Dennis Saputelli wrote:

> they said with a big plane it is harder to etch
>
> there must be at least a bit of truth to that because i have had this
> trouble with this type of board from 3 different shops - albeit not the
> highest tech shops kicking around
>
> the board was pretty long, about 15 inches, that may or may not be a
> factor

Boards with large density variations can cause a problem.  A single
gap in a large plane of copper is usally etched first, and large areas
of non-copper will locally deplete the etchant, preventing full etching
in that area.

Conversely, for plating, where most of the trace definition is done in the SMOBC
process, the large areas of copper may deplete the copper bath, and leave the
plating thinner there.

Anyway, modern process gear is a lot more tolerant of this sort of
variation, as the boards we design drive the industry to develop equipment
that can handle it without stressing the process to where it becomes
unreliable.

Jon

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