"One reason is the lower temperature requirement for the Sn100 alloy,"
(vs. SAC305)
Are you sure the cause of easier rework was temperature
MP ~217C for SAC305
MP ~227C for SN100C
Rex Waygood
Technical Manager
PartnerTech Poole Ltd
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 18 August 2008 21:54
To: [log in to unmask]
Subject: Re: [TN] FW: [LF] [TN] SN100 for Reflow Application
Thanks, Keith. This is very informative, and goes hand-in-hand with my
recent experiences with Sn100.
I had an opportunity to work with Kester K100LD Sn100 wire solder and
EasySpheres, and also Nihon Sn100CL "real RMA" cored flux wire and the
SnCuNi +Ge eBalls while performing some laser solder process development
and testing for a government customer three weeks ago. Last week I again
used the Kester K100LD while performing rework/repair during IPC
recertification at STI, during which I performed lots and lots of hand
soldering and hot gas rework, so I became intimately familiar with Sn100
wire. I confirmed the instructor's observation that Sn100 alloy performs
completely different from SAC305, SAC307, SAC407, etc, and is closest to
63/37. It proved to be much easier to solder in hot gas reflow, laser
soldering during the development work, and when hand soldering it
produced far superior solder joints from a wetting and appearance
perspective than did the SAC305/405 alloy solders I found these two wire
solders and solder ball products to be very similar to standard 63/37
while soldering and performing hand rework and BGA ball attach using
laser and convection. Both Kester and Nihon Sn100 solders performed very
well in vibration and shear testing, but not quite as good as Sn63/Pb37.
I will get temperature cycling data in about 4-5 weeks.
However, the laser-solder process with Sn100 from either Kester or Nihon
had much better test results than any other lead-free alloy that was
convection soldered, and also when the other Pb-free alloys were
laser-soldered. This proved to be a big factor in the vibration and
shear testing.
After having fun performing rework on some very difficult-to-remove
components that were soldered with SAC305 a few weeks ago, I can tell
you it is much easier to rework the same components when they are
soldered with Sn100. One reason is the lower temperature requirement for
the Sn100 alloy, and the other is that a certain amount of ductility
helps in removing the clinched leads without any pad or barrel damage.
My observation is that the ductility of the Sn100 is much greater than
SAC305, and for most purposes this would therefore be a better lead-free
solution in terms of reliability than SAC305. The ease of rework says a
lot for the use of Sn100, it presents less of a temperature shock than
is required with SAC30X.
But Sn63Pb37 is still the best choice in terms of reliability, if one is
allowed to use it.
How much more (or less) of a tin-whisker risk does Sn100CL present than
the SAC alloys?
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