I think we need to keep a sense of perspective in this area.
Saying that Bi is to be avoided at all costs is a bit like saying drinking a
glass of coke will be fatal. How so? It's obvious - coke contains phosphoric
acid, which is highly corrosive.
1) As Bev points below out the presence of Bismuth does not automatically
mean that solder joints will melt at 96C. Search back for references on
this as this has been aired a number of times on this forum.
2) The availability of Bi will not be affected by the ending of lead in
soldering. The laws of supply and demand would ensure that anyway, but even
if Bi could only be obtained by first smelting lead it wouldn't matter. This
is because total lead usage will reduce something like about 0.5% maximum
overall as a result of our efforts in lead-free.
3) Metals have a volume change on phase change. Usually it's a contraction,
but as it happens pure bismuth expands on freezing, as do some of its
alloys, but not all. For expansion you need over 50% Bi content.
4) If the EU even looks as though it wants to ban Bismuth, then I will for
one will give up and start digging a cave.
Regards
Mike
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, January 06, 2005 7:10 PM
To: [log in to unmask]
Subject: Re: [LF] The use of Bismuth
Ladies and Gentlemen,
There is NO actual or proposed EU legislation to ban the use of bismuth.
Period. Yes, Bi is a byproduct of lead mining but more and more of it now
is coming as a byproduct of mining other metals (tungsten). Check out the
US Geological Survey web page for bismuth.
http://minerals.usgs.gov/minerals/pubs/commodity/bismuth/bismumcs04.pdf
And as Pratap points out, it is not SnBi by itself that is bad, it is the
SnBiPb alloy that is the problem. Mixing SnBi with SnPb, as shown by Boeing
is REALLY bad. However, Tom Woodward (Boeing) has also shown that smaller
amounts of Bi is actually not a problem, at least not to the same extent. I
do not want to put words in Tom's mouth that everything is hunky dory about
lesser amounts than in the SnBi eutectic, but things do not look as bad as
first thought for alloys containing single digit amounts or Bi.
regards,
Bev Christian
Research in Motion
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Richard Schumacher
Sent: January 6, 2005 12:03 PM
To: [log in to unmask]
Subject: Re: [LF] The use of Bismuth
Dewey, what finish alloys use up to 3% Bi?
Genny, what indications have you seen that the EU may eventually want to ban
Bi?
> -----Original Message-----
> From: Leadfree [mailto:[log in to unmask]] On Behalf Of
> Whittaker, Dewey (AZ75)
> Sent: Thursday, January 06, 2005 10:30 AM
> To: [log in to unmask]
> Subject: Re: [LF] The use of Bismuth
>
>
> We are seeing components with this finish. There is data to
> support the acceptability of a final lead finish containing
> up to 3% Bismuth. Dewey
>
> -----Original Message-----
> From: Leadfree [mailto:[log in to unmask]]On Behalf Of Genny Gibbard
> Sent: Thursday, January 06, 2005 9:15 AM
> To: [log in to unmask]
> Subject: [LF] The use of Bismuth
>
>
> So I am curious, what are people thinking about the use of
> bismuth in lead free termination finishes. I am not talking
> about solder containing Bi. The only supplier I have come
> across so far specifically mentioning they use Bi is NEC.
> They have a doc on their website, called "Japan's best kept
> secret" http://www.cel.com/pdf/marcomnews/japan_best.pdf
> that claims
> that SnBi is recommended by JEITA, as opposed to the
> recommendation of JEDEC for Matte Sn. They make it sound as
> if a lot of companies are using this plating, but I haven't
> come across any other components so far that use it. The main
> concern I have is that I keep getting the impression that the
> next metal that the EU will be gunning for eliminating is Bi,
> so it doesn't sound like a smart direction to go.
>
> Thoughts?
>
> Genny Gibbard (mailto:[log in to unmask])
>
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