> >P99SE SP6, PCB Editor
> >
> >With Top Solder Mask and Outline (I name Mechanical 1 "Outline") enabled,
> >as initially displayed, with Outline being the current layer, only actual
> >primitives on the Solder Mask and Outline layers are displayed. The
> >calculated solder mask pads are not displayed.
<snip>
> >Abd ul-Rahman Lomax
>
> I suspect that we have all seen this sort of behavior in various
> conditions, it is irritating.  It is certainly worth bringing it up so it
> can be discussed and Altium may make it an official bug.

This has been a long standing aspect of Protel. My interpretation of what is
happening is that pads on the external copper layers (and the MultiLayer
layer) are "imaged" on the Solder Mask and Paste Mask layers, and as such,
the software released to date does not always properly display what is
really "present" on the Solder Mask and Paste Mask layers. (If the
MultiLayer layer is *not* displayed, even images of pads on that layer are
not always properly displayed on the Solder Mask layers.)

> I think that there is some relationship here with the fact that
multi-layer
> is a layer rather than a collection of other layers (subtle difference)
but
> it has significant ramifications during the various combinations and
> permutations of display configuration.
>
> I think I would like to be able to define named collections of layers that
> can be used during pad stack creation and display manipulation.  With this
> technique, multi-layer as an explicit layer is no longer needed - it
merely
> becomes a layer collection consisting of all copper layers.  Any pros or
> cons for this idea.
>
> Ian Wilson

There are arguments for and against providing the Multilayer layer. One
argument for retaining it, or at least for pad and via objects (if not for
arc, fill, track, and string objects), is that the *same* pad or via exists
on *different* copper layers, and that aspect matches "real world" vias and
"through-hole" pads.

OTOH, given that a hierarchical structure exists in PCB files (e.g.
component, polygon, coordinate and dimension objects), this could be
extended so that pad and via objects themselves have a hierarchical
structure. As such, users could define default settings for each layer,
while also having the ability to customise (i.e. over-ride) the settings for
each individual layer as required (including Solder Mask layers, Paste Mask
layers, and even Power Plane layers).

However, I also consider that efforts to change or enhance pad and via
objects would open a very large can of worms. Amongst the issues to consider
(but certainly not the only issues concerned) are whether properties
associated with the Solder Mask layers, Paste Mask layers, and Power Plane
layers should be set by Design Rules, or by dialog boxes, or by either of
those options. (I have spoken on that matter previously; at present,
listings of Design Rules do not "report" settings which have been customised
by usage of dialog boxes.)

Abd ul-Rahman Lomax has also recently mentioned that "blind" and "buried"
vias are sometimes inappropriately displayed. I concur that this could be
regarded as a bug, but apart from that, I personally don't regard the
MultiLayer layer as being "bad" in nature. It is a "special" layer, like the
Drill Draw, Drill Guide and Keep Out layers, but PCB applications differ
from general purpose CAD applications (such as Autocad) in that there is a
good case for "special" layers to be provided.

I think that pad and via objects could be enhanced. However, we should be
very careful about what we ask for...

Regards,
Geoff Harland.
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