Controlled Impedance Routing

[prapan]

controlled impedance routing

Hi all ,
I have a doubt. With respect to below given stack up ,Can we implement Controlled impedance routing in the TOP LAYER?If No why? If yes is the normal formula
Z = 87/Sqr(εr+1.41) +ln(5.98h/0.8w+t)
t= thickness of cuppoer foil
w = width of trace
H - Height of dielectric

work? Also what will be h?

Stack Up:

Top Layer -------------------------------
Signal Layer -------------------------------
GND Layer -------------------------------
''
''
Bottom Layer ---------------------------------

 

[FvM]

what will be h?

You should search the answer where you got the formula. Without knowing the unit definition, no one can verify it.

Generally, the top layer impedances strongly depends on the structures present in the below signal layer. At best, you get impedances in a certain range. Or you have to assure, that the signal layer is either empty or flooded below the trace of interest.

 

[prapan]

I was also thinkng about the unit ..does anyone have idea regarding the units fo this formula?
Also Stripline Config
Can the two layers sandwiching the trace layer be of different materials?I mean different dielectric.
Do we normally have stacks with different dielectric between layers.?

 

[prabhakar08]

er is dielectric matrl.
this formula is for strip line