PROCESS DEVELOPMENT AND RELIABILITY STUDY WITH ANISOTROPIC CONDUCTIVE FILM BONDING WITH MULTIPLE TYPES OF PCB SURFACE FINISHES
Authors: Jenson Lee, David Geiger, and Dongkai Shangguan, Ph.D. Company: Flextronics International Date Published: 5/19/2011
Abstract: ACF (Anisotropic Conductive Film) is a widely-used technology for flex-on-board (FOB) and flex-on-flex (FOF) assembly. Flexible Printed Circuit (FPC) boards enabled products to use three dimensions such as sliding cell phones, mp3 players, etc. In the past few years, the usage FPC made of polyimide, polyester or Teflon have continue grown substantially and become one of focus assembly technology in PCBAs. Anisotropic Conductive Film (ACF) is one type of Anisotropic Conductive Adhesive (ACA) that can be supplied. It is made up of two main components; first is the adhesive itself, typically a formulation of epoxy resins, acryl resins, or both combinations blended. The second component of ACF is the conductive particles used to conduct electricity for both side of interconnection conductors. It can be made from nickel-gold plated polymer spheres, gold plated nickel particles, or recently from lead-free solder materials This paper will report the development of 0.2mm fine pitch ACF bonding with different combination of PCB surface finishes (OSP, ENIG and I-Ag), the mechanical ACF bonding strength, and thermo-mechanical reliability of the ACF interconnection. . ACF material characteristics that contribute to the differences in yield will be discussed as well. Key words: OSP, ENIG, I-Ag, ACF, mechanical and thermo mechanical reliability.