Anisotropic Conductive Film (ACF)

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Anisotropic Conductive Film is a mature assembly technology with a long history and deep supporting infrastructure.

Starting with LCD assembly in the world’s first cheap LCD calculators in the early 1980’s, Anisotropic Conductive Adhesives  (ACA) have expanded use to cover the vast majority of flat panel displays being manufacturerd as well we a strong and growing segment within SMT processes. Anisotropic Conductive Film (ACF) is by far the dominant form of ACA, with well over 90% of the current market.

ACFs are used in all types of display assembly to attach the driver electronics to the display. These driver electronics may be flip chip ICs mounted directly to the display glass in an assembly called Chip-on-Glass or COG. They may take the form of TAB components that are bonded to the glass in a process called Flex-on-Glass, or FOG. And they may even take advantage of ACF’s ability to assemble flip chips to a variety of substrates by placing the IC first on a flex in a Chip-on-Flex (COF) process and then taking that assembly and using FOG to place it on the glass. All of these assemblies to glass of course require a similar interconnection to the board side, and ACF is widely used there to do what is called FOB, or Flex-on-Board bonding.

Outside of the display industry, Anisotropic Conductive Films are widely used as an alternative to solder in a variety of applications where the use of solder causes assembly or reliability problems. These are typically FOB or FOF (Flex-on-Flex) assembly processes and may be done using gold plated or OSP-coated boards or flexes. An example of a type of assembly often done with ACF is the FOB process to place a flex on to a camera module. These camera modules are often used in mobile phones or in the bezels of notebook PCs or tablets. ACF combines the ability to process at a much lower temperature than solder with extremely small z-axis height requirements to put the flex on the module. In many cases, the ability to remove the socket and replace it with an FPC can also lead to cost savings while improving design flexibility.

Anisotropic Conductive Film is also used to make more simple assemblies, such as bonding the tail of a COG display to a mobile phone’s motherboard. It is also used to increase economies of scale by attaching adapter flexes to short stub tail from a COG display. This allows the end user to purchase a higher volume of standardized displays and then to adapt them to different design requirements by using an ACF FOF process.

ACF technology is widely used and very mature. It is an advanced technology, however, and it requires training and experience to use it to its fullest capability. Ito Group has 25 years of history working with ACF and maintains two ACF Applications Labs where we help our customers design and debug processes. We can supply the ACF, ancillary materials, and all types of ACF assembly equipment. More importantly, we offer training, on-site support, and even turn-key systems where we select materials, design a process, and implement it in your factory to a required specification before turning it over to you.

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