With the rapid development of new energy vehicles, rail transit, photovoltaic power generation and other fields, the requirements for packaging materials for power semiconductor devices are becoming increasingly high. Insulated Gate Bipolar Transistor (IGBT), as the core device for energy conversion and control, is known as the "leader" in the field of power electronics; CPU"。 The harsh conditions such as high temperature, high humidity, and mechanical vibration generated during its working process pose severe challenges to the sealing materials.

At present, the mainstream high-power IGBT modules generally use the double-layer composite packaging structure of silicon gel+epoxy potting adhesive: the inner layer uses silicone gel to provide electrical insulation protection, and the outer layer usesEpoxy sealantProvide mechanical strength support. This article will systematically introduce the core advantages and application points of epoxy sealant in IGBT module packaging.

1、 What is IGBT module sealant?

1.1 Introduction to IGBT module

IGBT is a power semiconductor device that combines the advantages of high input impedance of MOSFET and low conduction voltage drop of bipolar transistor. It has the characteristics of simple driving, fast switching speed, and large on state current. Mainly used in the fields of new energy vehicle motor controllers, rail transit traction converters, photovoltaic/wind power inverters, industrial frequency converters, and smart home appliances.

1.2 Why is sealing necessary?

IGBT modules face multiple environmental pressures during operation: thermal stress (chip temperature can reach 150-200 ℃), electrical stress (high voltage can reach over 3300V), mechanical stress (vibration and impact causing wire breakage), and environmental erosion (moisture salt spray corroding metal components). Sealing adhesive is a key packaging material introduced to solve the above problems.

常见灌封胶类型对比：

2、 Eight core properties of epoxy sealant

Epoxy sealant is composed of special epoxy resin, curing agent, inorganic filler, and functional additives, and is one of the more widely used electronic packaging materials. Its core advantages are as follows:

1. Excellent mechanical protection capability

固化后形成坚硬致密的保护壳，有效抵御外部冲击和振动

2. Zhuoyue's chemical and environmental resistance

Can resist the erosion of chemical substances such as acid, alkali, and oil, and block moisture and salt spray

3. High electrical insulation

体积电阻率高、介电强度大，防止高压漏电和击穿

4. 优良的热稳定性

Can withstand a wide temperature range of -40 ℃ to+200 ℃

5. Anti oxidation and anti-corrosion

完全封闭内部空间，隔绝氧气水分，减少引线焊点氧化风险

6. Improve long-term reliability

可有效延长IGBT模块使用寿命2~3倍

7. 配方可定制性强

硬度从邵氏D70到D90+可调，支持室温至中温固化

8. 强大的粘接能力

能与铜、铝、陶瓷等多种基材形成牢固粘接

三、IGBT模块对灌封胶的特殊要求

与传统电子元器件灌封相比，大功率IGBT模块对灌封材料提出了更高要求：

• 高绝缘强度 — 保障"三结合点"（芯片-键合线-灌封胶界面）的绝缘可靠性

• 无副产物固化 — 避免气泡残留影响绝缘性能

• 极端耐温能力 — 内部工作温度可达180-200℃，需长期保持稳定

• 耐湿热与抗冲击 — 需通过85℃/85%RH标准测试及温度循环（-40℃↔+125℃）

 CTE热膨胀系数匹配 — 更关键指标

环氧树脂CTE通常为30-60ppm/℃，而硅芯片约2.6ppm/℃，铜衬板约17ppm/℃。CTE失配会在温度循环中产生巨大内应力，导致灌封体开裂、外壳脱离或绑定线断裂。降低CTE值并提高组件匹配性是研发的核心方向之一。

四、实际应用：双层复合灌封工艺

4.1 封装形式与灌封方式

4.2 双层复合灌封工艺流程

步骤1: IGBT芯片贴装 → 步骤2: 键合线互连 → 步骤3: 有机硅凝胶灌注（内层）

→ 步骤4: 凝胶固化 → 步骤5: 环氧胶二次灌封（外层加固）

→ 步骤6: 固化成型 → 测试验收

"先凝胶后环氧"方案的优势：

• 内层硅凝胶：提供柔性缓冲，吸收热应力；优异的电绝缘性防止局部放电

• 外层环氧层：形成坚硬外壳，提供机械强度和环境隔离

该方案在轨道交通用高压IGBT模块中应用尤为广泛。

4.3 技术发展方向

五、实验验证与选型建议

5.1 可靠性测试标准

国产环氧灌封胶在IGBT模块封装中的典型测试项目包括：

5.2 选型要点

1. 明确应用场景 — 工作温度范围、电压等级、是否户外使用

2. 确认工艺条件 — 是否支持真空灌注？固化炉温度上限？

3. 关注关键参数 — 优先考察CTE值、Tg、介电强度三大指标

4. 重视供应商资质 — 是否有IGBT行业案例和第三方检测报告

5. 小批量验证先行 — 完成可靠性测试后再批量导入

总结

环氧灌封胶凭借卓悦的机械强度、电气绝缘性和环境耐受性，在大功率IGBT模块封装中扮演着不可或缺的角色。尽管存在CTE匹配等技术挑战，但通过合理的配方设计和双层复合灌封工艺（硅凝胶+环氧胶），这些难题已得到有效解决。选择一款CTE匹配良好、经过充分可靠性验证的环氧灌封胶产品，是保障产品质量和长期可靠性的关键一步。

未来，环氧灌封胶正朝着超低CTE体系（<15ppm/℃）、高导热、快速固化、环保无卤阻燃的方向持续发展。