Hi Rex - there are a couple of different failure phenomena associated with 
the use of gold finishes: 1) gold embrittlement - the formation of a AuSn4 
microstructure phase which induces solder joint degradation by a brittle 
fracture in the solder joint bulk or in the Au/Sn phase. This is a 
soldering process root cause; 2) black pad - the formation of a corroded 
Au/Ni interface region which induces solder joint degradation by brittle 
fracture at the nickel interface region. this is a plating root cause.; 
3)solderability failure - the oxidation of the nickel plating which 
prohibits the formation of good solder joint wetting at the nickel 
interface region. This is a plating root cause or a storage environment 
root cause.  Gold isn't a bad surface finish - it just has some 
disadvantages that need to be recognized and dealt with in a proactive 
manner.

Dave



Rex Waygood <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
01/17/2008 02:41 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Rex Waygood <[log in to unmask]>


To
[log in to unmask]
cc

Subject
Re: [TN] Solderability of Tin-Gold Intermetallic






The thread has drifted into brittle fracture due to 'gold
embrittlement'.
We have experienced 'gold embrittlement' at levels (0.25%) which are
well below the threshold said to be 'safe'.
Maybe Murphy did his bit to ensure that the gold didn't distribute
evenly through the joint and therefore the failure initiated at
concentration points. In our situation the important thing was to solve
the problem quickly so we made an assumption it was 'gold embrittlement'
and took to double dipping to get rid of the plated 'excess' gold. The
joints stopped failing after double dipping.
I would now say that we tend to have a belief that gold in solder joints
should be avoided.



Rex Waygood
Technical Manager
 
PartnerTech Poole Ltd 
Benson Road
Poole
Dorset BH17 0RY
United Kingdom
 
Tel: +44 (0)1202 674333
Fax: +44 (0)1202 678028
DDI: +44 (0)1202 338222
Mob: +44 (0)7887 997403
 
[log in to unmask]
www.PartnerTech.co.uk

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: 16 January 2008 13:52
To: [log in to unmask]
Subject: [TN] Solderability of Tin-Gold Intermetallic

Technetters,
We all know that the tin-copper intermetallic has terrible
solderability.  I also know there are high melting tin-gold solders.  My
question is: what is the solderability of surfaces of tin with small
amounts of gold (<4%) in it? As good as 100% tin, better, worse?  If
worse, how much so?
Bev
RIM

---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential
information, privileged material (including material protected by the
solicitor-client or other applicable privileges), or constitute
non-public information. Any use of this information by anyone other than
the intended recipient is prohibited. If you have received this
transmission in error, please immediately reply to the sender and delete
this information from your system. Use, dissemination, distribution, or
reproduction of this transmission by unintended recipients is not
authorized and may be unlawful.

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please
visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

-------------------------------------------------------------------------------

The information contained within this e-mail and any attachments contained 
therein may be confidential and/or legally privileged and is for the use 
of the intended recipient only. If you are not the intended recipient 
please delete it from your system and notify the sender by return e-mail. 
The content of this e-mail may not be copied or disclosed to any third 
parties without prior permission from the sender. 

 

E-mail is susceptible to data corruption, interception, tampering and 
viruses. We do not accept any liability for any such incidents or any 
consequences thereof.
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to 
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to 
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 
for additional information, or contact Keach Sasamori at [log in to unmask] or 
847-615-7100 ext.2815
-----------------------------------------------------


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------