well your via drill is quite large. I think 0.3 or even 0.2 should be doable. (Would give you more annular ring then 0.1mm)
I normally use 0.2mm drill, 0.65mm size or 0.3/0.75, … (The fab i use can do lower annular rings but this would require them using their high precision drilling machine which adds an extra production step.)
Certainly worth investigating that could make a huge difference to the spacing issue. The cost of a prototype has gone from $250 to $1 - 1.2k now. 50/50 between blinds/buried and micro vias.
My understanding is a multi-layer board can’t avoid blind vias.
I’ve another example here where optimisation could be possible (and I don’t know it).
Layer 1: red (front),
Layer 2: yellow
Layer 3: purple (not shown)
Layer 4: green (back)
The MCU22 track comes in an down, then has a micro-via to the top layer, then a hole-through to the bottom layer where a track leads to the green MCU22 pad. Because space is a premium there is another pad underneath that going from Layer 3 to Layer 3.
Is it possible to join the micro and standard via to go from layer 2 to 4 rather than up to the surface and down?
Most of the Chinese fabs can do 0.3 mm drill and have a +/- 2 mil jitter without extra cost.
0.5 mm annular ring asks for trouble yes, but so far I haven’t had misses there. The drill always has been on the copper still. Can’t use the bottom of the pile of fabs with this though.
A 0.2 mm drill would be better for sure.
One more question, is there a way to consolidate points on a track? Effectively the opposite of right click -> break track.
Cheers,
Andrew
Always depends on the complexity of the circuit, experience of the layout guy, time constrains, …
But i would not just give up because somebody thinks it is impossible. If you are methodical you might be able to get away without micro vias at least and if you really have time you might even get away without buried vias.
My intention was to use these guys again. They’ve been good in the past and comms are excellent.
I see a 0.2mm drill capability there. I shall try and rid the board of the micro via’s first. My default via size is 0.4mm drill and 0.6mm diameter. What should I take the diameter down to with a 0.2mm drill?
Rene -> but how?
How do you route from Layer 1 to 3 without using a blind?
If you have a GND plane, why is there a yellow GND track?
Why don’t you go upwards from pad #11 on the back, place a via (1-4) and connect the track on layer 2 to it?
Just push the front tracks a bit to the left/up…
Yes, it is typical for blind/buried/micro vias to increase the cost aprox. 4x. Going from 4 to 6 layers would be more cost effective.
That is totally untrue. A via that is not blind or buried is a through-hole via. A though-hole via passes through through the board, it passes through all layers and can be connected to from all layers. So your MCU22 track on layer 2 can connect directly to the through-hole via.
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Well a normal via can connect all layers at once. (Buried vias have the added benefit of allowing you to not disturb copper on layers that are outside of your affected layers.)
So a normal via is like a trough hole pad in this case. The drill goes through all layers, the complete inner surface of the hole is made conductive. Connections are defined by where you have copper touching the drill hole.
And are you sure your fab can make a buried via from 1 to 3? Normally buried vias are only available between a limited set of layer pairs. (1 to 3 might need depth controlled drilling which adds to cost.)
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1.21Gigawatts -> perfect, that’s the bit I was missing. Right!
Joan_Sparky -> pushing the tracks up high enough was the original reason. It may be come possible with smaller via’s and I’m rejigging.
The yellow isn’t ground, there’s a red pad underneath it. Red is being used to supply it due to green being used on the rear for the bluetooth module.
Depends on your fab.
According to your link they claim a drill pos tolerance of +/- 0.05mm (2 mils).
The fab drills the hole a little bit bigger, to accommodate the plating that will shrink the drilled hole and try to hit your drill hole size (that’s how they interpret the drill diameter).
So if your annular ring is 0.1mm (0.2mm drill, 0.4 mm pad dia) and the drill moves to max tolerance, you have a residual ring of 0.05 mm at worst place. But as they will drill a bit larger (for the plating, might be 0.3-0.35) this will be even less and become worse. Sometimes this leads to the drill actually severing the pad from the track, as it drills right through the area where the track ‘enters’ the pad.
The older/cheaper the equipment, the worse the tolerance and the higher the chance to drill outside of the annular ring… which is also a reason people use teardrops on vias (gives some more wiggle room in that spot, by making the pad in that area bigger).
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I’m pretty sure @Joan_Sparky is referring to the yellow track near the bottom of the image labelled “GND” just above the one labelled “MCU21”.
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OpenGL canvas can do it as it also has the push&shove router option which doesn’t see tracks as stiff elements (you seem to run legacy)?
I do, I thought it was just for display purposes (i.e renderer).
1.21 -> I think he’s referring to MCU32/12 pad as that relates to the image he posted
Joan -> what do you recommend for the drill pad diameter then (with 0.2mm drill)?
Sadly your fab does not list a minimum annular ring. (you would need to calculate it from their tolerances. It also depends on your plating option because different platings have different thicknesses.)
IPC recommends at least 0.15mm annular ring -> 0.5mm via diameter for 0.2mm drill
(For nominal they suggest 0.175mm -> 0.55mm via diameter for 0.2mm drill)
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Hit F11 and enter a whole new world. 
Choose >preferences>interactive routing or start to route a track and hit e for a menu.
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To clarify the information given by @hermit
New features are only added to the open gl canvas. The default (legacy) canvas is only kept alive to keep people happy who are used to some features that have not (yet) been ported over to the open gl canvas.
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I’m looking at it now, it’s so dim - unusable unless I can increase the brightness.
Final question for now, is there a way to convert a blind/buried to a hole through? If not I have plenty of work to do…