The increasing complexity of electronic components and switches continually requires faster signal flow rates, and thus higher transmission frequencies. Because of short pulse rise times in electronic components, it has also become necessary for high frequency (HF) technology to view conductor widths as an electronic component.
Depending on various parameters, HF signals are reflected on circuit board, meaning that the impedance (dynamic resistance) varies with respect to the sending component. To prevent such capacitive effects, all parameters must be exactly specified, and implemented with the highest level of process control.
Critical for the impedances in high frequency circuit boards are principally the conductor trace geometry, the layer build-up, and the dielectric constant (er) of the materials used.
Design of HF circuit boards
Multi CB supports you starting immediately in the design phase. We help you to find appropriate substrates, dimensioning the conductor width and spacing, as well as with calculating the impedances.
The impedance defined by the customer is checked for manufacturability by our CAM station engineers. A calculation model is selected depending on the layer stackup, the circuit board layout, and the impedances requested by the customer. This results in possible modifications needed for the layer buildup, as well as necessary adjustments to the relevant trace geometries.
Materials used for HF circuit boards
For many applications, it is sufficient to use FR4 material with an appropriate layer buildup. In addition, we process high-frequency materials with improved dielectric properties. These have a very low loss factor, a low dielectric constant, and are primarily temperature and frequency independent.
Additional favourable properties are high glass transition temperature, an excellent thermal durability, and very low hydrophilic rate.
We use (among others) Rogers or PTFE materials (for example, Teflon from DuPont) for impedance controlled high frequency circuit boards. Sandwich buildups for material combinations are also possible.
