More Than Moore: Lux Semiconductors’ System-on-Foil Shrinks Circuits

March 28, 2023 by Aaron Carman

System-on-Foil may sustain semiconductor growth after the sun sets on Moore’s law.

In an effort to achieve “More than Moore,” Lux Semiconductors has secured seed funding for a new semiconductor process that better integrates silicon chips and their host boards by directly connecting the bare die to a thin interconnect foil. This technology, dubbed “System-on-Foil” (SoF), offers numerous advantages compared to traditional printed circuit board (PCB) approaches, earning Lux the support of the U.S. Air Force, U.S. Space Force, Lockheed Ventures, and many others.


Lux Semiconductor’s SoF technology

Lux Semiconductors' SoF technology allows bare die chips to be directly connected to the metal substrate, providing high-speed interconnects and denser integration. Image used courtesy of Lux Semiconductors


Electronics industry giant Gordon Moore sadly passed away last Friday. His famous Moore’s Law, while remaining true for many years, is running out of steam. As we reach the lower limit for transistor sizes, developers search for new techniques to sustain the momentum for the Internet of Things (IoT), smart wearables, and augmented/virtual reality (AR/VR).

Instead of focusing on transistors to continue semiconductor growth, Lux Semiconductors is instead focusing on packaging to effectively miniaturize circuits. This article takes a look at Lux’s SoF technology to understand how it works and why it’s poised to provide a powerful new perspective on large-scale integration.


Get Closer to the Board

In a conventional PCB approach, chip-level designs are packaged and bonded to a circuit board to provide an electrical connection between the required terminals. Designers can take several different approaches for their specific system, but two common ones are System-on-Chip (SoC) and System-in-Package (SiP).

Both SoC and SiP approaches require that the bare-die silicon be bound to its own package before it can interface with the rest of the board. This approach, while sufficient for low-density, low-frequency, and low-power designs, tends to break down for systems where better performance is required. This is why cutting-edge devices such as the Grace Hopper super chip tend to emphasize interconnects in addition to pure silicon performance.


SoF technology allows chip-level integration

SoF technology allows chip-level integration in a smaller form factor and with improved performance compared to conventional PCB approaches. Image used courtesy of Lux Semiconductors


In order to remedy the packaging requirement, Lux Semiconductors removes the need for a dedicated package altogether. By placing the bare-die silicon directly on the metal substrate, high-speed interconnects can be formed in a much smaller overall size, making chip-level integration simpler and more reliable.


A New Frontier for System-on-Foil

While the eventual benefits of SoF technology will likely be felt in all fields of engineering, Lux Semiconductors has already zeroed in on some target applications for its first generation of SoF devices. One of these applications is smart fabrics and wearables, where the flexibility of devices is crucial. In addition to the electrical benefits of SoF, the process also produces flexible devices, giving designers more freedom when integrating SoF into their own projects.


The relative neutron flux versus altitude

The relative neutron flux versus altitude highlights the radiation problem for satellites and helps to illustrate the need for smaller and more hardened devices. Image used courtesy of NASA


Another target application for SoF technology is Low Earth Orbit (LEO) satellites. As the demand for satellites grows, so too does the demand for full autonomy. However, complete autonomy requires a level of integration that, while achievable, increases the size of the satellite’s electronics immensely. Coupled with the need for heavy radiation shielding, this can quickly make autonomous spacecraft prohibitively expensive to launch. 

While SoF technology doesn't inherently offer any outstanding resilience to radiation, it does offer a new technique for miniaturizing electronics. As such, SoF is an attractive candidate for the next generation of LEO satellites because it can shrink the size of the payload and the cost of launching the satellite.


A Future Beyond Moore’s Law

As the sun sets on Moore’s law, designers may wonder what will happen once we reach the smallest transistor possible. While it may no longer be possible to shrink the transistor, it is still certainly possible to find weaknesses in the status quo and develop a solution, as is highlighted by Lux Semiconductors' System-on-Foil technology.

A PCB manufacturing technique that takes notes from silicon processes will allow for denser PCBs—something that is beneficial to all engineers. Lux Semiconductors' technology indicates the possibility of innovation outside Moore’s law, even if developers are stuck with the same transistor density.