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About the inverter industry: IGBT replacement and technology trends in China(1)

Dec 04, 2020

About the inverter industry: IGBT replacement and technology trends in China

The overall power semiconductor industry is growing steadily, with relatively small periodicity

Power semiconductors are the core of electric energy conversion and circuit control in electronic devices. They are mainly used to change voltage and frequency, DC and AC conversion in electronic devices. Power semiconductors are subdivided into power devices (a branch of discrete devices) and power ICs (a branch of integrated circuits). Ideally, a perfect converter has no voltage loss when it is turned on, and no power loss when it is switched on and off. Therefore, product and technological innovation in the field of power semiconductors is aimed at improving energy conversion efficiency.

According to IHS statistics, the global power semiconductor market in 2019 is about 40 billion U.S. dollars, and the global power semiconductor CAGR is expected to be 4.5% from 2019 to 2025. According to China Resources Micro's prospectus, China is the world's largest consumer of power semiconductors. The market demand scale in 2018 Reached 13.8 billion US dollars, a growth rate of 9.5%, accounting for 35.3% of global demand.

There are many levels of power semiconductor products, and IGBT is a typical product of the new generation

The evolution path of power discrete devices is basically diode → thyristor → MOSFET → IGBT, among which IGBT is a typical product in the new generation of power semiconductors. IGBT (Insulated Gate Bipolar Transistor), insulated gate bipolar transistor, is a fully controlled-voltage-driven power semiconductor composed of BJT (bipolar transistor) and MOSFET (insulated gate field effect transistor). IGBT has MOSFET Fast switching speed, high input impedance, low control power, simple drive circuit, low switching loss, and the advantages of low BJT conduction voltage, large on-state current, and low loss. It has the advantages of high voltage, high current, high speed, etc. Other power devices are incomparable, so it is an ideal switching device in the field of power electronics, and it is also known as the "CPU in power electronics."

According to Yole and other related statistics, about 50% of the global power semiconductors are power ICs, and the remaining half are power discrete devices; MOSFETs accounted for the highest proportion of power discrete device sales in 2017, accounting for about 31%, followed by diodes / Rectifier bridge accounted for about 29%, thyristor and BJT and other discrete devices accounted for about 21%, IGBT accounted for 19%, but its compound growth rate is the fastest of all products.

IGBT industry chain and three business models

The IGBT industrial chain includes upstream IC design, midstream manufacturing and packaging, and downstream includes industrial control, new energy, home appliances, electrical high-speed rail and other fields;

IGBT companies have three business models: IDM manufacturers, design manufacturers, and module manufacturers.

IDM: The IDM model is a vertically integrated manufacturer. It refers to an enterprise model that includes circuit design, wafer manufacturing, packaging and testing, and investment in the consumer market. The design of IGBT chips and fast recovery diode chips is just one of the departments, and the company owns Own fabs, packaging plants and test plants. This model has extremely high requirements for enterprise technology, capital and market share. At present, only a few international giants such as Infineon and Mitsubishi adopt this model;

Modules: such as Danfoss, Semikron, etc.;

Fabless mode: Fabless is a combination of Fabrication (manufacturing) and less (nothing). The Fabless model is a business model of the integrated circuit industry, that is, the company focuses on chip design and outsources chip manufacturing to foundry manufacturers. The chip foundry is responsible for purchasing silicon wafers and processing production. Companies in the Fabless mode do not need to invest in the establishment of a wafer manufacturing production line, which reduces investment risks and can quickly develop the chips required by the terminal.

Most foreign giants adopt IDM mode, while the Fabless+ module mode adopted by typical Chinese companies such as Star Semiconductor: The main reason why the Fabless mode is more popular in China is that power semiconductors do not require particularly sophisticated wafers. The payback period for the capital of a separate production line is very long. In addition, there are more mature process foundries in the mainland that are sufficient for their production capacity. Therefore, for most Chinese manufacturers who are latecomers, Fabless is also a comparison in the fast catch-up period. Good model.

IGBT products are updated slowly and prices are stable

Since the 1980s, IGBT chips have undergone 6 generations of upgrades, from planar punch-through type (PT) to trench type electric field-cut-off type (FS-Trench), chip area, process line width, on-state saturation voltage drop, off Various indicators such as off time and power loss have undergone continuous optimization, and the off-state voltage has also been increased from 600V to more than 6500V.

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IGBT product replacement is slow: At present, the IGBT 4 generation defined by Infineon is the mainstream of the market and has been used for more than ten years. Infineon launched IGBT7 at the end of 18, which reduces the area by 25% compared with the 4th generation. It is expected to reduce cost and power consumption. Large-scale promotion still takes 2-3 years. IGBT replacement is relatively slow, the chip plays a decisive role in product performance, and the module can only guarantee the performance of the chip. The new generation and the old generation of IGBT chips have their own advantages. The loss and area of the old generation may not be good, but the stability has been verified for a long time. A considerable number of customers still choose to use the old generation chips when the new generation comes out. Other Chinese and international companies have deployed IGBT 7-generation technology, but the product verification cycle is longer. Generally, customers need 5 to 10 years to verify reliability and application-side problems, so the iteration speed is slow. At present, the latest generation of IGBT Star is being researched and developed jointly with Hua Hong, and trial production is expected by the end of the year.

The price of IGBT is relatively stable: even in the downward trend in the industry, the ex-factory prices of major manufacturers have not fallen in 2019, showing a healthy price fluctuation. In summary, the replacement of IGBT chips is relatively slow, and it is a gradual innovation, continuous optimization and upgrading, specific to a certain IGBT product, it can be used as long as 10 years; at the same time, from the supply side, the IGBT industry giants are mainly German and Japanese manufacturers have relatively conservative styles and will not aggressively expand production capacity and fight price wars. The demand is stable and price fluctuations are relatively small, even in 2019 when the overall semiconductor demand is not good.

The core of circuit design lies in logic design, which can be through software such as EDA. Power semiconductors are similar to analog ICs. They need to be adjusted and compromised according to actual product parameters. Therefore, the engineers’ experience requirements are also higher. Excellent designers need 10 Years or more of experience. Some textbooks of power semiconductors and analog ICs in universities are basically equivalent to the "experience notes" of practitioners in the past few decades, and there is no relatively "standard paradigm" like digital integrated circuits, and R&D is through constant modification of parameters by the R&D engineer team. Performance and cost process.

Specifically, IGBT technology and barriers are extremely high, mainly reflected in the following aspects:

1), IGBT chip design

The IGBT chip is the core of the IGBT module: its design process is extremely complicated, not only to maintain the stable operation of the module in a large current, high voltage, and high frequency environment, but also to maintain switching and loss, short-circuit resistance and conduction voltage drop. balance. The fast recovery diode chip is used in conjunction with the IGBT chip in the IGBT module, and needs to withstand high voltage and large current, while requiring extremely short reverse recovery time and reverse recovery loss. Only when an enterprise has a deep technical background, strong innovation ability, and accumulated rich experience and knowledge reserves, can it gain a foothold in the industry. Therefore, latecomers in the industry often need to experience a long period of technical exploration and accumulation in order to compete with the companies that have already occupied technological advantages in the industry.

2), module design and manufacturing process

IGBT modules have high requirements for product reliability and quality stability, and the production process is complicated. A seemingly simple link in production often takes a long time to learn to master, such as aluminum wire bonding, which only needs to use aluminum for the circuit. Wires are connected, but the choice of bonding point, bonding strength, time and parameter settings of the bonding machine, fixture design applied in the bonding process, employee operation methods, etc. will affect the quality and yield of the product. As the core device of industrial products, IGBT modules need to adapt to various harsh working environments in different application fields, so the requirements for product quality are high. Such as the electric welding machine industry, consider the inverter welding machine.

The working environment is harsh and the load is heavy. When purchasing the core component IGBT module, the durability of the module will be given priority. Therefore, the reliability of the chip parameters and module manufacturing process is the core of the production of IGBT modules. Moreover, IGBTs are closely integrated with downstream applications, and it is often necessary for R&D personnel to have a better understanding of the downstream application industry to produce products that meet customer requirements. At present, there is still a shortage of R&D and technical personnel with relevant practices and rich experience in China. For new entrants to master the design and manufacturing process of IGBT chips or modules, and realize mass production, it takes a long time to cultivate talents and learn And technology accumulation.

The product stability of IGBT manufacturers needs to be verified for a long time, and the building of brand effect and reputation needs to be accumulated:

IGBT module is a key component in downstream products, and its performance, stability and reliability are very important to downstream customers. Therefore, the certification period is long and the replacement cost is high. For new IGBT suppliers, customers tend to maintain a cautious attitude. They will not only comprehensively evaluate the strength of the supplier, but also usually have to go through multiple links such as product single test, complete machine test, and multiple small batch trials. Make large-volume purchasing decisions, and the purchasing decision cycle is longer. Therefore, even if the new entrants in the industry develop and produce IGBT products, it will take a long time to win customer recognition.

The driving factors of the IGBT industry are clear, and the ceiling is strong

IGBT has a wide range of applications in many fields such as industrial control and automation, new energy vehicles, motor energy saving, solar power generation, wind power generation, etc.; used to improve the efficiency of power conversion, transmission and control in various circuits. Among them, new energy vehicles The drive system in is the most typical application.

In terms of global IGBT applications, industrial control accounts for 37%, which is the largest application field, electric vehicles 28%, new energy power generation 9%, and consumer fields 8%; while in China, due to China’s advanced high-speed rail, industrial control in downstream applications 29 %, rail transit 28%, new energy vehicles 12%, and new energy power generation 8%. However, with the continuous development of China's new energy sector, the demand for new energy vehicles, photovoltaics and wind power will continue to increase in the future.

In 2017, the global IGBT market was worth 5.255 billion U.S. dollars, an increase of 16.5% year-on-year in 2016. In 2018, the global IGBT market was about 5.836 billion U.S. dollars, an increase of 11% year-on-year. It is the most prosperous among power semiconductor segments.

Since the development of China's IGBT industry, great progress has been made. Although a large amount of imports is still needed, some enterprises have already had large-scale production capacity. In 2010, China's output of IGBT power electrical modules was 1.9 million, and in 2018 it increased to 11.15 million.

China’s IGBT demand growth far exceeds global growth: According to data from Zhiyan Consulting, the size of China’s IGBT market in 2018 was 16.19 billion yuan, a year-on-year increase of 22.19%, and the growth rate was significantly higher than the global average; benefited from new energy vehicles, wind power and With the continuous development of China's strong fields such as photovoltaics, it is expected that the compound growth rate of China's IGBT will continue to remain above 20% in the future.