oops.... you're RIGHT!
I used the wrong word. I should have said "vector" plotter, not "laser".
(as a friend gently corrected me privately, laser plotters rasterize)
and...
I partially disagree with one of the responses who said it is
out of our control, Ioan.
If you are working with a customer who consistently sends drawn
pads you may want to ask them about it. For our Mentor Boardstation
it is as simple as a mouse click on the menu item "Fill Aperture Table"
If I don't load them, it draws them with the default aperture width.
(education helps everyone)
(other softwares may vary)
onward thru the fog,
Jack
.
On Fri, Jan 30, 2009 at 10:42 AM, <[log in to unmask]> wrote:
>
> Don't mean to be overly picky, but gerber data has been around a lot longer
> than LASER plotters. Used to actually have a wheel with maybe 24 positions
> max. Laser allowed for 274X style gerber... back before there was light, we
> used black tape...
>
> fogward,
> -Chris
>
>
>
> *Jack Olson <[log in to unmask]>*
> Sent by: DesignerCouncil <[log in to unmask]>
>
> 01/30/2009 09:51 AM Please respond to
> "(Designers Council Forum)" <[log in to unmask]>; Please respond to
> Jack Olson <[log in to unmask]>
>
> To
> [log in to unmask] cc
> Subject
> Re: [DC] Aperture generation in gerber files
>
>
>
>
>
> I think I can answer that in a round-about way, but I have to say something
>
> to set the foundation...
>
> Gerber data formats were developed as a way to control laser photoplotters,
> instructing the machine to expose film (instead of drawing ink on paper).
> So, you can think of them as a type of plot file.
>
> Well, just as a camera lets light in through an aperture, a laser
> photoplotter
> can control feature sizes by using different sizes of apertures.
>
> Some apertures are called flashes, which moved the light source to a
> specific
> location and "flashed" the shape onto the film, like a rectangle or circle.
>
> Other apertures were called "draws" which opens the light source and THEN
> moves it to specific locations, effectively "drawing" a light beam of a
> specific
> width.
>
> Thinking about a circuit board film layer, you can imagine that usually all
> of
> the pads are created with flashes, and traces are created with draws.
>
> In the past the designer had to think of these things and supply a custom
> "aperture list" with every order.
> These days, gerber formats (274X) can embed the apertures directly into
> the file, and most modern CAD systems can assign the apertures
> automatically.
>
> Unfortunately, since most of this has been automated, many designers don't
> have a clue what is going on when they create the data files. On the
> upside,
> if the designer hasn't made flashes available, or no flash is the correct
> size when
> the data file is being made, the CAD system is smart enough to DRAW the
> feature (which far better than ignoring the feature, right?)
>
> Using draws makes it more difficult for DRC checking in CAM, but usually
> the
> front-end engineering will convert them to flashes as a normal part of the
> process, so their checks can run more optimally.
>
> The answer to your question really depends on the CAD system and the
> designer,
> so I'm sorry I can't be more specific, but usually YES, the designer can
> use flashes
> instead of draws for pad sizes if they know how to use their system.
>
> Anyway, I think I answered ONE of your questions, the technical names are
> DRAWs and FLASHes
>
> hope that helps,
> Jack
>
>
> .
> On Thu, Jan 29, 2009 at 9:41 PM, Ioan Tempea <[log in to unmask]> wrote:
> Dear Colleagues,
>
>
>
> The many gerber files I have seen can be divided into two categories,
> according to how the geometrical figures (apertures) of the land patterns
> are generated:
>
> o Apertures declared as stand alone geometrical figures (e.g. a
> rectangular 100x200 pad is declared as a 100x200 rectangle)
>
> o Apertures generated by successive positions of a smaller element
> (e.g. 100x200 rectangle generated by adjoining twenty 100x10 lines)
>
>
>
> The second version does not come handy at all when trying to measure the
> center of an aperture with a gerber viewer.
>
>
>
> Questions:
>
> o How is each of them generated?
>
> o Are there CAD systems that can only generate the latter?
>
> o Any precautions that can be taken by the designer so that only
> the first one be generated?
>
> o If I want to call each method by its technical name, what would
> that be?
>
>
>
> Thank you,
>
>
>
> Ioan Tempea, ing.
>
> Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
>
> * *
>
> *30 ans déjà! - Already 30 years!*
>
> 950 rue Bergar, Laval, Québec, H7L 5A1
>
> t : 450-967-7100 ext : 244
>
> Mtl : 514-990-5762
>
> f : 450-967-7444
>
> *[log in to unmask]* <[log in to unmask]>
>
> *www.digico.cc* <http://www.digico.cc/>
>
> *P* *N'imprimer que si nécessaire - Print only if you must*
>
>
>
> -------------------------------------------------------------------------------
> DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to *[log in to unmask]* <[log in to unmask]>with following text in the BODY (NOT the subject field):
> SIGNOFF DesignerCouncil
> To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks
> send: SET DesignerCouncil NOMAIL/(MAIL)
> Search previous postings at: *http://listserv.ipc.org/archives*<http://listserv.ipc.org/archives>
> Please visit IPC web site *
> http://www.ipc.org/contentpage.asp?Pageid=4.3.16*<http://www.ipc.org/contentpage.asp?Pageid=4.3.16>for additional information, or contact Keach Sasamori at
> *[log in to unmask]* <[log in to unmask]> or 847-615-7100 ext. 2815
>
> -------------------------------------------------------------------------------
>
>
> -------------------------------------------------------------------------------
> DesignerCouncil Mail List provided as a service by IPC using LISTSERV 1.8e
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field):
> SIGNOFF DesignerCouncil
> To temporarily stop/(start) delivery of DesignerCouncil for vacation breaks
> send: SET DesignerCouncil NOMAIL/(MAIL)
> Search previous postings at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16for additional information, or contact Keach Sasamori at
> [log in to unmask] or 847-615-7100 ext. 2815
>
> -------------------------------------------------------------------------------
>
>
>
>
>
>
> This e-mail message is intended only for the use of the intended recipient(s).
> The information contained therein may be confidential or privileged, and its disclosure or reproduction is strictly prohibited.
> If you are not the intended recipient, please return it immediately to its sender at the above address and destroy it.
>
>
>
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------
|
