Copper Area Fill to Pad Clearance

I designed a board that has copper fills with .005" clearance between fill, and copper pads and traces. When built up many of these boards worked, but many others have shorts from 5V power to GND that are difficult or impossible to find. I suspect strongly that .005" clearance is not sufficient and so there are hard to see places where solder is bridging from pad to fill. I suspect most especially all the through hole parts, and including under the plastic barrel of the Keystone 5010 test points.

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Now I am redesigning the board for the next builds and I am increasing clearances. Please tell me what is a commonly used clearance that will greatly reduce the odds of such solder bridges occurring.

I have already redesigned the test point pads to have a clearance that exceeds the 5010's plastic barrel's diameter so I can have visual confirmation there is no short there, and greatly reducing the odds of there being one there as well.

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Artist
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A lot of PCB houses charge higher prices on clearances below 7 or 8 mil. I try to use 8 as smallest usual and 10 as default, only dipping as tight as 6 or 7 only in the very tightest spots.

HTH

piglet

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piglet

usually manufacturers have guidelines, just follow them. For example:

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Bye Jack

Reply to
jack4747

You should ask your PCB house, what they can safely manufacture. This often varies with copper thickness and for outer or inner layers.

Many offer electrical test of the PCB to check for shorts or missing connections (at a price).

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Reinhardt
Reply to
Reinhardt Behm

Thanks all of you for your replies. But I am aware of, and have designed to, what a PCB can manufacture. My concern now is not just the minimum spacing limit a fab house can do, but what is sufficient to minimize solder bridge risk during assembly.

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Artist

Did you get electrical testing of the boards? That should eliminate 99.9% of the shorts or other defects on manufactured boards.

You can always do a one-point test for this short to at least find ones with

+5 shorted to ground. Send those back to the manufacturer and make them replace them. Test the boards before assembling parts on them.

Jon

Reply to
Jon Elson

How are you getting solder bridges to solder mask-covered pours?

Many PCB fabs will modify polygons for a wider clearance, like 10 mils. It's a good plan, even when covered in soldermask. Better to do it yourself, so they don't 'accidentally' cause narrow necks or breaks in the pour. Seen that, too.

Tim

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Tim Williams

solder mask is sufficient.

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Jasen Betts

snipped-for-privacy@gmail.com wrote on 9/28/2017 3:37 AM:

They don't make their info easy to read. Much of it is in an image rather than in text making it both hard to read and impossible to search. They also have some confusion in the tables. I see columns indicating both type R and RF pools. R is supposed to indicate the RF pool, so what does RF indicate??? I don't see SF mentioned in the tables, so I'm thinking it's a typo and should be SF. Much of it is just hard to read.

They give limits and then tell you not to use values next to the limits because of round off error in their tools. So what are the *real* limits?

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