all,
I have a few question concerning the types of alloys used for pastes,
wave
solders, and core wire solders used in Lead Free processes.
All of your help would be much appreciated...
>>>>>>>>>>>>>
I understand that SAC 305 is considered to be the industry standard and
there has been much testing to indicate that it performs well in all of
the
mentioned processes stated above. Of course there are other solder
compositions that are available to be used in these applications such as
SAC 359, SAC 387, SAC 396, and SN100C. In terms of the testing of
alternative compositions there is a measured amount of testing involved
with them as well - some favoring better in some areas than others.
The questions are:
- Is SAC 305 truly the safest bet for soldering in these process
arena's?
- Must you use the same solder composition for the smt, wave solder, and
core wire soldering area's? I understand that when one type is used in
wave
soldering and a different type used in the touch-up of the assemblies
that
the composition will change, but does that make a significant
difference.
Possibly in the realm of the Materials Declaration process it may
perhaps???? Don't know...
- Are there in your opinions better alloys than SAC 305 no matter the
cost?
- Are any of you using other allow compositions (non SAC 305) in smt,
wave
solder, and core solders? If so what drove you to use other
compositions?
Costs, larger process windows, better joint cohesion, etc... And what
are
you thoughts on using them?
- I heard in these rooms and others that the more silver content in the
composition the better in terms of solderability. Is this true in the Pb
Free arena as well?
>>>>>>>>>>>>>
We are currently in the process of setting up a Pb Free process for
these
core processes and I am not completely convinced that SAC 305 is the
right
choice for wave solder, it may be a good choice, but is it the absolute
best choice. Especially knowing that new allows are coming out all of
the
time and possibly better ones for the stated processes. I don't claim to
be
anything close to an expert in terms of Pb Free soldering or even
metallurgy compositions, but I certainly would like to know that
whatever
choice is made - it is the best choice for us right now.
I would appreciate your help in this matter. You help is much
appreciated
as always.
Thank You.
Chris Schaefer
Suntron Corporation
Process Engineer
540 N. Rogers Road
Olathe, Kansas 66062
913.393.5878
[log in to unmask]
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