Mr Manjunath K

[Manjunath K]

Dear Sir,

My name is Manjunath. I am working in GRAPES-3 Experiment ooty india as

PCB designer. I saw your video. Your tips are very helpful to me. Presently i am designing a

4 Layer pcb and the size is 360mm X 360mm. So if I made board thickness 2mm it is better or

1.6mm itself sufficient. My layer stack up is

Layer 1 Signal and Ground copper Pour

Layer 2 Ground Plane

Layer 3 Power Plane

Layer 4 Signal and Ground copper pour

it is ok. Please give your valuable suggestion.

Thanks,

With Regads,


K.Manjunath


Scientific Officer
COSMIC RAY LABORATORY

TIFR, OOTY
Off Mob No: 094877 30849

[robertferanec]

I do not have experience with behavior of large boards - maybe someone else can provide some feedback?

PS: In my opinion, 1.6mm still may be ok - standard PCBs are manufactured in large panels and they are ok. What I would not be sure about is possible bending after assembly - maybe that may require some special care e.g. copper thieving(?)

[qdrives]

I would say it depends on what you need.
Thinner boards are better for signal integrity, but that is mostly for higher speed.
Thicker board are more rigid, which may be needed if you have few mechanical mounting and possibly big heavy connectors.
All big boards I have seen (like 300x500mm) were the standard 1.6mm. I only worked with 2.4mm boards where the thickness was mechanically wanted, yet was 100x100mm. It also had depth routing, it was like a big washer (just to be sure you get the right one: https://en.wikipedia.org/wiki/Washer_(hardware)

[Manjunath K]

Thanks for your kind reply.

[Manjunath K]

I have another query. In my board I am planning to have 4 different voltages in power plane. I want connect those plane through VIAS for components. So the VIAS will take how much current. Please let me know. Suppose the current will be 5amps how many VIAS I have to put.

[qdrives]

First off - it is better to start a new thread for a new question. It allows others to see it too and answer.
My simple rule of thumb is: no more then 1A per via.
However, it depends on a lot of things, not to mention that there is no clear consensus on where a via is limited to a current os that it mainly are the tracks/planes.
Additional dependency are: via type, via diameter, via plating thickness and via height

[robertferanec]

Here is also a link to the calculator and a video about calculator what qdrives is using (it is a free software):

- Video: PCB Layout - Useful Calculations Which You Maybe Didn’t Know About (with Kenneth Wood) https://youtu.be/fJCRrEf_IH8
- Download: https://saturnpcb.com/saturn-pcb-toolkit/

[Manjunath K]

Thank you for you reply. I will go through the video.

[Manjunath K]

Dear Sir,
I send the 4 layer pcb manufacturing files to different vendors for getting quotation. In one manufacturer reply that. Drill they cannot make for 0% tolerance. They can make +or- 3% tolerance only. Please give suggestion for drill how much % tolerance we should keep.

thanks and regards,
K.Manjunath

[qdrives]

Naturally it is not possible to manufacture a via with 0% tolerance. Every fabricator should flag this, but apparently, most of them ignore it.
Personally, I would leave out the tolerance, unless it is absolutely critical. If you do not know if it is critical, then it is NOT critical.

[robertferanec]

I agree with qdrives - if it is not specially required, leave tolerances on the PCB manufacturer. They have to follow some standards and these standards specify the tolerances they need to use.