The effect of curing on the performance of ACF bonded chip‐on‐flex assemblies after thermal ageing

Abstract

About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -Anisotropic conductive film (ACF) is now an attractive technology for direct mounting of chips onto the substrate as an alternative to leadfree solders. However, despite its various advantages over other technologies, it also has many unresolved reliability issues. For instance, the performance of ACF assembly in high temperature applications is questionable. The purpose of this paper is to study the effect of bonding temperatures on the curing of ACFs, and their mechanical and electrical performance after high temperature ageing. Design/methodology/approach -In the work presented in this paper, the curing degree of an ACF at different bonding temperatures was measured using a differential scanning calorimeter. The adhesion strength and the contact resistance of ACF bonded chip-on-flex assembly were measured before and after thermal ageing and the results were correlated with the curing degree of ACF. The ACF was an epoxy-based adhesive in which Au-Ni coated polymer particles were randomly dispersed. Findings -The results showed that higher bonding temperatures had resulted in better ACF curing and stronger adhesion. After ageing, the adhesion strength increased for the samples bonded at lower temperatures and decreased for the samples bonded at higher temperatures. ACF assemblies with higher degrees of curing showed smaller increases in contact resistance after ageing. Conduction gaps at the bump-particle and/or particle-pad interfaces were found with the help of scanning electron microscopy and are thought to be the root cause of the increase in contact resistance. Originality/value -The present study focuses on the effect of bonding temperatures on the curing of ACFs, and their adhesion strength and electrical performances after high temperature ageing. The results of this study may help the development of ACFs with higher heat resistance, so that ACFs can be considered as an alternative to lead-free solders.

Study of Structure and Failure Mechanisms in ACA Interconnections Using SEM

“…For thermoset adhesives the bonding temperature together with the bonding time determine the degree of cure of the adhesive matrix. The higher the bonding temperature used the higher the degree of cure of the adhesive matrix is within the same amount of time (Chan & Luk, 2002a;Rizvi et al, 2005;Tan et al, 2004;Wu et al, 1997) as the higher temperature accelerates the crosslinking reaction (Uddin et al, 2004). Similarly, longer bonding time increases the degree of cure.…”

Hygrothermal Effects on the Tensile Properties of Anisotropic Conductive Films

“…12, 13, and 14, the effect of A 40 619 644 661 641 80 450 459 457 455 120 68 70 71 69 B 40 683 705 699 696 80 51 51 52 51 120 32 29 28 30 C 40 804 846 839 829 80 43 41 46 43 120 26 24 27 26 hygrothermal aging on the mechanical properties of the ACFs is likely to be divided into three phases: a first phase in which the effect of hygrothermal aging is dominant; then a second phase during which the effect of further curing inside the high-temperature chamber is dominant; 29 and finally a third phase during which the hygrothermal aging effect is again dominant after complete curing. Advanced testing is needed to provide quantitative analysis of these effects of hygrothermal aging.…”

Electrodeposition of the Sn-58 wt.%Bi layer for low-temperature soldering

“…Fukuda et al [10] investigated the addition of polyoxyethylenelaurylether (C 12 H 25 -O-(CH 2 -CH 2 -O) 6 -H) to the Sn-3wt.%Bi solution in order to overcome the big difference in E o between Sn and Bi. Dendrite formation at the electrodeposit is another problem during Sn-Bi electroplating.…”

“…However, the ACF process has drawbacks including unstable electrical reliability in a fine pitch joint [6], weakness in high humidity, and high production cost [7,8]. Meanwhile, the electroplating process in electronics packaging enables the achievement of a fine pitch, mass production, and low cost [9,10].…”