The newly formed company will expand General Electric’s unique Digital-Micro-Switch (DMS) platform to broader markets across multiple industries. The novel MEMS-based high power handling switch technology has been in the R&D stage for the last 12 years at GE who has been using it in its MRI systems for two years now.
eeNews Europe caught up with Menlo Micro’s CEO, Russ Garcia so he would share the story behind that launch. What MEMS technology are we looking at and why couldn’t GE keep this in house?
Garcia unfolded the story “Mechanical switches have been around for a long time, they can handle quite a lot of power, hundreds of volts and tens of amps. But they are bulky and expensive. SiC solid state switches have their own set of issues, they draw a lot of current and heat dissipation is also problem. GE being a power company, it uses a lot of power switches. About ten to twelve years ago, well before industrial IoT was popular, the company had a vision. What if we could make remotely programmable circuit breakers? “
“GE started looking for a source of commercially available remotely programmable circuit breakers but it couldn’t find any. It characterized all the MEMS switches available at the time but the reliability wasn’t there. Basically, GE’s engineers determined the failure mechanisms of the MEMS switches, the material fatigue, the stiction, and they figured out they had to solve the problem themselves. GE pooled its resources in house, the metallurgists from making fins for turbine engines and semiconductor physicists, it needed high power with RF performance and billions of switching events”, continued Garcia.
“The result was a new material solution that solved the reliability issue and could switch high power with a very low ‘on’ resistance and very low losses. They developed the technology from scratch, and tens of thousands of pieces were shipped inside GE. The first application was a PIN diode replacement in a MRI coil, handling hundreds of watts”, Garcia told eeNews Europe.
“But remember that originally, GE was looking for an external supplier, because the company is not a components supplier, it is a systems supplier. By spinning out a dedicated company, it wants the technology to be scaled to many other applications and benefit from the unit cost reduction when the switch will be produced in large volumes”.
But why couldn’t other MEMS players tune their materials and deliver this solution? We asked.
“The primary issue in MEMS is holding to the materials available in the fab you are going to. In the case of contact switches, they use pure metals. We’ve developed materials that you would not find in typical fabs”.
All Menlo Micro’s MEMS power switches rely on the same fixed unit cell, a micrometre-sized cantilever beam with an electrostatic actuation that establish a ohmic contact at its tip. A single switch only needs a few pA to function. By combining hundreds of such cells in series or in parallel, the startup can change the voltage or the current handling capability of its devices. The technology is scalable from milliwatts to kilowatts, has been rated to tens of billions of cycles and a given design layout requires less than a dozen mask layers, according to Menlo Micro’s literature.
“The MEMS can be built at a substantially lower cost than solid state switches and many product variants can be designed very quickly while always retaining the unit cell’s proven reliability”, explains Garcia.
“We’ve designed several cantilevers but for now we’ve only retained one because we got so close to an ideal switch. Putting them in series or in parallel is much more robust than figuring out another cantilever design. A unit cell is for us like a transistor for a given processor node, our next cantilever design will be like the next transistor node”, the CEO said, envisaging further technology refinement as the company grows.
Garcia explains that because the ‘on’ resistance is so low, the switches don’t require a heat-sink, making the end power solution more compact. He admits that if you need to switch in nanoseconds, then solid state switches are still a winner, but anything that needs switching power in microseconds could be competitively served by the MEMS switches.
Could you give us a practical example where these MEMS switches would displace incumbent solid state devices and how the final product would compare? eeNews Europe asked.
“A high power filter we had was using GaAs PIN diodes for the switches. It was a 2W UHF filter. With our MEMS, we reduced the component count from approximately 200 parts to 25 parts, we reduced the board size by 75% and power dissipation was reduced by an order of magnitude, from 1W to 100mW”, revealed Garcia.
“There were 40 or 50 PIN diodes plus support electronics, we replaced that with 6 MEMS devices. Several of our customers are designing this into high power filters. Because they are electrostatic devices, once they are ‘on’, there is no dissipation. In comparison, you have to draw current to keep GaAs or SiC devices ‘on’. The ‘on’ resistance will always be better for contact switches”, added the CEO, mentioning that Menlo Micro had developed a demonstrator relay handling 240V and 10 or 25A, with only tens of mOhms of ‘on’ resistance, all on a few square millimetres.
“GE was our first product customer, it has been using our MEMS switches in its MRI systems for the last two years. Menlo Micro has raised the money for product proliferation. We need to figure out the die size and the different combinations, so that we won’t be just selling a switch but subsystems and multi-channel switches”, Garcia said about the initial round of funding.
“We are still scaling up. We’ll have revenue this year but we’ll be moving to a commercial fab over the next two years (for now, the MEMS are produced at GE’s small fab) and we still have a lot of product development activity to finance. Our break-even target is about 30 months from now. GE continues investing in the company, it is our partner for advanced R&D on MEMS technology. Many startups don’t have a big brother like GE to support their R&D” Garcia continued.
“We use glass wafers, because of the isolation performance in RF, hence the interest from Corning as an investor”, the CEO concluded.
The startup will set it sight on high value applications including DC, AC and RF products, covering such diverse markets as battery management, home-automation, electric vehicles, medical instrumentation, and wireless base stations. Its first official product is the MM3100, a 25W continuous (200W pulsed) 6-channel SPST digital-micro-switch in an hermetic 6x6x1.3mm LGA package.
Visit Menlo Micro at www.menlomicro.com