Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

4 Layers PCB : Via holes

Status
Not open for further replies.

LandLack

Member level 3
Member level 3
Joined
Aug 8, 2013
Messages
54
Helped
1
Reputation
2
Reaction score
1
Trophy points
8
Activity points
526
Dear all,
I need to make a 4 layers PCB (the external two with SMT discrete components while the other two internal's are ground and power supply with two or three different types of voltages). I would like to know how much is the price difference between "through holes" and "blind holes", and how are these vias designed. I've seen one guy making the gerber files while projecting one layer+ground plane, and he said that he needed holes to connect with the ground plane; are these holes the vias, and if yes, do I need avoid them to be covered with the solder mask?
Can you also tell me the delay of the via lines, and how to connect them with the traces (I would like to put the power supply network + oscillator in the lowest layer, and give it to the highest layer)?
Thank you for your interest,

Regards,
LandLack
 

You are apparently designing your first multi-layer PCB. I don't believe that you should think about advanced techniques like blind vias, refer to an established standard technology suported by all PCB manufacturers, using standard design rules.
 
Thank you for your replies, which have been very useful.
I've seen a copper+dielectric+copper PCB (2 layers, right?). One copper layer was the ground, while the other had devices + traces , and I've been told that the gerber file with the holes (which passed through all the layers) indicated the connection with the ground. So these drilled holes are the vias, correct?
If yes, in my case I can't use a layer completely covered by copper to make a ground since it will be connected to the power source, right?
And the paths which end with a circle and a hole are the connection between the traces and the vias?
And how much should be the radius of the hole (if it's a via), to have characteristic impedance of 50 ohm?
I'm sorry for asking so many things, but as you've already guessed, this is my first PCB experience. (And I need to produce also a little bit complicated circuit).

Regards,
LandLack
 
Last edited:

You can design PCB traces with specific impedance, e.g. 50 ohms, but it's a matter of the selected transmission line structure and it's dimensions, e.g. microstrip or coplanar waveguide, respective trace width and distance between ground and signal. Via diameters can be chosen to fit the trace width but are only one (probably less important) of several parameters. You should tell the operation frequency of your PCB to make us understand if these parameters matter at all.
 

You can design PCB traces with specific impedance, e.g. 50 ohms, but it's a matter of the selected transmission line structure and it's dimensions, e.g. microstrip or coplanar waveguide, respective trace width and distance between ground and signal. Via diameters can be chosen to fit the trace width but are only one (probably less important) of several parameters. You should tell the operation frequency of your PCB to make us understand if these parameters matter at all.

Threre are 8 different tones: 130MHz ,250 MHz ,410MHz ,615MHz, 820,940,1190,1400 MHz . I need the vias to connect the oscillators on the lowest layer to the highest layer where the main operations will be done.
I've chosen Rogers RO4350b as the PCB technology (Er=3.48, Dielectric thickness=0.762mm, copper thickness=always 0.0177mm).
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top