Ideas and Innovation Blog

Low-Loss Materials Key for High-Frequency Applications

By Nashay Naeve

Global Product Marketing Manager, DuPont Electronics & Imaging

November 24, 2020

The ultra-connected future is here, making our everyday lives easier, as our homes, cars, cities and virtually everything in our environment becomes “smart.” Enabling this interconnectedness are several high-frequency applications whose increased need for faster data rates – and the necessity to minimize noise – has driven a rise in demand for materials that help prevent signal loss. What is considered high frequency depends on the application, but in general, the higher the data rate, the greater the risk of signal loss.

When selecting materials for device fabrication that help to minimize signal loss for these markets, two key properties come into play. The first, dissipation factor (DF), is a measure of the energy loss-rate of the electrical oscillation in the system. The second is the dielectric constant (Dk), an expression of the extent to which a material concentrates electric flux. Generally, substances with high dielectric constants break down more easily when subjected to intense electric fields than do materials with low dielectric constants. Thus, low-k, low-DF substrates are the best choices for “fast” materials that enable the lowest possible signal loss for high-frequency applications.

The three primary macro-drivers behind the growing need for low-loss materials are: the Internet of Things, particularly wearables and 5G handsets (which also represents the most immediate opportunity for a materials provider like DuPont); autonomous vehicles; and the 5G infrastructure that underpins all these devices, enabling them to reliably connect and communicate with one another. Semiconductor devices used in these markets are transmitting data at very high frequencies, creating a need by designers and OEM specifiers for low-loss materials that help to minimize noise in the system.

DuPont has developed a portfolio of laminate substrate materials designed to meet low-loss requirements. Laminates provide the backbone for increasingly complex circuits built on both rigid and flexible substrates. They provide mechanical integrity to flex circuits while allowing designers the freedom to fit circuits into the available footprint. All the materials in multilayer flex laminates must be chosen for their ability to combine mechanical flexibility with sufficient electrical performance – which is vital for each of these key markets.

Internet of Things/5G

5G is the next generation of mobile technology, focusing on higher frequencies than the current 4G network. With 5G (and 6G, on the horizon), the key requirements are to offer higher speeds and lower latency, i.e., the amount of time it takes for a set of data to be transmitted from point A to point B. Noise in the system can negatively impact latency, so low loss is extremely important. The 2.4GHz band (4G) has a total bandwidth of 60MHz, while the 5GHz band (5G) adds another 500MHz of bandwidth and the 6GHz band (6G) band will bring added channels and a substantial extension of 1200MHz in usable bandwidth. All this bandwidth will mean more users and even more demand for low signal loss.

The key material challenges in this market include losses at the interface; copper type and smoothness can affect loss as well. The flexibility of our materials provides a huge advantage – they can be bent to accommodate small spaces, enabling them to provide space and weight savings. Their low loss performance and reliability make them ideally suited for this space. A prime example is antennas in mobile phones – a key customer has specified our materials for this application, ensuring they’re already in place for new and soon-to-come 5G phones.

Autonomous Vehicles

Key applications for DuPont’s offerings within this space are automotive radar and automated driver-assistance systems (ADAS). In particular, several customers are already using our materials for radar, operating at the 77GHz level. Typically, low loss becomes a challenge above 10GHz, creating the need for new materials. For safety systems, the substrate of choice is polytetrafluoroethylene (PTFE) reinforced with glass fibers, with additional copper cladding for some applications. Crash avoidance systems that rely upon radar require high-frequency printed circuit boards (PCBs)--and PFTE meets this need.

Copper-clad laminates (CCL) for automotive use have some especially stringent requirements. It is important for such PCBs to avoid conductive anodic filaments, as defects in the dielectric can lead to shorts between the CCL and conductive traces. All these properties lead to a PCB that will be reliable and dimensionally stable in the automotive environment. This stability is particularly critical, given the mission-critical nature of these applications.

5G Infrastructure

As mentioned earlier, high-frequency, 5G radio-wave communication will enable faster data downloads for end users along with quick response times. The high-frequency signals result in significant transmission loss, require higher power and more efficient power supply, and generate more heat. The higher frequencies required to enable the 5G infrastructure result in shorter wavelengths, mean that the signals, while higher-energy, can’t travel as far. The multi-gigahertz transmission frequency of 5G limits the effective wireless transmission distance to a few thousand feet. Low-loss materials are needed not only for PCBs but also for the advanced packaging technology used to house the interconnects that help to power the infrastructure.

As the table below describes, the DuPont™ Pyralux® flexible circuit materials product line was developed specifically for high-frequency applications in each of these market segments. This includes not only flexible laminates, but also performance-compatible products such as films and adhesives.

To learn more about our offering of low-loss materials and how DuPont can help meet your needs for high-frequency applications, visit https://www.dupont.com/electronics-industrial/contact-us.html, or contact your DuPont sales representative.