----- Original Message -----
Sent: Tuesday, September 10, 2002 3:42
PM
Subject: Re: [TN] 2% Silver solder and
tombstoning...
J-STD-006 says eutectic at 179°C (354°F). Don't
know I always thought it had a plastic state as well . . .
Dave?
Hi All,
A while back there was
some discussion about 2% silver solder paste and the effect it had reducing
tombstones with 0402's.
I was skeptical at first, but I decided to
try it on a board we build here that quite often has a problem with 0402's
tombstoning.
To make a long story short, the results were dramatic.
Since we've been using the 2% silver paste on this board, tombstones are a
very rare exception.
I was asked by a new engineer here why I use 2%
silver paste to reduce tombstoning, I told him because it really works, I
seen it work with my own two eyeballs. But he asked why does that make a
difference? That's where I'm kind of stuck...I think I remember that it has
something to do with the 2% paste not really being a true eutectic solder,
that it's close, but there are slightly different temperatures for solidus
and liquidous for that alloy...can anybody educate me again?
I did a
search and found that Senju had done some studies and found that slight
additions of silver and antimony reduced tombstoning to below 10% of that
which occured with a 63/37 solder. I think it's either AIM or Multicore also
sells what's called a low tombstoning alloy as well.
As always,
thanks in advance!
-Steve Gregory-
P.S.
This is
non-technical, but I'd like to pass on something that was sent to me...
September 11th is tomorrow. On that day, wear red, white, and blue
to work or school to show your support for those who lost their lives on
9/11/01, and to honor the heroes who worked to save them, and the families
left behind. At noon your time on September 11th, 2002, no matter where you
are, or what you are doing, stop, put your hand over your heart, and say the
Pledge of Allegiance, and say a prayer for our nation. In addition, for
those of us that drive to work, please drive with your headlights on to also
give honor and rememberance to those that perished on September 11th.
If all of us work together in every time zone around the world, we
will have a powerful chain of thoughts surrounding us. Please share this
with your friends and family. On September 11th, hopefully enough people
will have read this and will join together in unity.
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to [log in to unmask]: SET Technet Digest Search the archives of previous posts
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http://www.ipc.org/html/forum.htm for additional information, or contact Keach
Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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