If it is " conformally coated so thick" as you mention, without air gaps,
tin whiskers can still form. DfR solutions has a few white papers on this
subject.
Clayton Bonn
Reliability Resources
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Dennis Fritz
Sent: Friday, October 14, 2011 2:27 PM
To: [log in to unmask]
Subject: Re: [LF] Has Toyoda transitioned to lead free manufacturing?
Oh, where do I begin?
This is a very good paper from CALCE, some of which was presented publicly
at the CALCE Whiskers Seminar in September. Also, this work was interactive
with the NASA Goddard investigation of the Toyota problem at the request of
the National Highway Transportation Administration. Remember, NHSTA put out
a report that buried the NASA Tin Whisker evidence on something like page
117 of a 160 page report. Of course the news media only read the summary of
the NHTSA report and headlined - "Toyota Exhonorated in Sudden Accleration
Report".
My understanding of the issues, from seminars, papers, and discussion last
week on the Wednesday Whiskers Telecon - from Jay Brusse and Henning
Liedecker of NASA is as follows:
1. From 2003-2006, Toyota used circuitry on the accelerator pedal position
sensor that was tin finished. I am not at all sure this is "going
lead-free", as Toyota may have not even used this configuration
intentionally.
2. That circuitry has been shown by both NASA and CALCE to be growing tin
whiskers - long ones.
3. A pedal position sensor that had failed in the "limp home" mode was sent
to NASA by the car owner - I think fromTexas.
4. NASA has shown that the tin whiskers found could have caused the
circuitry/performance issues the car owner described.
5. CALCE has estimated that the tin whiskers found on the Toyata pedal
assembly could cause 140 of every 1.000,000 Toyota Camrys to fail in this
same mode in some lifetime. Remember, this specific assembly is now about 8
years old, and it is unknown how many Camrys are still running - and might
fail. But, this is NOT the sudden acceleration failure mode that NHTSA was
so worried about.
6. The Toyota accelration pedal assembly sensor was changed in 2006 to a
different design - I don't know why, but doubt it was because Toyota had
themselves found tin whiskers on this specific part. I do know there is a
different (now US based supplier) of the pedal sensor assembly than in 2003
(Japanese based supplier).
7. We here at SAIC, Merrillville, IN took apart a 2009 ENGINE CONTROL MODULE
from a Camry, looking for tin whiskers. It was A) eutectic solder and B)
conformally coated so thick that I don't see how tin whiskers could grow
through it. I surmise that Toyota has not in North America - "gone
lead-free". I suspect that they are being much more careful in 2011 with
tin finish or Pb-free solder than they were back in 2003. However, they
could still be getting tin plated components, or using Pb-free solder with
mitigation for tin whiskers.
Stay tuned, I suspect the Toyota issue is not resting yet.
Denny Fritz
SAIC - Merrillville, IN
-----Original Message-----
From: Patten, Chuck <[log in to unmask]>
To: Leadfree <[log in to unmask]>
Sent: Fri, Oct 14, 2011 2:39 pm
Subject: Re: [LF] Has Toyoda transitioned to lead free manufacturing?
Remember this thread and our caution about assigning tin whiskers as a
iable culprit? Looks like Toyota still has a real lead-free problem...
http://www.calce.umd.edu/articles/abstracts/2011/Tin_whisker_Toyota_thro
tle_abstract.html
cheers,
huck...
-----Original Message-----
rom: Leadfree [mailto:[log in to unmask]] On Behalf Of Bob Landman
ent: Wednesday, March 03, 2010 9:06 AM
o: [log in to unmask]
ubject: [LF] Has Toyoda transitioned to lead free manufacturing?
The question has been asked - is there evidence that Toyota has gone
ead-free? I found this discussion on SMTNET that discusses the topic
we aren't the only ones debating this subject)
http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Th
ead_ID=14597&#Message61142
Toyota developed their own lead free alloy
ttp://sciencelinks.jp/j-east/article/200016/000020001600A0589899.php
Quote" Several engineers are readying the Toyota recall press daily to
ee whether Toyota - an early adapter of lead-free solder - is the first
asualty." unquote
ttp://retroworks.blogspot.com/2010/02/leadfree-solder-rohs-rumors.html
Quote "January 2001, we inaugurated our own company-wide lead free
roject, starting activities and efforts to eliminate lead thoroughly"
nquote
ttp://www.toyota-industries.com/csr/environment/product/erectoronic_02.
tml
Transforming Compliance into a Competitive Strategy
ttp://www.internetviz-newsletters.com/cincom/e_article000667816.cfm?x=,
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=61176)
Here's the details on their solder:
"A highly reliable Sn-Ag-Bi-In-Cu lead-free solder alloy was developed
y improving the melting property, the wettability and the mechanical
roperty of the Sn-Ag solder alloy which has a high thermal fatigue
esistance due to the addition of bismuth, indium and copper. The
ptimum alloy composition for the Sn matrix is 2.5-3.0mass%Ag,
.0mass%Bi, 1.0mass%In and 0.2-0.5mass%Cu. The additional elemental
ismuth contributed to the control of the solidus and liquidus
emperatures and the improvement of the wettability and tensile
trength. Indium contributed to the control of the solidus and liquidus
emperatures and the improvement of wettability. Copper contributed to
he improvement of the ductility which is degraded by the addition of
ismuth. In comparison with the Sn-3.5Ag eutectic solder, this new
ead-free solder alloy has a 19.DEG.C. lower solidus temperature,
-7.DEG.C. lower liquidus temperature, 4% higher spreading factor and
00% higher tensile strength. Its elongation is equal to and above
n-3.5Ag at 125.DEG.C. though it is half as long as that of Sn-3.5Ag at
5.DEG.C.. It was confirmed that this new lead-free solder joint has a
igh thermal fatigue resistance and the same electrochemical reliability
n comparison with the conventional Sn-37Pb solder joint. (author
bst.)"
I found the following report on their corporate website which is not
lear about the percentage of products which are lead free. Of course,
he components we all buy, are mostly lead-free tin plated.
ttp://www.toyota-industries.com/csr/library/pdf2003/P18-25.pdf
"Under the European Union's end-of-life vehicle (ELV) directive*, the
se of lead, mercury, cadmium and hexavalent
hromium will be banned from all vehicles sold in Europe starting from
uly 2003. In response to the ELV directive, Toyota
ndustries' Product Technology Subcommittee has established objectives
imed at reducing the company's reliance on
ubstances of concern in all of its business activities including its
on-vehicle related businesses.
uring FY 2002, Toyota Industries made changes to the design of parts
hat previously contained lead, cadmium or
exavalent chromium and switched to using alternative chemical
ubstances. Toyota Industries also asked its suppliers to
ubmit data regarding the inclusion and quantity of banned substances in
aterials and parts supplied to the company,
nd also requested that its suppliers submit plans for eventually
hasing out the use of banned substances. In addition,
oyota Industries revised its in-house guidelines for substances of
oncern to reflect the policy of banning certain
esignated chemical substances."
"Lead-Free Circuit Boards
Lead contained in solder used in circuit boards has been
oted for polluting the environment when it is not properly
isposed of. Consequently, Toyota Industries is trying to
witch to lead-free solder in its circuit boards for its industrial
achinery, automobiles and textile machinery products.
hen designing circuit boards with lead-free solder,
oyota Industries had to overcome various issues such as the
igh melting point of lead-free solder, which made it difficult
o control soldering temperatures while ensuring that parts
ould stand the heat. However, Toyota Industries was
uccessful in overcoming these issues and in January 2003
egan producing lead-free circuit boards for use in the
isplays for one of its electric reach truck models."
egards,
Bob Landman
&L Instruments, LLC
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