On this one I'll have to disagree and side with Rudy.
Richard,
On this one I'll have to disagree and side with Rudy. I'm not a
metallurgist but it is my understanding that solid state diffusion of
copper through nickel is extremely slow. Even if it did migrate to the
surface of the nickel what problem would it cause? Certainly not a
solderability problem. It is my understanding that most fluxes were
formulated to reduce copper oxide not nickel oxide. The flux chemistry
should certainly work better on the copper oxide on the surface than if
there was nickel oxide. From my old hybrid integrated circuit days I
was lead to believe that the people doing wire bonding wanted thick
nickel and thick gold. Their reasoning was that the nickel is a
leveling agent and provided a "hard" surface as will as prevented a
diffusion barrier. There is certainly lots of published work indicating
that thick nick was advantageous for wire bonding but I have not seen
any that has shown you need thick nickel to get good soldering. There
is certainly lots of published work indicating that you need a good
quality gold coating to protect the underlying nickel from oxidizing.
Regards,
George
George M. Wenger
Andrew Corporation Wireless Network Solutions
Senior Principal FMA / Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [Office] (732) 309-8964 [Cell]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, March 21, 2007 4:40 PM
To: [log in to unmask]
Subject: Re: [TN] Solderability problems on through holes only.
The nickel barrier may be too thin, allowing copper to migrate through.
This would lead to poor solderability.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
Sent: Wednesday, March 21, 2007 3:29 PM
To: [log in to unmask]
Subject: Re: [TN] Solderability problems on through holes only.
I would suspect quality of gold plate. If the gold plate was light,
and therefore porous, the Nickel under the gold might oxidize during the
SMT, and become unsolderable?
Rudy Sedlak
RD Chemical Company
Peter Wong <[log in to unmask]> wrote: Hi Technetters,
We are having a solderability problem confined to only through hole
locations where we need some help or advice.
We are soldering a no-clean SAC305 alloy to an ENIG finished board. All
SMT solder joints (both sides) are fine. During hand soldering in our
dedicated lead free area, we are having problems with solder wetting to
some of the annular rings and barrels of through hole locations, not all
holes. The assembly is an 0.062" thick 4 layer 1"x1" board so it is not
thermally challenging.
We've built thousands of these in the past without this particular
problem.
The time lag between smt and through hole assembly is 1-2 days.
We've tried using a more aggressive flux such as OA flux with no
improvement.
The only way that we can get solder to wet is to mechanically scrape the
annular rings with a pick.
Has anyone seen this before? Why would this only occur on some of the
through hole locations and not on smt pads?
We have isolated this to a specific lot code of boards and are waiting
for some advice from our board vendor as well.
Thanks
Peter
---------------------------------------------------
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
-----------------------------------------------------
---------------------------------
No need to miss a message. Get email on-the-go with Yahoo! Mail for
Mobile. Get started.
---------------------------------------------------
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
-----------------------------------------------------
------------------------------------------------------------------------------------------------
This message is for the designated recipient only and may
contain privileged, proprietary, or otherwise private information.
If you have received it in error, please notify the sender
immediately and delete the original. Any unauthorized use of
this email is prohibited.
------------------------------------------------------------------------------------------------
[mf2]
---------------------------------------------------
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
-----------------------------------------------------
|
