TECHNET Archives

April 2007

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Victor G. Hernandez" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 25 Apr 2007 12:27:10 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (92 lines)
Can you share a photo of ypue cross section for viewing?

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: Wednesday, April 25, 2007 12:19 PM
To: [log in to unmask]
Subject: [TN] SV: [TN] Quadpack solder joint failures

Hi Werner,
 
What I'm consternated by is the presence of Nickel where it's not
expected to be. The Quad is soldered on ENIG with 60Sn. Typically, the
solder flows a bit on outside of the board pads. The  joints are strong.
The Quad is drowned with a 15 Tg coating. The coating fills the space
around the leads, but does not fill the space between Quad and board. I
have polished samples of the board from the backside until I can see the
underside of the copper pads. On the photos, I can see the copper with
its nickel all around. On outside of the nickel I can see the solder. So
far it's normal. BUT, on the perimeter of the solder, I can see nickel
again, as well as nickel traces in the solder. Thought at first, that it
was smear, but whatever method we use, the result is the same. Normally,
such a lot of nickel can't be dissolved that short solder time at that
low temperature. The nickel along the perimeter is several micrometers
thick. I have seen poor nickel plating lifted from Kovar and flow around
as flakes in the solder, but never seen nickel leave copper that way.
The product is used all around, and works good, the solder joints being
acceptable, but a few failures have been reported, i.e. one or two or
three leads get solder joint cracks and electrical disrupts. Not many,
but enough to make us suspicious.  Randomly appearing, as it seems. No
red thread. Various places, various operating time, various everything.
My guess was that we have to do with some metallurgical issue, like
'black' pads or any other of the frequently discussed topics in this
forum, but the leads don't lift from the pad, instead the rupture is
typically somewhere between the IMC region and the Quad's lead. 
 
 Before start digging, I would like to get an idea about the strange
behaviour of the nickel. 
 
First pic shows the pads from the underside
Next two pics show nickel in the solder that flowed outside the pad. He
who is wise will see.
 
If someone got an idea, it would be you, Werner (lot's of butter)
 
Inge
 
PS. Sending my three photos to Steve's Center of Wicked Pictures
 
-----Ursprungligt meddelande-----
Från: [log in to unmask] [mailto:[log in to unmask]] 
Skickat: den 24 april 2007 23:38
Till: [log in to unmask]; [log in to unmask]
Ämne: Re: [TN] Quadpack solder joint failures
 
Hi Inge, 
FEA is not the savior when the wrong material properties are input
[Watch for my next column in GSMT&P on this subject].
But you are not giving us much to go on-is there in fact an "airgap
between Quad and board" or is that filled  (even partially) with the
conformal coating given the robotic "drowning." An even lifting
indicates a pretty uniform vertical displacement. Remember, this stuff,
particularly in a confined space, is essentially non-compressible.

Werner



**************************************
See what's free at http://www.aol.com.

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

ATOM RSS1 RSS2