High-powered Semiconductor Modules is the need of the hour

Hitesh Bhardwaj, General Manager, Semiconductors & Devices, Mitsubishi Electric India

Hitesh Bhardwaj, General Manager, Semiconductors & Devices, Mitsubishi Electric India

In a recently announced campaign, the Government of India offered subsidies to buyers of electric vehicles (EVs). As an all-India project, the government wants to promote the sale and use of electric vehicles in the country. World-over, just like the Indian Government, other governments are promoting the use of electric vehicles. Rising levels of pollution, climate risk, harsh weather conditions and a declining availability of fossil fuels have propelled the case of using electric vehicles.

Understanding the market demand
The Indian Government is already working on its ambitious plan to shift to hybrid, electric vehicles from combustion technology. Automobile manufacturers have realised the market demand for EVs. These offer unique features including energy-saving modes, pollution-free emission, and superior comfort.

An interesting aspect of this transformation is the use of premium, futuristic technology. Over the years, even EV manufacturers have regularly updated their technology on every front. The demand for EVs is also basis the demand from consumers, who now demand better technology-driven vehicles.

A part of the technology upgrade is high-power semiconductors modules that deliver reliability and offer high standards of safety.

What is a high-power semiconductor module?
A high-power semiconductor module is the core component in the power-train system of hybrid and electric vehicles. With the global interests and efforts to promote EVs, the automotive module has become one of the fastest-growing sectors of the power semiconductor industry. It will not be wrong to say that power semiconductors are driving the EV industry.

It is predicted that by 2030, more than half of the total vehicles present on the planet will be electric vehicles. Production and subsequent use of semiconductors will then be at a higher level. Manufacturers of high-power semiconductors offer some direct advantages:
• Low power loss and high reliability
• Compact and light weight package
• On-chip temperature and current sensors
• Evaluation kits available

These advantages conform to the needs of a fast-evolving segment that is going to become the necessity. Today the high-power modules play an important role in the success of electric, hybrid fuel cell vehicles – a change from other conventional electric vehicles designed in the initial adoption stage.

But a few concerns continue to be the impediments in the growth of the semiconductor modules. The development of automotive power module is facing comprehensive challenges in designing the structure, material, and assembly technology. On the material, the year 2020 has been a tough year, when supplies remained a problem.

Strong pioneers like the Mitsubishi Electric were prepared for situations like this. Despite odds, the Company continued supplying the latest tech-enabled J1-series power semiconductor modules for hybrid vehicles. Mitsubishi Electric pioneered the mass-production of power semiconductor modules for hybrid vehicles in 1997.

The new J1-Series, a direct water-cooling (pin-fin) structure, mainly for motor drive applications in electric and hybrid vehicles, is known to meet stringent safety standards and provides greater reliability.

Semiconductor modules offer special features. Some like the J1-Series contribute to further compactness, weight reduction and reduced power consumption in inverters for electric and hybrid vehicles.

It has cutting-edge features like reduced inverter size and weight, achieved through the extra compact package with high integration. The compact power semiconductor module features a highly integrated seventh generation IGBT with a carrier-stored trench-gate bipolar transistor (CSTBTTM) structure and seventh generation diodes. The direct cooling pin-fin structure achieves 30% lower thermal resistance and 40% smaller footprint.

Another important feature is that each IGBT chip is provided with a current sensor for short -circuit protection as well as an on-chip temperature sensing for over-temperature protection, which can directly monitor the chip temperature.

The new design adds to the efficiency: J1-series of Mitsubishi Electric, for instance, no longer uses heatsink grease as required by the previous formats; instead, it is equipped with a cooling fin integrated with the module to allow direct cooling and improve the cooling performance.

Also, by optimizing the shape and layout of the fin, and eliminating the solder layer beneath the isolation layer, the thermal resistance between the chip and the cooling water, Rth(j-w), is reduced by more than 30% from the level of the conventional product that consists of three J-series transfer-moulded power modules(T-PMs) mounted on the copper cooling fin with the heatsink grease between them.

The J1-series uses Aluminium as the cooling fin material to provide high corrosion resistance against water cooling & reduces the assembly weight significantly from the conventional product.

The new module is automotive-grade high quality and adopts Mitsubishi Electric’s original Direct Lead Bonding (DLB) structure. The DLB structure ensures power-cycle and temperature-cycle life spans 30 times longer than those of typical industrial power semiconductor modules.

The outlook
Extensive research and development are being undertaken to make EVs the main focus of the automotive industry. Furthermore, the development of HEV/EV is becoming the main policy of most governments and automotive industry, leading to worldwide adoption. This will increase the consumption and demand for high-powered semiconductors like the J1-Series.

The technology mentioned above is going to be adopted by most EV manufacturers. Going forward, technological advancements, along with a reduction in cost and size of components and systems, are expected to play a pivotal role in the growth of the automotive power electronics in the electric vehicles market. The popularity of EVs will grow and EVs will become the need of the masses.