Multilayer PCBs with 1-48 layers

Of course, to our customers are all multilayer high-tech technologies available, such as blind vias, buried vias and staggered vias or back drill, just to name a few. Just by the ever faster clocking frequencies, the demand for impedance controlled multilayers raises: We also perform impedance checks for you and help you with the calculation of layer thicknesses and spacing.

Calculate and order your Multilayer PCBs right here on our website. Is an immediate price quote not possible, due to special technology, you typically get an individual offer on the same day. Any questions about Multilayer PCBs or on another topic? We are at your disposal. Contact us by email or call us directly. Your Multi-CB Team

Multilayer PCBs, or multilayers for short, are PCBs that have additional inner layers. In contrast to simple PCBs with only two outer layers, multilayers contain several internal layers that are separated from each other by dielectrics (insulating materials).

For example, a typical 4-layer multilayer PCB consists of a signal layer TOP, a ground layer (earthing layer), a power layer and a signal layer BOT. These layers enable more complex circuit designs and a higher packing density.

The development of multilayers began in the 1980s when the electronics industry was confronted with increasing demands on the packing density and performance of printed circuit boards. The increasing complexity of microchips and the need to transmit electrical signals without interference led to the introduction of multilayers.

By integrating additional layers, it was possible to avoid crossovers of traces by routing signals via plated-through holes (vias) between the layers. This innovation made it possible to develop more compact and efficient circuits that met the requirements of modern electronics.

Through-hole vias

Multilayer-Leiterplatten nutzen verschiedene Arten von Durchkontaktierungen, um die einzelnen Lagen elektrisch zu verbinden:

• Through-hole vias: Connect the top and bottom sides (TOP and BOTTOM), with the option of electrically connecting all layers in between.
• Blind vias: Connect an outer layer with a defined inner layer.
• Buried vias: Connect only inner layers with each other, without contact to the outer layers.

Dielectric and prepregs

The individual layers of a multilayer PCB are separated by dielectrics, which typically consist of FR4 (a glass fibre reinforced epoxy resin). These separating layers, also known as prepregs, are glass fabrics impregnated with resin, which are fused to the copper layers under high pressure and temperature during the manufacturing process

Electromagnetic compatibility (EMC)

A decisive advantage of multilayers is the possibility of laying ground layers and supply voltages in the inner layers. This improves electromagnetic compatibility (EMC) and reduces interference from electromagnetic interference (EMI).

Multilayer printed circuit boards consist of several layers of copper foils and thin laminates, which are separated by prepregs (glass fabrics impregnated with resin). The manufacturing process is complex and requires high precision, especially when blind vias (connections between an outer layer and an inner layer) or buried vias (connections exclusively between inner layers) are used. These special vias often require multiple pressings in order to achieve the desired layer structure.

The process comprises the following steps:

1. Layer structure: The individual layers are precisely aligned and stacked. In the case of multilayers with blind or buried vias, this step is carried out in several phases, as partial assemblies (subcomponents) must first be produced, which are later pressed into an overall structure.

2. Partial pressing: If blind or buried vias are required, partial assemblies in which the internal vias have already been created are pressed first. These partial assemblies are then combined in further steps to form a complete multilayer structure.

3. Final pressing: All sub-assemblies and additional layers are fused under high pressure and high temperature to form a solid unit. The prepregs provide the necessary insulation and adhesion between the layers.

4. Through-hole plating: After pressing, the through-hole vias are drilled and coated with copper to create the electrical connections between the layers. In the case of blind and buried vias, this step is carried out during partial pressing.

5. Finishing: Finally, the PCBs are cleaned, coated and provided with a protective layer to protect them from environmental influences.

The possibility of integrating blind and buried vias means that even more complex circuit designs can be realised, enabling a higher packing density and improved signal integrity. However, this increases the complexity of the manufacturing process, as several pressing operations and precise drill holes are required.

Multilayer PCBs are used in a wide range of industries, including:

• Telecommunications: For compact and powerful mobile devices.
• Automotive: For control units and electromobility.
• Industrial electronics: For precise control and regulation systems.
• Medical technology: For highly reliable devices with a small footprint.

The advantages of multilayers lie in their high packing density, improved signal integrity and lower susceptibility to interference. They also enable the realisation of complex circuits that would not be possible with simple PCBs.

The future of multilayer technology will not be determined solely by increasing the number of layers, as this leads to higher costs and a greater risk of rejects. Instead, the focus will be on optimising existing technologies and developing new materials and processes to further increase the performance, reliability and efficiency of multilayers.

An important trend is the miniaturisation and higher packing density of printed circuit boards. By using advanced manufacturing techniques such as laser through-hole plating and precise etching processes, ever finer conductor paths and smaller vias can be realised. This enables the production of printed circuit boards that offer higher performance despite their smaller size.

Another focus is on improving signal integrity and reducing signal losses. By using high-frequency materials and optimised layer structures, multilayer PCBs can also be used for demanding applications such as 5G communication, high-speed data transmission and high-frequency technology.

The integration of functions directly into the PCB is also becoming increasingly important. In addition to embedded technology (embedding components in the inner layers), passive components such as resistors, capacitors and inductors are increasingly being integrated directly into the PCB. This reduces space requirements and improves electrical performance.

Another forward-looking approach is the development of flexible and rigid-flexible multilayers. This combination of rigid and flexible areas enables innovative designs that can be used in demanding environments such as aerospace, medical technology or automotive electronics. Flexible multilayers also offer advantages in terms of weight reduction and space optimisation.

Finally, sustainability is playing an increasingly important role in the development of multilayers. The use of environmentally friendly materials and the introduction of recyclable printed circuit boards are important goals for reducing the ecological footprint of the electronics industry.

Multilayer PCBs have revolutionised the electronics industry and are now an integral part of modern devices. Their ability to realise complex circuits in the smallest of spaces makes them an indispensable component of advanced technologies. With the further development of materials and manufacturing processes, multilayer technology will continue to play a central role in electronics in the future.