Thickness of prepreg and core materials in PCB

[engr_joni_ee]

Hi, I have found prepreg thickness codes, some of them are pp-106 (2 mil), pp-1080 (3 mil), pp-2113(4 mil), and pp-2116 (4.7 mil).

Is it possible have two prepreg together to get thickness which is not possible with one prepreg, for example combing pp-106 and pp1080 to get 5 mil prepreg.

How about thickness codes of core materials. I don't find it. Do we also have codes to define thickness of core materials ?

 

[KlausST]

Hi,

best is you discuss this with your PCB manufacturer. They will telll all they can provide with benefits and drawbacks.
Not all PCB manufacturers work on the same level. Different skills, different machines different core material....different cost.

Klaus

 

[FvM]

Prepregs can be freely combined to achieve specific thickness. For laminate thickness you'll refer to manufacturer datasheets and product catalogs. See e.g. https://industrial.panasonic.com/ww...cuit-board-materials/halogen-free/hfreer1566s

Qualified PCB makers are providing information about used material and respecive datasheets on their internet sites.

 

[engr_joni_ee]

I still have some basic questions. How do we describe laminate in PCB stackup, is it prepreg or core ? Is the dielectric constant of a prepreg depend on it's thickness ? Is there any table with dielectric of different prepreg ?

 

[senilicus]

You can find this information in the datasheets of the manufacturer. Like in the picture.

 

[FvM]

How do we describe laminate in PCB stackup, is it prepreg or core?

The sequence of prepreg and core is requested by the stackup type. For a standard multilayer stackup without buried vias, all layers are laminated at once which requires a specfic core assignment. In case of doubt, refer to manufacturer reference stackups.

Reading manufacturer datasheets and stackup examples thoroughly, you'll realize that for a given material, e.g. standard FR4, the permittivity mainly depends on the resin content. High resin prepregs have lowest Er, core and low resin prepregs have highest Er. There are technical reasons to use high or low resin prepregs which should be discussed with the PCB manufacturer based on your design requirements.