> Hello All,
>
>       We currently have a workmanship spec that was derived partly from
> the NASA spec which requires the use of a filler wire for the support of a
> via on double-sided PWB's. This requirement has caused some double-sided
> boards to needlessly become multilayer boards to avoid using a stitch
> wire. I noticed that the J-STD-001B 9.2.5 makes no distinction between
> double-sided or multilayer when it comes to interfacial connection
> definition.
>       Is there something I am missing or is there a reliability difference
> between a PTH VIA on a double-sided and a PTH VIA on a multilayer that I
> am not aware of? My assumption is that this NASA spec addressed an issue
> that may have been previlent in the earlier years of the PWB industry.
>
>       NASA-STD-8739.3
>       December 1997
>               11.2.4. Interfacial Connections.
>
>                               a. Double-Sided PWB's. Functional PTH's on
> double-sided PWB's require the use of filler wire for support if the PWB
> coupon has not been evaluated by construction analysis. No dedicated
> effort need be expended to remove solder in unused holes.
>
>                               b. Multilayer PWB's. Multilayer PWB PTH's
> used as vias do not require the use of filler wire nor shall they be
> solder filled. No dedicated effort need be expended to remove solder in
> unused holes.
>
>               Your comments are always appreciated.
>               Thanks,
>
Dave Brocious
 <<...OLE_Obj...>>
Space Systems Co.
Advanced Development
Design Specialist
100 Campus Drive
Newtown, Pa. 18940
Phone: 215-497-1732
Fax: 215-497-2719
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