Dale,
You say "We have about a 25% pass rate without reflowing the
QFP.", so why in the world would you think it might possibly be the
solder joint to the boards?
Must be an internal part problem. No amount of reflow is going to be
enough to metalurgically bond gold bond wires. Have you x-rayed the
things out of the box and after reflow? What type of solder is inside?
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dale Ritzen
Sent: Tuesday, July 22, 2008 8:44 AM
To: [log in to unmask]
Subject: [TN] They solder well... But they don't work!
Importance: High
Here's a good one for the collective "mind-meld"...
We have a two-sided, non-RoHS compliant, all-SMT assembly (no PTH parts)
that is reflowed under a leaded profile (cooler reflow temperatures than
Pb-free). There is one 44-pin QFP on the topside of the board that
consistently solders well (i.e. passes all IPC-A-610 Class 2 inspection
criteria), but fails test until it is reflowed with a hand iron, a
little
flux and wire solder. We have about a 25% pass rate without reflowing
the
QFP. That jumps to around 95% once the QFP is reflowed. Several
different
date codes of the device have been tried with similar results.
Thinking the ENIG pads under the device leads might be contaminated, we
cleaned them on several test case 4-up panels, with no change in yield.
Thinking it might be contaminated leads on the devices, our process guys
gently scraped off the tinned coating on the leads of several devices
and
took it down to the Beryllium Copper finish. Same resultant yield.
We've re-run the failing assemblies through a higher reflow temperature
with
extra "tacky flux" on them, trying to get a better reflow and use the
action
of the flux to purge any contamination that might be interfering in the
solder junction. When done, the solder junctions on the device look like
a
"Target - Class 1,2,3" picture from IPC-A-610, but the yield is still
around
25% unless we reflow the junctions with an iron, some flux and wire
solder.
There may be some things we're overlooking, but it's coming down to
where we
believe the wire bonds to the lead frame material could be the source of
the
problem. The intense, direct heat of the soldering iron might be enough
to
generate a reflow of the wire bond, resolving any bonding issues. But,
on
several different date codes? I will be getting the vendor involved
shortly
to test the devices and see if they come up with something. I'm fairly
skeptical about doing this as typically the normal answer I get is "all
is
working as designed".
We are all scratching our heads on this one... Any "words from the wise"
would be appreciated!
Thanks!
Dale Ritzen, CQA
Quality Manager/ISO Management Representative
Austin Manufacturing Services
Email: [log in to unmask]
---------------------------------------------------
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 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
-----------------------------------------------------
|
