Hi Guenter -
Our company has been in production with white immersion tin for 3-years,
currently processing Omikron-Plus.
Our experience is consistent with your statement "I believe that alloys on
tin/copper or tin/silver base can meet the demand of the world market.".
While the EC was our original motivation for turning to alternative surface
coatings in late 1995, we are now shipping product widely in the US, as well
as Canada and Mexico.
Bob Lazzara
Circuit Connect Tech Support
Georgia Service Bureau
TEL: 800.560.9457 FAX: 888.453.0520 BBS: 603.889.5385
alternate eMail: [log in to unmask]
-----Original Message-----
From: Guenter Grossmann <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, February 02, 1999 8:34 AM
Subject: [TN] Lead removal again
Hi Ed
The question is about alternatives to what we are talking.
1) Alternatives to HAL
2) Alternatives to Tin/Lead solder
And combinations of both
Now, since Bob asked me what pad surfaces I tested let me begin with
these:
I am sure that a lot of new surfaces are around. OSP's, NiAu, Omicron,
Alphalevel are about the ones I know of ( hey Bob since you are reading this
too, that might be the slot for your 2 cents ).
We did test OSP ( don't want to mention a brand name), NiAu ( but that's
5 years ago and the Au thickness was not very well controlled ), galvanic
tin and solid solder deposition ( SIPAD ).
The test we run was -20/100 deg. C with a gradient of 2 deg C /minute
and dwell times of 30 minutes.
We removed the specimen from the test chamber after 4000 cycles and
compared the crack length in the solder joints of some components with those
on HAL. OSP's and NiAu showed a higher average crack length than HAL, Sipad
or tin. But again, these data are not suitable for a reliability prediction
since they don't allow it to make a statement about the evolution of the
damage.
Alternatives to Tin lead solder many too. And also lots of problems are
there , as Oxonfenuk ( sorry fella didn't get your Christian name on the
mail ) pointed out. Just imagine all the world would start to solder with
any Indium solder. I'm sure the world recourses wouldn't last long. There
are Tin-Copper , Tin-Silver binary alloys but they all tend to have a high
liquidus temperature. So ternary alloys are used ( Tin/Copper/Silver,
Tin/Silver/Bismuth etc.) to lower the melting temperature. I have no data in
hand but you see, one big advantage of Tin/Lead solder is its ductility
which allows it to combine materials with high differences of the CTE. Maybe
Bob Willis or Collin Lea of ITRI ( are you on the Net Collin?) could give
some contributions. Principally there are now problems to be expected with
the use of ternary alloys ( Sn62Pb36Ag2 is a ternary alloy too ).
I believe that alloys on tin/copper or tin/silver base can meet the
demand of the world market.
I don't know whether anyone made thermal cycling tests with new alloys.
I mean thermal cycles not thermal shock, nor do I know who made research on
the deformation/degradation behaviour of these alloys.
I think the fluxes are not a big problem. What I see so far, tin will be
the main content of all lead-free alloys. And all the surfaces I saw so far
work well with fluxes used presently.
Best regards
Guenter
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