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January 2003

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Fri, 10 Jan 2003 08:30:29 +0800
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"Drawbridging" is a new(ish) term to me, and I reasoned that if
'Tombstoning' means a component standing on end (or tending in that
direction) and 'Billboarding' means components standing on their side,
'Drawbridging', if different from the other two, would nicely describe a
phenomenon I experienced a couple of times. Depends on your design of
drawbridge, however. In my mind, I had a picture of two halves of a bridge
rising from the middle, pivoting at either end.

The phenomenon I experienced was when a couple of chip resistors sustained
damage in a strange way - the end caps and their solder joints were present
on the board, but the main body of the thing had disappeared. My initial
thoughts were impact damage, but then one affected component was right in
the midst of a veritable metropolis of discrete components, while the other
was in a completely different area of the board. I noticed that the solder
volume in the joints for these was somewhat on the high side, and concluded
that while cooling, the contraction had been enough to pull the end caps
away from the component body enough for the body itself to fall out - i.e.
it seemed that both ends had tried to tombstone at the same time, resulting
in a failure in the middle.

If anyone can refute this deduction, I would be only to pleased to hear.

Peter



Werner Engelmaier <[log in to unmask]>    10/01/2003 12:40 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Engelmaier

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: Re: [TN] Help anyone!!!








Hi Steve,
In a message dated 01/08/2003 22:33:54, [log in to unmask] writes:
>First off, are these really "tombstones" or are they "drawbridges"? I
It has been my understanding for some 20 years that "tombstones" and
"drawbridges" are just different words for the same problem--has
soomethinng
changed?

Regards,
Werner Engelmaier

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