PCB newbie Q on copper islands

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stevech
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Posted by stevech: Sat. Aug 21, 2010 - 02:07 AM
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My second spin of a PCB I designed. I read about copper islands and kind of watched out for this. But my new boards have one flaw, where one region of copper fill (pour) became disconnected with ground. It was because a change I made, adding a via, caused that fill region to get isolated from ground due to a too-small area around the via. On my monitor, it is a very small sliver of copper left; in etching, it's an open circuit. Simple jumper wire fixes.

I might have caught this, using freeware expressPCB, had I clicked on the thing to highlight all pins in a net (ground) and had I noted that one pad, tied to ground, did not highlight as a member of the ground net.

Do costly professional packages find copper islands? To do so, it would have had to note that the sliver of copper was too small to assure etching wouldn't fail to leave continuity.

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Learning and Information, General Electronics
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ka7ehk
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Posted by ka7ehk: Sat. Aug 21, 2010 - 02:41 AM
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What layout software did you use?

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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glitch
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Posted by glitch: Sat. Aug 21, 2010 - 03:15 AM
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yes most good packages will identify copper islands. As for the sliver, good packages won't generate any features thinner than your minimum trace width, or will at least alert you to the existence of a feature that is thinner than the limit.

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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ka7ehk
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Posted by ka7ehk: Sat. Aug 21, 2010 - 03:21 AM
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I think even Eagle will, if you run a DRC (design rule check) on the layout.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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stevech
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Posted by stevech: Sat. Aug 21, 2010 - 09:15 PM
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The, er, good software I used for these little 2 x 3 in boards is, er, expressPCB.

To alert, it would have to have trace sliver width checks for less than x. On screen there is continuity; after etching, not so, due to trace width too small. It's at a crowded place with clearance problem created by a via.

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ka7ehk
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Posted by ka7ehk: Sat. Aug 21, 2010 - 09:18 PM
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Eagle WILL do that, pretty sure. Or just not draw it, in t he first place. Never had any problems with this and I've given it plenty of chances.

Jim

PS - I am not saying that Eagle is good. There are lots of things in the user interface that drive me ... (further than I already am). It just what I've been using so that is the reference I can compare to.

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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nleahcim
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Posted by nleahcim: Sat. Aug 21, 2010 - 11:02 PM
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Eagle will catch that with a DRC. Altium Designer will catch it as well.

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stevech
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Posted by stevech: Sun. Aug 22, 2010 - 06:30 PM
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Twice now I've invested several hours with Eagle. Both times I gave up due to the less than horrible UI.

So for expediency I used expressPCB. Of those I tried, DipTrace looked best, but learning time was too long vs the project's schedule.

Do the pro level PCB tools warn that there's a possible copper island because somewhere in the pour area there's a sliver that might disappear in etching? Doing so breaks electrical continuity to the ground plane.

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leon_heller
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Posted by leon_heller: Sun. Aug 22, 2010 - 06:48 PM
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Most have a setting for minimum copper width, so the problem shouldn't arise. There are programs that are used by some board manufacturers that check the Gerbers for that sort of thing, as well as copper slivers that might work loose and cause a short.

Leon Heller G1HSM

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nleahcim
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Posted by nleahcim: Sun. Aug 22, 2010 - 07:05 PM
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stevech wrote:
Twice now I've invested several hours with Eagle. Both times I gave up due to the less than horrible UI.

So for expediency I used expressPCB. Of those I tried, DipTrace looked best, but learning time was too long vs the project's schedule.

Do the pro level PCB tools warn that there's a possible copper island because somewhere in the pour area there's a sliver that might disappear in etching? Doing so breaks electrical continuity to the ground plane.


Yes. That is a standard DRC rule. I haven't used Eagle for a number of years now, but I suspect even Eagle checks for that. I could be wrong though - I was never very impressed with that package. (you get what you pay for!)

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curtvm
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Posted by curtvm: Sun. Aug 22, 2010 - 07:43 PM
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DipTrace will do what you want with copper pours, and is about as easy as it gets. It has island removal and clearance options that should handle most situations, I would guess.

It seems to me that DipTrace has about as normal an interface as you can get with pcb software, and you won't be struggling with the user interface. I think its almost as easy to use an ExpressPCB.

In addition to the normal user interface, I like the 'pin limit' way of restricting the free version vs limiting board size in Eagle.

/advertisementover

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alank2
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Posted by alank2: Mon. Aug 23, 2010 - 12:55 AM
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Hi,

I also use expresspcb and manually check for ungrounded islands. See my thread here:

https://www.avrfreaks.net/index.p...

Page 2 I have sort of a checklist I go through to design a PCB, I'm not sure if it will help, but you might take a look at it.

Thanks,

Alan

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https://www.avrfreaks.net/forum/wts-standalone-pdiisp-auto-programmers

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stevech
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Posted by stevech: Tue. Aug 24, 2010 - 04:12 AM
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Thank you all, esp. Alank2 for the thread pointer.

I think I'll try DipTrace for my next boards. The time I spent with it indicated that it was the best of the 4 or so I tried (as a novice).

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alank2
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Posted by alank2: Tue. Aug 24, 2010 - 12:11 PM
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Hi,

I too have been trying my luck at DipTrace. It looks like it has a lot of features.

Thanks,

Alan

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https://www.avrfreaks.net/forum/wts-standalone-pdiisp-auto-programmers

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alank2
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Posted by alank2: Tue. Sep 21, 2010 - 01:02 PM
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Hi,

Well, I had diptrace crash on me a couple of times and since the "Eagle" is so strong I decided to really give it a game effort to learn. It took me about 4 evenings work, but I finally got it figured out and converted one of my expresspcb boards to eagle. I have to say that I am quite pleased with Eagle now that I've been working with it. Their forum was helpful in answering questions. I agree their UI is a bit backwards, but once figured out it isn't too bad. Their pour handling is excellent however - it won't create ungrounded orphans unless you tell it to. It also creates a smooth flowing pour without all the jagged edges that expresspcb creates that you must manually go back through and exclude. I am quite pleased to have made the transition and it was less painful than I thought it would be.

Good luck,

Alan

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https://www.avrfreaks.net/forum/wts-standalone-pdiisp-auto-programmers

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devils4ever
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Posted by devils4ever: Wed. Sep 22, 2010 - 01:01 AM
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I'm using Kicad for schematic capture and PCB layout. So far, I'm very impressed with it. It won't let you route traces over other traces or violate minimum clearances. It's a little tricky getting used to using it. But, all PCB software is quirky. Kicad is free for both commercial and private use.

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