Hi TechNet! - First, thanks for the replies to the spoke question that 
     was posted (see wayyy below). The replies were detailed and covered a 
     wide variety of both pro's and con's in relation to the problem 
     (aren't electronics wonderful!). Second, a couple of people asked how 
     a repair would be made. See below! And yes the repair can be a risky 
     endeavor (that's why the question was originally asked!).
     
     The Repair: It depends on the circumstance.  Common ways are: 1) 
     Jumper the grounded through to the nearest similar grounded through 
     (Internal connections must be considered) 2) Wrap a wire to the lead 
     occupying the grounded through and lap solder the wire to the adjacent 
     clad with an 1/8-1/4 inch overlap of wire to clad  3) Remove a similar 
     grounded pad from a scrap board with a 1/8-1/4 inch clad section 
     attached and solder the pad over the existing pad. The length of 
     attached clad is lap soldered to the adjacent clad area. 
     
     
     I haven't looked in IPC R 700 but I'll bet these repairs are listed 
     there.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: Re: Design
Author:  [log in to unmask] at ccmgw1
Date:    9/16/96 10:13 PM


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 
>
>
>*************************************************************************** 
>* TechNet mail list is provided as a service by IPC using SmartList v3.05 * 
>*************************************************************************** 
>* To unsubscribe from this list at any time, send a message to:           * 
>* [log in to unmask] with <subject: unsubscribe> and no text.        * 
>*************************************************************************** 
>
>
>
     
*************************************************************************** 
* TechNet mail list is provided as a service by IPC using SmartList v3.05 * 
*************************************************************************** 
* To unsubscribe from this list at any time, send a message to:           * 
* [log in to unmask] with <subject: unsubscribe> and no text.        * 
***************************************************************************
     

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************