How to estimate the number of via??

[Sakr]

Alsalmo Alykom

Is there is a way to roughly estimate the number of vias in a double layer PCB before placing and routing.

and also can I get no. of vias as function of package used (SMD or through hole, DIP, BGA, etc. )

I need to know no. of vias for cost estimation...

thank you

 

[Nyar]

For a board that has mostly SMD components I'd use

(SMD pin count) / 2


This way you have reserved one via per interconnection.

 

[electron_boy]

salam

* for any board it is necessary that u have least vias for ur clock traces. so not more than 2 vias for each clock trace to take it through the critical layers.

* and each signal trace must be taken through vias to travel across the horizontal & vertical traces so i think an average number of vias required per signal trace cannot exceed 4 at worst.

* u ll be knowing the number of nets in ur board

* using a rule of thumb (i think it is kent's rule: refer black magic book- howard johnson,- ground planes and layer stacking chapter) the rule goes like this : u have four quadrants in ur board, the total number of traces that stay within is 50% and the traces that flow out of the quadrant is 50%...

* frm these u can group the traces length wise

* shorter traces take average count of 2 vias

* longer traces take average of 4 vias

* so with these u can calculate the number of vias

...i think im clear

 

[Alexj]

I agree with the "electron_boy" , see how many nets there, and consider the pcb size and the quantity of components.