Using tiny polymer spheres coated with gold will allow an electrical connection to be made between a die and substrate.
Using tiny polymer spheres coated with gold will allow an electrical connection to be made between a die and substrate. ACF (Anisotropic Conductive Film) is a material commonly used to conduct the electrical signal in the Z direction. This film process has been used for many years, mostly in LCD technology applications for attaching/bonding the driver chip to an LCD panel. As universal LCD technology continues to evolve (more pixels, more I/O’s, etc), mostly in the home television and computer monitor markets, the need for ACF bonding is becoming more and more mainstream.
There are many process variations in ACF bonding. The need for heat to the substrate and die, and also generating the proper force needed to compress the small Au spheres until an electrical connection has been achieved — are issues that must be considered when utilizing ACF bonding.
ACP (paste) bonding is a variation of ACF. Instead of using the medium in a film, it is dispensed as a paste. One of the main challenges when using ACP is the proper distribution of the gold spheres within the ACP. If the spheres are not distributed evenly, the circuit could have an “open”. For this reason, in many cases the use of ACF is preferred. When a film is manufactured, the manufacturer can setup a process to validate the number of Au spheres relative to the surface area. This makes ACF a more repeatable process, but being a film material ACF requires some special handling. Finetech can advise you on both ACF and ACP processes.
If you are curious about ACF or ACP bonding, please reach out to us. We work closely with ACF and ACP manufacturers and understand the processes quite well. In addition, we have worked with several companies on unique processes, like ACF Rework. Yes…ACF Rework.
10/09/2014, created by: Robert Avila