General Advice PCB, Planes

[goldfinger]

Hi Guys,
I'm designing my first pcb for manufacturing and I'm hoping I can get some advice on people's general thoughts on gnd planes. I'm working on a two layer board with most of gnd traces running on bottom with exception of a few traces.

My question is what should be a standard clearance between the pad and ground pour for through holes that aren't connected to the gnd plane? Most of the tH are between 0.8-1.1mm with pads between 1.5-2.5mm, my main concern is soldering and ensuring that I don't short to the ground plane. Also, for TH for screws mounting (I'm thinking m3 screws) what sort of clearance around should I aim for?

Is there any general guidelines at all?


Any advice would be appreciated, I'm using circuit maker.


Thanks guys!

[DerekG]

what should be a standard clearance between the pad and ground pour for through holes that aren't connected to the gnd plane?

It really depends on how tightly packed your board is. If you have plenty of room then 30mil (30 thousandths of an inch) or 35mil is a good clearance.

Also, for TH for screws mounting (I'm thinking m3 screws) what sort of clearance around should I aim for?

3.2mm would give you a clearance of 0.1mm around the screw. If you want it a little more sloppy you could go to 3.3mm.

Make sure you don't plate through the mounting holes if these boards are going to be wave soldered. If you do, the plating will suck the solder through the holes ending up with spillage on the top side of the board.

I hope this helps.

[DTJ]

For pad to tracks I usually use 10mil or even 8mil.

For mounting screws, say M3, I place a pad with a 3.5mm hole and make the pad diameter so that its one or two mm bigger in diameter than the screw head or nut driver socket that will be used to fasten the board down. Putting a silk screen circle around the mounting holes can help as a placement guideline when pushing parts around and routing.

[goldfinger]

what should be a standard clearance between the pad and ground pour for through holes that aren't connected to the gnd plane?

It really depends on how tightly packed your board is. If you have plenty of room then 30mil (30 thousandths of an inch) or 35mil is a good clearance.

Also, for TH for screws mounting (I'm thinking m3 screws) what sort of clearance around should I aim for?

3.2mm would give you a clearance of 0.1mm around the screw. If you want it a little more sloppy you could go to 3.3mm.

Make sure you don't plate through the mounting holes if these boards are going to be wave soldered. If you do, the plating will suck the solder through the holes ending up with spillage on the top side of the board.

I hope this helps.

Thanks for feedback appreciated

[goldfinger]

For pad to tracks I usually use 10mil or even 8mil.

For mounting screws, say M3, I place a pad with a 3.5mm hole and make the pad diameter so that its one or two mm bigger in diameter than the screw head or nut driver socket that will be used to fasten the board down. Putting a silk screen circle around the mounting holes can help as a placement guideline when pushing parts around and routing.

Thanks for feedback!!!  I ended up with a 4.2mm keep out around the m3

[technotronix]

3.2mm would be better to get perfect clearance.