The internet’s fastest speed was 56 kbps when it was first introduced. Only universities, a few private companies, and the government had access to ARPANET at the time—named after the Advanced Research Projects Agency (ARPA), a division of the Defense Department that sponsors cutting-edge research. Today, data flows across the internet at light speed.

Optical electronics play a significant role in high-speed communications, especially for aerospace systems. However, the utilization of high-speed PCBAs and electronics for defense, energy, automotive, semiconductor, industrial, and commercial applications is what enabled the development of advanced, data-dependent technologies such as 5G, IoT, and AI. The best of these boards are developed by designers and manufacturers who understand the importance of prioritizing the selection of PCB dielectric materials for high speed applications.

Why Are Dielectric Materials Important for High-Speed PCBAs?

Electronics manufacturers incorporate dielectric materials in components and devices to provide insulation, electrical storage, or current flow resistance. PCB material companies leverage these characteristics to construct board substrates and laminates. During PCBA development, engineers, board developers, and CMs seek the optimal arrangement of dielectric materials to maximize signal integrity or the fidelity of signal propagation along surface and internal layer traces.

There are several material properties, which are influenced by the type and thickness of the dielectric material, that can affect your RF signals, especially at high speeds. They include the following:

Important PCB Dielectric Material Properties for High Speed Applications

• Dielectric constant
  The dielectric constant defines the material impedance, or the ability to isolate positive electrical charges from negative ones and resist current flow.

• Dielectric loss
  Dielectric loss is the amount of electrical energy that is lost during signal propagation.

• Dissipation factor
  The dissipation factor is also a measurement of the amount of loss for periodic signals.

• Resistivity
  The surface resistivity defines the board's ability to resist current flow on the surface. Volume resistivity, which is susceptible to changes in temperature, is the board construction’s overall resistance to current flow.

• Electrical strength
  A board’s electrical strength, which is measured perpendicular to the external surface, defines its ability to resist electrical breakdown.

The parameters listed above provide a wealth of information to aid you in selecting the best dielectric materials that can meet your reliability and durability requirements for high-speed applications.

Choosing the Best PCB Dielectric Materials for High Speed Applications

Over the last few decades, the demand for smaller electronic products with greater capabilities has led to the proliferation of multilayer boards and SMT components. Consequently, the PCB stackup, which may consist of several to dozens of layers separated by a dielectric, is a more significant aspect of board design. In contrast to single or double-sided circuit boards where a single dielectric separates two conducting copper layers, stackups have multiple dielectrics that may have different physical characteristics. Therefore, multiple layers make determining the best dielectric materials for high-speed applications more complex.

To simplify dielectric selection, many engineers opt for fixed impedance where dielectrics in the stackup have a uniform impedance or dielectric constant. Both techniques are impedance control methods intended to manage signal integrity. When calculating your impedance control, it is important to employ impedance matching where the impedance of the signal source, trace, and load match enables maximum power transfer while concurrently mitigating electromagnetic interference.

After committing to a control method, select your dielectric material according to the guidelines outlined in the table below.

BEST DIELECTRIC MATERIAL ATTRIBUTES FOR HIGH-SPEED PCBAs
Parameter		Attribute
Dielectric constant		Remains constant over the frequency range of operation
Dielectric loss		As low as possible (lower than 0.02)
Dissipation factor		As low as possible (approaching 0.001 is a good value)
Surface resistivity		As high as possible (1010 Ω-cm is a good value)
Volume resistivity		As high as possible (1010 Ω-cm2 is a good value)
Electrical strength		As high as possible (approaching 1500 V/mil is a good value)