Best practices in automated underfill dispensing

Automating the underfill dispensing process for robust production can be challenging as package sizes decrease, underfill materials advance, and tolerances tighten. The best practices for automated underfill dispensing are discussed for various types of underfill packages. The modern production environment requires "hands-off" calibration and operation. Methods for calibrating dispensing volumes are given and how they affect accuracy and overall process speed are discussed. Differences in automating dispensing for singulated packages and substrates containing multiple die are discussed. Subjects include part heating, automated alignment calibration, and controlling dispensing tolerances. Methods for fillet width control and avoiding air entrapment through the dispensing pattern are given. The advantages of multiple dispensing passes and their limitations on fillet control with fast flowing underfill materials are given. Recommendations for improvement of process speed are discussed. Advantages and disadvantages of various fluid delivery technologies, with supporting data, are given. Time pressure dispensing, auger pump dispensing, and linear piston pump dispensing are included in this discussion. Data is presented which show how the underfill encapsulant rheology can be changed by the dispensing device. The goal is to provide the reader with variety of methods that will help define a robust, production ready process.