About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
ECTC 2013
Conference paper
NiFe-based Ball-limiting-metallurgy (BLM) for microbumps at 50μm pitch in 3D chip stacks
Abstract
In this work, Pb-free microbumps at 50μm pitch with NiFe-based Ball-limiting-metallurgy (BLM) are fabricated and tested. Detailed microstructural analysis has been performed, which shows a uniform thin layer (∼0.2μm) of FeSn2 Intermetallic Compound (IMC) is formed between the Pb-free solder and NiFe BLM after the first reflow. In comparison, the NiCuSn IMC can grow more than 2μm in microbumps with the conventional Ni BLM or solder-caped Cu pillar after the first reflow. An excessive lateral 'thermal-undercut' has been discovered in NiFe BLM structures during solder reflows due to good edge wettability of NiFe. A dual-layer BLM structure is proposed and demonstrated to mitigate the 'thermal-undercut'. Moreover, addition of NiFe layer on a micro-Cu pillar structures have been demonstrated and characterized. © 2013 IEEE.