The Over-Bump Applied Resin Wafer-Level Underfill Process: Process, Material and Reliability

The over bump applied resin (OBAR) process is a wafer-level underfill (WLUF) process in which a filled resin is applied over the bumps of a wafer, dried, diced into coated chip which are aligned and joined through a substrate resulting in an underfilled flip chip package. This process has been evaluated by IBM on several test vehicles in close cooperation with Henkel (formerly Abelstik) which developed a material specifically to fit this process. The critical steps to make this technology work are alignment of OBAR coated chip to a substrate, elimination of significant voids and formation of a fillet with appropriate shape and size. The reliability of the material was evaluated after capping and BGA ball mount through JEDEC level 3 pre-con followed by DTC (deep thermal cycling), T&H (temperature and humidity), and HTS (high temperature storage). While some difficulties still exist, the OBAR process has been shown to be a viable alternative to capillary underfill application.

By: Claudius Feger; Nancy LaBianca; Michael Gaynes; Steven Steen; Zhen Liu; Raj Peddi; Mark Francis

Published in: RC24851 in 2009


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to .