Evaluation of the Delamination in a Flip Chip Using Anisotropic Conductive Adhesive Films Under Moisture/Reflow Sensitivity Test

Abstract

Anisotropic conductive adhesive films (ACFs) have been used for electronic assemblies such as the connection between a liquid crystal display panel and a flexible printed circuit board. ACF interconnection is expected to be a key technology for flip chip packaging, system-in-packaging, and chip size packaging. This paper presents a methodology for quantitative evaluation of the delamination in a flip chip interconnected by an ACF under moisture/reflow sensitivity tests. Moisture concentration after moisture absorption was obtained by the finite element method. Then, the vapor pressure in the flip chip during solder reflow process was estimated. Finally the delamination was predicted by comparing the stress intensity factor of an interface crack due to vapor pressure with the delamination toughness. It is found that the delamination is well predicted by the present methodology.Index Terms-Anisotropic conductive adhesive films (ACFs), delamination toughness, flip chip, moisture/reflow sensitivity test, reliability, stress intensity factor.

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

“…Moisture absorption has also been reported as a reliability issue for spherical particle ACFs. This moisture tends to induce mechanical failures at the interface between the chip and the ACF or between the substrate and the ACF [4], [7].…”

“…In practice, the modulus of the matrix is negligible compared with the modulus of the fiber (E m E f ) thus, the longitudinal modulus of the ACF based on vertical fibers depends essentially on the fiber Young's modulus E f [see in (7)] whereas in (1) to (4) the spherical particle ACF's modulus depends on the modulus of the matrix E m .…”

Anisotropic conductive adhesives in electronics

“…in addition the work deals with an extensive process study concerning the bonding conditions. Ikeda et al (2006) studied the delamination behavior in 200 mm-pitch assemblies under moisture-reflow conditions. To this end they introduced a so-called 'delamination toughness factor', which is the total stress intensity factor of an interface crack between two materials in the presence of a beginning delamination.…”

Material properties of anisotropic conductive films (ACFs) and their flip chip assembly reliability in NAND flash memory applications

“…In the PCT, two failure modes of the COB assemblies can be considered, ACF swelling by moisture absorption in the ACF layer and moisture penetration along the ACF/chip interface. Generally, the major failure site in the PCT is the ACF/chip interface due to moisture penetration [5,6]. As mentioned, the B1 ACF had high die adhesion strength; hence, it is difficult for moisture to penetrate the chip-ACF interface.…”