[tinwhiskers] Re: R: Re: New study on coating to mitigate whiskers
- From: "Ron Southworth" <southworthrg@xxxxxxxxxxx>
- To: <tinwhiskers@xxxxxxxxxxxxx>
- Date: Tue, 19 May 2009 01:51:23 +1000
Thanks Judy
Ron Southworth
_____
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Little, Judy W (EHCOE)
Sent: Tuesday, 19 May 2009 1:35 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: R: Re: New study on coating to mitigate whiskers
Denny,
Have you seen the wonderful video lessons in observing whiskers on the NASA Tin
Whisker website? If not, just go to:
http://nepp.nasa.gov/whisker/video/inspection/index.html
Judy Little
Honeywell, Clearwater, Florida
_____
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Fritz, Dennis D.
Sent: Sunday, May 17, 2009 20:16
To: tinwhiskers@xxxxxxxxxxxxx
Subject: RE: [tinwhiskers] R: Re: New study on coating to mitigate whiskers
We will have that capability, in addition to several versions of ring lights,
fiber-optic "goose neck" lights, etc. Seems to me that the "shine' or the
reflection off the whisker is important. I have the JEDEC spec.
Denny
_____
From: tinwhiskers-bounce@xxxxxxxxxxxxx on behalf of Gabriele Sala
Sent: Sat 5/16/2009 5:45 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] R: Re: New study on coating to mitigate whiskers
Hi Denny,
Here (from JEDEC Std. 22-A121A ) you can find some help.
In my experience Optical Stereo from 40X to 150X is good enough, it depends
how deep you want to investigate.
You must be careful when handling boards because whiskers are very fragile
Just my 2 € ‘ cents
Best Regards
Gabriele Sala
CT-91
--------------------
From the free download JEDEC Standards
http://www.jedec.org/download/default.cfm
Look for
JEDEC Standard No. 22-A121A
Test Method for Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes
(Revision of JESD22-A121.01, December 2005)
Last level JULY 2008
Page 3
4.3 Optical stereomicroscope (Optional)
Optical stereomicroscope with adequate lighting capable of 50X to 150X
magnification and capable
of detecting whiskers with a minimum length of 10 microns, per Annex B. If tin
whiskers are
measured with an optical system, then the system must have a stage that is able
to move in three
dimensions and rotate, such that whiskers can be positioned perpendicular to
the viewing direction
for measurement.
4.4 Optical microscope (Optional)
Optical microscope with adequate lighting capable of 100X to 300X magnification
and capable of
measuring whiskers with a minimum length of 10 microns, per Annex B. For tin
whisker
measurements, the optical system must have a stage that is able to move in
three dimensions and
rotate, such that whiskers can be positioned perpendicular to the viewing
direction for
measurement.
4.5 Scanning electron microscope
Scanning electron microscope (SEM) capable of at least 250X magnification. An
SEM fitted with
an X-ray detector is recommended for elemental identification.
From: <mailto:tinwhiskers-bounce@xxxxxxxxxxxxx>
tinwhiskers-bounce@xxxxxxxxxxxxx [ <mailto:tinwhiskers-bounce@xxxxxxxxxxxxx?>
mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Fritz, Dennis D.
Sent: Friday, May 15, 2009 11:41 AM
To: <mailto:tinwhiskers@xxxxxxxxxxxxx> tinwhiskers@xxxxxxxxxxxxx;
<mailto:tinwhiskers@xxxxxxxxxxxxx> tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: New study on coating to mitigate whiskers
What is your whiskers inspection methodology?
I am getting ready to do a study with Purdue undergraduate interns (who work
for a VERY attractive price for our program). We will determine both the
extent of whiskers growth on commercial boards - scrap cell phones and laptops,
and the ease of measurement by "semi-skilled" operators. We will be using
optical microscope, enhanced digital microscope, and simple SEM.
Can you share your proceedures?
Denny Fritz
SAIC - Merrillville, IN
_____
From: <mailto:tinwhiskers-bounce@xxxxxxxxxxxxx>
tinwhiskers-bounce@xxxxxxxxxxxxx on behal f of Jim Bunn
Sent: Fri 5/15/2009 10:55 AM
To: <mailto:tinwhiskers@xxxxxxxxxxxxx> tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: New study on coating to mitigate whiskers
I think they are saying it works if the thickness is at least 2mils. Or maybe
that the coating is better than nothing.
We have a lot of uncoated stuff out there running a test right now. And it's
pretty comprensive considering the voltage levels that we are using in the
PCUs. I'm suprised that we have not had some kind of problem.
________________________________
From: <mailto:tinwhiskers-bounce@xxxxxxxxxxxxx>
tinwhiskers-bounce@xxxxxxxxxxxxx on behalf of Pedro Tort
Sent: Thu 5/14/2009 7:48 AM
To: <mailto:tinwhiskers@xxxxxxxxxxxxx> tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] New study on coating to mitigate whiskers
The National Physics Laboratory in UK has undertaken a study on the capability
of different coatings to mitigate tin whiskers growth. The results of this
investigation reinforces the findings of Jay Bruse and Dr. Henning Leidecker
who back in 2007 found the Uralane 5750 Polyurethane was an effective
mitigation strategy for tin whiskers provided the nominal coating thickness was
2mils.
I quote from the first issue of the NPL Electronics Interconnection Newsletter:
"The use=2 0of conformal coatings is seen as the only practical means of
controlling whisker growths shorting adjacent conductors on a PCB. NPL has
studied three types of coating, to assess their effectiveness for inhibiting
whisker growth.
Two coatings, polyurethane and paraxylene both were found to reduce the growth
of whiskers for up to 150 days of testing, compared with failure of 14 days for
uncoated samples. The acrylic coating was found not to perform as well as the
others in parallel tests. All coatings failed to provide sufficient protection
in areas of insufficient coating coverage, at corners and sides of the test
samples."
Pedro Tort
Quality Manager
DigiProces, S.A.
Solsones, 87 - P.I. Pla de la Bruguera
P.O. Box 127
E-08211 CASTELLAR DEL VALLES
TEL. +34 937 142 132
FAX. +34 937 142 072
<http://www.digiproces.com/> www.digiproces.com
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