The mechanical via that PCB manufacturer can be done

Why HTDcircuits discuss the smallest mechanical via?

This paper is focus on the smallest mechanical via.
In fact we have announce our PCB manufacturing capability.
And we have mention the smallest drill size.
There were many customers ask questions about the smallest mechanical via HTD can be done.
So we have to discuss this topic.

The mechanical via that PCB manufacturer can be done

If they are true vias where the finished size is NOT of any consequence, we say, “Why not call them out as +.003” minus the entire hole size?”
At that point I tell them that we can drill smaller and require less signal pad and anti-pad size, which opens the customer up for some routing for these fine-pitch parts. While we are at it, let’s talk about pitch. 
Many times, we are approached by customers talking about a specific pitch between mounts or pads, such as .4mm or .5mm pitch. 
Understand that without a design to see the via image data, it is difficult for a fabricator to properly understand what pitch means to the customer.
The pitch is the distance from the center of a given entity to the center of an adjacent entity.

The smallest mechanical via related to SMT

This can mean different things based on pad/mount size. Let me give you an SMT pad as an example:
A .5mm pitch means .0197” between the centers of two BGA pads or surface mounts. This seems like a very reasonable distance, given today’s circuit board geometries. 
However, what if the designed surface mount pad width is .015” wide? This would mean a .5mm pitch would leave only .0047” edge to edge between the mounts. 
This gives you little or no room to route a trace between mounts at that width and pitch.
Clearly as the pitch between parts decreases based on today’s shrinking chip footprints, the associated surface mount or BGA pad widths need to decrease as well to be able to route even a .003” or .004” trace between them.