Evaluation of Anisotropic Conductive Films Based on Vertical Fibers for Post-CMOS Wafer-Level Packaging

Abstract

Abstract-In this paper, we investigate the mechanical and electrical properties of an anisotropic conductive film (ACF) on the basis of high-density vertical fibers for a wafer-level packaging (WLP) application. As part of the WaferBoard, a reconfigurable circuit platform for rapid system prototyping, ACF is used as an intermediate film providing compliant and vertical electrical connection between chip contacts and a top surface of an active wafer-size large-area IC. The chosen ACF is first tested by an indentation technique. The results show that the elastic-plastic deformation mode as well as the Young's modulus and the hardness depend on the indentation depth. Second, the efficiency of the electrical contact is tested using a uniaxial compression on a stack comprising a dummy ball grid array (BGA) board, an ACF, and a thin Al film. For three bump diameters, as the compression increases, the resistance values decrease before reaching low and stable values. Despite the BGA solder bumps exhibit plastic deformation after compression, no damage is found on the ACF film. These results show that vertical fiber ACFs can be used for nonpermanent bonding in a WLP application.

Investigation of Process Parameters and Characterization of Nanowire Anisotropic Conductive Film for Interconnection Applications

“…It is concluded that the contact resistances can be the major contributing factor in this bonding system. A comparable finding is reported in [31] with the ACF based on vertical fibers where the contact resistance of such ACF under a compression interconnect system is the major contributor in the total resistance. However, the possible causes for the contact resistance in this paper may be different.…”

Electrochemiluminescence Imaging Based on Bipolar Electrochemistry Using Commercially Available Anisotropic Conductive Films

“…Conductive fibers have also been used instead of particles for ACFs. (31) Herein, the configuration of the electrode is the same as that of BPE films in ECL imaging. Therefore, we assume that commercially available ACFs can be used as BPE films for ECL imaging.…”