what is Prepreg and Core ?

[madhu.b]

Hello Everyone,

I would like to know each and every question which I have mentioned below,

Prepreg:

1) What is Prepreg ?
2) Why it is using in the multi layer boards ?
3) What is the purpose to use ?
4) In which layer we suppose to use in the multi layer boards ?

Core:
1) What is Core ?
2) Why it is using in the multi layer boards ?
3) What is the purpose to use ?
4) In which layer we suppose to use in multi layer boards ?

In some other posts they mentioned that in 6 layer PCB's, it has 2 cores and 4 prepregs. So, why should use these combination and why not other combination ?


Please can you answer me clearly as soon as possible.

 

[shaiko]

Prepreg is glass fabric impregnated in adhesive resin.
Core is a material used between layers of prepreg.
Using the 2 interchangeably creates a multiplayer composite laminate.

Maybe you'll find this interesting:
https://www.youtube.com/watch?v=w27u-Nw0iss

 

[Ahou]

Multi-layer PCBs are made up by two or more PCBs which are stacked together with reliable predefined mutual connection between them. The space between each layer of the board can be either core or prepreg. Cores are made up of a copper-plated glass-reinforced epoxy laminate sheets. Prepreg (also known as PP) is primarily composed of resin and strengthening material that is then classified into glass-fiber cloth, paper base, compound material etc. Its main function is to stack all layers into a whole board by high temperature stack-up.

The position of Prepreg & Core in multi-layer PCBs depend on your boards' total layer number, attached is PCBCart's standard PCB Layer stackup for 4-layer PCB & 6-layer PCB. (please kindly noted the PCB Layer stack-up varies from one fabricator to another fabricator.)


Actually, the pattern and thickness of each type of core & prepreg are't always stable and some adjustments will possibly be made to meet specific board thickness requirement. When making decision, factors including thickness of inner layer, product design thickness requirement or technique requirement, prepreg type, practical performance and the actual thickness after stack-up trial should be taken into consideration.

 

[Mattylad]

Also watch https://www.youtube.com/watch?v=sIV0icM_Ujo&t=33s