MLCCs and NTC thermistors meeting automotive application demands

The market need for capacitors with stable performance and high voltage tolerance

Resonant and snubber circuits are crucial for efficient power conversion and the suppression of current and voltage peaks. In both circuits, repeated exposure to high voltage and high current can cause even slight variations in component performance, leading to efficiency loss, heat generation, and potentially resulting in malfunction or failure. Furthermore, recent trends in power switching devices indicate a shift from silicon MOSFETs to silicon carbide (SiC) MOSFETs, which enable higher efficiency and faster switching speeds. SiC MOSFET applications typically require a breakdown voltage of 1.2kV, creating a growing demand for capacitors with ratings exceeding this specification. These applications demand capacitors capable of maintaining stable performance across a wide temperature range, minimizing power loss, and withstanding high operating voltages. Consequently, the need for capacitors with voltage ratings higher than this level is increasing.
 
In power circuits for Electric Vehicle (EV) onboard chargers and consumer devices, resonant circuits for efficient power conversion and snubber (or absorption) circuits for curbing current and voltage peaks are commonly employed. Since these circuits are subjected to repeated high voltage and high current stress, minor changes in component performance can lead to reduced efficiency, device heating, and potentially cause operational abnormalities or failures. Therefore, the market urgently requires capacitors that offer stable performance under varying temperatures, low loss, and high voltage tolerance.

Large capacitance MLCCs compatible with SiC MOSFETs

Addressing automotive application needs, Murata leverages its proprietary ceramic body and internal electrode thinning technology to introduce an MLCC achieving a large capacitance of 15nF within the compact 1210-inch (3.2 x 2.5mm) size, with a rated voltage of 1.25kV and C0G characteristics. Compatible with SiC MOSFETs, the C0G characteristic provides low loss and stable capacitance over temperature, making it suitable for resonant and snubber (absorption) circuits. This product can be used in Onboard Chargers (OBCs) and power supply circuits for high-performance consumer electronic devices, contributing to efficient power conversion and stable operation under high-voltage conditions.
 
Utilizing Murata's unique ceramic and electrode materials, thin-layer molding technology, and high-precision stacking technology, this new 1.25kV MLCC meets these demands and supports the latest SiC MOSFET technology. Compliant with the EIA standard C0G characteristic, it offers the inherent advantages of low loss and stable capacitance across an operating temperature range of -55°C to +125°C, making it an ideal choice for resonant and snubber circuits. To provide design flexibility, its capacitance range spans from 4.7nF to 15nF, with a tolerance of ±1% to ±5%.
 
Murata continues to advance the miniaturization of MLCCs, expand capacitance values, and increase rated voltages, broadening its product portfolio to meet market demands and thereby supporting the miniaturization, high performance, and multi-functionality of electronic devices. Simultaneously, Murata aims to reduce environmental impact through more efficient use of natural resources, waste reduction, and promoting recycling initiatives within its MLCC manufacturing processes.
 
The GCM series MLCC, model GCM32E5C3B153FWAA# (where the "#" at the end denotes the packaging specification code), is designed for automotive powertrain/safety equipment. It can be used in drive control systems for engine ECUs, airbags, ABS, and other safety equipment, and automotive infotainment/comfort systems. It is an AEC-Q200 compliant capacitor for automotive applications and has passed temperature cycling and humidity load tests under conditions more stringent than those for general-purpose products (GRM series).
 
The GCM series capacitors come in compact sizes ranging from 0.6x0.3mm to 5.7x5mm. They support rated voltages from 2.5Vdc to 1,250Vdc and capacitance values from 0.1pF to 220µF. The product lineup includes versions rated for operating temperatures of 125°C and 150°C. The external electrodes are tin-plated, providing excellent solderability.

Thermistor is key component for temperature sensing, thermal protection, and system reliability management

In recent years, as automobiles become increasingly electronic and feature-rich, the importance of high-output, high-efficiency power semiconductors has grown significantly. However, power semiconductors generate substantial heat, making the risk of damage due to high temperatures a critical issue that needs addressing. To manage this, thermistors are employed to detect temperature rises in power semiconductors, enabling cooling or operation-limiting measures.
 
Historically, because high voltage is applied to the mounting pads of semiconductors, conventional thermistors could not withstand such voltage and had to be placed far from the semiconductor. This made accurate temperature detection difficult, necessitating measures to limit operation to temperatures below the actual heat-resistant threshold to prevent damage from overheating, consequently preventing the semiconductor's performance from being fully utilized.
 
Amidst the rapid development of automotive electrification, thermistors (primarily NTC type) are key foundational components for temperature sensing, thermal protection, and system reliability management. Their main applications include temperature monitoring and system status feedback, widely used for monitoring temperatures in powertrain systems, battery modules, motors, power semiconductors, and cabin environments. Furthermore, thermistors are critical components for electrification and battery safety. They are extensively deployed in Battery Management Systems (BMS) to detect abnormal temperatures in individual battery cells or modules, preventing thermal runaway, which has a decisive impact on driving safety and battery lifespan.
 
Additionally, thermistors are used for inrush current suppression and power protection, safeguarding DC/DC converters, inverters, and power modules during system power-on to reduce the risk of component damage and enhance system reliability. Thermistors for automotive use must also support high reliability and meet automotive standards. They need to comply with automotive-grade standards like AEC-Q200 and possess good long-term stability and consistency to meet the stringent safety and quality requirements of highly electronic vehicles.

NTC thermistors featuring resin-molded and wire-bonding structure

Murata has also introduced the "FTI Series" (FTN21XH502F0SRU) NTC thermistor for power semiconductors. This product is Murata's first NTC thermistor featuring a resin-molded structure and supporting wire-bonding, enabling accurate temperature measurement by being placed close to power semiconductors. It is the world's first thermistor to achieve both a resin-molded design and wire-bonding compatibility in a single component. The integration of these two innovations provides unprecedented flexibility for the design and assembly of printed circuit boards (PCBs).
 
Furthermore, Murata FTI series NTC thermistors have a guaranteed operating temperature range is -55°C to 175°C, reaching a top industry level and ensuring stable operation in high-temperature environments. It is suitable for automotive powertrain/safety equipment applications that generate significant heat, including systems such as Electric Vehicle (EV) inverters, DC-DC converters, and onboard chargers that transmit power from the source to the wheels to drive the vehicle.
 
The resin-molded structure and wire-bonding compatibility ensure high dielectric strength due to the resin package, allowing installation even on high-voltage electrodes. It ensures insulation and permits direct placement on the mounting pads of power semiconductors, enabling closer proximity to power semiconductor devices and providing excellent mechanical strength. Moreover, because it supports wire-bonding technology, it can be installed near high-voltage heat sources and connected to thermistor pads. This facilitates accurate temperature detection near power semiconductors, eliminating the need for dedicated sensor mounting pads. This avoids the traditional drawbacks of limiting layout options and increasing board size while allowing full utilization of the semiconductor's performance.
 
The FTI Series thermistor can ensure safety while fully leveraging performance. Therefore, even if the number of power semiconductors is reduced, equivalent performance to previous designs can be maintained, which also helps reduce mounting area and cost. Consequently, design engineers gain greater freedom in PCB design, enabling more compact and efficient modules. This is particularly important in modern EVs, where electronic control systems must be highly integrated within tight spaces.
 
Another key strength of the FTI Series is its high-temperature operational capability. Leveraging Murata's proprietary external electrode bonding technology, the thermistor ensures reliable performance even in harsh environments, with a maximum operating temperature of 175°C. This is crucial for next-generation automotive applications, especially in powertrains and other high-power modules where thermal management is a constant challenge. With such excellent heat resistance, automotive designers can ensure system safety, stability, and longevity even under demanding conditions found in EV inverters and DC-DC converters.
 
The FTI Series enables precise and rapid temperature measurement directly adjacent to semiconductor devices, thereby reducing temperature margins in system design. This means that power semiconductor performance can be maximized without the need for over-engineering for excessive safety margins. It creates opportunities to reduce chip size or the number of chips used in parallel, ultimately leading to smaller module sizes and lower overall costs. Moreover, this cost-saving feature does not come at the expense of reliability or performance, making the FTI Series thermistor an ideal solution for manufacturers seeking to optimize their designs both technically and economically.
 
The FTI Series comes in a compact 2012 mm / 0805-inch package. It exhibits a resistance at 25°C (R25) of 5 kΩ ±1% and a B-constant (25°C / 50°C) of 3380K ±1%. It supports a maximum voltage of 5V and a maximum operating current (at 25°C) of 0.148mA. Its typical dissipation constant (at 25°C) is 1.1mW/°C. The product features wire-bonding electrodes on the top side for electrical connection to internal components and electrodes on the bottom side for mounting on a substrate, supporting reflow soldering.
 
To meet the increasingly sophisticated demands of the automotive market, Murata remains committed to expanding its product lineup to include a broader range of resistance values and offering new variations, such as models compatible with silver sintering processes in addition to traditional solder-mounted types. Murata will continue to provide innovative, reliable, and cost-effective solutions, contributing to the advancement of high-functionality semiconductor applications like those in electric vehicles and the broader automotive industry.

Conclusion

As automotive electronic architectures continue to evolve towards higher power density, greater integration, and enhanced reliability, passive components have become key foundational elements determining system stability and safety. MLCCs, with their excellent electrical characteristics and automotive-grade reliability design, provide stable support for various automotive power and signal circuits. NTC thermistors play an irreplaceable role in precise temperature monitoring, inrush suppression, and thermal safety protection. Murata offers a comprehensive range of MLCCs and NTC thermistors that fully meet automotive application demands, capable of long-term stable operation in harsh automotive environments, thereby supporting the ongoing evolution of electrified, intelligent, and safety-oriented automotive technologies.