No problem measuring the resistance real time, it is the same as
Interconnect Stress Testing, but I would never even attempt it on a
"real" product, not practical at all. Are you saying that IST type
measurments are not a valid?
As you say, real products can be very difficult; about all I have ever
managed on a "real" product is an internet switch running a broadcast
storm under thermal cycling and vibration. That will definitely tell you
you have a problem, but then of course you have to go find it.....
John Burke
Senior Manager - Operations , Optichron
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W: 510 249 5233
M: 408 515 4992
http://www.optichron.com
Profile: https://www.linkedin.com/e/fps/2665502/
-----Original Message-----
From: Vladimir Igoshev [mailto:[log in to unmask]]
Sent: Wednesday, February 22, 2006 7:36 AM
To: (Leadfree Electronics Assembly Forum); John Burke
Subject: RE: [LF] Accelerated testing
Hi John,
I wouldn't be that optimistic about the possibility of measuring "the
resistance real time and look for degradation trends". The technique
doesn't "feel" a crack unless it occupies at least 90% of a joint
(so-called "crown" effect").
As far as testing an actual product is concerned, then it's difficult
sometimes to figure out whether it does fail or not and which component
to suspect. The product functionality can go "on and off",
unfortunately. :-)
Regards,
Vladimir
Vladimir Igoshev, Ph. D.
Senior Materials Researcher
Research in Motion
451 Phillip St.
Waterloo, ON, N2L 3X2
Voice: (+1) 519-888-7465, ext. 5283
Fax: (+1) 519-886-0863
E-mail: [log in to unmask]
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of John Burke
Sent: Tuesday, February 21, 2006 4:16 PM
To: [log in to unmask]
Subject: Re: [LF] Accelerated testing
Genny the difference here is that a test vehicle has many interconnect
paths being monitored; if one fails you can push right on to see when
more fail.
Additionally with the correct design it is very easy and fast to find
the failure area.
Also with resistive interconnect paths it is possible to measure the
resistance real time and look for degradation trends (same as
Interconnect stress testing).
With an actual product you are absolutely right, when it fails it fails.
You will have a little trouble finding where it failed, but will have no
idea how early the issue started to develop which would give you the
option of monitoring the event more closely. To continue the test you
will have to repair the defect and carry on testing.
In my opinion, the only real use of using an actual product as a test
vehicle is where the previously built product in a leaded version has
undergone extensive testing - generally destructive such as HALT, and
the HASS screen developed from that testing has been applied to a
statistically significant number of units.
If you apply that same test to a lead free identical assembly it will
tell you whether the unit is going to be more or less reliable given
enough samples, but that is about it. It will not tell you whether tin
whiskers will kill the product etc.
I would go with a test vehicle every time.
And a note to the whole forum - no one is producing electronics as an
end product. The end products here are bottom line corporate dollars.
Let's make sure we protect the end product.
Kind regards,
John
John Burke
Senior Manager - Operations , Optichron
[log in to unmask]
W: 510 249 5233
M: 408 515 4992
http://www.optichron.com
Profile: https://www.linkedin.com/e/fps/2665502/
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Tuesday, February 21, 2006 12:36 PM
To: [log in to unmask]
Subject: Re: [LF] Accelerated testing
I guess I don't understand #3. once it fails, isn't it failed...?
I should be able to see a failure if my product no longer operates the
way it should, if I am using real devices...?
I've been asking if I could go to the workshop, but,...I don't know.
They (the people holding the money) don't seem to want to let me leave
cold SK, Canada for someplace I might actually enjoy being in March...
I am reviewing SM-785 right now, and may have further questions in a
little while.
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: 20-Feb-06 9:14 PM
--snip--
Second, MIL-HDBK-217 is utterly useless as far as solder joint
reliability is concerned.
Third, ATC [accelerated temperature cycling] of actual product is rather
time consuming because you may not know when failures have
occurred-remember, solder joint failures show up as very short-duration
intermittents.
...
By the way, you may want to attend my LF-Soldering Reliability Issues
workshop at the IPC/JEDEC conference in Santa Clara on March 7, and
perhaps the first
3 SJ Reliability Series parts on March 6 as well.
Werner
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