Hi George! You are 50% correct - the JSTD-002/003 committee completed
extensive investigation into the flux chemistry for testing and the
Standard Test Flux #1 in the specification does improve the gauge R&R for
the test methods. Additionally, some of the newer pwb and component
surface finishes, when tested with the basic rosin flux, resulted in false
negative test results due to finish metallurgy and oxidation reactions.
The committee did not revision the flux chemistry to make component
fabricators "happy" - a large number of component vendors and assembly
engineers participated in the investigation with the goal of improving
the specifications.
Dave
"Wenger, George M." <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
08/11/2009 08:49 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Wenger, George M." <[log in to unmask]>
To
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cc
Subject
Re: [TN] PCB wetting issue saga, final question
"I can get
My comments are DITTO to those of Richard & Vladimir,
"I can get good solder coverage on a toothpick"
"Nothing tests soldering better than soldering"
There is nothing basically wrong with IPC-JTD-002 and 003. They are good
solderability tests but one needs to understand that they don't tell you
everything you need to know about solderability. If you run 002 or 003
and the parts fail the established criteria you can best believe you have
a severe solderability issue. If you pass 002 and 003 that does not
guarantee that those parts won't have a solderability issue when soldered
using your actual soldering process. What I really like about 002 and 003
is that they are established industrial tests with defined conditions so
they are great when used to do "A" to "B" comparisons. I like Greg Munie
am a person who liked the older versions where non-activated water white
rosin flux was used to do solderability testing. If you pass
solderability testing with a non-activated flux you have a much better
assurance that you probably will have good solderability when used in the
actual assembly process than if you had tested with an activated flux. It
is my (maybe not everyone's) understanding that the switch was made from a
non-activated water white rosin flux to a flux with a known activation for
two reasons; one being you get better gage R&R results with activated flux
and the other being less components will fail a solderability test and
that makes component vendors happy.
Regards,
George
George M. Wenger
Andrew Solutions
Senior Principal FMA/Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 (Office) (732) 309-8964 (cell)
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, August 11, 2009 9:26 AM
To: [log in to unmask]
Subject: Re: [TN] PCB wetting issue saga, final question
I could not agree more with what Vladimir stated. Wetting balance tests
and even dip-and-look solderability tests do not compare with the actual
"test" of assembly and soldering of the board and components. If there are
issues, one needs to put a TC on the PWB and find out exactly what the
profile is, and if it appears to be adequate but there are still issues
with wetting then those need to be determined using other means such as
micro-sectioning, etc. Just because component leads and/or board pads
solder up by themselves does not mean they can be eliminated. As a
well-known reliability expert who occasionally contributes to this forum
once said, "I can get good solder coverage on a toothpick."
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Tuesday, August 11, 2009 8:11 AM
To: [log in to unmask]
Subject: Re: [TN] PCB wetting issue saga, final question
Hi Ioan,
Unfortunately, any of the solderabilty tests (even the wetting balance
one) very often are far away from the real life (real re-flow profiles)
and the level of "comfort" they can give one can be very deceptive.
I always say that in order to solve a problem, one would have to get down
to its root cause.
It case of "solderabilty issues" the real root cause may have absolutely
nothing to do with solderabilty of either component or the board. You can
take a look at the case history on our website.
Regards,
Vladimir
SENTEC
------Original Message------
From: Ioan Tempea
Sender: TechNet
To: [log in to unmask]
ReplyTo: TechNet E-Mail Forum
ReplyTo: Ioan Tempea
Sent: Aug 11, 2009 08:51
Subject: [TN] PCB wetting issue saga, final question
Hello Technos,
I have been asking questions on Technet about some wetting issues we see
on a particular board and got many useful answers. In the end we've had
the boards tested for solderability by respectable labs and the bare
boards passed J-STD-003 testing with flying colors.
To back track a little bit, the original doubt came from the fact that in
reflow, the solder does wet very well on both the board and the component
in the component pin area, but would stop spreading pretty far from the
land's end. It just stops spreading, even though the wetting angles at the
stop points are very low, so denoting excellent wetting.
And here comes the question: why is testing per J-STD-003 done at 235 C
and with a rather aggressive flux, when the reflow soldering takes place
at 205 C (HASL finish) using a milder flux (I am using WS, but it could
very well be no-clean...)?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
30 ans déjà! - Already 30 years!
950 rue Bergar, Laval, Québec, H7L 5A1
t : 450-967-7100 ext : 244
Mtl : 514-990-5762
f : 450-967-7444
[log in to unmask] <mailto:[log in to unmask]>
www.digico.cc <http://www.digico.cc/>
P N'imprimer que si nécessaire - Print only if you must
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