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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