- 0.2 - 0.3 μm tin layer to protect copper from corrosion
- Copper pillar covered with 0.2 μm of tin
- FIB cut of tin plated on copper pillar side wall
Immersion Tin for Corrosion Protection
The Stannolyte portfolio consists of pre-treatment solutions, wetting agents for oxide removal, and immersion tin plating chemistries used for the electroless deposition of tin for pillar sidewall protection.
The latest trends in flip chip technology are moving towards smaller pitch sizes and increased density of integrated circuits. Standard solder packaging technology will soon reach its technical limitation and consequently new solutions are needed to meet the future challenges for advanced packaging. Atotech has developed a process to address the requirements for flip chip technology using through mask plating. The plating process begins with the electrochemical depositions of Spherolyte copper for pillar formation, followed by Spherolyte nickel and Spherolyte tin for solder capping. After removal of the plating mask and seed layer, the sidewall of the copper pillar is exposed. Following the flip chip solder process, the exposed copper sidewalls are directly connected to the underfill material. Stannolyte immersion tin is used to protect the pillar sidewalls from oxidation and enhance the adhesion of the pillar to the underfill material.
Features and Benefits
In copper pillar applications, superior adhesion of the pillar sidewall to the underfill material is the main requirement. Stannolyte was developed to support the adhesion performance and successfully delivers the following process advantages.
- Defect-free tin deposition
- Superior adhesion to the underfill material
- Highest thickness uniformity
- Whisker and dendrite inhibited process