What is Prepeg In PCB Design ?

[vikasveshan]

Hi all ,

i want to know what actually Prepeg is ?
Is it dielectric material used between layers for PCB board manufacturing .
and if Yes then :-

While Designing Impedence Controlled multi layer PCBs ,what Prepeg Height should be considered for Zo calculation .?

Is it Height between Layers of PCB or total Height of Dielectric used .?

Pls Guide me .

Thanks & Regards !!
V V

 

[senilicus]

https://www.edaboard.com/threads/107407/

 

[marce]

The only way to get accurate impedance figure is to talk to your PCB manufacturer. The problem with pre-preg thickness is during pressing some of the resin will fill the gaps in the etching below, reducing the gap between layers. So depending on how much copper is on the adjacent layers, determines the final layer thickness (also what prepreg thickness and glass weave is used, 1080,2116, 7628 etc).
On high speed boards I get figures from the manufacturer, and feed these back into my CAD system.

 

[info_req]

core is the basic dielectric or insulator material. You can say that insulator between a double layer PCB is core material. Prepreg is sandiched btween middle layers of a multilyer PCB. it has sheets of much smaller thickness such as 50 micron. core material has more thickness as 1mm. However, bth are insulation material used for conductive layers separation.

It may help you?

 

[marce]

Core and pre-preg are the same material, cores can be as thin as 0.1mm for FR4 boards.
A core is a prepreg with copper boned to either side of it forming effectively a 2 layer board.
For Si and Impedance calculations FR4 relative permitivity is approx 4.5, this applies for both cores and prepregs when using FR4.
The attached shows the different methods of doing multilayer boards Core vs Foil construction.
https://pcbtalk.com/data/upload/Designing_Balanced_PCBs.pdf

 

[vikasveshan]

Thanks for the information guys !!

Also
What is the Dielectric constant for following prepeg Material :-

a) Type 1080 , 0.08 mm
b) Type 7628 , 0.22 mm
c) Type 2116 , 0.13 mm


If possible also share the reference for the same !!


Thanks & Regards !!

V V

 

[marce]

Hi, I've answered your e-mail.
For most requirements I would use a figure of 4.5 for all the above prepregs and thicknesses for FR4.
Marc

 

[jalnaghar]

hello
help me for subject the antennas in package for 2.4 GHZ

mi problem is design example for antenna 5*5 multilayer or in package at 2.4

GHz because using this antenna in SiP (System in package).

wat the technologies using for resolution the problem?

tank you