Technical Information

Multilayer build-up types

Multilayer build-up system

Apart from the number of layers and the final thickness the build-up of a multilayer also determines the electrical properties of the multilayer board in terms of electric strength, thermal dimensional stability, dielectric constant and electromagnetic compatibility (EMC).

Standard multilayer materials:
As a standard, the following material thicknesses (excluding copper) are used to manufacture the inner layers which represent the core of the multilayer:

0,10mm

0,15mm

0,20mm

0,36mm

0,51mm

0,76mm

0,96mm

1,20mm

Some base material, board thickness and copper thickness combinations are not available directly ex stock.

These materials have a thickness tolerance of +10%. With increasing thickness of the material the dimensional stability of the core and thus of the complete ML board also increases.

Prepreg material types:
Prepreg materials are used with three different types of weave and thus three different final thicknesses.

Prepreg type 1080:	final thickness 70µ	+10%
Prepreg type 2116:	final thickness 130µ	+10%
Prepreg type 7628:	final thickness 180µ	+10%

With increasing prepreg thickness the dimensional stability of the weave increases. With decreasing prepreg thickness the resin content increases. With increasing copper thickness of the internal layers more prepregs or prepregs with a higher resin content are required to fill the areas where the copper has been etched away.

Multilayer without customer-specified build-up:
If the customer does not define a specific build-up the multilayer build-up will be designed by Richter Elektronik, based on manufacturing experience and material availability. Information about the chosen build-up is available on request. The build-up may be changed as a consequence of technological advancements.

Multilayer with customer-specified build-up:
If the customer defines a specific multilayer build-up Richter Elektronik will verify this build-up in terms of manufacturability and availability of materials. It is recommended that the ML build-up and the availability be agreed in advance, particularly in conjunction with impedance and EMC issues. If the verification succeeds the build-up specified by the customer will be implemented. If the verification fails Richter Elektronik will submit an alternative suggestion which will be implemented subject to the customer’s approval. This build-up definition shall be maintained until cancelled for all future follow-up orders for the production of this type of multilayer board.

Copper pattern:
The copper pattern is generated by a series of photographic, plating and etching process steps. Changes in the pattern caused by undercutting result in narrower track widths and reduced annular ring geometries. These losses depend on the thickness of the base copper and have to be accepted to a certain extent.