Omikron is a white tin! (crystallographically speaking) it is different
structurally than the grey tin... Bev is correct!  Regardless his steel toe
safety shoes...
http://205.133.80.137/omikron.htm
                                      jk
At 07:47 PM 6/15/00 EDT, you wrote:
>In a message dated 06/15/2000 5:20:22 PM Central Daylight Time,
>[log in to unmask] writes:
>
>> Bev
>>
>>   Please follow your own suggestions and check the TechNet
>>   archived.  I talked about this several months ago.  I have used the term "
>> Immersion White Tin" since 1995 to describe a coating called OMIKRON.  I
>took
>>  the name from  an IBM research paper published back in 1984.  They used
>that
>>  term to describe a long term solderable immersion tin finish.  It has
>> nothing to do with your definition.
>>
>>  Rich Edgar
>
>Hi Rich!
>
>The "White Tin" in the term "Immersion White Tin" is what sometimes confuses
>many people. Bev described exactly what "white tin" is from the periodic
>table of elements. So you are right, his description of "White Tin" has
>nothing to do with OMIKRON, just as the words "White Tin" in "Immersion White
>Tin" has nothing to do with the actual description of White Tin in the
>periodic table of elements.
>
>Bev is probably more knowledgable in material sciences than many people,
>that's why he has his PHD. Not to speak for him, but I'd bet he was talking
>about white tin as it's clearly defined from the periodic table...not from
>your "trade name"...
>
>There's some pastes below from a few web pages that talk about white tin,
>organic tin, white immersion tin...whatever you want to call it. This ought
>to confuse everybody :)
>
>-Steve Gregory-
>
>From: http://pearl1.lanl.gov/periodic/elements/50.html
>
>Properties
>
>Ordinary tin is composed of nine stable isotopes; 18 unstable isotopes are
>also known. Ordinary tin is a silver-white metal, is malleable, somewhat
>ductile, and has a highly crystalline structure. Due to the breaking of these
>crystals, a "tin cry" is heard when a bar is bent.
>
>Forms
>
>The element has two allotropic forms at normal pressure. On warming, gray, or
>alpha tin, with a cubic structure, changes at 13.2 degrees C into white, or
>beta tin, the ordinary form of the metal. White tin has a tetragonal
>structure. When tin is cooled below 13.2 degrees C, it changes slowly from
>white to gray. This change is affected by impurities such as aluminum and
>zinc, and can be prevented by small additions of antimony or bismuth. This
>change from the alpha to beta form is called the tin pest. There are few if
>any uses for gray tin. Tin takes a high polish and is used to coat other
>metals to prevent corrosion or other chemical action. Such tin plate over
>steel is used in the so-called tin can for preserving food.
>
>Alloys of tin are very important. Soft solder, type metal, fusible metal,
>pewter, bronze, bell metal, Babbitt metal, White metal, die casting alloy,
>and phosphor bronze are some of the important alloys using tin.
>
>Tin resists distilled sea and soft tap water, but is attacked by strong
>acids, alkalis, and acid salts.Oxygen in solution accelerates the attack.
>When heated in air, tin forms Sn2, which is feebly acid, forming stannate
>salts with basic oxides. The most important salt is the chloride, which is
>used as a reducing agent and as a mordant in calico printing. Tin salts
>sprayed onto glass are used to produce electrically conductive coatings.
>These have been used for panel lighting and for frost-free
>windshields. Most window glass is now made by floating molten glass on molten
>tin (float glass) to produce a flat surface (Pilkington process).
>
>Of recent interest is a crystalline tin-niobium alloy that is superconductive
>at very low temperatures. This promises to be important in the construction
>of superconductive magnets that generate enormous field strengths but use
>practically no power. Such magnets, made of tin-niobium wire, weigh but a few
>pounds and produce magnetic fields that, when started with a small battery,
>are comparable to that of a 100 ton electromagnet operated continuously with
>a large power supply.
>
>
>From: http://www.omnigraph.com/omnireview.html
>
>Organic White Tin
>
>About six months ago we sent out samples of white tin finish on printed
>circuit
>boards. Some people liked it and some did not. Those that did not like it had
>solderability issues. It didn't wet as well as Hasl. We had difficulty in
>figuering out why it did not wet as well. Was there a difference when the
>assembler used
>a water soluable or no-clean flux? Did the soldering temperture make a
>difference?
>
>It turns out the biggest problem was the plating thickness in our process. We
>thought if it looks good then it should work. We discovered that .2 microns of
>white tin look good but there will be de-wetting. And .4 microns wets fine
>for a
>single thermal pass, but will cause difficulty on subsequent thermal passes.
>For
>multiple thermal passes, .6 to .8 microns of plating is required. We have
>decided
>to be on the safe side and plate .8 to 1 microns on all our boards.
>
>To refresh your memory, here are some characteristics of white tin.
>
>THE HASL REPLACEMENT IMPROVED IMMERSION WHITE TIN
>Compatible with all fluxes and solder pastes
>Capable of multiple assembly cycles
>Uniform flat and dense pads
>Shelf life equal to hasl
>No solder pot contaminaton
>Can be electrically tested after coating
>
>This coating will not add cost to your board and will guarantee your product
>acceptability in the Japanese and European market in 2002 and thereafter.
>
>We will be sending more samples out to you for testing.
>
>Please try this process again.
>
>
>From: http://www.filtranmicro.com/desgui.html
>
>B) White Immersion Tin
>
>    Filtran provides immersion tin processing using Omikron chemistry.
>Typical
>    thickness will be under 40 microinches (1 micron).  This finish is thin
>and will not
>    affect the circuit resolution as will 300-500 microinches of tin-lead
>solder.
>    Immersion tin acts as an acceptable solderable coating with a shelf life
>of 6 -
>    12 months if stored under ideal conditions.  Tarnishing can occur when
>    exposed to moderately hostile environments.  In such cases, a mild acid
>    cleaning and/or light abrasive cleaning immediately prior to soldering is
>    recommended.
>
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