On 3/8/2013 1:52 AM, Michael A. Terrell wrote:

Paul Drahn wrote:

On 3/7/2013 5:51 AM, Michael A. Terrell wrote:

Paul Drahn wrote:

Just read this statement from a Boeing engineer:

"Sinnett, the 787’s chief project engineer, said that in each of the
power-panel incidents electrical arcing inside a circuit board — “a low
energy arc that lasted milliseconds, very small” — had damaged the board
and shut down some of the plane’s electrical power.

He said the small spark inside the circuit boards produced no safety
hazard, only a loss of function that was handled by the plane’s
multiple, redundant power systems.

In January, Boeing had not yet found the root cause, but Sinnett said
the problems had been traced to a batch of faulty circuit boards inside
the power-distribution panels, which are located, like the batteries,
inside an electronics bay.".

Faulty because they use lead-free solder and the Humiseal didn't stop
the growth of the tin whiskers.

Paul



The Aerospace industry is exempt from lead free solder for just this
reason. Medical& Telcom are exempt, as well. That's because the
Belgian bureaucrats knew it is crap and will cause failures.
Yes, that is true. We build several circuit boards for aviation oxygen
systems using leaded solder.

However, both Boeing and EADS decided early on to use lead-free solder
on their circuit boards. I attended a seminar in Beaverton, OR before
the lead-free requirement went into effect. One session was sponsored by
Boeing and a couple of their engineers and board builders told how they
were using lead-free solder on boards for a new version of the 747, and
it was company policy to use lead-free on all future airplane builds.
Eads did the same and this is why they had so much trouble with the
A380, etc.

At the time Boeing's problem wasn't tin whiskers, so much, it was mainly
having the components pop off the circuit boards during the standard
vibration tests.


Lead free solder is pure crap. It grows whiskers, it's brittle and
it's weak.
All true, but still 60%of our business and growing! The worst is the
fumes from the flux needed to hand solder the through-hole components.

Paul