Wärmemanagement für Leistungselektronik 2024-2034: Prognosen, Technologien, Märkte und Trends

IDTechEx has observed a growing trend towards 800V platforms and beyond, driven by several automotive OEMs including GM, Hyundai, VW, and Lucid Motors. These platforms, operating at higher voltages, are enhancing efficiency by minimizing joule losses and enabling the downsizing of high-voltage cabling, thereby reducing weight. This transition is facilitated by the adoption of new technologies and materials, particularly silicon carbide (SiC) MOSFETs, which incorporate innovative thermal management techniques and materials such as double-sided cooling (DSC), advanced Ag sintered die-attach, alongside the use of high-performance thermal interface materials.

 

Moving from traditional silicon IGBTs to SiC MOSFETs also entails changes in thermal architecture design. Examples include the implementation of DSC, copper ribbon bonding, and direct liquid cooling to eliminate the need for thermal interface materials (TIMs).

 

In its report titled "Thermal Management for Power Electronics 2024-2034: Forecasts, Technologies, Markets, and Trends", IDTechEx offers a comprehensive market forecast for power electronics thermal management strategies, segmented by SiC MOSFET, Si IGBT, and GaN technologies. The report provides detailed projections for die-attach, substrate-attach, and TIM area, volume, and market value by SiC, Si, and GaN, as well as a breakdown of die-attach methods including traditional solders, Ag sintering, and emerging Cu sintering. Additionally, the report covers the market for liquid-cooled inverters, segmented by air, oil, and water-glycol cooling methods.

 

As power semiconductors experience increased power density and heat flux, coupled with the transition from Si IGBT to SiC MOSFET, the thermal architecture of power semiconductor packaging is anticipated to undergo significant changes. The diagram provided illustrates the key layers of materials in power modules, comprising die-attach materials, substrate-attach materials, wire bonding, and thermal interface materials.

 

The semiconductor dies are affixed to a double-bonded ceramic (DBC) substrate using die-attach materials. Subsequently, the DBC is connected to a baseplate via another substrate-attach material. Communication between the dies and circuitry is facilitated through wire bonding, traditionally using aluminum but with a growing preference for copper. To ensure protection and stability, the package is potted with thermally conductive silicone gels.

 

 

 

Die-attach and substrate-attach materials typically consist of solder alloys like SnPb or SAC (Sn-Ag-Cu). These alloys are chosen for their high bulk thermal conductivity, and upon soldering, they form intermetallics between components, resulting in low interfacial thermal resistance. This maintains low package stress and processing temperature while also mechanically fastening the heat sink. The typical thermal conductivity of solder alloys is around 50W/mK, with melting temperatures around 200°C.

 

However, as heat flux increases due to the transition from Si IGBT to SiC MOSFET, junction temperatures are expected to surpass 175°C, or even 200°C in some cases, posing challenges for traditional solders. This shift has led to a transition from solders to sintered die-attach materials. Some leading automotive OEMs, including Tesla, Hyundai, and BYD, have already begun adopting Ag-sintered die-attach materials. Nonetheless, Ag-sintered pastes are significantly more expensive than traditional solder alloys. While costs are influenced by customer relationships, order volume, and various other factors, IDTechEx estimates that Ag-sintered pastes can be 5 times more expensive than traditional solder alloys. In the short to medium term, it is expected that silver sintered paste will primarily be adopted by leading automotive OEMs due to their greater bargaining power with higher volumes to reduce costs. There is also scope for people to replace Cu-sintered die-attach thanks to their theoretically lower costs compared with Ag-sintered die-attach. However, as of 2024, IDTechEx has not seen any large-scale commercial examples of Cu-sintered die-attach materials. This report compares and analyzes the benefits and drawbacks of Ag and Cu-sintered die-attach, along with the market forecast of these two technologies. Despite the benefits of sintering, many semiconductor suppliers and automotive OEMs will remain with solder alloys due to their reduced cost and advances happening with their application.

 

TIM2 typically comes in two forms in EV power semiconductors: thermal grease, employed between the baseplate and the heatsink, and thermal gel, often utilized as potting materials. The market in 2024 sees thermal greases typically exhibiting a thermal conductivity between 2.5 and 3.5W/mK and a density of around 2.5g/ml. However, there have been advancements in TIMs, such as Honeywell's PTM7000 used in onsemi's VE-Trac, demonstrating a thermal conductivity of 6.5W/mK. IDTechEx predicts a trend towards higher thermal conductivity due to the increasing heat flux resulting from the adoption of SiC technology. Further to this, phase change materials (PCM) also gain significant momentum thanks to their superior latent heat capacity. The thermal impedance using PCM can reduce by over 50% compared with traditional thermal grease, although this largely depends on the materials used, configurations, and many other factors. The report benchmarks a number of commercial TIM2 options and conducts a granular analysis of their mechanical properties.

 

The Thermal Management for Power Electronics report also summarizes the emerging trends in thermal architecture evolution. Take the two trends below as an example.

1. Double-sided cooling (DSC): Double-sided cooling has been implemented in some mid- to high-end electric vehicles, such as the Porsche Taycan and Audi e-tron. This approach offers superior cooling capacity where the junction temperature can be reduced by 40%. However, the adoption of double-sided cooling results in a more complicated and expensive design. In contrast to single-sided cooling, DSC replaces wire bonding with lead frames and may potentially double the amount of die attach and TIM used.

2. Direct liquid cooling: Another emerging trend is the transition from traditional cooling methods to direct liquid cooling, where the double-bonded copper (DBC) is directly affixed to a pin-fin structured heatsink. This configuration allows for the elimination of the cold plate and thermal grease.

 

The chart below provides a summary of a few examples of power semiconductors utilizing double-sided cooling.

 

 

 

The report forecasts that the combined market size of die-attach materials, substrate-attach materials, and TIM2 for EV power electronics will reach approximately US$900 million by 2034, presenting significant market opportunities. As thermal power continues to rise, it is expected that more advanced thermal management strategies will be adopted, thereby accelerating market growth at a double-digit Compound Annual Growth Rate (CAGR) from 2024 to 2034.

 

For a deeper understanding of the market opportunities, active players, competitive landscape, technology benchmarking, and recent market developments, readers are encouraged to refer to IDTechEx's latest report, "Thermal Management for Power Electronics 2024-2034: Forecasts, Technologies, Markets, and Trends".

 

This report provides critical market intelligence about the area, volume, weight, and market value of die-attached solders, substrates, and TIM2s for electric vehicle power electronics, in particular, Si IGBT, SiC MOSFET, and GaN.

 

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