IGBT， Insulated Gate Bipolar Transistor (IGBT) is a composite fully controlled voltage driven power semiconductor device that integrates BJT (Bipolar Transistor) and MOS (Insulated Gate Field Effect Transistor). It cleverly combines the high input impedance of MOSFET with the low conduction voltage drop of GTR, retaining the characteristics of GTR's reduced saturation voltage and high current density, while overcoming its shortcomings of high driving current. At the same time, it also inherits the advantages of MOSFET's low driving power and fast switching speed, and improves its limitations of high conduction voltage drop and low current density. Therefore, IGBT plays an excellent role in converter systems with DC voltages of 600V and above, such as AC motors, frequency converters, switching power supplies, lighting circuits, and traction drives.

IGBT module is a modular semiconductor product composed of IGBT chip and FWD chip bridged and packaged through carefully designed circuits. This modular design enables IGBT modules to be directly applied in devices such as frequency converters and UPS uninterruptible power supplies, without the need for cumbersome installation steps. IGBT modules are not only energy-saving and efficient, but also have convenient installation and maintenance characteristics and stable heat dissipation performance. In today's market, this type of modular product dominates, and the commonly referred IGBT also specifically refers to IGBT modules. With the increasing popularity of energy-saving and environmental protection concepts, the market demand for IGBT modules will continue to grow. As a key component for energy conversion and transmission, IGBT modules are known as the "CPU" of power electronic devices and occupy a pivotal position in national strategic emerging industries. They are widely used in various fields such as rail transit, smart grids, aerospace, electric vehicles, and new energy equipment.

Manufacturing process and workflow of IGBT modules
The manufacturing process of IGBT modules involves multiple fine steps, including screen printing, automatic SMT, vacuum reflow soldering, ultrasonic cleaning, defect detection (via X-ray), automatic wire bonding, laser marking, shell encapsulation, shell gluing and curing, as well as terminal forming and functional testing. These steps together constitute the complete manufacturing process of IGBT modules, ensuring the quality and performance of the product.

Packaging Technology of IGBT Modules
It is the key to improving its service life and reliability. With the trend of market demand for IGBT modules with smaller size, higher efficiency, and stronger reliability, the research and application of IGBT module packaging technology have become increasingly important. At present, the popular IGBT module packaging forms include lead type, solder pin type, flat plate type, and disc type, and the module packaging technology is diverse. Each manufacturer's name also has its own characteristics, such as Infineon's 62mm package, TPDP70, etc.

The IGBT module consists of three key connection parts: the aluminum wire bonding point on the silicon wafer, the welding surface between the silicon wafer and the ceramic insulation substrate, and the welding surface between the ceramic insulation substrate and the copper substrate. The damage to these contacts often stems from the stress and material thermal deterioration caused by the difference in thermal expansion coefficients between the two materials at the contact surface.

Packaging Technology of IGBT Modules
It covers multiple aspects, mainly including heat management design, ultrasonic terminal welding technology, and high reliability soldering technology. In terms of heat dissipation management, the chip layout and size have been optimized through encapsulated thermal simulation technology, resulting in an increase of approximately 10% in output power under the same Δ Tjc conditions. The ultrasonic terminal welding technology directly connects the copper pad with the copper bonding wire, which not only has a high melting point and strength, but also eliminates the difference in linear expansion coefficient, ensuring high reliability. In addition, high reliability soldering technology has also attracted attention, among which Sn Ag In and Sn Sb soldering still maintain their strength after 300 temperature cycles, demonstrating excellent high-temperature stability.

Packaging process of IGBT module
It includes several steps, such as primary welding, primary bonding, secondary welding, secondary bonding, assembly, upper shell and sealant coating, curing, silicon filling gel, aging screening, etc. It should be noted that these processes are not fixed, but may vary depending on the specific module. Some may not require multiple welding or bonding, while others may require it. At the same time, there are auxiliary processes such as plasma treatment, ultrasonic scanning, testing, and marking, which together constitute the complete packaging process of IGBT modules.

The packaging function of IGBT modules
This is mainly reflected in several aspects. Firstly, colloidal isolation technology is adopted to effectively prevent potential explosions that may occur during the operation of the module. Secondly, its electrode structure is specially designed as a spring structure, which can buffer the impact on the substrate during installation and reduce the risk of substrate cracking. Furthermore, the meticulous processing of the bottom plate is closely integrated with the radiator, significantly enhancing the thermal cycling capability of the module. Specifically, the bottom plate design adopts a midpoint approach to ensure minimal deformation under specified installation conditions, achieving an ideal connection with the radiator. In addition, in the application process of IGBT, the impact of the turn-on phase is relatively mild, while the turn off phase is more stringent. Therefore, most damage situations occur during the turn off process due to exceeding the rated value.

Technical Explanation of IGBT Module Packaging Process
Firstly, let's talk about welding technology. The soldering quality between the chip and DBC substrate is crucial in achieving excellent thermal conductivity. It directly affects the heat transfer efficiency of the module during operation. We use vacuum welding technology to clearly observe the porosity of DBC and substrate, ensuring that no heat accumulation occurs and protecting IGBT modules from damage.

Next is bonding technology. The main function of bonding is to achieve stable electrical connections. In high current environments, such as 600A and 1200A, IGBT needs to conduct all current, and the bonding length becomes particularly important at this time. The bond length and notch design directly affect the size and current parameters of the module. If the bonding design is improper, it may lead to uneven current distribution, thereby damaging the IGBT module.

In addition, the installation of the casing is also a critical step in the packaging process. The IGBT chip itself does not directly come into contact with the environment such as air, and its insulation performance is mainly guaranteed by the casing. Therefore, the shell material needs to have multiple characteristics such as high temperature resistance, deformation resistance, moisture resistance, and corrosion resistance to ensure the stable operation of IGBT modules.

The third is tank sealing technology. IGBT modules face challenges such as rain, humidity, high altitude, and dust in harsh environments such as high-speed trains, bullet trains, and locomotives. In order to ensure the isolation of IGBT chips from the external environment and achieve stable operation, the selection of can sealing materials is crucial. This material not only requires stable performance and non corrosiveness, but also insulation and heat dissipation functions, while having low expansion and contraction rates. During the packaging process, we will also add a buffer layer to cope with the heating and cooling processes during chip operation. If the thermal expansion coefficient of the filling material is not consistent with that of the shell, it may lead to delamination. Therefore, adding appropriate fillers such as buffer materials in IGBT modules can effectively prevent this problem.

The fourth is the quality control process. After production is completed, we need to conduct comprehensive performance testing on high-power IGBT modules to ensure their quality. This includes testing the flatness of the flat facility base plate, as flatness directly affects the contact performance and thermal conductivity of the radiator. In addition, the push-pull test is used to evaluate the strength of the bonding point, while the hardness tester is used to ensure that the hardness of the main electrode is moderate. Ultrasonic scanning technology is used to detect the welding process and product quality after welding, including porosity, which is crucial for controlling thermal conductivity. At the same time, electrical monitoring methods are also essential, mainly monitoring whether the parameters and characteristics of IGBT modules meet design requirements, as well as conducting insulation tests.