sponsoredE-MOBILITY Power Module Integration Center established to accelerate EV development

As a response to the rapid expansion of the global EV market, auto manufacturers and powertrain suppliers are rushing to develop components for EVs. In particular, power modules, which are used to drive motors are attracting attention as a key component that improves fuel efficiency and prevents overheating from long driving times.

Conventional evaluation and simulation of components have been the responsibility of automobile manufacturers, powertrain suppliers and certainly power semiconductor manufacturers. Resonac's PMiC aims to facilitate a faster development of EVs as a core material developer by implementing evaluation and simulation on their behalf as part of integrated services.

A rapid shift to EVs being observed globally

Statistics from the International Energy Agency (IEA) indicate that global sales of new EVs in 2021 totaled 6.6 million units, showing a year-on-year growth of 2.2 times. This is described by President Hidehito Takahashi of Resonac as the “shift to EVs progressing more rapidly than expected.”

The shift from gasoline-powered vehicles to EVs is accelerating particularly quickly in Europe and China. The global market for automotive power modules in 2021 is expected to record an increase of 43.1 % year-on-year to 265.692 billion yen on a shipment basis. Sales of power modules using silicon carbide (SiC) power semiconductors, in which Resonac has a competitive edge, grew by 61.4 % year-on-year to 50.656 billion yen.

Power modules at the heart of EVs

An EV, which uses electricity to drive its motor, houses a metal case roughly the size of four or five laptop computers stacked together. The case is mounted between the power supplying battery and the motor, and controls vehicle movement. The power module (PM) consists of integrated circuits packaged inside the case.

PMs perform the following functions:

(1) Alternately switching the direction of flow of direct current power to create alternating current to rotate the motor

(2) Converting excess alternating current power from the motor into direct current and returning it to the battery

As you depress the accelerator pedal, the frequency of the switching of direction of current and the frequency of the alternating current itself increases. This eventually increases the rpm of the motor and causes the EV to accelerate as a result. As a critical component for controlling EVs, PMs can be thought of as the heart of a vehicle.

Thermal management

One of the challenges with PM development is thermal management. PMs are made mainly of semiconductor devices. If currents are turned on and off repeatedly, or the current is large, the amount of heat generated in a circuit suddenly increases, causing high temperatures and heat fluctuations. These can adversely affect insulating substrates, wire bonds inside the semiconductor devices and the module itself if the thermal stress is greater than assumed.

The performance of PMs depend on how successfully energy loss is reduced during the heat generation that inevitably accompanies power conversion. It also depends on how the heat generated is dissipated into the air. It is difficult for automobile and semiconductor manufacturers to address these problems alone as materials need to be improved in order to deliver enhanced functions. The PMiC has been established to solve these issues from a materials perspective.

“The PMiC serves as a hub for Resonac’s operating departments involved in PM development and manufacturing. It is a one-stop application center that enables the whole process up to mass production,” says the PMiC’s director, Seiji Matsushima.

Analyzing data using a range of equipment

With a floor area of approximately 150 m², the performance evaluation room is the core facility of the PMiC, housing a variety of testing instruments to evaluate the performance of PMs.

• Power cycling tester: Confirms the reliability of a module by turning the current on and off

• Temperature cycling tester: Confirms the reliability of a material by repeatedly changing the ambient temperature

• Ultrasonic flaw detector: Inspects conditions of bonding in a semiconductor device

• Thermography equipment: Analyzes and visualizes infrared rays radiated from semiconductors

The PMiC builds test modules using a variety of components made by Resonac in order to evaluate their performance with these analytical instruments. Simulation is also used to correct evaluation results to reflect the characteristics of power modules made by different companies. These evaluation and simulation functions were previously applied only to internal material developments but are now made available to Resonac's customers in the automotive and semiconductor industry.

Co-creation efforts with automotive and semiconductor manufacturers started

The launch of the PMiC marks the start of a new work model: Powertrain companies and power semiconductor manufacturers present technical requirements and challenges faced in order for Resonac to build, evaluate and verify prototypes according to those requirements and eventually provides a particular design proposal.

As shown in the diagram on the left (see Figure 5), the time required from R&D to mass production for Resonac's customers can be shortened by fulfilling the functions in the evaluation of power modules according to their technical specifications. In addition, if Resonac and partner companies' can work together to select materials and evaluate module performance, such customer or partner companies' workload will be substantially reduced.

“Whether we make proposals or jointly develop a product with a customer; sharing our knowledge of processes which are used to evaluate components and module performances will significantly increase the possibility of our products being adopted by customers”, says Director Matsushima.

Oyama Plant, the main factory to manufacture aluminum products has been fostering a technology for evaluating PMs, the core component of EVs for seven years. The PMiC is now capable of assembling optimum components into a test module and precisely testing the impact of heat on the performance of the module under various voltage and current conditions. Therefore, the PMiC is ready to offer its evaluation technology to outside manufacturers.

Such technology development has been enabled by our knowledge gained through more than ten years of evaluating and verifying power modules by an engineering team who has extensive experience in power module developments. The engineers at PMiC are from various companies within the power semiconductor industry.

Responding with agility to new material SiC

PMs are made of semiconductors, the main material of which is shifting from the currently dominant silicon to silicon carbide (SiC), which exhibits low electrical resistance. It has been proven that using SiC chips with low electric resistance results in less energy loss and extended driving distance. SiC is therefore largely used in power module applications.

The PMiC receives various consulting and service requests from PM manufacturers. Although information concerning chips to be used for a PM is classified by the manufacturers as “top secret,” Director Matsushima sees a trend. “Based on the expertise developed from evaluating various types of PMs,” he says, “we can tell if a customer is intending to use SiC chips for its PM, and the number of such cases is undoubtedly increasing.”

Our major know-how so far has been with silicon-based chips. However, since its inauguration, delivering SiC solutions has been a primary task of the PMiC. Meanwhile Resonac accounts for 25 % of the global market share for SiC epitaxial wafers which is the semiconductor material that greatly affects the driving distance of EVs.

“As this different material becomes more and more available it will greatly influence the choice of components. We have already launched our endeavor for SiC chips,” says Director Matsushima. Thus R&D for the next generation technologies has already begun at the new PMiC center.

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