Michael,
Look at your raw components, perform a simple 'dip
and look' test using a type R flux and a tinning pot or static solder bath.
If you don't see good wetting, look at the lead finish process. Plated
finish, if inadequate thickness or improperly applied, can allow for
oxidation of the underlying base metals that isn't easily visible to the
naked eye. This test method is documented in EIA/JESD22-B102-C available
from JEDEC at http://www.jedec.org/download/search/22b102c.pdf
<http://www.jedec.org/download/search/22b102c.pdf> , and also in
MIL-STD-883, available at
http://www.dscc.dla.mil/Programs/MilSpec/ListDocs.asp?BasicDoc=MIL-STD-883
<http://www.dscc.dla.mil/Programs/MilSpec/ListDocs.asp?BasicDoc=MIL-STD-883>
.
If you want to perform a test that simulates actual
SMT processing conditions, you can use the Surface Mount Solderability Test,
documented by Texas Instruments at
http://www.ti.com/sc/docs/products/logic/package/palladm/smt2col.htm
<http://www.ti.com/sc/docs/products/logic/package/palladm/smt2col.htm> .
Also verify the leadframe material/finish type,
Alloy 42 and palladium finishes are notorious for difficulty in soldering.
Higher reflow temperatures may be required than what the part is currently
seeing, solder a thermocouple to the board at the joint using high-temp
solder and profile the part to see what temp you are reaching. Texas
Instruments also has information on their website regarding processing of
palladium lead finishes.
I had a similar experience with a 16 pin j-leaded
inductor package a while back that exhibited the same type of 'foot in the
mud' joint. Looked good from the outside, but popped right out under any
load. When we asked the vendor, they readily knew the leadframe material &
plating were non-standard and required a high time/temp to properly wet. The
vendor also had the same part available in an Sn/Pb dipped version that they
fluxed, solder dipped & cleaned at a high enough temperature to properly wet
to the leadframe material. Once we switched to this pre-tinned part, no more
problems. Your vendor may offer something similar, or you can have them
processed by a third party. Good luck....
Mike McMonagle
Senior SMT Engineer
Telxon Corporation
www.telxon.com <http://www.telxon.com>
-----Original Message-----
From: Wenger, George M (George)
[mailto:[log in to unmask]]
Sent: Friday, October 27, 2000 9:57 AM
To: [log in to unmask]
Subject: Re: [TN] Re] Contamination
of leads
I have a question for Ron and three comments
for Michael.
Ron,
If your situation wasn't a contamination
issue what kind of an issue was it?
Michael,
1. It's almost impossible to mesure
contamination on leads that when through
an assembly process because you can't tell
if what you find was there to
start with or a result of the assembly
material. You'll need to analyze
component leads before assembly.
2. Our experience indicates surface
contamination seldom is the cause for
our solderability/soldering problems.
3. The "imprint" appearance you discribe
shoulds a lot like what we call
"Foot-in-the-Mud" which we believe to be a
combination of lead
solderability, solder paste activity,
stencil print height, lead
coplanarity.
Regards,
George
George M. Wenger, DMTS Bell Laboratories
Princeton
Supply Network Solutions
PO Box 900, Princeton NJ 08542-0900
Route 569 Carter Rd., Hopewell, NJ 08525
(609)-639-2769 (Office), 3210 (Lab), 2343
(Fax)
[log in to unmask]
-----Original Message-----
From: Hollandsworth, Ron
[mailto:[log in to unmask]]
Sent: Friday, October 27, 2000 7:34 AM
To: [log in to unmask]
Subject: [TN] Re] Contamination of leads
Michael:
I had a similar situation on an Avionics
project within the last year. The
customer's first thought was a contamination
issue. We decided to bring in
a third party with the expertise to tell us
what direction we needed to take
on the issue. I contacted Contamination
Studies Labs (CSL) in Kokomo,
Indiana. Terry Munson visited our facility
within just a couple days to
review our process and also make
arrangements to have some tests performed
of which CSL would analyze. To make a long
story short, CSL provided the
detail analysis that gave
objective/empirical evidence that there was no
contamination. In addition the response was
very fast which the customer
liked. The point I am trying to make is
CSL/Terry provided the information
needed, regardless of who was right or wrong
in the ongoing debate, so we
could react properly to our customer. In
this particular case there was no
contamination issue and the customer was
satisfied that we were able to
produce the evidence to prove that which
then gave them the warm fuzzy
feeling they were looking for.
You can reach CSL pretty fast by e:mailing
[log in to unmask]
<mailto:[log in to unmask]> and brief Terry
Munson on the issue.
Ron Hollandsworth
ITT A/CD
************************************
If this email is not intended for you, or
you are not responsible for the
delivery of this message to the addressee,
please note that this message may
contain ITT Privileged/Proprietary
Information. In such a case, you may not
copy or deliver this message to anyone. You
should destroy this message and
kindly notify the sender by reply email.
Information contained in this
message that does not relate to the business
of ITT is neither endorsed by
nor attributable to ITT.
************************************
----------------------------------------------------------------------------
-----
Technet 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
Technet
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
----------------------------------------------------------------------------
-----
----------------------------------------------------------------------------
-----
Technet 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
Technet
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
----------------------------------------------------------------------------
-----
---------------------------------------------------------------------------------
Technet 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 Technet
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
---------------------------------------------------------------------------------
|
