Steve:

Assuming that the Gerber files you are viewing are in RS-274 format you may
want to manually enter all of the apertures rather than allowing the
program to guess which type of aperture file you have. If the apertures
used for the QFP are described in such a way that the software cannot
interpret them, it may just ignore them. Although I'm not too familiar with
the Lavenir Viewmate, this does happen on some aperture conversion programs
that we use.

If the Gerber data is RS-274X or RS-274D, with embedded apertures, the
problem may be that the CAD system Gerber output is slightly incompatible
with your Gerber input. Often, these incompatibilities show up in the way
the two systems interpret arcs and circles, as well as hatched or filled
areas.

There are several other shareware Gerber viewers available that you may
want to try to see if the problem can be duplicated. One that I recently
installed for our salespeople is Graphicode's GC-Prevue. It can be found at
http://www.graphicode.com

Good Luck.

John Lennox
Process Engineer
EMC



At 02:23 PM 2/23/99 EST, you wrote:
>Hey Ya'll!
>
>     I'm no designer, I'll state that right up front, so if what I'm about to
>ask seems pretty dumb, or it doesn't seem real clear, please bear with me.
>Here's the problem. We're trying to do a prototype build of 10 boards for a
>customer of ours. I was sent the Gerbers to get a foil made (I do only foils
>for prototypes because 9 times out of 10 the board will roll after the first
>build, saves some bucks that way). Anyhoo, the board has a custom 176-pin,
>20-mil pitch QFP on it. When I get gerbers from a customer, I use Lavenir
>Viewmate to eyeball things before I send them off to the stencil vendor.
>
>     Lavenir has been able to look at everything that's been sent to me so
>far. When I first got the gerber in question, the QFP footprint wasn't there.
>So I informed our customer of the problem, and it was acknowledged that there
>was a problem indeed. The gentleman spent yesterday re-doing things and then
>emailed me the gerbers again in the afternoon. I opened them up this morning
>and the problem still exists...the QFP ain't there. I can see everything else
>but not this QFP?!? Weird huh? I've already left a voicemail and sent a email
>to the designer (he's not in yet), but what could be the problem?
>
>     I think he's using a package called "Tango"...the reason I say that
>(here's where my ignorance about PCB CAD systems come in, I know just enough
>to be extremely dangerous...hehehe), is because when I'm bringing a gerber
>file into Lavenir, I have to do a "Import Apertures" and pick out the
Aperture
>files in the gerbers. Then there's a button in the dialog box that says
"Guess
>Type" you click on it and it will automatically fill in what type it
is...I've
>seen it come up Pads, GAP, Tango, etc....so that's where I came up with
Tango.
>I'm sure our customer will figure it out (hopefully) but so I can learn a
>little something more (so I can become even MORE dangerous...hehehe), can
>anybody shed some light on this?
>
>-Steve Gregory-
>

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