I. Fundamentals of Insulation Materials in Semiconductor Modules
In high-power semiconductor devices such as IGBTs and IPMs (Intelligent Power Modules), the materials used to electrically isolate live circuits from the module baseplate are collectively referred to as insulation materials.
Insulation performance directly determines the module’s voltage withstand capability, operational stability, and service life, making it a critical parameter that cannot be overlooked in power semiconductor design.
In the manufacturing of high-power semiconductor devices, ceramic materials are commonly used as high-performance insulating substrates due to their excellent dielectric strength and thermal conductivity.
In addition, materials such as polyimide and epoxy resin are also widely used. These insulation layers are typically thinner and provide stable electrical insulation, but their thermal resistance is significantly higher than that of ceramic substrates, which requires additional optimization in thermal management design.
II. IGBT Insulation Characteristics and Common Substrate Types
As a core device in power electronics, the IGBT (Insulated Gate Bipolar Transistor) is widely used across industries such as electric vehicles, renewable energy, and 5G communications.
Its insulation characteristics are closely related to substrate selection. Differences in insulation performance, heat dissipation, and cost across substrate types directly impact the application range and lifetime of IGBT modules and IPM modules.
1. IMS Substrate: Preferred for Low-Cost, Low-Power Applications
The IMS (Insulated Metal Substrate) is widely used in low-cost, low-power IGBT and IPM module applications.
Its manufacturing structure involves applying an insulation layer directly onto a metal base. A dielectric film is laminated onto the copper layer, followed by precise etching based on circuit design patterns.
The advantages of IMS substrates include:
- Low manufacturing cost
- Fine circuit patterning capability
- Easy integration of control, driver, and protection circuits
- Strong mechanical stability and resistance to deformation
These features make IMS substrates ideal for cost-sensitive and lower power applications, such as industrial control systems and home appliances.
2. Advantages of HXIPMSEMI Customized IMS Substrates for IGBT and IPM Modules
As a professional power module brand, HXIPMSEMI adopts customized IMS substrates across its full range of IGBT and IPM modules.
Compared with conventional DCB substrates on the market, HXIPMSEMI’s solution achieves a better balance between thermal performance and insulation capability.
It retains the key benefits of IMS substrates—such as fine circuit layout and cost efficiency—while enhancing:
- Insulation voltage withstand capability
- Heat dissipation efficiency
This enables more stable insulation performance and improved thermal management during long-term high-power operation, effectively reducing the risk of failure.
3. Limitations of Thin Insulation Layers and Thermal Optimization Solutions
The insulation layer in IMS substrates is relatively thin. While this helps reduce module size, it can also introduce challenges:
- Higher parasitic capacitance, which may interfere with circuit signals
- Reduced heat dissipation capability when copper layers are too thin
- Increased chip temperature due to inefficient heat transfer
These factors can negatively impact IGBT insulation performance and device lifetime.
To address these issues, common industry solutions include:
- Adding additional metal heat-spreading layers
- Using aluminum heat dissipation structures beneath the chip
- Creating improved thermal paths to enhance heat transfer
These approaches help balance insulation performance and thermal efficiency.
4. DCB and AMB Substrates: Standard for High-Power and High-Voltage Applications
In high-voltage and high-power IGBT and IPM modules, DCB (Direct Copper Bonded) substrates are widely used.
A typical DCB structure consists of:
- A ceramic insulation layer (commonly aluminum oxide, Al₂O₃)
- Copper layers bonded on both sides
Through a high-temperature process above 1063°C, a thin copper oxide layer forms on the ceramic surface, enabling strong bonding between copper and ceramic. This results in excellent insulation strength and voltage withstand capability.
Another important substrate type is AMB (Active Metal Brazed). AMB substrates use titanium-containing brazing materials to bond copper or aluminum foils onto ceramic substrates such as aluminum oxide or aluminum nitride. The top copper layer is then etched into circuit patterns for power module applications.
In DCB structures, the bottom layer is either:
- Soldered directly to the module baseplate, or
- Mechanically clamped to a heat sink using a dedicated housing
This ensures both reliable insulation and stable heat dissipation.
III. Key Factors Affecting IGBT Insulation and Voltage Withstand Capability
The main advantage of ceramic substrates (DCB and AMB) lies in their thermal expansion coefficient, which is very close to that of silicon chips.
Under repeated temperature cycling, this minimizes thermal stress and helps maintain long-term insulation integrity.
In contrast, IMS substrates use metals such as copper and aluminum, which have significantly different thermal expansion coefficients compared to silicon. During temperature fluctuations:
- Mechanical stress develops between the substrate and the chip
- Stress increases further during module operation
This places greater demands on the insulation material’s dielectric strength and voltage withstand capability, making insulation performance more challenging.
Overall, the insulation and voltage withstand capability of IGBT modules are influenced by multiple factors, including:
- Substrate thickness
- Insulation material type
- Material uniformity
- Package housing design
- Encapsulation materials
- Chip layout
- Soldering and bonding processes
Currently, most mainstream IGBT and IPM power modules on the market have insulation voltage ratings in the range of 2.5 kV to 9 kV (RMS). These values vary depending on power level and substrate type, allowing adaptation to different high-voltage application scenarios.
IV. Conclusion
The insulation characteristics of IGBT modules are fundamental to their safe and reliable operation, and substrate selection directly determines both insulation performance and thermal efficiency.
- IMS substrates offer high cost-performance and are suitable for low-power applications
- DCB and AMB substrates provide strong voltage withstand capability and are ideal for high-power environments
- HXIPMSEMI optimizes IMS substrate design to achieve a balance between insulation reliability and heat dissipation
This makes HXIPMSEMI IGBT and IPM modules a reliable choice for applications in industrial control, renewable energy, and home appliances.