Hello All- Sorry for asking a stupid question, but when you are building thru-hole library parts, don't you need to define an inner layer for the holes? Looking at older parts, some of them have inner layers defined, some don't.
I do define the pad stack on inner layer. I do not like leaving out. Sometimes I make it bigger or smaller and even different shape as outer layers. For example for pin one on IC I like using a square pad but the same pad on inner layer I will use round pad.
It looks like in the existing thru-hole parts, if the hole is plated it has an inner layer defined. It needs to have this. But if the holes is un-plated, such as mounting pins on a connector, the inner layer is not defined. If it it done this way, I'm not sure how you would get a hole thru the inner holes when you generate gerber.
I would prefer to do it as you mention, defining the inner layer whether it's plated or not.
If it is a MTG none plated hole I will not worry about it. As a matter of fact for outer layers I whould make a pad smallet then a drill size.
Yes, I'm building library parts for connectors with the non-plated mtg holes. That's where I'm confused. So if you don't have an inner layer defined what keeps you from running traces where the hole will be?
In Design Rules you will find Hole to Trace clearance that will be used with DRC and Verification. Some people chose to add Keepout around MTG hole for all layers in Decal to make sure no traces come closer than required.
So basically if I add a padstack with a hole, plated or not, the design rules will keep me out of trouble when I route my board. And inner layers are used if the hole needs to make an internal electrical connection.
I knew this, but for some reason it wasn't making sense today.
I make it a rule of thumb on all 4 layer & up boards for all Non-Plated mounting holes to add that keepout for all layers to at least
the largest dia of the hardware being used. Because star lock washers are used sometimes and having a pwr plane there can be a problem.
Also if a hole size ever wants to be opened up it can be done if there is enough clearance provided in planes.
Never hurts to have the clearance there, it does come in handy sometimes.
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