Solid-state switches and electromechanical relays help manage power in everything with an electrical current. Despite their ubiquity, traditional switches and relays have major shortcomings including energy loss, cost, weight, size, performance, and reliability. These inherent limitations compromise the ability to design and deploy next-generation 5G networks and the electrification of everything – the rapid transition to electric vehicles, sustainable energy sources and a smarter electric grid.
Menlo Micro has overcome the limitations of solid-state switches and mechanical relays with a micromechanical switch design that leverages Corning HPFS Fused Silica glass (HPFS) materials and copper-filled through-glass-via (TGV) technology. This case study presents how Menlo Micro collaborated with Corning’s Precision Glass Solutions to create switch products based on Corning’s HPFS glass. The resulting Ideal Switch products can operate up to 1000x faster than mechanical relays, can operate longer lifetime, can handle kilowatts of power, and are built in a microstructure smaller than a human hair, enabling the creation of micromechanical switches that can operate for decades under high-stress conditions.
A new type of relay
Technology is taking giant leaps forward as the IoT, artificial intelligence, 5G connectivity and the electrification of everything are changing how we connect, share information, and understand and control the world around us. To make this leap forward, we need to design and build microelectronics in new and disruptive ways.
A case in point: We need next-generation switches and relays that are faster, smaller, and more resilient and energy efficient than traditional solid-state and electromechanical devices. Solid-state switches are based on CMOS process technology that most integrated circuits (ICs) are manufactured on silicon wafers. However, because silicon is a semiconductor material (i.e., a partial conductor), it’s not very efficient and subject to leakage, resulting in considerable energy loss and heat dissipation. While microelectronics engineers can push isolation performance in CMOS to higher levels, they eventually run into fundamental physics issues. There are limits to what can be achieved with silicon wafers to optimize energy efficiency and minimize leakage. And with more advanced technologies and applications, like 5G New Radio, these limitations will become even more pronounced. The problem with electromechanical switches comes down to the need to reduce size, weight, power, and cost (SWaP-C). These reductions will be fundamental for decreasing energy consumption and accelerating the transition to next-generation 5G infrastructure, medical technology, and electric vehicles. An important key to solving these challenges lie with innovations in materials science and a commonly available material: glass.
Glass is an insulator; ideal material as a dielectric substrate for switch to replace high-resistivity silicon (HR-Si) wafers. Glass has a resistivity several orders of magnitude higher than HR-Si, which means electricity cannot pass through it and no energy is lost. Corning’s collaboration with Menlo Micro is expanding the possibilities of what can be achieved with glass wafers.
Corning and Menlo Micro collaboration
(Image source: Menlo Micro)
Corning and Menlo Micro share an historic connection with one of the greatest inventors of all time, Thomas Edison, the so-called “Wizard of Menlo Park.” Menlo Micro was born out of a decade-long research effort at Edison-founded General Electric (GE). Both Corning and Menlo Micro are focused on reinventing something that Edison pioneered in the 1800s: the mechanical relay.
A relay is an electrically operated switch used to control, power, and protect anything that operates with an electrical current. Switches are critical components in nearly every electrical device we use today. There are two traditional types of switches and relays – electromechanical and solid-state – and both have major shortcomings. Electromechanical switches can handle high levels of power, but they are large, slow, clunky, and notoriously unreliable. While solid-state switches are small, fast, and reliable, they leak power and generate heat because, as semiconductor devices, they are never fully “off.”
Engineers have been trying to overcome these shortcomings for decades, but the end result has been a series of compromises rather than a near-perfect solution to the fundamental challenges posed by solid-state switches and mechanical relays.
Menlo Micro has engineered a micromechanical switch technology that solves the major problems associated with existing switches and relays. Menlo Micro switches are smaller, lighter, faster, more efficient, better able to handle high power, and have longer operating lifetimes than electromechanical relays. They are also more RF-friendly (providing higher linearity) than solid-state switches. This new switch technology can be applied to a wide range of applications, from medical devices and communications infrastructure to aerospace and consumer electronics.
Menlo Micro was able to solve the switch challenge, in part, because of its technology collaboration with Corning. The Menlo Micro switch is built on highly pure silica glass from Corning, which enables a smaller, more energy-efficient switch design. Menlo Micro also added another layer of glass on top of the switch containing tiny copper-filled holes known as through-glass-vias (TGVs), which are designed to route current to and from the switch. Transmitting the signal through glass shrinks the distance electricity must travel by 70%, reducing the size and cost of the relay and boosting electrical performance.
The founders of Menlo Micro began their research and development work with Corning when they were still GE employees. The team spent years developing a glass process from the ground up. With more than $40 million in support from GE and more than 12 years of R&D, the Menlo Micro team developed a technology that would ultimately lead them to a solution to today’s electronic switch. Their experiences at GE sparked a new way of thinking, resulting in a new category of switches with the capacity to cost-effectively scale micromechanical switch manufacturing.
Menlo Micro’s collaboration with Corning’s Precision Glass Solutions played a key role in the new switch design; Corning’s Precision Glass Solutions division is a manufacturer of high purity fused silica glass wafers. The inherent properties of glass –excellent electrical performance, tight geometrical tolerances, and pristine surface quality – make it a suitable material for next-generation microelectronics devices.
The Corning/Menlo Micro team started their collaboration with Corning HPFS Fused Silica glass, which is 99.999% pure silica (silicon dioxide) and provides consistent, repeatable performance. For the base layer, Corning processed the HPFS glass into 8-inch wafers that are half a millimeter thick. For the TGV layer, Corning processed a thinner wafer and used lasers to drill 100,000 holes, each half the width of a human hair, and all without cracking the glass and finally filling these holes with copper for passing electricity through the glass. The resulting small-footprint device measures 5.6 cubic mm in size. This Menlo Micro switch offers the power handling and RF performance of an electromechanical relay with the size, weight, reliability, and speed of a solid-state switch.
Corning and Menlo Micro demonstrated the integration of TGV packaging technology, which enabled the development of high-performance RF and power products to ultra-small wafer scale packaging. TGV enables Menlo Micro to shrink the size of its relay products by more than 60% compared to traditional wire bond packaging technologies, making it suitable for applications where increased channel density and SWaP-C reductions are critical.
In addition to significant size reduction, TGV technology brings other benefits to relay products. By eliminating wire bonds and replacing them with short, well-controlled metallized vias, Menlo Micro was able to reduce package parasitics by more than 75%. This design supports higher frequencies, which are becoming increasingly important in 5G networks, test instrumentation, and numerous aerospace and defense applications. Additionally, the unique properties of glass versus traditional substrate materials like silicon (CMOS) enable lower RF losses and higher linearity, which translates into lower power consumption and higher overall efficiency.
Implementing TGV technology in hermetically sealed glass eliminates the unnecessary interconnects that have limited switch and relay performance for decades. This approach also enhances switch performance and reduces overall device size and cost to levels that will benefit many applications.
Menlo Micro and Corning are currently working together to ramp production of the switches while making them more cost-effective to manufacture. Corning has received interest from other companies seeking to take advantage of TGV technology for applications such as glass packaging and bezel-less high-end displays. Corning has also developed a proprietary via design and process to provide hermetic, copper interconnects that enable high reliability and reduced package size, opening a path for mass production of TGV-enabled devices.
Using proprietary materials, designs and wafer-level processing techniques, Menlo Micro’s switch technology has demonstrated high reliability in applications typically exceeding 10 billion switching operations with a roadmap to exceed 20 billion, all while handling hundreds of volts and tens of amps of current. This development in advanced materials science has resulted in unprecedented power handling (kilowatts) in a micromechanical device with excellent electrical performance, size, cost, and reliability compared to traditional electromechanical relays and solid-state switches.
Leveraging TGV packaging, Menlo is developing RF relay products handling bandwidths from DC-26 GHz, with a roadmap to extend beyond 50 GHz. Menlo Micro’s micromechanical relay platform enables RF and AC/DC applications for diverse markets such as battery management, home automation, electric vehicles, military, and professional radios, 5G base stations and the IoT.
Menlo Micro has been shipping products based on its switch technology from its 8-inch high-volume production line since October 2020, delivering to more than 60 lead customers to date. Unlike traditional electromechanical relays, which are built one at a time on assembly lines, thousands of Menlo Micro switch devices can be manufactured at one time in a batch process. Menlo Micro uses the same manufacturing approach leveraged by the semiconductor industry: wafer-based fabrication. This entirely automated batch process enables massively scalable switch manufacturing.
Over its 170-year history, Corning has developed many types of glass products that now have broad application in our daily lives, from the creation of the first lightbulbs to the proliferation of advanced glass materials used in smartphone screens and fiber optic cables. Corning has teamed up with Menlo Micro to rethink the traditional electromechanical relay and solid-state switch. Together, they are making tiny, energy-efficient micromechanical switches manufactured with high-purity glass a practical reality for the next-generation technologies that will enable the electrification of everything.
— Chris Giovanniello is the co-founder and SVP of Worldwide Marketing at Menlo Micro.
Menlo Micro was featured as one of EE Times top 100 emerging startups to watch, now in its 21 st edition.
The Silicon 100 is a list of electronics and semiconductor startups that grabbed our attention during the preceding year.
>> This article was originally published on our sister site, EE Times Europe.
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