More info on this from the good folks at NIST. Jack
------------
Date: Wed, 05 Feb 1997 16:32:53 -0500
From: [log in to unmask] (Ursula_Kattner_x6044)
Subject: Re: Alloy contamination
To: [log in to unmask]
Cc: [log in to unmask], [log in to unmask],
[log in to unmask]
>A phase diagram for Ag-Pb-Sn is published in: P. Villars, A. Prince
>and H. Okamoto, "Handbook of Ternary Alloy Phase Diagrams" Vol.3,
>ASM International, Materials Park, OH, 1995. In this book the
>sources of the diagrams are given as A. Prince et. al., private
>communication, and three more references.
>The system has a ternary eutectic L = Ag3Sn + (Pb) + (Sn) at 180 C
>with a liquid composition of 1.5 wt.% Ag, 35.0 wt.% Pb (1.9 at.% Ag,
>23.5 at.% Pb), the compostions of the solid phases can be assumed
>to be identical to the corresponding binary systems.
>The addition of Sn will lower the liquidus and solidus approximately
>with the same slopes as in the Sn-Pb binary system. Simultaneous
>addition of Pb will decrease the effect. It should be noted that
>the solidus for the given composition is the (Pb) + Ag3Sn tie-line.
>The equilibrium ternary ternary eutectic begins to form when the
>the tie-line of Sn-saturated (Pb) + Ag3Sn is crossed. However, due
>to the effects of non-equilibrium solidification (segregation) the
>ternary eutectic may be observed earlier.
>
>Hope this information helps,
>Ursula R. Kattner
>Metallurgy Division, Materials Science & Engineering Laboratory
>Bldg. 223, A153
>NIST, Gaithersburg, MD 20899
>Phone: 301-975-6044 Fax: 301-975-4553
>e-mail: [log in to unmask]
>
>| From [log in to unmask] Wed Feb 5 14:40:57 1997
>| Date: Wed, 05 Feb 1997 14:38:59 -0500
>| From: Carol Handwerker <[log in to unmask]>
>| Subject: Re: Alloy contamination
>| X-Sender: [log in to unmask]
>| To: [log in to unmask]
>|
>| Please respond to this person who has a question about the effect of tin
>| additions on liq. and sol. temps. Thanks.
>| Carol
>|
>| >Return-Path: <[log in to unmask]>
>| >Date: Wed, 5 Feb 1997 13:54:39 -0500
>| >X-Sender: [log in to unmask]
>| >To: [log in to unmask]
>| >From: [log in to unmask] (Jack Crawford)
>| >Subject: Re: Alloy contamination
>| >Cc: [log in to unmask], [log in to unmask]
>| >
>| >Following from the EMPF Helpline, prepared by our metallurgist John=
>| Greaves:
>| >
>| >Increasing the Sn content will lower the liquidus and solidus, and once the
>| >Sn content increases beyond a point (I am not sure what that point is) a
>| >low melting binary eutectic phase will form ( eutectic SnPb, melts at
>| >183=B0C). The person to ask about this is Carol Handwerker at NIST. Her
>| >phone is 301-975-6158, and her email is : [log in to unmask]
>| >
>| >
>| >If she can't help you then your answer doesn't currently exist.
>| >
>| >Hope this helps,
>| >
>| >John Greaves
>| >
>| >----------
>| >>From: [log in to unmask]
>| >>Date: Wed, 5 Feb 1997 07:08:08 -0600
>| >>To: <[log in to unmask]>
>| >>Subject: ASY: Alloy contamination
>| >>
>| >>
>| >>Here's one for the metallurgist. I have been unable to locate a
>| >>Pb93.5/Sn5/Ag1.5 (305C liquidus; 309C solidus) ternary phase diagram
>| >>to date. I have been told that one of the technical issues is simply
>| >>soldering to SnPb plated and/or SnPb hot-dipped coated components with
>| >>this PbSnAg solder will realize a drop in the melting point. My
>| >>question is how much ? Assuming, for instance a lead finish
>| >>composition of Sn63/Pb37 with solder coat thickness of 3 to 4 mils or
>| >>a CERDIP package with leads that are 100% Sn electroplated (200 to
>| >>500micons).
>---------------------------------------------------------------
***ALL NEW EMPF PHONE NUMBERS***
Jack Crawford, HelpLine Coordinator
Electronics Mfg. Productivity Facility
****NEW--317.655.3688
****FAX 317-655-3699
714 N Senate Ave, Suite 100
Indianapolis IN 46202-3112
VISIT OUR HOME PAGE AT: http://www.empf.org
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