Re: [PROTEL EDA USERS]:More trouble with P99SESP5 and gerber read back

[Abd ul-Rahman Lomax <marjan@vom.com>]

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At 12:40 AM 10/18/00 -0500, Jon Elson wrote:

>Well, a pad master is not really a PC board layer, it is just a drawing.

Drawing isn't the best word, but yes. And, in fact, Protel's "padmaster" is 
not really a padmaster.

>I turn all these unneeded plots off to reduce confusion.

Absolutely a good idea.

However, I have found one use for the top and bottom padmasters: In making 
an assembly drawing, I write gerber for, say, the top overlay and top 
padmaster. Then I bring these gerbers back in to the mechanical layer I am 
using for the assembly drawing. The padmaster includes only component pads, 
whether they be surface mount or through-hole. Thus the pads together with 
the overlay usually make a good picture of the components, much better than 
one will get from the overlay alone.

This film is not what we used to call a padmaster -- which goes back to the 
days of tape and mylar --, because the old padmasters also included vias.

Padmasters were used, sometimes, for bombsighting as well as to generate 
solder masks, but the primary usage for me, as a designer, was in creating 
overlay artwork: I would make a mylar layer with all the component and via 
pads, and then add other layers as needed for top and bottom or inner layer 
traces. Thus the pads on all layers would register perfectly. (the various 
mylar layers were pin-registered). This process was called "Padmaster 
artwork," and, believe it or not, right up until the arrival of CAD, there 
were designers who refused to use the technique, instead doing what they 
had done for years: making separate artworks for each layer; while one 
could use register pins with such separate artworks, at one place I worked 
the designers refused to even use pins when I gave them pins. They would 
align the layers with targets each time they worked with them. After a few 
changes it was impossible to get good register on anything, and I found 
that there were problems in assembly with bad solder masks resulting from 
all this sloppiness.

I did not invent padmaster artwork, but I did start using the technique 
before I learned that others were doing the same. I had been a printer and 
graphic artist, and printers also had a need for good layer register; the 
register pins I bought were made for use in the graphic arts.

marjan@vom.com
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433



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