At first glance, thick PCBs seem like the opposite of miniaturization. After all, from the history of electronics, we are used to PCBs becoming thinner, lighter and more finely structured over the decades. From the first hand-assembled PCBs, which were often several millimetres thick, to standardization to 3.2 mm in the industrial sector and extremely thin PCBs - the trend seemed clear: ever more compact, narrower, more delicate.
However, in many applications, thick PCBs make a decisive contribution to making systems more compact. The reason: significantly more functions can be integrated into a modern, thick multilayer PCB - instead of installing several individual boards with cables and connectors, a single, robust PCB is often sufficient. This saves space, reduces interfaces and increases reliability at the same time.
PCBs up to a thickness of 5 mm are available from KSG.
Advantages of thick printed circuit boards
- High current carrying capacityThicker copper layers enable the safe transmission of large currents and often save additional heat sinks due to better heat distribution.
- Mechanical stability: Thick circuit boards are robust against vibrations and loads - ideal for demanding environments.
- Functional integration: The power section, signal processing and control can be combined on a single circuit board, eliminating the need for cables and connectors.
- More compact systems: The integration of several functions creates a space-saving overall design that still provides high performance.
- Reliability: Fewer interfaces and the robust design result in greater reliability.
- Efficient heat dissipationImproved thermal management protects components and extends their service life.
- Sustainability: The longer service life and lower material wear make thick PCBs particularly efficient and resource-saving.
Challenges with thick printed circuit boards
- Design restrictions
Very small holes or extremely fine structures are more difficult to implement with very thick PCBs. This can cause restrictions in terms of track widths, drill diameters and number of layers. - Adjustments to the layout and coordination with the manufacturer must be taken into account when designing the printed circuit board.
- Effects on delivery time, availability and costs due to the complex processes and tight manufacturing tolerances (longer drill holes and thicker substrates, single-package processing and increased inspection effort to avoid delamination and cracks)
- Limited choice of suppliers: Not every manufacturer can produce thick PCBs
- Adapted assembly and soldering processes - Thick PCBs absorb more heat, which can affect reflow and wave soldering. Soldering profiles must be adapted, otherwise there is a risk of "cold solder joints".
Areas of use/applications
Telecommunications/data centers
- Backplanes in switches or servers:
In the past, many individual boards were required, connected via cables and plug-in modules.
Today, thick multilayer backplanes with 20+ layers replace this complex cabling.
The result: less space required in the rack, better signal quality, fewer sources of error.
Aerospace
Systems in airplanes or satellites must Vibration-resistant, reliable and space-saving be.
Thick PCBs often replace metal carriers or housing parts because they already provide the necessary stability - this reduces the overall height and saves weight - a critical advantage in the aerospace sector.
Medical technology
- Imaging systems (e.g. CT, MRT) or Laboratory equipment require high reliability with a compact design.
Thick multilayer printed circuit boards allow, Signal processing, power supply and control in a single board. This eliminates cable harnesses and additional circuit boards, which saves space and makes the devices smaller and lighter - important in an environment where ergonomics and transportability are crucial.
Automotive industry - E-mobility
- In power electronics such as on-board chargers or inverters, thick PCBs enable high currents to be conducted and thermal management to be integrated at the same time. Without thick PCBs, additional heat sinks and carriers would be necessary - which would cost more installation space. Thick PCBs therefore help to ensure that chargers, control units and sensor modules Smaller and lighter can be integrated into vehicles.
Only those who understand how the design, materials, layer structure and copper thicknesses interact can make the most of the advantages and correctly classify the challenges. The key features of thick PCBs that enable their high performance, stability and functionality are explained below.
Technical details
Materials
The choice of base materials is crucial for the performance of printed circuit boards. At the customer's request, we use materials in the medium and high Tg range. For high copper thicknesses on inner layers, materials with a higher resin content are preferably used. In general, all base materials approved by KSG can also be used for very thick PCBs; however, we do not recommend the use of unfilled low-Tg materials.
Number of layers
The realized layer structures vary from 2 to 20 layers. This flexibility makes it possible to realize high insulation and copper cross-sections, especially for high-layer backplane structures.
Copper thickness
The thickness of the copper has a significant influence on the current carrying capacity. A high platinum thickness enables the realization of high conductor cross-sections, whereby the copper thickness per layer is limited to a maximum of 400 µm. For a coil application with a platinum thickness of 5 mm, for example, 20 layers with a copper thickness of 105 µm can be realized.
Higher platinum thicknesses increase stability and bending stiffness, which is particularly important in the soldering process.
Tips for designers
- The Technical feasibility should be examined at an early stage.
- Drill holesKeep drill holes only as small as necessary. A maximum aspect ratio of 1:8 allows a minimum drilling diameter of 0.6 mm with a platinum thickness of 5 mm.
- Restring widths: Should be provided generously. If possible greater than 150 µm (depending on the number of layers and construction)
- Surface finishingChemical Ni/Au is recommended to increase the mechanical stability of the vias.
Trends, innovations & future prospects
The demand for thick PCBs is growing, especially in sectors such as e-mobility and Industry 4.0. New materials such as high-temperature resistant resins and special copper alloys and new processes could further revolutionize the production of thick PCBs.
The future of thick PCBs lies in their ability to adapt to the requirements of modern electronic systems. By combining high-current capability, advanced materials, automation and sustainability, they will play a key role in the development of efficient and high-performance electronic products. Companies that recognize and implement these trends early on will be able to offer innovative solutions to the challenges of the future.
Conclusion
Thick printed circuit boards initially appear to be the "opponents" of miniaturization, but are in fact its "opponents". Enabler - They reduce cabling, bundle functions, replace additional components and increase mechanical stability. This creates space for smaller, lighter and more powerful end devices in a wide range of industries. KSG is your reliable partner for PCBs with a final thickness of up to 5 mm.
Questions?
Do you have questions about thick PCBs or need support with the layout and development process?
Please feel free to contact the experienced experts at our Technical Support department.
