Automotive power semiconductor packaging today and in the future (Part 1)

Summary

There is no doubt that the automotive industry is undergoing an electronics revolution. With this growth comes the opportunity for investors to increase their revenue while adding functionality and economic value to the end user. Whether it is autonomous driving, infotainment systems or vehicle electrification applications, performance, reliability and cost determine the differentiation strategy of each player. As a result, there is tremendous innovation from both integrated device manufacturers (IDMs) and outsourced assembly and test (OSAT) suppliers. This article will provide a brief overview of value creation in the electrification segment, specifically in the field of power semiconductor packaging.

market trend

Environmental, economic and social factors are influencing future vehicle designs and powertrain choices. Considering carbon dioxide (CO2) emission policies, tax incentives and the development of charging infrastructure, the strategic layout of powertrains will undergo significant evolution in the short and long term. Power semiconductors are key components of the powertrain systems of electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs). It is understood that the semiconductor content of each electric vehicle may exceed $750, compared with the average semiconductor content of $330 in fuel vehicles, with most of the value share occupied by power devices such as the main inverter, on-board charger and DC-DC converter. As the number of electric vehicles and electric vehicles (HEVs and PHEVs) increases, the demand for complex power electronics solutions that will reduce power losses, system weight and total cost will increase.

At present, power devices based on silicon (Si) technology, such as MOSFET and IGBT, play an important role due to the maturity of technology, manufacturability and the establishment of supply chain. In general, MOSFET covers the low voltage (<200V) field, while IGBT contributes to high voltage (>600V) related applications. In terms of packaging, power discrete packages such as transistor outline package (TO), small outline transistor package (SOT), quad flat no-lead plastic package (PQFN) and high current application (TOLL) package are well used in low power consumption (<5kW) application fields. However, for high power (>50kW) subsystems, molded or frame power modules are required. The product portfolios of multiple power equipment suppliers include discrete, molded and frame modules, with configurations such as single switch, half bridge, full bridge and three-phase designs.

As electric vehicle (xEV) solutions increase, the cost ($/kW) and power density (kW/Kg or kW/l) requirements for power electronics also increase. Currently, cost control is around $5/kW, while power density is around 12 kW/l. By 2035, these costs are expected to reach $3/kW and 60 kW/l. Existing semiconductor device technology, packaging technology and system-level architecture cannot achieve these future roadmap goals. This trend may diverge into two paths: fully integrated solutions with co-design of electric motors and power electronics or a single power management converter to manage the entire vehicle power.

Technology iteration: SI-SiC & GaN

To meet the requirements of automotive and system manufacturers, semiconductor suppliers need to provide excellent solutions in multiple areas. From a semiconductor technology perspective, silicon power devices will continue to play a key role as performance increases. Therefore, new wide bandgap materials such as silicon carbide (SiC) and gallium nitride (GaN) are expected to play a greater role in the coming decades, especially in high-power traction inverters and medium-power converter applications. As shown in Table 1, these new materials offer better thermal and electrical performance than traditional silicon devices, but there are challenges in manufacturability, integration and cost. In order to maximize the potential benefits of wide bandgap semiconductor materials, advanced components, converter topologies and integrated circuits need to be jointly developed.

At the packaging level, high temperature performance, integration and reliability are the three major trends driving innovation. For the high temperature performance of power discretes and modules, better thermal interface materials (TIMs), novel substrate concepts and improved packaging technologies are required for design. In addition, new materials need to be continuously innovated to provide better mechanical stability and robustness, as well as improved bonding mechanisms to better withstand extended power and temperature cycles. As silicon carbide and gallium nitride devices become more and more popular, but because they cannot completely replace silicon devices, current packaging solutions need to be optimized. For example, with the introduction of wide bandgap materials and the reduction in the number of passive components, significant space savings will be achieved, enabling package-level integrated solutions with gate drivers and filters.

At the same time, current inverter and converter architectures will improve efficiency due to incremental improvements in existing silicon devices. To provide further functionality, hybrid strategies such as integrated SiC rectifiers or GaN transistors, as well as efficient designs such as distributed architectures are expected to meet market demand. In the future, in order to fully tap the potential of wide bandgap devices, further innovations in circuit design will be made, combining high-frequency switching, soft switching and resonant switching to provide more efficient and higher power density solutions. In addition, the market trend of integrating motors and power converters will bring challenging packaging requirements, mainly in terms of mechanical, thermal and electrical performance requirements. For SiC and GaN devices, current packaging technology may limit performance through stray inductance causing switching losses and parasitic capacitance causing common-mode currents.

Summarize

From the perspective of development trend, SiC and GaN will be the main force of power semiconductors. With the continuous improvement of high temperature performance, integration and reliability, the active and passive components inside the car will also gradually increase. For packaging technology, if you want to keep up with these steps, you must undoubtedly achieve technological innovation.

The next article will focus on the development process of the packaging industry chain and the main technologies and products of OSAT manufacturer Amkor, to further understand the evolution of power semiconductor packaging technology.