everything PE recently interviewed Yunji Liu Corcoran, Chairwoman and CEO at SMC Diode Solutions. SMC Diode Solutions specializes in designing and manufacturing semiconductor devices.
Q. Can you give us a brief history of SMC Diode Solutions? When was the company founded and what was the goal?
Yunji Liu Corcoran: SMC is a semiconductor company focused on designing and manufacturing power device chips.
Established in 1997, SMC manufactures a wide variety of products that service the power discrete market. Our goal is to be a discrete power semiconductor solutions provider to our customers. Discrete power devices are used everywhere. The applications of our products range from commercial aerospace, medical, PV, TV power boards, Server power supply, and many more.
Our customers include top companies around the world with rigorous standards for quality and performance, which our team consistently meets.
Since 2014, we have entered the SiC market, added SiC products, and extended our product offerings which enabled us to service more customers and extend the coverage in the market.
Q. Can you tell us more about your product portfolio?
Yunji Liu Corcoran: We manufacture silicon-based diodes and power rectifiers. To be more specific, we have Schottky rectifiers, both planar and trench, ultrafast rectifiers, TVS, Zener, and more. While we have produced many different types of products over the years, today we’re more focused on current 1 A and larger. We also have silicon carbide diodes from 650 V to 1700 V, 1200 V, and 1700 V silicon carbide MOSFET in our portfolio.
Our portfolio is constantly growing and evolving, and we also collaborate with partners to create products that fit their needs.
Q. Which market segments do you cater to?
Yunji Liu Corcoran: In general, we work with any market segment that has to do with power conversions and protections such as power supply, DC-DC converters, and inverters. We also create products for the aerospace, automotive, and medical industries. With the opening of our new fab, we are entering into the electrical vehicle and renewable energy market.
Q. How do you differentiate your Transient Voltage Suppressors from those offered by other manufacturers?
Yunji Liu Corcoran: A portion of our Transient Voltage Suppressors (TVS) are designed to have higher reliability for commercial aerospace applications. The design is different from the common TVS offered in the market to ensure reliability. Our SPD4-1 package uses licensed patent technology for large power TVS.
STPK30KP Series Transient Voltage Suppressor
Q. How do Trench Schottky diodes compare to standard Schottky diodes in terms of performance? What are the applications of Trench Schottky diodes in the automotive sector?
Yunji Liu Corcoran: When a Trench Schottky diode is in reverse bias mode, it has a much lower leakage current due to the trench “pinch off” effects. This gives device designers the ability to use lower barrier Schottky contact to reduce the forward conduction loss. This results in an increase in efficiency. The newest and largest market for Trench Schottky diodes is for photovoltaic junction boxes. Most junction boxes from what we have seen have been converted to trench Schottky diodes. In automotive applications, we saw it being used in lighting and other places where planar Schottky diodes were used. However, the traditional Schottky diode process is simple and cheaper. They are still widely used.
Q. What are Ultra-Fast Recovery Rectifiers? How do they differ from Schottky rectifiers?
Yunji Liu Corcoran: Recovery time means the time (in ns) needed to change from conduction mode in a diode to blocking mode (reverse recovery time trr) or vice versa (forward recovery time tfr). Ultra-Fast Recovery Rectifiers can change from one mode to another very fast (in nanosecond level). Schottky diodes can also recover very fast, but usually can only operate at 200 V or less. Above 200 V, most Schottky diodes have too high forward voltage which causes lower efficiency in circuits. Once the application calls for greater than 200 V block voltage, the ultrafast rectifiers are used since the forward voltage is lower than Schottky diodes. This is where silicon carbide diodes come in. Silicon carbide JBS diodes can replace the ultrafast rectifier and increase the efficiency of the circuits.
Q. Can you tell us about the key features of SMC's power modules? How do they perform in high-current applications?
Yunji Liu Corcoran: Most of SMC’s current power modules are epoxy-filled structures. This structure gives the best thermal performance in high-current applications. We offer many diode modules with current ranging from 30A to 600A and voltage ranging from 15 V to 1200 V.
Q. How do SMC's ESD protection devices provide reliable protection against transient voltage spikes and electrostatic discharges?
Yunji Liu Corcoran: During normal operation, the ESD diode is in an open circuit state. Static electricity is a problem for electronic devices as many systems are prone to damage by ESD. Due to this, most devices, like phones, have protection products which are designed to be placed next to input connections such as keyboards, buttons, cables etc. When there is static electricity outside, the ESD diode undergoes avalanche breakdown and forms a bypass path, protecting the internal circuit or gate.
SMC ESD and Transient Voltage Suppression Devices (TVS’s) can abate these high fields/voltages within electronic connectors, circuits and devices, essentially by transmitting most of the voltage/current to ground and clamping the voltage at a safe level.
The way in which SMC does this is by use of a diode which will break down at a set voltage when in reverse mode and have a normal forward diode current, i.e. will not allow the voltage to exceed the designed maximum whose value depends upon the circuit to be protected.
The diode design has to have an extremely fast response time to ensure any ESD fast transients are not let through to the main circuits. They also must not load the line with too much capacitance or inductance which may influence normal input signals on that line. Silicon diode devices are one of the smallest, simplest and best for this purpose.
A transient-voltage-suppression diode can respond to over-voltages faster than other common over-voltage protection components such as varistors or gas discharge tubes. The actual clamping occurs in roughly one picosecond, but in a practical circuit, the inductance of the wires leading to the device imposes a higher limit. This makes transient-voltage-suppression diodes useful for protection against very fast and often damaging voltage transients.
Q. Why is SMC's new fab in Nanjing significant for the EV industry?
Yunji Liu Corcoran: The opening of SMC’s new fab has increased our capacity by over four times. Together with our existing fab, SMC can produce over 1.5 million wafers per year at full capacity. We’re now able to produce products such as the Trench Schottky Rectifiers and others that are used in the EV industry for applications like charging stations and OBC. That said, we will continue to offer both silicon and silicon carbide products to our clients in the EV industry. With our advanced technology and increased capacity, we will play a more important role in the EV industry.
Q. How does SMC contribute to the safety of electric vehicle batteries? What specific products does SMC offer for battery management in EVs?
Yunji Liu Corcoran: SMC can provide a TVS and TVS array, which can effectively avoid failures caused by surges. The maximum protection voltage of TVS can reach 400 V. The minimum protection voltage of TVS array can reach 3.3 V, and the maximum voltage can reach 24 V, which can be applied to different types of battery protection systems.
Q. SMC has recently partnered with Atlantic Tech Marketing LLC. How will this partnership benefit SMC's market reach and customer base?
Yunji Liu Corcoran: This partnership will benefit SMC's market reach and customer base because Atlantic Tech works directly with OEM’s at the design level, meeting with engineers throughout the design cycle. SMC is now part of Atlantic Tech’s focused line card of synergistic product lines getting visibility and exposure to Atlantic Tech’s customer base.
Q. Are there any new developments or upcoming products in SMC's roadmap in 2024?
Yunji Liu Corcoran: On the silicon side, we are developing more application specific Trench Schottky diodes and ultrafast rectifiers. For silicon carbide, we have diodes ranging from 650 V to 3300 V and are working on extending the range to cover 650 V to 3300 V MOSFET. We are also in the planning phase for a business unit specializing in building the power modules. As a company, we’re always working with research institutes to develop and design the newest, most innovative products, so keep an eye out on our website and social media for updates.
About Yunji Liu Corcoran
Dr. Yunji Corcoran is the Chairwoman and CEO of SMC Diode Solutions. Dr. Corcoran has managed a successful career in the power semiconductor field for over 30 years, specializing in design, manufacturing, and global sales. She holds a bachelor’s degree in physics from Nanjing University and a PhD in semiconductor materials from Stony Brook University in New York. She currently focuses on management functions but still considers herself to be a dedicated engineer. Outside of the semiconductor business, Dr. Corcoran is passionate about traveling, cooking, and collecting cookbooks from around the world.
