Development of an Underfill Rework Process and Evaluation of Underfill Reworkability
Authors: Jenny England, Ph.D., Brian Toleno, Ph. D., and Jonathan Israel Company: Henkel Electronics Materials LLC Date Published: 9/28/2014
Abstract: The use of reworkable underfill materials has increased significantly in recent years. One of the factors for this increase is the higher density circuitry on printed circuit boards (PCBs), which increases the value of the PCB, leading to more interest in using reworkable underfills. The goal of using the reworkable underfill material is to reduce the amount of scrap generated and extend the life of high-value PCBs. These savings can easily be negated if the rework process is overly complex or if the board and/or adjacent packages are destroyed in the rework process. In this paper, the authors will discuss a rework process that utilizes the assistance of a semi-automated rework machine. A three-stage rework profile will be introduced. The authors will present the tools required and the methodology recommended for easier removal of an underfilled component, while reducing the possibility of failures such as solder mask damage, pad pull-out, and solder extrusion on adjacent devices.
To benchmark material rework performance, a rework scoring matrix was developed and the reworkability of three underfills is compared using this scoring matrix.