How are electric vehicles impacting technology innovation within the power module market?

The power module market is expected to double in size by 2028, reaching $14 billion, according to Yole Intelligence recent analysis in the Status of the Power Module Packaging Industry 2023 report.

As one of the key components within converters and inverters, the power module market has traditionally been driven by industrial applications. The market is now responding, however, to increased demand within the electric vehicle space, which is now the market’s main driver – and this demand is set to continue because the number of electrified cars produced is rapidly increasing every year.

But as this evolving market causes a shift in requirements, module makers must achieve a balance between performance, reliability and cost. In this article, Yole experts Shalu Agarwal and Amine Allouche analyse how the EV market is affecting the development of power modules today (using real-world examples), and discuss how this impacts the overall supply chain.

The EV market has much more stringent requirements than industrial applications – not least of all in terms of power, efficiency, robustness, reliability, cost, size, and safety – which is impacting technological innovation in the overall power module market.

Traditional power module packaging components that would have been sufficient for industrial use are now being replaced with more innovative components that provide higher performance and reliability, albeit at a higher cost.

Many module makers are moving from silicon IGBT-based dies to silicon carbide, particularly as EVs move to higher powers (400V to 800V for ultrafast charging). Though more costly than Si IGBT, SiC MOSFET systems provide higher efficiency, allowing power module makers to deliver higher powers while meeting the stringent size constraints in EVs.

However, to maximise the benefits of SiC, suitable power module packaging solutions must be used alongside it, which is leading to many innovations across the available substrate, encapsulation, die attach, substrate attach and electrical interconnection solutions.

For example, regarding electrical interconnections, the industry is seeing a shift from aluminium wires to low inductance copper wire. Wire-free power modules using ribbon bonding, top lead frames, flexible foils and customised options such as clips will see considerable growth.

The market is also seeing innovation in the copper-based flat baseplates. In order to better integrate the cooling system and the power module, as well as to minimize the number of different layers in the thermal dissipation path, structured baseplate solutions such as pin-fin designs are being proposed for high power density applications.

In terms of the die attach material, module makers are moving from soldering to high-temperature-compatible silver sintering and are already evaluating other solutions like copper sintering.

The substrate being used is also shifting from direct bonding copper (DBC), such as aluminum oxide-DBC ceramic substrate, to active metal brazed (AMB) ceramic substrates, such as silicon nitride-AMB. Silicon nitride-AMB offers better thermal conductivity and therefore higher reliability.

In addition, a shift from single to double-side power module cooling is providing improved thermal dissipation and heat management.

But while these innovations in the power module are improving performance and reliability, they are also increasing the cost of the overall module considerably. Because many modules on the market today already offer comparable high performances, integrating every innovation possible at a high cost may not be the smartest move for module makers to differentiate themselves. With cost a crucial factor – particularly among consumers buying electric vehicles – module makers are now moving from an ‘excellent’ to ‘good enough’ design approach to achieve a balance between technical innovation and cost.

With SiC die the most expensive part of the power module – accounting for more than  70% of the total power module cost – some companies are choosing to keep Si IGBT dies but are using more advanced substrates, electrical interconnects, or packaging solutions. In this way, companies can provide a ‘good enough’ performance while reducing cost.

For example, Vitesco Technologies’ IGBT module within the inverter of Jaguar’s I-Pace model uses innovative interconnections based on customised patterned silver clips, and innovative double sided silver sintering on both the bottom and top side of the die. The base plate features a copper cooling header, which has a closed structure with an inlet and outlet for the external cooling liquid. This is quite unique from the open pin fin designs normally seen on the market, highlighting how more and more module makers are innovating the base plate to improve heat dissipation.

Yole Group experts have performed a teardown of many modules on the market today, in their report SEMIKRON-Danfoss IGBT Power Module in IM L7 Electric Vehicle Inverter.

Another example of a Si IGBT module used alongside innovative components is the SEMIKRON-Danfoss DCM module integrated in the inverter of the IM L7 car from Chinese automaker IM Motors. The base plate design features the company’s proprietary ‘Shower Power’ technology that offers efficient direct liquid cooling without temperature gradients across the power module assemblies. For the interconnections, SEMIKRON-Danfoss uses an innovative three-step process in which copper ribbons are attached on a DBB copper foil, which is silver sintered onto the die. SEMIKRON-Danfoss also offers this technology within a SiC-based module, in what would provide an ‘excellent’ performance but at a higher cost. Today, silicon carbide is used more commonly in vehicles targeting 800V, and many companies are marketing SiC systems, where the benefit of such technology warrants the increase in cost.

The power module plays a crucial role in the overall performance of the electric vehicle, and the variety of systems on the market today demonstrates how car makers are getting closer to the design and development of the systems. Whereas power module makers’ customers used to be inverter makers, their main customers are now car makers, highlighting a re-shaping of the supply chain. In addition, some automakers – Tesla, BMW and others – are building in-house R&D facilities so they can be more actively involved in the design process.

The heavy focus on design has also resulted in many new players – particularly from China – entering the market with new packaging solutions.

The rapidly-growing power module market has experienced much change and exciting innovation in recent years, which shows no sign of slowing down. Follow Yole to hear first about the latest innovations, trends and business updates within this evolving market.

Shalu Agarwal, PhD. is Power Electronics and Materials Analyst at Yole Intelligence, part of Yole Group, within the Power & Wireless division. Based on Seoul, Shalu is engaged in the development of technology & market reports as well as the production of custom consulting studies.
Shalu has more than 10 years’ experience in Electronic Material Chemistry. Before joining Yole, she worked as a project manager and research professor in the field of electronic materials, batteries and inorganic chemistry.
Shalu Agarwal received her master’s and Ph.D. degree in Chemistry from the Indian institute of Technology (IIT) Roorkee (India).

Amine Allouche serves as a Technology & Cost Analyst, Power Electronics, at Yole SystemPlus, part of Yole Group.
With strong expertise in the field of power electronics, Amine produces reverse engineering & costing analyses while also working on custom projects. He collaborates closely with the laboratory team, defining objectives of the analyses and determine the methodologies necessary to reveal the structure of a device.
Amine holds a master’s degree in Micro & Nanotechnologies with a focus on integrated systems from Grenoble’s Polytechnic Institute (France). He also graduated from the Ecole Polytechnique Fédérale de Lausanne (EPFL) (Lausanne, Switzerland) and the Politecnico di Torino (Italy).