Electronics > PCB/EDA/CAD

Advantages with 4 layers without blind/burried vias?

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okw:
I see cheap manufacturers offer 4 layer boards very cheap, but without blind or burried vias.
In JLCPCBs DRC file, they've only set up 1-16 (top-bot) layer vias.
If I can't access the middle ones, why do I need them (except shielding the bottom from top layer)?
Or can I set up vias from top (1) to middle-top (2), and bot (16) to middle-bottom (15)? So I can reach 1-2 without problems (or excessive tooling cost)? And if I want to reach 1-15, i need to go 1-16, then 16-15?

tszaboo:
You can reach much higher density without blind vias, just try it. You have 2 times the space for routing.
Normally the so-called stackup is: Routing - GND - Power supply - routing. It's better for EMC, and even if you don't care about that stuff, it will work on higher frequency better.

thm_w:
You can access the middle layers. The via is drilled through (1-4), then you connect a trace to it wherever you want. You can have trace on layer 1 go to layer 2, or 3, etc.

Look at the "through hole" image here: https://www.pcbgogo.com/Blog/PCB_Vias__Something_You_Need_To_Know.html

Doctorandus_P:
Both blind and buried via's are quite special, and they require separate process steps (which also costs extra, so you won't get them for rock bottom prices) But that still leaves "normal" / "regular" via's. A regular via is made by drilling a hole through the whole PCB, and then plating the hole on the inside. So such a via always reaches all layers of the PCB, but of course it does not have to have a copper track connected at each layer. If you're interested, go watch some youtube video's about PCB manufacturing.

mikeselectricstuff:

--- Quote from: okw on April 26, 2023, 06:31:46 pm ---I see cheap manufacturers offer 4 layer boards very cheap, but without blind or burried vias.
In JLCPCBs DRC file, they've only set up 1-16 (top-bot) layer vias.
If I can't access the middle ones, why do I need them (except shielding the bottom from top layer)?

--- End quote ---
You misunderstand - through vias access all copper layers, not just the outer ones.

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