Limited or Reduced Underfill Fillet Size for Improved Flip-Chip PBGA Reliability
Original Publication Date: 2002-Aug-20
Included in the Prior Art Database: 2002-Aug-20
Abstract—Encapsulation of flip chip packages with underfill epoxy is critical for package reliability. However, underfill materials crack during stressing and cause electrical failures. The underfill fillet is essential in lowering the stress on the die and improving moisture resistance in the package, but is mainly where the underfill material cracks originate. By reducing the size of the underfill fillet below a specified limit, the stress reduction on the die and moisture resistance are maintained. The reduced fillet results in fewer cracks and electrical failures thereby improving reliability.