At 09:35 PM 7/31/2002 -0700, Michael Reagan (EDSI) wrote:

>Abdul   wrote

Thanks. China is quite a place.... not what I expected.

> > Suppose the worst designer reading this list knows how to accomplish the
> > task? Should he keep it to himself?
> >
>No that automatically requalifies the  worst designer as the best of the

Let's put it this way. If the worst designer tries to help others, he or 
she will probably develop rapidly. Nothing brings the real experts out of 
the woodwork better than bad advice given publicly. Of course, if this 
designer is not willing to admit errors or to learn better ways, not much 
is going to be learned.

But what this arrogant and ignorant designer says might still be correct 
and useful. Even a stopped clock is right twice a day.

>.>It is generally not necessary  to pour in more than one direction.........
>That we havent tried.   I might have mentioned this is a backplane.... I saw
>it for the first time today,  it has 42,000 pads

I think we now know why the pour is taking a bit long.

> > If one desired pour track to pass between pins with a narrow width, it is
> > not necessary to set the entire pour to that width. Instead. Make a
> > pass-through pattern for a part and copy that pattern over the part with
> > the pour already done. Protel will assign these copied tracks the proper
>That is too risky and cumbersome of a solution if we have to edit the
>design,   but thanks

It seems to not have been understood that any mistakes in placing the 
pass-through track (if you even need it, you might not) will be caught by 
DRC. So it is not at all risky. As to cumbersome, that depends on how it is 

> > First, route the ground (if that's the net being used) with track entirely
>we decided to "BAG" ( our terms means Sh- can )  the merge system becuase
>the we can not control verification on a board that cost 10K a pop .  POP
>means each for you down under.    We will attempt dividing the design into 4
>quadrants and pour separately.

It may have been overlooked that a merge plot as I described it is verified 
by DRC. In fact, I first developed this method in order to check negative 
planes on an old Calma system, which otherwise could be done only by 
painstaking visual inspection. The tie track guarantees connection. And no 
connections are made to the plane except with the tie track. So such a plot 
is more fully verified than is an inner plane in Protel 99SE.

As you know, via blowouts can easily isolate an area and DRC cannot detect 
this. But if a plane is built by using negative blowouts and then adding 
pads and tie traces (i.e., the usual top layer, if this is a top layer 
pour), any islands will be detected by DRC. (Such an island is nothing more 
than an incomplete route).

Typically one creates a pour with greater air gap than the board minimum, 
to improve manufacturability. But a tie track can approach pads at the 
board minimum, so it can pass between pads whose blowouts might touch and 
otherwise create a break in the copper.

It is with multiple, split planes that visual check becomes crucial, since 
the correct isolation of each plane section is not guaranteed. Likewise the 
isolation of non-plane track on the layer being poured is not checked by DRC.

But (1) the isolation is the result of a process that treats the whole 
layer at once, so it is not necessary to check each individual piece of 
track. (2) incorrect isolation will stand out like a sore thumb if the 
layer is appropriately viewed.

I used this technique with Tango many times without problems; however, once 
or twice I modified a complex split plane design without going through the 
full process. In other words, I'd recommend, if you change anything on such 
a merged plane, start from scratch, don't try to re-use the stuff generated 
by the process I described. The tie track, of course, can be kept, and 
plane split track (isolation) can also be kept; one only needs to take care 
that tie tracks do not cross a split, since they would short the split 
sections together. Again, this can be verified with ease visually if one 
has the appropriate display settings.

Note that a tie track can cross into the area of an isolation trace as long 
as it maintains clearance from the *other* side of the isolation area. But 
such tracks make it more difficult to check such a plain because they will 
stand out when seen with the same settings that make violations visible.

Note also that it is not necessary to check (in Protel) the blowouts of the 
pads and vias, since these are correctly created by generating the solder 
mask, and a trace cannot cause a short by crossing these blowouts without 
also creating a DRC (short or clearance) error.

Basically, merged split planes are easier to verify thoroughly than are 
Protel inner planes, and I haven't noticed Protel designers refusing to use 
inner planes because they are not completely DRCd. Both should still be 
looked over in CAMtastic or whatever.

If the board were a through-hole board with only one plane which covers the 
entire board, and no routing track on that layer, there would be no need to 
verify it, since it would be completely verified by DRC. But SMT components 
require fanouts and thus it gets a little more complex.

It would be fairly simple to write a utility that would create the blowout 
track necessary to isolate the fanout or other routing track on the layer 
from the pour. It is almost trivial if there is only one net for the pour, 
because it would only be necessary to create blowout track for all tracks 
which are not part of the poured plane net. This is, as I described, what 
one does using global edits, in the absence of a utility.

* Tracking #: 817743620A24024E898D815FB16D36BB976B33DA

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