Application case of thermal conductive silicone grease for electric drive system of new energy vehicles

Introduction: Challenges in Thermal Grease Selection for NEV Thermal Management

In the thermal management of new energy vehicle (NEV) electric drive systems, the heat dissipation efficiency of power semiconductors (such as IGBT and SiC modules) directly determines the vehicle’s power performance and reliability. As the critical medium connecting the chip and the heat sink, the selection of thermal interface grease is of paramount importance. High-quality thermal conductivity grease can effectively reduce contact thermal resistance, ensuring that IGBT heat dissipation and SiC module thermal conduction remain within safe limits. This case study explores how a NEV manufacturer scientifically selected thermal paste for power electronics in an inverter to solve thermal management challenges under extreme operating conditions.

Application Scenario Description: Harsh Thermal Environment in Inverters

The inverter in this NEV manufacturer’s electric drive system features a compact internal space, where IGBT/SiC modules generate extremely high heat flux density during peak power output. Due to continuous vibration during driving and mechanical stress caused by the mismatch in thermal expansion coefficients between the power module and the heat sink, traditional thermal greases are highly susceptible to the “pump-out effect" or oil bleeding. This not only leads to the drying and failure of the thermal interface material but also triggers local hot spots, severely threatening driving safety. Therefore, the system demands exceptionally high anti-creep, pump-out resistance, and long-term thermal cycling stability from thermal paste for power electronics.

Product Recommendation and Matching Solution: Combination Strategy of G-776 and G-775/G-777

To address the complex requirements of the electric drive system, we recommend a combination solution using Shin-Etsu grease: utilizing G-776 as the primary thermal interface material, supplemented by G-775 or G-777 for reinforcement or differentiated design in specific areas. G-776, diluted with isoparaffinic solvents, maintains low viscosity (58 Pa·s) for easy automated dispensing while demonstrating superior pump-out resistance and anti-creep performance compared to general-purpose products, making it ideal for high-reliability thermal interfaces like IGBTs and CPUs. For edge areas subjected to greater mechanical stress or requiring ultimate long-term reliability, G-775 with high viscosity (500 Pa·s) or G-777 with extremely stable physical properties can be paired to build a multi-layered thermal protection barrier.

Product Comparison Analysis: Key Parameters of Three White Thermal Greases

To more intuitively demonstrate the basis for selection, the following table compares the core parameters of three white thermal greases: G-775, G-776, and G-777. G-776 achieves the best balance between thermal conductivity (3.1 W/m·K) and application convenience; G-775 provides ultimate pump-out resistance with its high specific gravity and high viscosity; while G-777 ensures a service life of up to ten years with an extremely low volatile content (0.1%).

Implementation Results and Data: Thermal Resistance Reduction and Lifespan Extension

After introducing the Shin-Etsu grease solution with G-776 as the primary and G-777 as the secondary material, the inverter demonstrated excellent performance during continuous operation tests at a junction temperature of 150℃. Measured data indicates that the interface thermal resistance of the IGBT module decreased by approximately 18% compared to the previous generation of general-purpose grease, and the peak junction temperature dropped by 4.5℃. After 2,000 hours of high-temperature, high-humidity, and thermal shock cycling tests, no significant oil bleeding or drying was observed at the G-776 interface. The thermal resistance growth rate was kept below 5%, perfectly meeting the 15-year/300,000 km full lifecycle thermal management requirements for NEVs.

FAQ: Frequently Asked Questions

1. Why can’t general-purpose thermal grease be used directly in NEV electric drive systems?

General-purpose grease is prone to the pump-out effect under continuous vibration and thermal expansion/contraction, leading to cooling failure. Electric drive systems must use thermal paste for power electronics with high anti-creep and pump-out resistance.

2. Will the low viscosity of G-776 affect long-term reliability?

No. G-776 uses a special solvent formulation; its initial low viscosity facilitates automated application, and after solvent evaporation, its anti-creep and oil-bleeding resistance outperform most general-purpose products, specifically designed for high-reliability scenarios like IGBTs.

3. When should G-775 be chosen over G-776?

When the application area is subjected to extreme mechanical stress, or when the heat sink has poor flatness requiring a thicker bond line to fill gaps, G-775’s high viscosity (500 Pa·s) and high specific gravity provide ultimate pump-out resistance and structural support.

4. How does the volatile content of thermal grease affect the system?

High volatile content causes the grease to dry and harden at high temperatures, increasing thermal resistance. With a volatile content of only 0.1%, G-777 ensures stable physical properties for up to ten years at 200℃, making it suitable for maintenance-free electric drive systems.

5. How to evaluate the application compatibility of Shin-Etsu grease?

The low viscosity of G-776 makes it perfectly compatible with automated processes like dispensing and screen printing. It also exhibits excellent wetting before curing, effectively filling micro-level interface voids to reduce contact thermal resistance.

6. Is this combination solution suitable for SiC module heat dissipation?

Absolutely. SiC modules have higher heat flux density and stricter requirements for interface materials. The G-776/G-777 combination possesses excellent high-temperature stability and low thermal resistance, making it an ideal choice for SiC module thermal conduction.

Conclusion and Contact Guidance

In the thermal management of NEV electric drive systems, selecting the appropriate thermal interface grease is the cornerstone of ensuring long-term system stability. Through the scientific combination of G-776 and G-775/G-777, the pain points of pump-out and drying in IGBT heat dissipation and SiC module thermal conduction can be effectively resolved.