Bi/Sn has long been a low MP alternative alloy for special situations.
Now that Pb containing surfaces have washed out of the system with move to
Pb-free, Bi based alloys are being more widely used when a low MP is needed.
The key is to use a low temperature flux to go with the low MP alloy. The
rate of joint formation is also slower due to low tin content so the flux
has to be capable of sustaining a longer reflow time.
Finally many people favour use of an alloy with a small addition of Ag, this
makes the alloy more ductile
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com
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Registered office: (Not for correspondence)
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman
Sent: Tuesday, October 07, 2008 10:13 PM
To: [log in to unmask]
Subject: Re: [TN] Sn-Bi Alloy for soldering
Amol,
In a prior life (or two), I tried soldering SnBi with hand soldering and
reflow soldering. My impression was that it did not wet well, despite the
lower melting point. At that time, if I had to select a Lead Free Solder, I
would not go with SnBi.
However, that was several years ago and I have not tried it since then.
Assuming that the solder manufacturers increased the flux activity since, I
would consider it for non aerospace applications where I have heard that it
has been used successfully. Otherwise, I would not use it for high
reliability or aerospace applications, IMHO.
Hope this helps.
Good Luck.
Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
Sent: Tuesday, October 07, 2008 11:57 AM
To: [log in to unmask]
Subject: [TN] Sn-Bi Alloy for soldering
Does anybody have any experience with Sn-Bi alloy used for soldering
lead-free boards? I am looking at literature available out there and see
Sn-Bi used as a surface finish for components, but I have not yet found a
reference where it is used for soldering.
Looking for pros/cons, good/bad experiences and things to look out for
during soldering.
The application is all SMT, with a temp sensitive part. The manufacturer
therefore wants to use Sn-Bi alloy as this is a lower melting point alloy
Regards,
Amol
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