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Sniper2 , 01-16-2024, 07:52 PM

is there any minimal via drill size for this PCB classification?
Also does this standard allow for vias to touch SMD pads? (not via in pad)

QDrives , 01-16-2024, 11:19 PM

Let me see if I get what you are asking.
IPC-7351 is for land patterns.
Class 3 -- you mean the Performance Classification as is in IPC-6011?
But then 3 B Via.... do you mean IPC-4761 type 3B via (plugging)? https://resources.altium.com/p/IPC-vias

I would say that the minimum drill size can (should) be given by the fabricator.

Does any standard not allow you to have a via touch a SMD pad? Not wise, sure, but (not) allow...
There are 3 problems with via's 'touching' SMD pads:
1) There are often solder mask slivers.
2) Paste can flow towards the via that in turn can cause a multitude of component problems (tombstoning, etc.)
3) Paste and flux can flow into the via.
Naturally, problem 3 is solved with type 3B via's, the other 2 are not.

Sniper2 , 01-17-2024, 04:58 AM

The normal pcb density

Sniper2 , 01-17-2024, 04:58 AM

That is b

Sniper2 , 01-17-2024, 04:58 AM

Manufacturing rating is A

QDrives , 01-17-2024, 09:04 PM

I do not understand your last comment.
"Density" is a thing used for footprints. With 3 defined by IPC: Least, Nominal and Most.
Is your question related to footprints, vias, classes, or something else?

Sniper2 , 01-17-2024, 09:09 PM

normal=nominal , ops english glitched

Sniper2 , 01-17-2024, 09:10 PM

i was asking if there is a standard minimal drill size for a standard manufacturability PCB with a nominal density rating .2 .3 mm something like that i expect but i am not sure that is why i asked

Sniper2 , 01-17-2024, 09:11 PM

regarding the via next to pad it is like this:
how much % of the area of a SMD pad can my via cover and still be ok ? is like 5-10% ok? (like in a corner )

QDrives , 01-17-2024, 09:57 PM

The IPC performance classes specify minimum elements of vias, such as drill ratio, annular ring, etc.
However, the performance class is something else than the density. The performance does add requirements to the footprint too.
Check out this video https://www.youtube.com/watch?v=cMxXea16Hxc

"Still be ok" -- Ok to what extend? I mentioned 3 issues with vias 'toughing' SMD pads. It is not a question of "fail" or "no problem", there is a chance production (and run-time) problems occur.
How bad the problems will be depends on your design, what modifications the fabricator does to it and the modifications and process adjustments the assembly company makes.
One way to solve your problem would be to fill the via and plate over it (VIPPO, Via In Pad Plated Over), but you already mention not to want that.
But you also have not answered the question if you mean Type 3B vias.

Sniper2 , 01-18-2024, 05:14 PM

THX, ill take a lok

Sniper2 , 01-18-2024, 05:15 PM

look*