Anisotropic conductive adhesives with enhanced thermal conductivity for flip chip applications

Abstract

This paper presents the development of new anisotropic conductive adhesives (ACAs) with enhanced thermal conductivity for improved reliability of adhesive flip chip assembly under high current density condition. As the bump size in the flip chip assembly is reduced, the current density through the bump also increases. This increased current density causes new failure mechanisms, such as interface degradation due to intermetallic compound formation and adhesive swelling resulting from high current stressing. This process is found especially in high current density interconnection in which the high junction temperature enhances such failure mechanisms. Therefore, it is necessary for the ACA to become a thermal transfer medium that allows the board to act as a new heat sink for the flip chip package and improve the lifetime of the ACA flip chip joint. We developed the thermally conductive ACA of 0.63 W/m·K thermal conductivity by using a formulation incorporating the 5-µm Ni-filled and 0.2-µm SiC-filled epoxy-based binder system. The current carrying capability and the electrical reliability under the current stressing condition for the thermally conductive ACA flip chip joints were improved in comparison to conventional ACA. This improvement was attributed to the effective heat dissipation from Au stud bumps/ACA/PCB pad structure by the thermally conductive ACA.

Review of Recent Advances in Electrically Conductive Adhesive Materials and Technologies in Electronic Packaging

“…An ACA, normally a thermally poor conductor, is required to be a thermal transfer medium which allows the board to act as new heat sink for the flip chip package and improve the lifetime of ACA flip chip joint under high current density application. The effect of thermal conductivity of ACA on the current carrying capability of flip chip joints was investigated [91]. Figure 17 shows comparison results of I-V characteristics for two different ACA materials: one is a conventional ACA without any thermal filler and the other is the thermally conductive ACA with 100 phr SiC filler.…”

Electrical Contact Resistance Theory for Anisotropic Conductive Films Considering Electron Tunneling and Particle Flattening

“…The recent work by Jackson and Green [20] derives this critical interference analytically using the von Mises yield criterion. The resulting equation is (1) where is (2) and…”

“…When the ACF is compressed between surfaces the epoxy adheres the surfaces together and the conductive particles provide paths for the electrical current to travel. Several works provide experimental and numerical investigations of this technique [1]- [6]. However, the experimental and theoretical results still do not agree very well [2].…”

Easy and Large Scale Synthesis Silver Nanodendrites: Highly Effective Filler for Isotropic Conductive Adhesives

“…As their main alternatives, leadfree alloys and isotropic conductive adhesives (ICAs) have been developed (Ref 5). Owing to high melting temperatures of many lead-free alloys, their use has been somewhat limited (Ref 6,7). As a result, environmentally friendly ICA, which is easy to prepare and has advantages, such as low working stress on the substrates, short distances between the electrical lines in circuits, low processing temperature, and low cost, are now the most promising alternative to tin-lead solder under mild processing conditions (Ref [8][9][10][11].…”