2. Silicone Gel:

Silicone gel is a special silicone rubber that exists in both liquid and solid states, characterized by 'solid-liquid coexistence'. It is very soft and does not exert mechanical stress on the IGBT chip, maintaining its softness even at temperatures ranging from -50°C to 200°C, effectively protecting the IGBT chip from moisture erosion, achieving insulation, moisture-proofing, dust-proofing, shock absorption, and corrosion resistance. When selecting silicone gel for specific IGBT applications, the following key characteristics need to be considered:

① High-Temperature Resistance: Silicone gel needs to maintain stable performance within the operating temperature range of the IGBT module, which is typically -40°C to 150°C, but some applications may require higher temperature tolerance, such as IGBT modules in new energy vehicles that may face higher temperature challenges.

② Electrical Insulation Performance: Silicone gel should have high dielectric strength and volume resistivity to ensure reliable insulation protection under high voltage.

③ Temperature Cycling Resistance: IGBT modules will experience temperature cycling in practical applications, so silicone gel needs to have good temperature cycling resistance to maintain long-term reliability.

④ Low Stress and Flexibility: Silicone gel should have low internal stress and good flexibility to reduce mechanical stress on the IGBT chip and improve packaging reliability.

⑤ Moisture and Water Resistance: Silicone gel needs to effectively prevent moisture and water from eroding the IGBT module, protecting the device from the effects of humid environments.

⑥ Shock Resistance: Silicone gel should have good shock resistance to protect the IGBT module from damage during mechanical impacts.

⑦ Chemical Stability: Silicone gel needs to have good chemical stability, not easily reacting adversely with other materials, ensuring long-term stability.

⑧ Thermal Aging Characteristics: Silicone gel needs to have good thermal aging characteristics during long-term use, especially in high-temperature environments, to maintain its performance without degradation.

⑨ Environmental Adaptability: Silicone gel needs to adapt to various environmental conditions, including ozone resistance, radiation resistance, and weather aging resistance.

⑩ Material Compatibility: Silicone gel needs to have good compatibility with other materials in the IGBT module (such as substrates, heat sinks, etc.) to ensure the overall reliability of the packaging.

Depending on different application requirements, other characteristics of silicone gel, such as transparency, yellowing resistance, and curing speed, may also need to be considered. By comprehensively considering these factors, suitable silicone gel packaging materials for specific IGBT applications can be selected.

Ordinary linear polydimethylsiloxane (PDMS) gel becomes brittle after being stored at high temperatures above 175°C for more than 1000 hours, with significant declines in mechanical and dielectric properties, and may even crack. As the packaging forms of IGBT modules continue to evolve, higher demands are placed on the organic silicone gels used for packaging. The high purity, high-temperature resistance, and high dielectric properties of organic silicone gels for IGBT module packaging are key development directions that need to be focused on. The insufficient purity of organic silicone gels is due to the purity of raw materials and the preparation process. Organic silicone gels with excessively high ionic content can undergo yellowing, hardening, and metal ion migration in long-term high-temperature and high electric field environments, directly affecting the reliability of IGBTs. Therefore, the issue of organic silicone gel purity needs to be given special attention.

4. Application of Epoxy Resin in IGBT Packaging

Epoxy resin is a high molecular material that contains more than two epoxy groups in its molecular chain segments. It has strong processability, good dielectric properties, and high mechanical strength, making it widely used in various fields. Epoxy resin materials are mainly used in IGBT module packaging for potting.

The epoxy potting adhesive used for IGBT module potting is generally applied after the silicone gel potting is completed. After curing, it forms a dense and hard protective layer on top of the silicone gel, which can protect and enhance the integrity of the module, providing practical significance for improving the module's resistance to mechanical shock. This packaging structure is more commonly used in IGBT modules for rail transportation.

 

Performance requirements for epoxy resin adhesives in IGBT packaging:

The epoxy adhesive used for IGBT module potting mainly adopts a two-component form, made from special epoxy resin, inorganic fillers, and additives. Its cured product has high flame retardancy and a low CTE value, effectively isolating the impact of adverse external environments.

Epoxy potting adhesives made from ordinary bisphenol A epoxy resin can shrink and crack at low temperatures of -40°C, leading to packaging failure. At high temperatures exceeding 150°C, they can soften, losing some mechanical and dielectric properties. After a period at temperatures above 200°C, there is a possibility of chemical bond breakage, resulting in the generation of small molecular volatile substances. Therefore, there are many issues with the packaging of silicon carbide IGBT modules operating at temperatures reaching 200°C. The high-temperature resistance, crack resistance, low CTE value, and improvements in the application process of epoxy adhesives for IGBT module potting are key development directions that need to be focused on.

 

Shanghai Hinnel New Materials Technology Co., Ltd. has developed an epoxy adhesive suitable for IGBT potting using bisphenol A epoxy and anhydride. Its performance can withstand over 1000 cycles of cold and hot shock tests from -40°C to 125°C. Based on this, a model equation for the viscosity of the epoxy adhesive was established, predicting the flow characteristics of the epoxy adhesive within 50-90°C, providing valuable references for the application process. To develop a better heat-resistant IGBT epoxy potting adhesive, the technical team researched and used high-temperature resistant special epoxy resin as the main resin, combined with high-temperature resistant silicon carbide and flame-retardant aluminum hydroxide as fillers, to prepare an IGBT epoxy potting adhesive with good mechanical properties and high dielectric properties at high temperatures. Its glass transition temperature exceeds 200°C, meeting the potting requirements of high-power IGBT modules.

 

5. Recommended Adhesives for IGBT Module Packaging

Product Category	Product Type	Product Model	Adhesive Application Points	Curing Method	Main Performance
Organic Silicone Sealant	Dehydration Type	HN733T	Shell Frame Sealing	Room Temperature Curing	Room Temperature Curing, Low Viscosity Transparent
Organic Silicone Sealant	Dehydration Type	HN736W	Shell Frame Sealing	Room Temperature Curing	Titanate System, Not Easily Causes Silicone Gel Poisoning
Organic Silicone Sealant	Addition Type	HN818 Series	Shell Frame Sealing	Heating Curing	High Temperature Fast Curing, Will Not Cause Silicone Gel Poisoning
Organic Silicone Gel	Addition Type	HN5272 Series	Potting Protection	Heating Curing	Low Hardness, Very Soft, High Purity, Resistant to Yellowing
Epoxy Resin Adhesive	Anhydride Type	HN6300 Series	Potting Protection	Heating Curing	Low Viscosity, High TG, High Temperature Resistance, Crack Resistance

Conclusion: In the packaging process of high-performance power semiconductor devices such as IGBT (Insulated Gate Bipolar Transistor) and SiC MOSFET (Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor), choosing the right packaging adhesive is crucial. These advanced materials must not only possess good electrical insulation, high thermal stability, and chemical corrosion resistance but also meet the increasing demands for power density and long-term reliability. The organic silicone and epoxy resin packaging adhesive solutions provided by Shanghai Hinnel New Materials are developed based on a profound understanding of these needs. Organic silicone packaging adhesives, with their excellent high-temperature and aging resistance, as well as good flexibility and adhesion, are ideal choices for protecting power modules from environmental erosion and enhancing overall lifespan. Epoxy resin, due to its cost-effectiveness, good processability, and high mechanical strength, occupies a place in cost-effective packaging applications. Both ensure excellent sealing effects and thermal management performance during the packaging process through precise formulation and advanced processes, providing solid guarantees for the efficient and stable operation of power devices such as IGBT/SiC MOSFET.

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