Your PCB design program doesn't always tell the complete truth --most of the board houses I use recommend the use of a Gerber Viewer before shipping the design off to them. Here's an example of why it's important -- these traces appear to be sufficiently separated on the computer screen but the Gerber Viewer shows them to be too close for comfort. I use the Pentalogic product which is a free download:
Attachments
What about using design rules in your PCB CAD program? When the design rules are properly setup (e.g. min 7mil clearance for anything), then no matter what the display shows, you can rest assured that there can be no errors if your DRC covers them.
I do use gerber viewers (CAM350 is my fav) but for other purposes. The PCB CAD tools that I use have built in gerber viewing (e.g. PADS, Allegro).
If you want to be a little exotic, VALOR checks are great. I use that for work but not for my diyaudio projects.
I do use gerber viewers (CAM350 is my fav) but for other purposes. The PCB CAD tools that I use have built in gerber viewing (e.g. PADS, Allegro).
If you want to be a little exotic, VALOR checks are great. I use that for work but not for my diyaudio projects.
I had been fooling around with the pcbs for about 3 years. 1st time when I sent to a fab house was about 1.5 years ago. My pcb software, the Autotraxeda, really sucks. The fab house told me that a short trace was probably missing on the gerber files. (They were able to spot it because they check my work with the layers super-imposing on each other, just like what we see when we were using our pcb software to design the board.) So I look at it again but it was there (with my AUTOTRAXEDA) It was there. So I tried regenerating the gerbers and view it wtih GC-prevue, the track was missing. I go as far as deleting everything around that area and redraw everything back, regenerating the gerber again. The trace is still missing. I never know why tha A-sh*t is doing this. The story end up that the fab house add in that trace for me and tell me to recheck with GCprevue That is my story why we need to use gerber viewers to check our work.
Lucky that I made a mistake in the 1st time (or I did not make it myself) work with the fab house. Now for every work I sent them, I check with gerber viewers first which has become a habit or must if I should say.
Lucky that I made a mistake in the 1st time (or I did not make it myself) work with the fab house. Now for every work I sent them, I check with gerber viewers first which has become a habit or must if I should say.
Arius said:
Design rules are in effect -- with a 10 mil trace clearance.
I think that there are just "sometimes" operational problems -- and this was for a power amplifier with about 50 components -- we aren't doin' work for Cisco here.
The one good thing about Multisim and Ultiboard --- since EWB was taken over by National Instruments things seem to be working more smoothly.
I never fully trust any one piece of equipment or software. I always check my files in a Gerber viewer and then if they look good I have confidence. I do the same thing on the bench, DMMs along with scope. If both agree then I feel the number(s) are right. Takes two or more for me to believe I am seeing truth. I think it best if you always give a quick look over a layout in a Gerber file view. Sometimes it just helps to spot something you missed before.
-SL
-SL
ACD said:I have never experienced this kind of problems....
I use Easy-PC for pcb-layout and always check my files with Macaos (which is the program I ship my gerber files in to the manufactorer)
Unlike ACD I have had a problem. I too have used various incarnations of EPC, and just once, my PCB manufacturer phoned me to say they had spotted an error in one Gerber plot file which cause a large track aberration. The Design Rule Check that the software has, should have shown this short-circut, even if my eyes had not. After re-routing the area and re-plotting, the files came good.
Since then I use a free Gerber viewer to give the design a "once over" before sending, or leave the plotting to the PCB house - send them the .pcb file and ask them to extract.
Just like human work, you always want 'SOMEONE' else to check your work, because if you put in there by mistake, your mind is biased that that's right in the beginning. Not that easy to spot your own mistake, I mean the conceptual ones, not the careless.
I would say the best we do is (if possible) that whatever your fab house use to check your work, use the same thing to check it yourself first.
PMA : I think most of the guys here are non-pros, although many know the subject far better than some so-call pros. In our place, most people would do something different for a hobby instead of treating their work as one.
I would say the best we do is (if possible) that whatever your fab house use to check your work, use the same thing to check it yourself first.
PMA : I think most of the guys here are non-pros, although many know the subject far better than some so-call pros. In our place, most people would do something different for a hobby instead of treating their work as one.
jackinnj said:
Jack,
I see what you're saying, but were these tracks *really* closer
than the DRC limit? Displays can't be counted on to show these things.
I have probably layed out 100's of pcb's in my life using layout programs with DRC checks, and never had an issue with this, although the display often shows problems with too close tracks.
Even when you use a gerber viewer, what does that tell you? You're still looking at the display screen.
Unless your gerber viewer has a DRC check built in, but then you're back to the same tool type in the pcb layout program.
Moral: never trust the display, trust the DRC check in your program/gerber viewer. A few remaining problems could exist from bugs in your software, but that should be very, very seldom.
Jan Didden
I would recommend GC Prevue to anyone whom looking for a free Gerber viewer. Reliable and good user interface.
It is a good practice to use a third party viewer to check your own CAD file(s) before sending them to the PCB fab house. You may suprise what you have found and save yourself for another pass.
Regards
Max
It is a good practice to use a third party viewer to check your own CAD file(s) before sending them to the PCB fab house. You may suprise what you have found and save yourself for another pass.
Regards
Max
Another great Gerber Viewer is "DFM Now!" - a Free Gerber Viewer.
Run a full DRC/DFM Check, Netlist compare, Area Calculation + more... and then send your Gerber's directly to reliable PCB Manufacturers and receive quotes instantly. All of this with DFM Now!
This really saves you al ot of time and money.
Run a full DRC/DFM Check, Netlist compare, Area Calculation + more... and then send your Gerber's directly to reliable PCB Manufacturers and receive quotes instantly. All of this with DFM Now!
This really saves you al ot of time and money.
very good habit to do this IMO. its exactly the same as running soft and hard proofs with offset printing before sending to plate or image-setter with graphic design (showing my age) postscript errors can and will happen and it has nothing to do with the screen and what is showing on it. i presume pcb layout files and gerbers to be parallel to design layout files and postscript; with design it is always best to do at the minimum a high res PDF file including colour separations to spot errors in the postscript, just as it is here with gerbers.
there can be errors in the way the curves/splines and objects are converted to vector information and it will not matter if you have design rules to prevent it, just as having snap to grid set in a layout will not guarantee you with enough certainty correctness enough to print 10000 books on a screen preview.
there can be errors in the way the curves/splines and objects are converted to vector information and it will not matter if you have design rules to prevent it, just as having snap to grid set in a layout will not guarantee you with enough certainty correctness enough to print 10000 books on a screen preview.
How much time does it take to use a Gerber viewer to review before sending off the CAM files to a boardhouse, compared to dealing with those issues after production? Not much time, it is well worth it. Many boardhouses will do DRC on prototype designs to find those hard to see anular ring issues. Sometimes it's hard to see when vias come close to traces. And then you have to deal with the boardhouse PR (and BS) and re-send files risking 'issues' and confusion. I try to stay within a min of 10mil space, more if possible between traces, even though most houses can do 8mil with no problem.
Sometimes it's hard to see when vias come close to traces. And then you have to deal with the boardhouse PR (and BS) and re-send files risking 'issues' and confusion. I try to stay within a min of 10mil space, more if possible between traces, even though most houses can do 8mil with no problem.- Status
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