The Eurocircuits Buildup Wizard

The buildup wizard we have developed is one of the key instruments of our “smart menus”. You can choose from

over 700 Multilayer builds, accessed by number of layers, board thickness build and copper weight. If you can use

a pre-set build you get your offer faster, the boards are easier to build and so the price is lower.

Builds also include Blind and Buried vias.

Every Multilayer build-up is constructed out of Cores, Pre-pregs and Copper Foils.

You can think of a core as a double-sided PCB. It is a rigid piece of base laminate with copper pre-bonded onto

each side. If you go to the pre-defined build-ups for a 4 layer, you will see that the standard build has a core in

the centre containing the copper tracking/planes for layers 2 (= inner layer 1) & 3 (= inner layer 2).

On each side there are one or more sheets of pre-preg and then a sheet of copper foil. Pre-preg is glass fiber

cloth pre-(im)preg(nated) with uncured resin. The sheets of pre-preg and foil are bonded onto the core using heat

and pressure. This cures the resin in the pre-preg as well as bonding the whole build. The resulting “sandwich”

is then drilled and plated like a 2-sided board. For more information on the process see our page on

PCB Multi-layer Fabrication – Lay-up and Bond

We do not use depth-controlled laser drilling in our production to manufacture blind and buried vias. We use the

sequential buildup method. We first drill a core and then plate through the holes before we build and press the

stack. This process can be repeated several times. To keep the overview at a practical level and to keep costs

down, we have set forth some straightforward rules:

1. A via always has to cut through an even number of copper layers.

2. A via cannot end at the top side of a core

3. A via cannot start at the bottom side of a core

So on a standard 4-layer build, we can only drill buried vias between layers 2 & 3. If we do this, blind vias become

impossible. If you look at reversed build you will see that instead of a single core at the centre between layers 2

& 3, there are two cores on the outside of the board between layers 1 & 2 and 3 & 4. Now we can drill blind vias

between 1 & 2 and 4 & 4 but no buried vias as the dielectric between 2 & 3 is pre-preg which cannot be separately

drilled.

A special build follows the same procedures but with different thicknesses at higher prices.

Asymmetrical builds are not possible. The build must be the same on either side of the centre. The main reason is

to avoid bow and twist after pressing of the PCB.

Higher layer counts work in the same way.