Author Topic: Multiple vias - multilayer board.  (Read 2141 times)

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Offline mikolaj612Topic starter

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Multiple vias - multilayer board.
« on: September 09, 2015, 11:13:43 pm »
Hello everyone.
At the begining sorry for my bad english - I'm now native speaker.

I use CadSoft Eagle for making project, but I have some question related to vias and placing it near components.
I know that vias are always used to connnect SMD components to ground or power planes, but how about THT components?

Should I place some additional GND vias near pads of THT elements? I saw many design almost always there is no additional vias, but I have one multilayer PCB at home and there are vias near main mounting hole.
Second question is similar because how about using additional vias to connect THT element to power plane?
Third question is how about routing AC as a power plane (inner layer) should I place it inside board or maybe it should be routed on top/bottom?

I know that many vias are used to connect SMD components because this will provide low impedance connection to plane and small vias have probably some current limit.

I attach picture to show what I'm talking about.

My board stack up is classic:
1. TOP - signall/hi speed signal + GND,
2. GND plane,
3. VCC surrounded by guard ring connected with multiple vias to GND,
4. GND plane + sometimes some not critical signals like enable pin or something like that.

 

Offline Bassman59

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Re: Multiple vias - multilayer board.
« Reply #1 on: September 10, 2015, 04:05:45 pm »
Hello everyone.
At the begining sorry for my bad english - I'm now native speaker.

I use CadSoft Eagle for making project, but I have some question related to vias and placing it near components.
I know that vias are always used to connnect SMD components to ground or power planes, but how about THT components?

The holes for the component's leads are sufficient.
 

Offline Neilm

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Re: Multiple vias - multilayer board.
« Reply #2 on: September 10, 2015, 06:51:27 pm »
I have done vias with a through hole component, but only when I needed very low resistances with very high currents. I was worried that the thermal relief around component leg would not take 50A.
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Offline mikolaj612Topic starter

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Re: Multiple vias - multilayer board.
« Reply #3 on: September 11, 2015, 06:02:19 am »
I do not use thermal is Eagle.
My project is medium to low current (voltage regulator from few hundrets mA to 1.5-2A max), RAW section is always below 3A.

How about inner layers? Should I use it for AC power plane (for diode rectifier/s) ? Or maybe it should be places TOP/BOTTOM plane?
I downloaded may EVM datasheets from TI, and almost always voltage regulatos EVM are 2 layer boards, sometimes 4 layers but with multiple GND planes for better thermal resistance.

How should I place power planes if I have some AC planes (for rectifiers), RAW DC and regulated DC.
I use some THT elemets like capacitors (electrolitic and foil), hybrid chokes (Murata PLY10 series), and ARK/PTR/XH connectors.
But there is also some SMD capacitors, resistors and VQFN/MSOP/DFN chips.

And thank you for helping me out ;)


I also know that 0,3mm (I use it widely) have current capabilities about ~ 0.7A peak.
 


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