In the beginning Iwant to say that then you are designing multilayer PCB there are a lot ofissues that can’t be described in one article. In this first article I want totell you a little bit about stackup designing and calculating as a base ofevery multilayer PCB. multilayer PCB It is not a problem to make a 4 or 6layer multilayer PCB 1.6 mm thick, because you can use various type of pre pregand cores. In the 1.6mm multilayer PCB you have a lot of space even for 8layers.

8 layers, 35um each = 280 um, + 40 um forsolder mask on Top and Bottom = 320.

So if we take awaya copper and solder mask from a pcb thickness we will get a space that need tobe filled with dielectric.

1600 – 320 = 1280 um

Now in the 8 layermultilayer PCB we have a 7 dielectric between a copper layers

1280/7 = 180 um

Approximately youwill have a 180 um space for each pre preg, multilayer PCB so themanufacturer has some room to pick a pre preg and core that he has in stock.

The problems beginif you need to place a 14 or even 16 layers into a 1.6mm multilayerPCB with impedance controlled high-speed signals. The problem is thatwe need to use a very thin pre pregs and not every manufacturer has them or canuse them. When you need to make this type of multilayer PCB you always need todiscuss your stuck up with your manufacturer, multilayer PCB becauseyou can make a design that can’t be produced or will be way too expensive foryour customer. In the conclusion I want to give you a couple of advice that mayhelp you in your work:

·        Before start calculating stackup look at the powers ofyour manufacturer, what materials he has, what pre pregs, what cores etc.

·        If you don’t has a specified manufacturer look at acouple average manufacturers, but not the most powerful, because it willprobably be more expansive.

·        When you calculated your stackup always send it to amanufacturer to check if they can produce it.