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December 2015

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Subject:
From:
Ricardo Moncaglieri <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Ricardo Moncaglieri <[log in to unmask]>
Date:
Thu, 3 Dec 2015 09:53:39 -0300
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This event makes much to reflect. Procedures not right well accomplished
from pilots taking desicions out of procedures. Too many ground
maintenances after so many events/alerts , did they really repair
ckacked solders.......? Did they investigate for root cause....? photo
shows an oxidation process or something so apparently since long time
ago.... I wonder if this solder junction is not lacking of enough solder
(quantity), solder meniscus seems (as per photo) to be minor than
acceptable....  
....I´ve been (these last hours) making myself the same questions as
Garcia Rigo´s..... 

>>> Mike Fenner <[log in to unmask]> 03/12/2015 06:40 >>>
I only have a very broad over view of the situation with Pb free and
Airbus
but I believe it was their intention about 6? years -possibly a couple
more
- ago to go Pb free. Whether that was for new designs only or was
retrospective (re-engineer all prior Pb containing) I don't know.
In any case whether Pb+ or Pb- it doesn't change the number of times
they
seemingly "repaired" the cracked joints. If ground people really did
repair
unit every couple of weeks or so instead of pulling it for
investigation for
root cause (and presumably looking for the same fault in other units
etc,)
then it's entirely possible that the worst case scenario applied: the
maintenance/service people simply touched up/reflowed the joint and put
unit
back in service. Its hard to see how they could do that so many times
though
without causing more damage. Anyway they wouldn't would they? Aren't
there
rules for this sort of thing?
Whatever the ground people did ignoring it and simply sticking it to
the air
people/pilots seems rather inadequate and a trifle scary.

-- 
Regards 

Mike 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Thursday, December 03, 2015 2:11 AM
To: [log in to unmask]
Subject: Re: [TN] Airbus crash pinned (in part) on solder joint
failures

As I mentioned before, cd containing solder would be better for high
fatigue requirement.  I am not aware of any lead free can be a drop in
fit
to replace it.  Except the wishful thinking of politically corrected
type.
Hopefully, the design was late enough, with full qual, not change
material in the mid of design phase..
> Hi Dave - yes, I would agree with you in terms of the PTH technology
use
> due to a high vib/shock product environment. I was thinking more in
terms
> of component evolution/introduction timeline rather than a product
use
> environment.
>
> Dave
>
> On Wed, Dec 2, 2015 at 1:59 PM, Dave Schaefer
<[log in to unmask]>
> wrote:
>
>> "based on the time history listed in the report, the appearance
>> of the solder joint and the technologies on the board (plated thru
>> hole), I
>> would surmise that the solder alloy is tin/lead and not lead-free.
>> However,
>> there is no technical information listed in the report to confirm
that
>> assumption."
>>
>> It is conceivable that this assembly was deliberately designed
using
>> thru
>> components due to the high shock / vibe operating environment.
>> Although what appears to be a lack of secondary mechanical means of
>> support on larger components raises some doubt to that thought.
>>
>> The cracked joint/lifted land appears to be bottom side ... could be
the
>> result of an improperly inserted component subjected to vibration?
>>
>
>
>
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