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Oops, I sent this to Dave Rooke, but forgot to send it to the Net.
Howard F
>Date: Tue, 17 Sep 1996 12:59:33 -0400
>To:[log in to unmask] (D. Rooke)
>From:[log in to unmask] (Howard Feldmesser)
>Subject:Re: Design
>
>Dave(s),
> I assumed that the via was actually an active hole and that a lead
>would be coming through it when the assembly was complete. (Note: we do PWB
>fab and assembly here.) The repair with a lead in the hole is not rocket
>science (We do that here, too.(:>)).
> Howard Feldmesser
>
>>I'm curious to know how you would repair the missing conductor of an
>>isotherm spoke connection and not compromise the drilled hole connection?
>>
>>Dave Rooke
>>Circo Craft - Pointe Claire
>>
>>_______ reply separator ________
>>>Dave Hillman posted:
>>>> What is the effect, if any, of
>>>> one of the four "spokes" going from a grounded pad to the clad area
>>>> being broken. I've been under the opinion that one of the four
>>>> "spokes" being disrupted would not cause significant reduction in the
>>>> electrical or thermal properties of the grounded through. Would you
>>>> gentlemen please give your opinion of the effect of one spoke being
>>>> damaged and whether you feel a repair is needed."
>>>>
>>>>
>>>> Dave Hillman
>>>> Rockwell Collins
>>>> [log in to unmask]
>>>Dave,
>>> The effect of one spoke being broken is the loss of 25% of the
>>>copper crossectional area of the path to that via. This would create
>>>additional power loss in the rest of the spokes and would increase the
>>>temperature of the copper and the board at that point. The result is some
>>>loss of the reliability of that particular hole and some (probably very
>>>small) increase in the total voltage drop in that net. Whether or not to
>>>repair the missing spoke is impossible to answer without knowing the end
>>>use (ie, required MTBF of the board) and the built in redundancy (ie, how
>>>many holes can fail before the whole board is a failure). Here, where most
>>>of work goes into far away and unrepairable locations and we do
>>>one-of-a-kind stuff, we'd repair it.
>>> Howard Feldmesser
>>> Johns Hopkins University Applied Physics Laboratory
>>>
>>>
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>>
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