intermetallic formation

**Intermetallic formation** is the **metallurgical reaction at bonding interfaces where wire and pad metals form compound layers during and after bonding** - controlled intermetallic growth is necessary for strong and reliable bonds. **What Is Intermetallic formation?** - **Definition**: Creation of metal-compound phases at bonded interfaces under thermal and ultrasonic energy. - **Bonding Context**: Occurs in wire-to-pad and wire-to-lead interfaces across package types. - **Growth Behavior**: Intermetallic thickness changes over time with temperature and current stress. - **Material Dependence**: Different wire-pad combinations form distinct compound systems. **Why Intermetallic formation Matters** - **Bond Strength**: Initial intermetallic layer is required for mechanical and electrical connection. - **Reliability Risk**: Excessive growth can embrittle interfaces and increase failure probability. - **Resistance Stability**: Interface chemistry affects long-term electrical resistance drift. - **Process Qualification**: Intermetallic profile is a key indicator in bond-process health. - **Failure Analysis**: IMC morphology often reveals root cause of bond degradation modes. **How It Is Used in Practice** - **Material Matching**: Select wire and pad metallization combinations with proven IMC behavior. - **Thermal Management**: Limit post-bond thermal exposure to control excessive IMC thickening. - **Cross-Section Review**: Periodically inspect IMC thickness and morphology during qualification. Intermetallic formation is **a central metallurgy mechanism in bonded-interconnect reliability** - balanced intermetallic control is essential for durable electrical contacts.