[tinwhiskers] Re: Toyota report
- From: "Bob Landman" <rlandman@xxxxxxxxxxxxxxxxx>
- To: <tinwhiskers@xxxxxxxxxxxxx>
- Date: Tue, 15 Feb 2011 16:47:53 -0500
Rod,
From page 118
6.6.2.3 Evaluation of Consumer VOQ #10304368
In general, the NESC assessment focused on failures that would not generate a
DTC. However,
while reviewing the VOQ data, the NASA and NHTSA teams encountered a VOQ (NHTSA
VOQ #10304368) related to a defective potentiometer accelerator pedal, where
the consumer
stated that she still possessed the defective assembly. After contacting the
consumer, NHTSA
was able to obtain the defective pedal for analysis. The NESC team was able to
inspect, analyze,
simulate and test the defective potentiometer (resistive) accelerator. The
investigation revealed a
resistive short between the sensor outputs (between VPA1 and VPA2) and an
unexpected (not as
described by the manufacturer) ETCS-i response under some system conditions.
Further
investigation of the accelerator pedal revealed the cause of the pedal
resistive short as a tin
whisker. This section describes the team's activities associated with this
particular defective
accelerator pedal.
......
From page 127
While inspection of several accelerator pedal assemblies (5 Potentiometer type;
1 CTS and 1
Denso Hall Effect types) for presence or likelihood of tin whiskers was quite
extensive, physical
inspection on other components of the ETC was limited. The pedal signal/power
circuit paths in
the ECM are in an area of most interest since resistive shorts in this
component would have the
same effect as in the pedals. There are numerous versions (up to 4 different
circuit card versions
per year) of the Camry ECMs over the 8-year time period. Examination of one MY
2007 ECM
concentrated on inspecting the printed circuit board, its components and its
housing, for evidence
or precursors that could produce electrical resistive shorts or open circuits.
The examination revealed that the solder used on the printed circuit board was
a "lead free" tin
alloy called Sn-Ag-Cu ("SAC"), which is less prone to formation of tin whiskers
than pure tin
solder. There were no traces of pure tin coating on connector pins and no
solder cracks or cold
solders. The examination found that the printed circuit board is not conformal
coated and part of
the enclosure of the ECM is made out of an aluminum-zinc alloy which can
develop whiskers.
However, the inspection of this ECM revealed no tin or zinc metallic whisker
growth, nor
precursors that sometimes predict the later growth of metal whiskers.
===============
There's more but you get the idea....
A single sample the customer still had and it had whiskers. How many Toyotas
are on the road?
How many other auto brands? How many are constructed lead-free?
Seems to me to be very likely there are more whiskers out there, doesn't it?
Bob Landman
H&L Instruments, LLC
www.hlinstruments.com
LDF Coatings, LLC
www.ldfcoatings.com
-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Rod
Sent: Tuesday, February 15, 2011 5:16 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Toyota report
www.emtworldwide.com/article.aspx?ArticleID=39816
regards, Rod
rod.dalitz@xxxxxxxxxxxxxxxx
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