what exactly dielectric thickness in 4layer stackup means?

[ssankurathri]

hi
am just messed up with terminology prepreg, core, dielectric thickness in the stackup...
could anyone plz provide some reference (preferrably pictorial view) for 4layer board.

regards
skr

 

[mh123sh]

Re: what exactly dielectric thickness in 4layer stackup mean

Core : a laminate with both sides coated with copper (copper thickness 0.5oz, 1z..)
Prepreg: only dielectric material.

Prepregs are used stack the cores together.
Cores are used to form the inner layers

typical 1.6mm (63mil) 4 layer stackup
GND,POWER is 1oz (1.3mil) copper

TOP -------------------------signal 1
PREPREG (10mil)
------------------------------GND
CORE(40mil)
------------------------------POWER
PREPREG (10mil)
BOT -------------------------signal2

Hope this will help you to undersatnd.

 

[ssankurathri]

Re: what exactly dielectric thickness in 4layer stackup mean

thanks...that was really helpful....
just a quick one...can the core be also treated as a dielectric? i read it somewhere that core is nothing but prepreg mixed up with some resin an will be dielectric in nature.

 

[nathan80]

Re: what exactly dielectric thickness in 4layer stackup mean

the core layer has copper traces on the top and bottom to form the inner layers.

core is definately a dielectric; otherwise power plane and gnd will be shorted.

 

[venkat_kvr]

Re: what exactly dielectric thickness in 4layer stackup mean

hi
am just messed up with terminology prepreg, core, dielectric thickness in the stackup...
could anyone plz provide some reference (preferrably pictorial view) for 4layer board.

regards
skr

this will help u

 

[maniana]

Re: what exactly dielectric thickness in 4layer stackup mean

Hi,

I also wanted to ask a question about core/prepreg stuff.
If I design a several layer PCB can I define the stack in whatever way I want?
I mean, is the order:
top-prepreg-mid1-core-mid2-prepreg-bottom
equivalent to:
top-core-mid1-prepreg-mid2-core-bottom ?

Can the controlled impedance tracks be made between the copper layers with core material inside only or can they be also made between the layers with prepreg in between as well?

Is the Er of prepreg the same as Er of core ? assuming FR4 material.

Thanks,
Przemek

 

[buenos]

hello,
check this:

Accurate Impedance Control, Printed Circuit Design and Fabrication Magazine November 2009

Part-1: **broken link removed** page-20.

Part-2: http://www.publish-it-online.com/publication/?i=32550 page-30.