Dear Sir,

 The shrinkage of the surface of  lead free solder is appeared by difference
solidification time. Tin Silver and Tin Copper makes inter metallic
compounds that are higher melting points than Tin Silver's and Tin Copper's
eutectic melting point. So that, after pile up intermetalic compounds then
liquid solder solidifies with decreasing volume between intermetalic
compounds.
Another things, I have studied if contained small amounts of Nickel in
Copper contained solder, such as Sn-0.7Cu, the shrinkage is much smaller
than before adoption Ni. I believe Tin Nickel inter metallic compounds makes
Tin Copper intermetalic compounds very small particles. If you interested in
this, I want to discuss farther with you.

********************************************
 西村哲郎　Tetsuro Nishimura (Executive Director)
 ㈱日本スペリア社　Nihon Superior Co.,Ltd.
 TEL +81(06)6380-1121
 FAX+81(06)6380-1262
 E-mail : [log in to unmask]
 HP : http://www.nihonsuperior.co.jp
********************************************
----- Original Message -----
From: Guenter Grossmann <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, December 06, 2000 5:12 PM
Subject: [LF] Antw: [LF] Pb-free appearance


Kirk

Two possies I know of for dull Pb free solder:

- Intermetallics swimming on the surface of the liquid solder.

- Shrink cracks along primarily solidified phases. These cracks are not
deep. They form because SnAg phases solidify like dendrites leaving a
certain amount of liquid solder so that a gap forms when the solder joint
cools down. Eric reported about this not eutectic solidification.

Have a great day


Guenter

Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

----------------------------------------------------------------------------
-----
Leadfee Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (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
----------------------------------------------------------------------------
-----

---------------------------------------------------------------------------------
Leadfee Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Leadfree
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (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
---------------------------------------------------------------------------------